Completes coding of the PWM module

git-svn-id: https://nuttx.svn.sourceforge.net/svnroot/nuttx/trunk@4200 7fd9a85b-ad96-42d3-883c-3090e2eb8679

10 files changed, 6927 insertions, 0 deletions

diff --git a/nuttx/drivers/usbhost/Make.defs b/nuttx/drivers/usbhost/Make.defs
new file mode 100644
index 000000000..cc28e874d
--- /dev/null
+++ b/nuttx/drivers/usbhost/Make.defs
@@ -0,0 +1,57 @@
+############################################################################
+# drivers/usbhost/Make.defs
+#
+#   Copyright (C) 2010-2011 Gregory Nutt. All rights reserved.
+#   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+#
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in
+#    the documentation and/or other materials provided with the
+#    distribution.
+# 3. Neither the name NuttX nor the names of its contributors may be
+#    used to endorse or promote products derived from this software
+#    without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+# COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+# OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+############################################################################
+
+CSRCS  += hid_parser.c
+
+ifeq ($(CONFIG_USBHOST),y)
+
+# Include built-in USB host driver logic
+
+CSRCS  += usbhost_registry.c usbhost_registerclass.c usbhost_findclass.c
+CSRCS  += usbhost_enumerate.c usbhost_storage.c usbhost_hidkbd.c
+
+# Include add-on USB host driver logic (see misc/drivers)
+
+ifeq ($(CONFIG_NET),y)
+  RTL8187_CSRC  := ${shell if [ -f usbhost/rtl8187x.c ]; then echo "rtl8187x.c"; fi}
+  CSRCS += $(RTL8187_CSRC)
+endif
+endif
+
+# Include USB host driver build logic
+
+DEPPATH += --dep-path usbhost
+VPATH += :usbhost
+CFLAGS += ${shell $(TOPDIR)/tools/incdir.sh $(INCDIROPT) "$(CC)" $(TOPDIR)/drivers/usbhost}
diff --git a/nuttx/drivers/usbhost/hid_parser.c b/nuttx/drivers/usbhost/hid_parser.c
new file mode 100644
index 000000000..a0ca6066b
--- /dev/null
+++ b/nuttx/drivers/usbhost/hid_parser.c
@@ -0,0 +1,529 @@
+/****************************************************************************
+ * drivers/usbhost/hid_parser.c
+ *
+ *   Copyright (C) 2011 Gregory Nutt. All rights reserved.
+ *
+ * Adapted from the LUFA Library:
+ *
+ *   Copyright 2011  Dean Camera (dean [at] fourwalledcubicle [dot] com)
+ *   dean [at] fourwalledcubicle [dot] com, www.lufa-lib.org
+ *
+ * Permission to use, copy, modify, distribute, and sell this
+ * software and its documentation for any purpose is hereby granted
+ * without fee, provided that the above copyright notice appear in
+ * all copies and that both that the copyright notice and this
+ * permission notice and warranty disclaimer appear in supporting
+ * documentation, and that the name of the author not be used in
+ * advertising or publicity pertaining to distribution of the
+ * software without specific, written prior permission.
+ *
+ * The author disclaim all warranties with regard to this
+ * software, including all implied warranties of merchantability
+ * and fitness.  In no event shall the author be liable for any
+ * special, indirect or consequential damages or any damages
+ * whatsoever resulting from loss of use, data or profits, whether
+ * in an action of contract, negligence or other tortious action,
+ * arising out of or in connection with the use or performance of
+ * this software.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <assert.h>
+#include <errno.h>
+#include <debug.h>
+
+#include <nuttx/usb/hid.h>
+#include <nuttx/usb/hid_parser.h>
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+ 
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+struct hid_state_s
+{
+  struct hid_rptitem_attributes_s attrib;
+  uint8_t rptcount;
+  uint8_t id;
+};
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: hid_parsereport
+ *
+ * Description:
+ *   Function to process a given HID report returned from an attached device,
+ *   and store it into a given struct hid_rptinfo_s structure.
+ *
+ * Input Parameters:
+ *    report   Buffer containing the device's HID report table.
+ *    rptlen   Size in bytes of the HID report table.
+ *    filter   Callback function to decide if an item should be retained
+ *    rptinfo  Pointer to a struct hid_rptinfo_s instance for the parser output.
+ *
+ * Returned Value:
+ *  Zero on success, otherwise a negated errno value.
+ ****************************************************************************/
+
+int hid_parsereport(FAR const uint8_t *report, int rptlen,
+                    hid_rptfilter_t filter, FAR struct hid_rptinfo_s *rptinfo)
+{
+  struct hid_state_s           state[CONFIG_HID_STATEDEPTH];
+  struct hid_state_s          *currstate = &state[0];
+  struct hid_collectionpath_s *collectionpath = NULL;
+  struct hid_rptsizeinfo_s    *rptidinfo = &rptinfo->rptsize[0];
+  uint16_t                     usage[CONFIG_HID_USAGEDEPTH];
+  uint8_t                      nusage = 0;
+  struct hid_range_s           usage_range = { 0, 0 };
+  int                          i;
+
+  DEBUGASSERT(report && filter && rptinfo);
+
+  memset(rptinfo, 0x00, sizeof(struct hid_rptinfo_s));
+  memset(currstate, 0x00, sizeof(struct hid_state_s));
+  memset(rptidinfo, 0x00, sizeof(struct hid_rptsizeinfo_s));
+
+  rptinfo->nreports = 1;
+
+  while (rptlen > 0)
+    {
+      uint8_t  item = *report;
+      uint32_t data = 0;
+
+      report++;
+      rptlen--;
+
+      switch (item & USBHID_RPTITEM_SIZE_MASK)
+        {
+        case USBHID_RPTITEM_SIZE_4: /* 4 bytes of little endian data follow */
+          data    = (uint32_t)(*report++);
+          data   |= (uint32_t)(*report++) << 8;
+          data   |= (uint32_t)(*report++) << 16;
+          data   |= (uint32_t)(*report++) << 24;
+          rptlen -= 4;
+          break;
+
+        case USBHID_RPTITEM_SIZE_2: /* 2 bytes of little endian data follow */
+          data    = (uint32_t)(*report++);
+          data   |= (uint32_t)(*report++) << 8;
+          rptlen -= 2;
+          break;
+
+        case USBHID_RPTITEM_SIZE_1: /* 1 byte of data follows */
+          data    = (uint32_t)(*report++);
+          rptlen -= 1;
+          break;
+
+        case USBHID_RPTITEM_SIZE_0: /* No data follows */
+        default:
+          break;
+        }
+
+      switch (item & ~USBHID_RPTITEM_SIZE_MASK)
+        {
+        case USBHID_GLOBAL_PUSH_PREFIX:
+          if (currstate == &state[CONFIG_HID_STATEDEPTH - 1])
+            {
+              return -E2BIG;
+            }
+
+          memcpy((currstate + 1),
+                 currstate, sizeof(struct hid_rptitem_s));
+
+          currstate++;
+          break;
+
+        case USBHID_GLOBAL_POP_PREFIX:
+          if (currstate == &state[0])
+            {
+              return -EINVAL; /* Pop without push? */
+            }
+
+          currstate--;
+          break;
+
+        case USBHID_GLOBAL_USAGEPAGE_PREFIX:
+          if ((item & USBHID_RPTITEM_SIZE_MASK) == USBHID_RPTITEM_SIZE_4)
+            {
+              currstate->attrib.usage.page = (data >> 16);
+            }
+
+          currstate->attrib.usage.page = data;
+          break;
+
+        case USBHID_GLOBAL_LOGICALMIN_PREFIX:
+          currstate->attrib.logical.min = data;
+          break;
+
+        case USBHID_GLOBAL_LOGICALMAX_PREFIX:
+          currstate->attrib.logical.max = data;
+          break;
+
+        case USBHID_GLOBAL_PHYSICALMIN_PREFIX:
+          currstate->attrib.physical.min = data;
+          break;
+
+        case USBHID_GLOBAL_PHYSMICALAX_PREFIX:
+          currstate->attrib.physical.max = data;
+          break;
+
+        case USBHID_GLOBAL_UNITEXP_PREFIX:
+          currstate->attrib.unit.exponent = data;
+          break;
+
+        case USBHID_GLOBAL_UNIT_PREFIX:
+          currstate->attrib.unit.type = data;
+          break;
+
+        case USBHID_GLOBAL_REPORTSIZE_PREFIX:
+          currstate->attrib.bitsize = data;
+          break;
+
+        case USBHID_GLOBAL_REPORTCOUNT_PREFIX:
+          currstate->rptcount = data;
+          break;
+
+        case USBHID_GLOBAL_REPORTID_PREFIX:
+          currstate->id = data;
+
+          if (rptinfo->haverptid)
+            {
+              rptidinfo = NULL;
+
+              for (i = 0; i < rptinfo->nreports; i++)
+                {
+                  if (rptinfo->rptsize[i].id == currstate->id)
+                    {
+                      rptidinfo = &rptinfo->rptsize[i];
+                      break;
+                    }
+                }
+
+              if (rptidinfo == NULL)
+                {
+                  if (rptinfo->nreports == CONFIG_HID_MAXIDS)
+                    {
+                      return -EINVAL;
+                    }
+
+                  rptidinfo = &rptinfo->rptsize[rptinfo->nreports++];
+                  memset(rptidinfo, 0x00, sizeof(struct hid_rptsizeinfo_s));
+                }
+            }
+
+          rptinfo->haverptid = true;
+
+          rptidinfo->id = currstate->id;
+          break;
+
+        case USBHID_LOCAL_USAGE_PREFIX:
+          if (nusage == CONFIG_HID_USAGEDEPTH)
+            {
+              return -E2BIG;
+            }
+
+          usage[nusage++] = data;
+          break;
+
+        case USBHID_LOCAL_USAGEMIN_PREFIX:
+          usage_range.min = data;
+          break;
+
+        case USBHID_LOCAL_USAGEMAX_PREFIX:
+          usage_range.max = data;
+          break;
+
+        case USBHID_MAIN_COLLECTION_PREFIX:
+          if (collectionpath == NULL)
+            {
+              collectionpath = &rptinfo->collectionpaths[0];
+            }
+          else
+            {
+              struct hid_collectionpath_s *ParentCollectionPath = collectionpath;
+
+              collectionpath = &rptinfo->collectionpaths[1];
+
+              while (collectionpath->parent != NULL)
+                {
+                  if (collectionpath == &rptinfo->collectionpaths[CONFIG_HID_MAXCOLLECTIONS - 1])
+                    {
+                      return -EINVAL;
+                    }
+
+                  collectionpath++;
+                }
+
+              collectionpath->parent = ParentCollectionPath;
+            }
+
+          collectionpath->type       = data;
+          collectionpath->usage.page = currstate->attrib.usage.page;
+
+          if (nusage)
+            {
+              collectionpath->usage.usage = usage[0];
+
+              for (i = 0; i < nusage; i++)
+                usage[i] = usage[i + 1];
+
+              nusage--;
+            }
+          else if (usage_range.min <= usage_range.max)
+            {
+              collectionpath->usage.usage = usage_range.min++;
+            }
+
+          break;
+
+        case USBHID_MAIN_ENDCOLLECTION_PREFIX:
+          if (collectionpath == NULL)
+            {
+              return -EINVAL;
+            }
+
+          collectionpath = collectionpath->parent;
+          break;
+ 
+        case USBHID_MAIN_INPUT_PREFIX:
+        case USBHID_MAIN_OUTPUT_PREFIX:
+        case USBHID_MAIN_FEATURE_PREFIX:
+          {
+            int itemno;
+            for (itemno = 0; itemno < currstate->rptcount; itemno++)
+              {
+                struct hid_rptitem_s newitem;
+                uint8_t tag;
+
+                memcpy(&newitem.attrib, &currstate->attrib,
+                       sizeof(struct hid_rptitem_attributes_s));
+
+                newitem.flags          = data;
+                newitem.collectionpath = collectionpath;
+                newitem.id             = currstate->id;
+
+                if (nusage)
+                  {
+                    newitem.attrib.usage.usage = usage[0];
+
+                    for (i = 0; i < nusage; i++)
+                      {
+                        usage[i] = usage[i + 1];
+                      }
+                    nusage--;
+                  }
+                else if (usage_range.min <= usage_range.max)
+                  {
+                    newitem.attrib.usage.usage = usage_range.min++;
+                  }
+
+                tag = (item & ~USBHID_RPTITEM_SIZE_MASK);
+                if (tag == USBHID_MAIN_INPUT_PREFIX)
+                  {
+                    newitem.type = HID_REPORT_ITEM_IN;
+                  }
+                else if (tag == USBHID_MAIN_OUTPUT_PREFIX)
+                  {
+                    newitem.type = HID_REPORT_ITEM_OUT;
+                  }
+                else
+                  {
+                    newitem.type = HID_REPORT_ITEM_FEATURE;
+                  }
+
+                newitem.bitoffset              = rptidinfo->size[newitem.type];
+                rptidinfo->size[newitem.type] += currstate->attrib.bitsize;
+
+                /* Accumulate the maximum report size */
+
+                if (rptinfo->maxrptsize < newitem.bitoffset)
+                  {
+                    rptinfo->maxrptsize = newitem.bitoffset;
+                  }
+
+                if ((data & USBHID_MAIN_CONSTANT) == 0 && filter(&newitem))
+                  {
+                    if (rptinfo->nitems == CONFIG_HID_MAXITEMS)
+                      {
+                        return -EINVAL;
+                      }
+
+                    memcpy(&rptinfo->items[rptinfo->nitems],
+                           &newitem, sizeof(struct hid_rptitem_s));
+
+                    rptinfo->nitems++;
+                  }
+              }
+          }
+          break;
+        }
+
+      if ((item & USBHID_RPTITEM_TYPE_MASK) == USBHID_RPTITEM_TYPE_MAIN)
+        {
+          usage_range.min = 0;
+          usage_range.max = 0;
+          nusage = 0;
+        }
+    }
+
+  if (!(rptinfo->nitems))
+    {
+      return -ENOENT;
+    }
+
+  return OK;
+}
+
+/****************************************************************************
+ * Name: hid_getitem
+ *
+ * Description:
+ *   Extracts the given report item's value out of the given HID report and
+ *   places it into the value member of the report item's struct hid_rptitem_s
+ *   structure.
+ *
+ *   When called on a report with an item that exists in that report, this
+ *   copies the report item's Value to it's previous element for easy
+ *   checking to see if an item's value has changed before processing a
+ *   report. If the given item does not exist in the report, the function
+ *   does not modify the report item's data.
+ *
+ * Input Parameters
+ *   report  Buffer containing an IN or FEATURE report from an attached
+ *               device.
+ *   item        Pointer to the report item of interest in a struct hid_rptinfo_s
+ *               item array.
+ *
+ * Returned Value:
+ *   Zero on success, otherwise a negated errno value.
+ *
+ ****************************************************************************/
+
+int hid_getitem(FAR const uint8_t *report, FAR struct hid_rptitem_s *item)
+{
+  uint16_t remaining = item->attrib.bitsize;
+  uint16_t offset    = item->bitoffset;
+  uint32_t mask      = (1 << 0);
+
+  if (item->id)
+    {
+      if (item->id != report[0])
+        {
+          return -ENOENT;
+        }
+
+      report++;
+    }
+
+  item->previous = item->value;
+  item->value    = 0;
+
+  while (remaining--)
+    {
+      if (report[offset >> 3] & (1 << (offset & 7)))
+        {
+          item->value |= mask;
+        }
+
+      offset++;
+      mask <<= 1;
+    }
+
+  return OK;
+}
+
+/****************************************************************************
+ * Name: hid_putitem
+ *
+ * Desription:
+ *   Retrieves the given report item's value out of the Value member of the
+ *   report item's struct hid_rptitem_s structure and places it into the correct
+ *   position in the HID report buffer. The report buffer is assumed to have
+ *   the appropriate bits cleared before calling this function (i.e., the
+ *   buffer should be explicitly cleared before report values are added).
+ *
+ *   When called, this copies the report item's Value element to it's
+ *   previous element for easy checking to see if an item's value has
+ *   changed before sending a report.
+ *
+ *   If the device has multiple HID reports, the first byte in the report is
+ *   set to the report ID of the given item.
+ *
+ * Input Parameters:
+ *   report  Buffer holding the current OUT or FEATURE report data.
+ *   item    Pointer to the report item of interest in a struct hid_rptinfo_s
+ *           item array.
+ *
+ ****************************************************************************/
+
+#if 0 /* Not needed by host */
+void hid_putitem(FAR uint8_t *report, struct hid_rptitem_s *item)
+{
+  uint16_t remaining = item->attrib.bitsize;
+  uint16_t offset    = item->bitoffset;
+  uint32_t mask      = (1 << 0);
+
+  if (item->id)
+    {
+      report[0] = item->id;
+      report++;
+    }
+
+  item->previous = item->value;
+
+  while (remaining--)
+    {
+      if (item->value & (1 << (offset & 7)))
+        {
+          report[offset >> 3] |= mask;
+        }
+
+      offset++;
+      mask <<= 1;
+    }
+}
+#endif
+
+/****************************************************************************
+ * Name: hid_reportsize
+ *
+ * Description:
+ *   Retrieves the size of a given HID report in bytes from it's Report ID.
+ *
+ * InputParameters:
+ *  rptinfo Pointer to a struct hid_rptinfo_s instance containing the parser output.
+ *  id      Report ID of the report whose size is to be retrieved.
+ *  rpttype Type of the report whose size is to be determined, a valued from the
+ *          HID_ReportItemTypes_t enum.
+ *
+ *  Size of the report in bytes, or 0 if the report does not exist.
+ *
+ ****************************************************************************/
+ 
+size_t hid_reportsize(FAR struct hid_rptinfo_s *rptinfo, uint8_t id, uint8_t rpttype)
+{
+  int i;
+  for (i = 0; i < CONFIG_HID_MAXIDS; i++)
+    {
+      size_t size = rptinfo->rptsize[i].size[rpttype];
+
+      if (rptinfo->rptsize[i].id == id)
+        {
+          return ((size >> 3) + ((size & 0x07) ? 1 : 0));
+        }
+    }
+
+  return 0;
+}
diff --git a/nuttx/drivers/usbhost/usbhost_enumerate.c b/nuttx/drivers/usbhost/usbhost_enumerate.c
new file mode 100644
index 000000000..8e1cd80e7
--- /dev/null
+++ b/nuttx/drivers/usbhost/usbhost_enumerate.c
@@ -0,0 +1,517 @@
+/*******************************************************************************
+ * drivers/usbhost/usbhost_enumerate.c
+ *
+ *   Copyright (C) 2011 Gregory Nutt. All rights reserved.
+ *   Authors: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ *******************************************************************************/
+
+/*******************************************************************************
+ * Included Files
+ *******************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/types.h>
+#include <stdint.h>
+#include <string.h>
+#include <errno.h>
+#include <assert.h>
+#include <debug.h>
+
+#include <nuttx/arch.h>
+#include <nuttx/usb/usb.h>
+#include <nuttx/usb/usbhost.h>
+
+/*******************************************************************************
+ * Definitions
+ *******************************************************************************/
+
+/*******************************************************************************
+ * Private Types
+ *******************************************************************************/
+
+/*******************************************************************************
+ * Private Function Prototypes
+ *******************************************************************************/
+
+static inline uint16_t usbhost_getle16(const uint8_t *val);
+static void usbhost_putle16(uint8_t *dest, uint16_t val);
+
+static inline int usbhost_devdesc(const struct usb_devdesc_s *devdesc,
+                                  struct usbhost_id_s *id);
+static inline int usbhost_configdesc(const uint8_t *configdesc, int desclen,
+                                     struct usbhost_id_s *id);
+static inline int usbhost_classbind(FAR struct usbhost_driver_s *drvr,
+                                    const uint8_t *configdesc, int desclen,
+                                    struct usbhost_id_s *id, uint8_t funcaddr,
+                                    FAR struct usbhost_class_s **class);
+
+/*******************************************************************************
+ * Private Data
+ *******************************************************************************/
+
+/*******************************************************************************
+ * Public Data
+ *******************************************************************************/
+
+/*******************************************************************************
+ * Private Functions
+ *******************************************************************************/
+
+/****************************************************************************
+ * Name: usbhost_getle16
+ *
+ * Description:
+ *   Get a (possibly unaligned) 16-bit little endian value.
+ *
+ *******************************************************************************/
+
+static inline uint16_t usbhost_getle16(const uint8_t *val)
+{
+  return (uint16_t)val[1] << 8 | (uint16_t)val[0];
+}
+
+/****************************************************************************
+ * Name: usbhost_putle16
+ *
+ * Description:
+ *   Put a (possibly unaligned) 16-bit little endian value.
+ *
+ *******************************************************************************/
+
+static void usbhost_putle16(uint8_t *dest, uint16_t val)
+{
+  dest[0] = val & 0xff; /* Little endian means LS byte first in byte stream */
+  dest[1] = val >> 8;
+}
+
+/*******************************************************************************
+ * Name: usbhost_devdesc
+ *
+ * Description:
+ *   A configuration descriptor has been obtained from the device.  Find the
+ *   ID information for the class that supports this device.
+ *
+ *******************************************************************************/
+
+static inline int usbhost_devdesc(const struct usb_devdesc_s *devdesc,
+                                  struct usbhost_id_s *id)
+{
+  /* Clear the ID info */
+
+  memset(id, 0, sizeof(struct usbhost_id_s));
+
+  /* Pick off the class ID info */
+
+  id->base     = devdesc->class;
+  id->subclass = devdesc->subclass;
+  id->proto    = devdesc->protocol;
+
+  /* Pick off the VID and PID as well (for vendor specfic devices) */
+
+  id->vid = usbhost_getle16(devdesc->vendor);
+  id->pid = usbhost_getle16(devdesc->product);
+
+  uvdbg("class:%d subclass:%04x protocol:%04x vid:%d pid:%d\n",
+        id->base, id->subclass, id->proto, id->vid, id->pid);
+  return OK;
+}
+                                
+/*******************************************************************************
+ * Name: usbhost_configdesc
+ *
+ * Description:
+ *   A configuration descriptor has been obtained from the device.  Find the
+ *   ID information for the class that supports this device.
+ *
+ *******************************************************************************/
+
+static inline int usbhost_configdesc(const uint8_t *configdesc, int cfglen,
+                                     struct usbhost_id_s *id)
+{
+  struct usb_cfgdesc_s *cfgdesc;
+  struct usb_ifdesc_s *ifdesc;
+  int remaining;
+
+  DEBUGASSERT(configdesc != NULL && cfglen >= USB_SIZEOF_CFGDESC);
+
+  /* Verify that we were passed a configuration descriptor */
+
+  cfgdesc = (struct usb_cfgdesc_s *)configdesc;
+  uvdbg("cfg len:%d total len:%d\n", cfgdesc->len, cfglen);
+
+  if (cfgdesc->type != USB_DESC_TYPE_CONFIG)
+    {
+      return -EINVAL;
+    }
+
+  /* Skip to the next entry descriptor */
+
+  configdesc += cfgdesc->len;
+  remaining   = cfglen - cfgdesc->len;
+
+  /* Loop where there are more dscriptors to examine */
+
+  memset(id, 0, sizeof(FAR struct usb_desc_s));
+  while (remaining >= sizeof(struct usb_desc_s))
+    {
+      /* What is the next descriptor? Is it an interface descriptor? */
+
+      ifdesc = (struct usb_ifdesc_s *)configdesc;
+      if (ifdesc->type == USB_DESC_TYPE_INTERFACE)
+        {
+          /* Yes, extract the class information from the interface descriptor.
+           * Typically these values are zero meaning that the "real" ID
+           * information resides in the device descriptor.
+           */
+ 
+          DEBUGASSERT(remaining >= sizeof(struct usb_ifdesc_s));
+          id->base     = ifdesc->class;
+          id->subclass = ifdesc->subclass;
+          id->proto    = ifdesc->protocol;
+          uvdbg("class:%d subclass:%d protocol:%d\n",
+                id->base, id->subclass, id->proto);
+          return OK;
+        }
+
+     /* Increment the address of the next descriptor */
+ 
+      configdesc += ifdesc->len;
+      remaining  -= ifdesc->len;
+    }
+
+  return -ENOENT;
+}
+
+/*******************************************************************************
+ * Name: usbhost_classbind
+ *
+ * Description:
+ *   A configuration descriptor has been obtained from the device.  Try to
+ *   bind this configuration descriptor with a supported class.
+ *
+ *******************************************************************************/
+
+static inline int usbhost_classbind(FAR struct usbhost_driver_s *drvr,
+                                    const uint8_t *configdesc, int desclen,
+                                    struct usbhost_id_s *id, uint8_t funcaddr,
+                                    FAR struct usbhost_class_s **class)
+{
+  FAR struct usbhost_class_s *devclass;
+  const struct usbhost_registry_s *reg;
+  int ret = -EINVAL;
+
+  /* Is there is a class implementation registered to support this device. */
+
+  reg = usbhost_findclass(id);
+  uvdbg("usbhost_findclass: %p\n", reg);
+  if (reg)
+    {
+      /* Yes.. there is a class for this device.  Get an instance of
+       * its interface.
+       */
+
+      ret = -ENOMEM;
+      devclass = CLASS_CREATE(reg, drvr, id);
+      uvdbg("CLASS_CREATE: %p\n", devclass);
+      if (devclass)
+        {
+          /* Then bind the newly instantiated class instance */
+
+          ret = CLASS_CONNECT(devclass, configdesc, desclen, funcaddr);
+          if (ret != OK)
+            {
+              /* On failures, call the class disconnect method which
+               * should then free the allocated devclass instance.
+               */
+
+              udbg("CLASS_CONNECT failed: %d\n", ret);
+              CLASS_DISCONNECTED(devclass);
+            }
+          else
+            {
+              *class = devclass;
+            }
+        }
+    }
+
+  uvdbg("Returning: %d\n", ret);
+  return ret;
+}
+
+/*******************************************************************************
+ * Public Functions
+ *******************************************************************************/
+
+/*******************************************************************************
+ * Name: usbhost_enumerate
+ *
+ * Description:
+ *   Enumerate the connected device.  As part of this enumeration process,
+ *   the driver will (1) get the device's configuration descriptor, (2)
+ *   extract the class ID info from the configuration descriptor, (3) call
+ *   usbhost_findclass() to find the class that supports this device, (4)
+ *   call the create() method on the struct usbhost_registry_s interface
+ *   to get a class instance, and finally (5) call the configdesc() method
+ *   of the struct usbhost_class_s interface.  After that, the class is in
+ *   charge of the sequence of operations.
+ *
+ * Input Parameters:
+ *   drvr - The USB host driver instance obtained as a parameter from the call to
+ *      the class create() method.
+ *   funcaddr - The USB address of the function containing the endpoint that EP0
+ *     controls
+ *   class - If the class driver for the device is successful located
+ *      and bound to the driver, the allocated class instance is returned into
+ *      this caller-provided memory location.
+ *
+ * Returned Values:
+ *   On success, zero (OK) is returned. On a failure, a negated errno value is
+ *   returned indicating the nature of the failure
+ *
+ * Assumptions:
+ *   - Only a single class bound to a single device is supported.
+ *   - Called from a single thread so no mutual exclusion is required.
+ *   - Never called from an interrupt handler.
+ *
+ *******************************************************************************/
+
+int usbhost_enumerate(FAR struct usbhost_driver_s *drvr, uint8_t funcaddr,
+                      FAR struct usbhost_class_s **class)
+{
+  struct usb_ctrlreq_s *ctrlreq;
+  struct usbhost_id_s id;
+  size_t maxlen;
+  unsigned int cfglen;
+  uint8_t maxpacketsize;
+  uint8_t *buffer;
+  int  ret;
+
+  DEBUGASSERT(drvr && class);
+
+  /* Allocate TD buffers for use in this function.  We will need two:
+   * One for the request and one for the data buffer.
+   */
+
+  ret = DRVR_ALLOC(drvr, (FAR uint8_t **)&ctrlreq, &maxlen);
+  if (ret != OK)
+    {
+      udbg("DRVR_ALLOC failed: %d\n", ret);
+      return ret;
+    }
+
+  ret = DRVR_ALLOC(drvr, &buffer, &maxlen);
+  if (ret != OK)
+    {
+      udbg("DRVR_ALLOC failed: %d\n", ret);
+      goto errout;
+    }
+
+  /* Set max pkt size = 8 */
+
+  DRVR_EP0CONFIGURE(drvr, 0, 8);
+
+  /* Read first 8 bytes of the device descriptor */
+
+  ctrlreq->type = USB_REQ_DIR_IN|USB_REQ_RECIPIENT_DEVICE;
+  ctrlreq->req  = USB_REQ_GETDESCRIPTOR;
+  usbhost_putle16(ctrlreq->value, (USB_DESC_TYPE_DEVICE << 8));
+  usbhost_putle16(ctrlreq->index, 0);
+  usbhost_putle16(ctrlreq->len, 8);
+
+  ret = DRVR_CTRLIN(drvr, ctrlreq, buffer);
+  if (ret != OK)
+    {
+      udbg("ERROR: GETDESCRIPTOR/DEVICE, DRVR_CTRLIN returned %d\n", ret);
+      goto errout;
+    }
+
+  /* Extract the correct max packetsize from the device descriptor */
+
+  maxpacketsize = ((struct usb_devdesc_s *)buffer)->mxpacketsize;
+  uvdbg("maxpacksetsize: %d\n", maxpacketsize);
+
+  /* And reconfigure EP0 */
+
+  DRVR_EP0CONFIGURE(drvr, 0, maxpacketsize);
+
+  /* Now read the full device descriptor */
+
+  ctrlreq->type = USB_REQ_DIR_IN|USB_REQ_RECIPIENT_DEVICE;
+  ctrlreq->req  = USB_REQ_GETDESCRIPTOR;
+  usbhost_putle16(ctrlreq->value, (USB_DESC_TYPE_DEVICE << 8));
+  usbhost_putle16(ctrlreq->index, 0);
+  usbhost_putle16(ctrlreq->len, USB_SIZEOF_DEVDESC);
+
+  ret = DRVR_CTRLIN(drvr, ctrlreq, buffer);
+  if (ret != OK)
+    {
+      udbg("ERROR: GETDESCRIPTOR/DEVICE, DRVR_CTRLIN returned %d\n", ret);
+      goto errout;
+    }
+
+  /* Get class identification information from the device descriptor.  Most
+   * devices set this to USB_CLASS_PER_INTERFACE (zero) and provide the
+   * identification informatino in the interface descriptor(s).  That allows
+   * a device to support multiple, different classes.
+   */
+
+  (void)usbhost_devdesc((struct usb_devdesc_s *)buffer, &id);
+
+  /* Set the USB device address to the value in the 'funcaddr' input */
+
+  ctrlreq->type = USB_REQ_DIR_OUT|USB_REQ_RECIPIENT_DEVICE;
+  ctrlreq->req  = USB_REQ_SETADDRESS;
+  usbhost_putle16(ctrlreq->value, (uint16_t)funcaddr);
+  usbhost_putle16(ctrlreq->index, 0);
+  usbhost_putle16(ctrlreq->len, 0);
+
+  ret = DRVR_CTRLOUT(drvr, ctrlreq, NULL);
+  if (ret != OK)
+    {
+      udbg("ERROR: SETADDRESS DRVR_CTRLOUT returned %d\n", ret);
+      goto errout;
+    }
+  up_mdelay(2);
+
+  /* Modify control pipe with the provided USB device address */
+
+  DRVR_EP0CONFIGURE(drvr, funcaddr, maxpacketsize);
+
+ /* Get the configuration descriptor (only), index == 0.  Should not be
+  * hard-coded! More logic is needed in order to handle devices with
+  * multiple configurations.
+  */
+
+  ctrlreq->type = USB_REQ_DIR_IN|USB_REQ_RECIPIENT_DEVICE;
+  ctrlreq->req  = USB_REQ_GETDESCRIPTOR;
+  usbhost_putle16(ctrlreq->value, (USB_DESC_TYPE_CONFIG << 8));
+  usbhost_putle16(ctrlreq->index, 0);
+  usbhost_putle16(ctrlreq->len, USB_SIZEOF_CFGDESC);
+
+  ret = DRVR_CTRLIN(drvr, ctrlreq, buffer);
+  if (ret != OK)
+   {
+      udbg("ERROR: GETDESCRIPTOR/CONFIG, DRVR_CTRLIN returned %d\n", ret);
+      goto errout;
+    }
+
+  /* Extract the full size of the configuration data */
+
+  cfglen = (unsigned int)usbhost_getle16(((struct usb_cfgdesc_s *)buffer)->totallen);
+  uvdbg("sizeof config data: %d\n", cfglen);
+
+  /* Get all of the configuration descriptor data, index == 0 (Should not be
+   * hard-coded!)
+   */
+
+  ctrlreq->type = USB_REQ_DIR_IN|USB_REQ_RECIPIENT_DEVICE;
+  ctrlreq->req  = USB_REQ_GETDESCRIPTOR;
+  usbhost_putle16(ctrlreq->value, (USB_DESC_TYPE_CONFIG << 8));
+  usbhost_putle16(ctrlreq->index, 0);
+  usbhost_putle16(ctrlreq->len, cfglen);
+
+  ret = DRVR_CTRLIN(drvr, ctrlreq, buffer);
+  if (ret != OK)
+    {
+      udbg("ERROR: GETDESCRIPTOR/CONFIG, DRVR_CTRLIN returned %d\n", ret);
+      goto errout;
+    }
+
+  /* Select device configuration 1 (Should not be hard-coded!) */
+
+  ctrlreq->type = USB_REQ_DIR_OUT|USB_REQ_RECIPIENT_DEVICE;
+  ctrlreq->req  = USB_REQ_SETCONFIGURATION;
+  usbhost_putle16(ctrlreq->value, 1);
+  usbhost_putle16(ctrlreq->index, 0);
+  usbhost_putle16(ctrlreq->len, 0);
+
+  ret = DRVR_CTRLOUT(drvr, ctrlreq, NULL);
+  if (ret != OK)
+    {
+      udbg("ERROR: SETCONFIGURATION, DRVR_CTRLOUT returned %d\n", ret);
+      goto errout;
+    }
+
+  /* Free the TD that we were using for the request buffer.  It is not needed
+   * further here but it may be needed by the class driver during its connection
+   * operations.
+   */
+ 
+  DRVR_FREE(drvr, (uint8_t*)ctrlreq);
+  ctrlreq = NULL;
+
+  /* Was the class identification information provided in the device descriptor?
+   * Or do we need to find it in the interface descriptor(s)?
+   */
+
+  if (id.base == USB_CLASS_PER_INTERFACE)
+    {
+      /* Get the class identification information for this device from the
+       * interface descriptor(s).  Hmmm.. More logic is need to handle the
+       * case of multiple interface descriptors.
+       */
+
+      ret = usbhost_configdesc(buffer, cfglen, &id);
+      if (ret != OK)
+        {
+          udbg("ERROR: usbhost_configdesc returned %d\n", ret);
+          goto errout;
+        }
+    }
+
+  /* Some devices may require this delay before initialization */
+
+  up_mdelay(100);
+
+  /* Parse the configuration descriptor and bind to the class instance for the
+   * device.  This needs to be the last thing done because the class driver
+   * will begin configuring the device.
+   */
+
+  ret = usbhost_classbind(drvr, buffer, cfglen, &id, funcaddr, class);
+  if (ret != OK)
+    {
+      udbg("ERROR: usbhost_classbind returned %d\n", ret);
+    }
+
+errout:
+  if (buffer)
+    {
+      DRVR_FREE(drvr, buffer);
+    }
+
+  if (ctrlreq)
+    {
+      DRVR_FREE(drvr, (uint8_t*)ctrlreq);
+    }
+  return ret;
+}
diff --git a/nuttx/drivers/usbhost/usbhost_findclass.c b/nuttx/drivers/usbhost/usbhost_findclass.c
new file mode 100644
index 000000000..f08aff580
--- /dev/null
+++ b/nuttx/drivers/usbhost/usbhost_findclass.c
@@ -0,0 +1,199 @@
+/****************************************************************************
+ * drivers/usbhost/usbhost_findclass.c
+ *
+ *   Copyright (C) 2010 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/types.h>
+#include <stdbool.h>
+#include <debug.h>
+
+#include <nuttx/usb/usb.h>
+#include <nuttx/usb/usbhost.h>
+#include <arch/irq.h>
+
+#include "usbhost_registry.h"
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: usbhost_idmatch
+ *
+ * Description:
+ *   Check if the class ID matches what the host controller found.
+ *
+ * Input Parameters:
+ *   classid - ID info for the class under consideration.
+ *   devid - ID info reported by the device.
+ *
+ * Returned Values:
+ *   TRUE - the class will support this device.
+ *
+ ****************************************************************************/
+
+static bool usbhost_idmatch(const struct usbhost_id_s *classid,
+                            const struct usbhost_id_s *devid)
+{
+  uvdbg("Compare to class:%d subclass:%d protocol:%d vid:%04x pid:%04x\n",
+         classid->base, classid->subclass, classid->proto,
+         classid->vid, classid->pid);
+
+  /* The base class ID, subclass and protocol have to match up in any event */
+
+  if (devid->base     == classid->base &&
+      devid->subclass == classid->subclass &&
+      devid->proto    == classid->proto)
+    {
+      /* If this is a vendor-specific class ID, then the VID and PID have to
+       * match as well.
+       */
+
+      if (devid->base == USB_CLASS_VENDOR_SPEC)
+        {
+          /* Vendor specific... do the VID and PID also match? */
+
+          if (devid->vid == classid->vid && devid->pid == classid->pid)
+            {
+              /* Yes.. then we have a match */
+
+              return true;
+            }
+        }
+      else
+        {
+          /* Not vendor specific?  Then we have a match */
+
+          return true;
+        }
+    }
+
+  /* No match.. not supported */
+
+  return false;
+}
+  
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: usbhost_findclass
+ *
+ * Description:
+ *   Find a USB host class implementation previously registered by
+ *   usbhost_registerclass().  On success, an instance of struct
+ *   usbhost_registry_s will be returned.  That instance will contain all of
+ *   the information that will be needed to obtain and bind a struct
+ *   usbhost_class_s instance for the device.
+ *
+ * Input Parameters:
+ *   id - Identifies the USB device class that has connect to the USB host.
+ *
+ * Returned Values:
+ *   On success this function will return a non-NULL instance of struct
+ *   usbhost_registry_s.  NULL will be returned on failure.  This function
+ *   can only fail if (1) id is NULL, or (2) no USB host class is registered
+ *   that matches the device class ID.
+ *
+ ****************************************************************************/
+
+const struct usbhost_registry_s *usbhost_findclass(const struct usbhost_id_s *id)
+{
+  struct usbhost_registry_s *class;
+  irqstate_t flags;
+  int ndx;
+
+  DEBUGASSERT(id);
+  uvdbg("Looking for class:%d subclass:%d protocol:%d vid:%04x pid:%04x\n",
+        id->base, id->subclass, id->proto, id->vid, id->pid);
+
+  /* g_classregistry is a singly-linkedlist of class ID information added by
+   * calls to usbhost_registerclass().  Since this list is accessed from USB
+   * host controller interrupt handling logic, accesses to this list must be
+   * protected by disabling interrupts.
+   */
+
+  flags = irqsave();
+
+  /* Examine each register class in the linked list */
+
+  for (class = g_classregistry; class; class = class->flink)
+    {
+      /* If the registered class supports more than one ID, subclass, or
+       * protocol, then try each.
+       */
+
+     uvdbg("Checking class:%p nids:%d\n", class, class->nids);
+     for (ndx = 0; ndx < class->nids; ndx++)
+        {
+          /* Did we find a matching ID? */
+
+          if (usbhost_idmatch(&class->id[ndx], id))
+            {
+              /* Yes.. restore interrupts and return the class info */
+
+              irqrestore(flags);
+              return class;
+            }
+        }
+    }
+
+  /* Not found... restore interrupts and return NULL */
+
+  irqrestore(flags);
+  return NULL;
+}
+
diff --git a/nuttx/drivers/usbhost/usbhost_hidkbd.c b/nuttx/drivers/usbhost/usbhost_hidkbd.c
new file mode 100644
index 000000000..baf18703d
--- /dev/null
+++ b/nuttx/drivers/usbhost/usbhost_hidkbd.c
@@ -0,0 +1,2048 @@
+/****************************************************************************
+ * drivers/usbhost/usbhost_hidkbd.c
+ *
+ *   Copyright (C) 2011 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/types.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <poll.h>
+#include <semaphore.h>
+#include <time.h>
+#include <fcntl.h>
+#include <assert.h>
+#include <errno.h>
+#include <debug.h>
+
+#include <nuttx/kmalloc.h>
+#include <nuttx/fs.h>
+#include <nuttx/arch.h>
+#include <nuttx/wqueue.h>
+
+#include <nuttx/usb/usb.h>
+#include <nuttx/usb/usbhost.h>
+#include <nuttx/usb/hid.h>
+
+/* Don't compile if prerequisites are not met */
+
+#if defined(CONFIG_USBHOST) && !defined(CONFIG_USBHOST_INT_DISABLE) && CONFIG_NFILE_DESCRIPTORS > 0
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+/* Configuration ************************************************************/
+/* This determines how often the USB keyboard will be polled in units of
+ * of microseconds.  The default is 100MS.
+ */
+
+#ifndef CONFIG_HIDKBD_POLLUSEC
+#  define CONFIG_HIDKBD_POLLUSEC (100*1000)
+#endif
+
+/* Worker thread is needed, unfortunately, to handle some cornercase failure
+ * conditions.  This is kind of wasteful and begs for a re-design.
+ */
+
+#ifndef CONFIG_SCHED_WORKQUEUE
+#  warning "Worker thread support is required (CONFIG_SCHED_WORKQUEUE)"
+#endif
+
+/* Signals must not be disabled as they are needed by usleep.  Need to have
+ * CONFIG_DISABLE_SIGNALS=n
+ */
+
+#ifdef CONFIG_DISABLE_SIGNALS
+#  warning "Signal support is required (CONFIG_DISABLE_SIGNALS)"
+#endif
+
+/* Provide some default values for other configuration settings */
+
+#ifndef CONFIG_HIDKBD_DEFPRIO
+#  define CONFIG_HIDKBD_DEFPRIO 50
+#endif
+
+#ifndef CONFIG_HIDKBD_STACKSIZE
+#  define CONFIG_HIDKBD_STACKSIZE 1024
+#endif
+
+#ifndef CONFIG_HIDKBD_BUFSIZE
+#  define CONFIG_HIDKBD_BUFSIZE 64
+#endif
+
+#ifndef CONFIG_HIDKBD_NPOLLWAITERS
+#  define CONFIG_HIDKBD_NPOLLWAITERS 2
+#endif
+
+/* The default is to support scancode mapping for the standard 104 key
+ * keyboard.  Setting CONFIG_HIDKBD_RAWSCANCODES will disable all scancode
+ * mapping; Setting CONFIG_HIDKBD_ALLSCANCODES will enable mapping of all
+ * scancodes; 
+ */
+
+#ifndef CONFIG_HIDKBD_RAWSCANCODES
+#  ifdef CONFIG_HIDKBD_ALLSCANCODES
+#    define USBHID_NUMSCANCODES (USBHID_KBDUSE_MAX+1)
+#  else
+#    define USBHID_NUMSCANCODES 104
+#  endif
+#endif
+
+/* Driver support ***********************************************************/
+/* This format is used to construct the /dev/kbd[n] device driver path.  It
+ * defined here so that it will be used consistently in all places.
+ */
+
+#define DEV_FORMAT          "/dev/kbd%c"
+#define DEV_NAMELEN         11
+
+/* Used in usbhost_cfgdesc() */
+
+#define USBHOST_IFFOUND     0x01 /* Required I/F descriptor found */
+#define USBHOST_EPINFOUND   0x02 /* Required interrupt IN EP descriptor found */
+#define USBHOST_EPOUTFOUND  0x04 /* Optional interrupt OUT EP descriptor found */
+#define USBHOST_RQDFOUND    (USBHOST_IFFOUND|USBHOST_EPINFOUND)
+#define USBHOST_ALLFOUND    (USBHOST_RQDFOUND|USBHOST_EPOUTFOUND)
+
+#define USBHOST_MAX_CREFS   0x7fff
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+/* This structure contains the internal, private state of the USB host
+ * keyboard storage class.
+ */
+
+struct usbhost_state_s
+{
+  /* This is the externally visible portion of the state */
+
+  struct usbhost_class_s  class;
+
+  /* This is an instance of the USB host driver bound to this class instance */
+
+  struct usbhost_driver_s *drvr;
+
+  /* The remainder of the fields are provide o the keyboard class driver */
+  
+  char                    devchar;      /* Character identifying the /dev/kbd[n] device */
+  volatile bool           disconnected; /* TRUE: Device has been disconnected */
+  volatile bool           polling;      /* TRUE: Poll thread is running */
+  volatile bool           open;         /* TRUE: The keyboard device is open */
+  volatile bool           waiting;      /* TRUE: waiting for keyboard data */
+  uint8_t                 ifno;         /* Interface number */
+  int16_t                 crefs;        /* Reference count on the driver instance */
+  sem_t                   exclsem;      /* Used to maintain mutual exclusive access */
+  sem_t                   waitsem;      /* Used to wait for keyboard data */
+  FAR uint8_t            *tbuffer;      /* The allocated transfer buffer */
+  size_t                  tbuflen;      /* Size of the allocated transfer buffer */
+  pid_t                   pollpid;      /* PID of the poll task */
+  struct work_s           work;         /* For cornercase error handling by the worker thread */
+
+  /* Endpoints:
+   * EP0 (Control):
+   * - Receiving and responding to requests for USB control and class data.
+   * - IN data when polled by the HID class driver (Get_Report)
+   * - OUT data from the host.
+   * EP Interrupt IN:
+   * - Receiving asynchronous (unrequested) IN data from the device.
+   * EP Interrrupt OUT (optional):
+   * - Transmitting low latency OUT data to the device.
+   * - If not present, EP0 used.
+   */
+
+  usbhost_ep_t            epin;         /* Interrupt IN endpoint */
+  usbhost_ep_t            epout;        /* Optional interrupt OUT endpoint */
+
+  /* The following is a list if poll structures of threads waiting for
+   * driver events. The 'struct pollfd' reference for each open is also
+   * retained in the f_priv field of the 'struct file'.
+   */
+
+#ifndef CONFIG_DISABLE_POLL
+  struct pollfd *fds[CONFIG_HIDKBD_NPOLLWAITERS];
+#endif
+
+  /* Buffer used to collect and buffer incoming keyboard characters */
+
+  volatile uint16_t       headndx;      /* Buffer head index */
+  volatile uint16_t       tailndx;      /* Buffer tail index */
+  uint8_t                 kbdbuffer[CONFIG_HIDKBD_BUFSIZE];
+};
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+/* Semaphores */
+
+static void usbhost_takesem(sem_t *sem);
+#define usbhost_givesem(s) sem_post(s);
+
+/* Polling support */
+
+#ifndef CONFIG_DISABLE_POLL
+static void usbhost_pollnotify(FAR struct usbhost_state_s *dev);
+#else
+#  define usbhost_pollnotify(dev)
+#endif
+
+/* Memory allocation services */
+
+static inline FAR struct usbhost_state_s *usbhost_allocclass(void);
+static inline void usbhost_freeclass(FAR struct usbhost_state_s *class);
+
+/* Device name management */
+
+static int usbhost_allocdevno(FAR struct usbhost_state_s *priv);
+static void usbhost_freedevno(FAR struct usbhost_state_s *priv);
+static inline void usbhost_mkdevname(FAR struct usbhost_state_s *priv, char *devname);
+
+/* Keyboard polling thread */
+
+static void usbhost_destroy(FAR void *arg);
+static inline uint8_t usbhost_mapscancode(uint8_t scancode, uint8_t modifier);
+static int usbhost_kbdpoll(int argc, char *argv[]);
+
+/* Helpers for usbhost_connect() */
+
+static inline int usbhost_cfgdesc(FAR struct usbhost_state_s *priv,
+                                  FAR const uint8_t *configdesc, int desclen,
+                                  uint8_t funcaddr);
+static inline int usbhost_devinit(FAR struct usbhost_state_s *priv);
+
+/* (Little Endian) Data helpers */
+
+static inline uint16_t usbhost_getle16(const uint8_t *val);
+static inline void usbhost_putle16(uint8_t *dest, uint16_t val);
+static inline uint32_t usbhost_getle32(const uint8_t *val);
+static void usbhost_putle32(uint8_t *dest, uint32_t val);
+
+/* Transfer descriptor memory management */
+
+static inline int usbhost_tdalloc(FAR struct usbhost_state_s *priv);
+static inline int usbhost_tdfree(FAR struct usbhost_state_s *priv);
+
+/* struct usbhost_registry_s methods */
+ 
+static struct usbhost_class_s *usbhost_create(FAR struct usbhost_driver_s *drvr,
+                                              FAR const struct usbhost_id_s *id);
+
+/* struct usbhost_class_s methods */
+
+static int usbhost_connect(FAR struct usbhost_class_s *class,
+                           FAR const uint8_t *configdesc, int desclen,
+                           uint8_t funcaddr);
+static int usbhost_disconnected(FAR struct usbhost_class_s *class);
+
+/* Driver methods.  We export the keyboard as a standard character driver */
+
+static int usbhost_open(FAR struct file *filep);
+static int usbhost_close(FAR struct file *filep);
+static ssize_t usbhost_read(FAR struct file *filep,
+                            FAR char *buffer, size_t len);
+static ssize_t usbhost_write(FAR struct file *filep,
+                             FAR const char *buffer, size_t len);
+#ifndef CONFIG_DISABLE_POLL
+static int usbhost_poll(FAR struct file *filep, FAR struct pollfd *fds,
+                        bool setup);
+#endif
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/* This structure provides the registry entry ID informatino that will  be 
+ * used to associate the USB host keyboard class driver to a connected USB
+ * device.
+ */
+
+static const const struct usbhost_id_s g_id =
+{
+  USB_CLASS_HID,            /* base     */
+  USBHID_SUBCLASS_BOOTIF,   /* subclass */
+  USBHID_PROTOCOL_KEYBOARD, /* proto    */
+  0,                        /* vid      */
+  0                         /* pid      */
+};
+
+/* This is the USB host storage class's registry entry */
+
+static struct usbhost_registry_s g_skeleton =
+{
+  NULL,                    /* flink     */
+  usbhost_create,          /* create    */
+  1,                       /* nids      */
+  &g_id                    /* id[]      */
+};
+
+static const struct file_operations usbhost_fops =
+{
+  usbhost_open,            /* open      */
+  usbhost_close,           /* close     */
+  usbhost_read,            /* read      */
+  usbhost_write,           /* write     */
+  0,                       /* seek      */
+  0                        /* ioctl     */
+#ifndef CONFIG_DISABLE_POLL
+  , usbhost_poll           /* poll      */
+#endif
+};
+
+/* This is a bitmap that is used to allocate device names /dev/kbda-z. */
+
+static uint32_t g_devinuse;
+
+/* The following are used to managed the class creation operation */
+
+static sem_t                   g_exclsem; /* For mutually exclusive thread creation */
+static sem_t                   g_syncsem; /* Thread data passing interlock */
+static struct usbhost_state_s *g_priv;    /* Data passed to thread */
+
+/* The following tables map keyboard scan codes to printable ASIC
+ * characters.  There is no support here for function keys or cursor
+ * controls.
+ */
+
+#ifndef CONFIG_HIDKBD_RAWSCANCODES
+static const uint8_t ucmap[USBHID_NUMSCANCODES] =
+{
+  0,    0,      0,      0,       'A',  'B',  'C',    'D',  /* 0x00-0x07: Reserved, errors, A-D */
+  'E',  'F',    'G',    'H',     'I',  'J',  'K',    'L',  /* 0x08-0x0f: E-L */
+  'M',  'N',    'O',    'P',     'Q',  'R',  'S',    'T',  /* 0x10-0x17: M-T */
+  'U',  'V',    'W',    'X',     'Y',  'Z',  '!',    '@',  /* 0x18-0x1f: U-Z,!,@  */
+  '#',  '$',    '%',    '^',     '&',  '*',  '(',    ')',  /* 0x20-0x27: #,$,%,^,&,*,(,) */
+  '\n', '\033', '\177', 0,       ' ',  '_',  '+',    '{',  /* 0x28-0x2f: Enter,escape,del,back-tab,space,_,+,{ */
+  '}',  '|',    0,      ':',     '"',  0,    '<',    '>',  /* 0x30-0x37: },|,Non-US tilde,:,",grave tidle,<,> */
+  '?',  0,       0,      0,      0,    0,    0,      0,    /* 0x38-0x3f: /,CapsLock,F1,F2,F3,F4,F5,F6 */
+  0,    0,       0,      0,      0,    0,    0,      0,    /* 0x40-0x47: F7,F8,F9,F10,F11,F12,PrtScn,sScrollLock */
+  0,    0,       0,      0,      0,    0,    0,      0,    /* 0x48-0x4f: Pause,Insert,Home,PageUp,DeleteForward,End,PageDown,RightArrow */
+  0,    0,       0,      0,      '/',  '*',  '-',    '+',  /* 0x50-0x57: LeftArrow,DownArrow,UpArrow,Num Lock,/,*,-,+ */
+  '\n', '1',     '2',    '3',    '4',  '4',  '6',    '7',  /* 0x58-0x5f: Enter,1-7 */
+  '8',  '9',     '0',    '.',    0,    0,    0,      '=',  /* 0x60-0x67: 8-9,0,.,Non-US \,Application,Power,= */
+#ifdef CONFIG_HIDKBD_ALLSCANCODES
+  0,    0,       0,      0,      0,    0,    0,      0,    /* 0x68-0x6f: F13,F14,F15,F16,F17,F18,F19,F20 */
+  0,    0,       0,      0,      0,    0,    0,      0,    /* 0x70-0x77: F21,F22,F23,F24,Execute,Help,Menu,Select */
+  0,    0,       0,      0,      0,    0,    0,      0,    /* 0x78-0x7f: Stop,Again,Undo,Cut,Copy,Paste,Find,Mute */
+  0,    0,       0,      0,      0,    ',',  0,      0,    /* 0x80-0x87: VolUp,VolDown,LCapsLock,lNumLock,LScrollLock,,,=,International1 */
+  0,    0,       0,      0,      0,    0,    0,      0,    /* 0x88-0x8f: International 2-9 */
+  0,    0,       0,      0,      0,    0,    0,      0,    /* 0x90-0x97: LAN 1-8 */
+  0,    0,       0,      0,      0,    0,    '\n',   0,    /* 0x98-0x9f: LAN 9,Ease,SysReq,Cancel,Clear,Prior,Return,Separator */
+  0,    0,       0,      0,      0,    0,    0,      0,    /* 0xa0-0xa7: Out,Oper,Clear,CrSel,Excel,(reserved) */
+  0,    0,       0,      0,      0,    0,    0,      0,    /* 0xa8-0xaf: (reserved) */
+  0,    0,       0,      0,      0,    0,    '(',    ')',  /* 0xb0-0xb7: 00,000,ThouSeparator,DecSeparator,CurrencyUnit,SubUnit,(,) */
+  '{',  '}',    '\t',    \177,   'A',  'B',  'C',    'D',  /* 0xb8-0xbf: {,},tab,backspace,A-D */
+  'F',  'F',     0,      '^',    '%',  '<', '>',     '&',  /* 0xc0-0xc7: E-F,XOR,^,%,<,>,& */
+  0,    '|',     0,      ':',    '%',  ' ', '@',     '!',  /* 0xc8-0xcf: &&,|,||,:,#, ,@,! */
+  0,    0,       0,      0,      0,    0,   0,       0,    /* 0xd0-0xd7: Memory Store,Recall,Clear,Add,Subtract,Muliply,Divide,+/- */
+  0,    0,       0,      0,      0,    0,   0,       0,    /* 0xd8-0xdf: Clear,ClearEntry,Binary,Octal,Decimal,Hexadecimal */
+  0,    0,       0,      0,      0,    0,   0,       0,    /* 0xe0-0xe7: Left Ctrl,Shift,Alt,GUI, Right Ctrl,Shift,Alt,GUI */
+#endif
+};
+
+static const uint8_t lcmap[USBHID_NUMSCANCODES] =
+{
+  0,    0,       0,      0,      'a',  'b', 'c',     'd',  /* 0x00-0x07: Reserved, errors, a-d */
+  'e',  'f',     'g',    'h',    'i',  'j', 'k',     'l',  /* 0x08-0x0f: e-l */
+  'm',  'n',     'o',    'p',    'q',  'r', 's',     't',  /* 0x10-0x17: m-t */
+  'u',  'v',     'w',    'x',    'y',  'z', '1',     '2',  /* 0x18-0x1f: u-z,1-2  */
+  '3',  '4',     '5',    '6',    '7',  '8', '9',     '0',  /* 0x20-0x27: 3-9,0 */
+  '\n', '\033',  '\177', '\t',   ' ',  '-', '=',     '[',  /* 0x28-0x2f: Enter,escape,del,tab,space,-,=,[ */
+  ']',  '\\',    '\234', ';',    '\'', 0,   ',',     '.',  /* 0x30-0x37: ],\,Non-US pound,;,',grave accent,,,. */
+  '/',  0,       0,      0,      0,    0,   0,       0,    /* 0x38-0x3f: /,CapsLock,F1,F2,F3,F4,F5,F6 */
+  0,    0,       0,      0,      0,    0,   0,       0,    /* 0x40-0x47: F7,F8,F9,F10,F11,F12,PrtScn,ScrollLock */
+  0,    0,       0,      0,      0,    0,   0,       0,    /* 0x48-0x4f: Pause,Insert,Home,PageUp,DeleteForward,End,PageDown,RightArrow */
+  0,    0,       0,      0,      '/',  '*', '-',     '+',  /* 0x50-0x57: LeftArrow,DownArrow,UpArrow,Num Lock,/,*,-,+ */
+  '\n', '1',     '2',    '3',    '4',  '4', '6',     '7',  /* 0x58-0x5f: Enter,1-7 */
+  '8',  '9',     '0',    '.',    0,    0,   0,       '=',  /* 0x60-0x67: 8-9,0,.,Non-US \,Application,Power,= */
+#ifdef CONFIG_HIDKBD_ALLSCANCODES
+  0,    0,       0,      0,      0,    0,   0,       0,    /* 0x68-0x6f: F13,F14,F15,F16,F17,F18,F19,F20 */
+  0,    0,       0,      0,      0,    0,   0,       0,    /* 0x70-0x77: F21,F22,F23,F24,Execute,Help,Menu,Select */
+  0,    0,       0,      0,      0,    0,   0,       0,    /* 0x78-0x7f: Stop,Again,Undo,Cut,Copy,Paste,Find,Mute */
+  0,    0,       0,      0,      0,    ',', 0,       0,    /* 0x80-0x87: VolUp,VolDown,LCapsLock,lNumLock,LScrollLock,,,=,International1 */
+  0,    0,       0,      0,      0,    0,   0,       0,    /* 0x88-0x8f: International 2-9 */
+  0,    0,       0,      0,      0,    0,   0,       0,    /* 0x90-0x97: LAN 1-8 */
+  0,    0,       0,      0,      0,    0,   '\n',    0,    /* 0x98-0x9f: LAN 9,Ease,SysReq,Cancel,Clear,Prior,Return,Separator */
+  0,    0,       0,      0,      0,    0,   0,       0,    /* 0xa0-0xa7: Out,Oper,Clear,CrSel,Excel,(reserved) */
+  0,    0,       0,      0,      0,    0,   0,       0,    /* 0xa8-0xaf: (reserved) */
+  0,    0,       0,      0,      0,    0,   '(',     ')',  /* 0xb0-0xb7: 00,000,ThouSeparator,DecSeparator,CurrencyUnit,SubUnit,(,) */
+  '{',  '}',    '\t',    '\177', 'A',  'B', 'C',     'D',  /* 0xb8-0xbf: {,},tab,backspace,A-D */
+  'F',  'F',     0,      '^',    '%',  '<', '>',     '&',  /* 0xc0-0xc7: E-F,XOR,^,%,<,>,& */
+  0,    '|',     0,      ':',    '%',  ' ', '@',     '!',  /* 0xc8-0xcf: &&,|,||,:,#, ,@,! */
+  0,    0,       0,      0,      0,    0,   0,       0,    /* 0xd0-0xd7: Memory Store,Recall,Clear,Add,Subtract,Muliply,Divide,+/- */
+  0,    0,       0,      0,      0,    0,   0,       0,    /* 0xd8-0xdf: Clear,ClearEntry,Binary,Octal,Decimal,Hexadecimal */
+  0,    0,       0,      0,      0,    0,   0,       0,    /* 0xe0-0xe7: Left Ctrl,Shift,Alt,GUI, Right Ctrl,Shift,Alt,GUI */
+#endif
+};
+#endif /* CONFIG_HIDKBD_RAWSCANCODES */
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: usbhost_takesem
+ *
+ * Description:
+ *   This is just a wrapper to handle the annoying behavior of semaphore
+ *   waits that return due to the receipt of a signal.
+ *
+ ****************************************************************************/
+
+static void usbhost_takesem(sem_t *sem)
+{
+  /* Take the semaphore (perhaps waiting) */
+
+  while (sem_wait(sem) != 0)
+    {
+      /* The only case that an error should occr here is if the wait was
+       * awakened by a signal.
+       */
+
+      ASSERT(errno == EINTR);
+    }
+}
+
+/****************************************************************************
+ * Name: usbhost_pollnotify
+ ****************************************************************************/
+
+#ifndef CONFIG_DISABLE_POLL
+static void usbhost_pollnotify(FAR struct usbhost_state_s *priv)
+{
+  int i;
+
+  for (i = 0; i < CONFIG_HIDKBD_NPOLLWAITERS; i++)
+    {
+      struct pollfd *fds = priv->fds[i];
+      if (fds)
+        {
+          fds->revents |= (fds->events & POLLIN);
+          if (fds->revents != 0)
+            {
+              uvdbg("Report events: %02x\n", fds->revents);
+              sem_post(fds->sem);
+            }
+        }
+    }
+}
+#endif
+
+/****************************************************************************
+ * Name: usbhost_allocclass
+ *
+ * Description:
+ *   This is really part of the logic that implements the create() method
+ *   of struct usbhost_registry_s.  This function allocates memory for one
+ *   new class instance.
+ *
+ * Input Parameters:
+ *   None
+ *
+ * Returned Values:
+ *   On success, this function will return a non-NULL instance of struct
+ *   usbhost_class_s.  NULL is returned on failure; this function will
+ *   will fail only if there are insufficient resources to create another
+ *   USB host class instance.
+ *
+ ****************************************************************************/
+
+static inline FAR struct usbhost_state_s *usbhost_allocclass(void)
+{
+  FAR struct usbhost_state_s *priv;
+
+  DEBUGASSERT(!up_interrupt_context());
+  priv = (FAR struct usbhost_state_s *)kmalloc(sizeof(struct usbhost_state_s));
+  uvdbg("Allocated: %p\n", priv);;
+  return priv;
+}
+
+/****************************************************************************
+ * Name: usbhost_freeclass
+ *
+ * Description:
+ *   Free a class instance previously allocated by usbhost_allocclass().
+ *
+ * Input Parameters:
+ *   class - A reference to the class instance to be freed.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+static inline void usbhost_freeclass(FAR struct usbhost_state_s *class)
+{
+  DEBUGASSERT(class != NULL);
+
+  /* Free the class instance. */
+
+  uvdbg("Freeing: %p\n", class);;
+  kfree(class);
+}
+
+/****************************************************************************
+ * Name: Device name management
+ *
+ * Description:
+ *   Some tiny functions to coordinate management of device names.
+ *
+ ****************************************************************************/
+
+static int usbhost_allocdevno(FAR struct usbhost_state_s *priv)
+{
+  irqstate_t flags;
+  int devno;
+
+  flags = irqsave();
+  for (devno = 0; devno < 26; devno++)
+    {
+      uint32_t bitno = 1 << devno;
+      if ((g_devinuse & bitno) == 0)
+        {
+          g_devinuse |= bitno;
+          priv->devchar = 'a' + devno;
+          irqrestore(flags);
+          return OK;
+        }
+    }
+
+  irqrestore(flags);
+  return -EMFILE;
+}
+
+static void usbhost_freedevno(FAR struct usbhost_state_s *priv)
+{
+  int devno = 'a' - priv->devchar;
+
+  if (devno >= 0 && devno < 26)
+    {
+      irqstate_t flags = irqsave();
+      g_devinuse &= ~(1 << devno);
+      irqrestore(flags);
+    }
+}
+
+static inline void usbhost_mkdevname(FAR struct usbhost_state_s *priv, char *devname)
+{
+  (void)snprintf(devname, DEV_NAMELEN, DEV_FORMAT, priv->devchar);
+}
+
+/****************************************************************************
+ * Name: usbhost_destroy
+ *
+ * Description:
+ *   The USB device has been disconnected and the refernce count on the USB
+ *   host class instance has gone to 1.. Time to destroy the USB host class
+ *   instance.
+ *
+ * Input Parameters:
+ *   arg - A reference to the class instance to be destroyed.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+static void usbhost_destroy(FAR void *arg)
+{
+  FAR struct usbhost_state_s *priv = (FAR struct usbhost_state_s *)arg;
+  char devname[DEV_NAMELEN];
+
+  DEBUGASSERT(priv != NULL);
+  uvdbg("crefs: %d\n", priv->crefs);
+ 
+  /* Unregister the driver */
+
+  uvdbg("Unregister driver\n");
+  usbhost_mkdevname(priv, devname);
+  (void)unregister_driver(devname);
+
+  /* Release the device name used by this connection */
+
+  usbhost_freedevno(priv);
+
+  /* Free the interrupt endpoints */
+
+  if (priv->epin)
+    {
+      DRVR_EPFREE(priv->drvr, priv->epin);
+    }
+
+  if (priv->epout)
+    {
+      DRVR_EPFREE(priv->drvr, priv->epout);
+    }
+
+  /* Free any transfer buffers */
+
+  usbhost_tdfree(priv);
+
+  /* Destroy the semaphores */
+
+  sem_destroy(&priv->exclsem);
+  sem_destroy(&priv->waitsem);
+
+  /* Disconnect the USB host device */
+
+  DRVR_DISCONNECT(priv->drvr);
+
+  /* And free the class instance.  Hmmm.. this may execute on the worker
+   * thread and the work structure is part of what is getting freed.  That
+   * should be okay because once the work contained is removed from the
+   * queue, it should not longer be accessed by the worker thread.
+   */
+
+  usbhost_freeclass(priv);
+}
+
+/****************************************************************************
+ * Name: usbhost_mapscancode
+ *
+ * Description:
+ *   Map a keyboard scancode to a printable ASCII character.  There is no
+ *   support here for function keys or cursor controls in this version of
+ *   the driver.
+ *
+ * Input Parameters:
+ *   scancode - Scan code to be mapped.
+ *   modifier - Ctrl,Alt,Shift,GUI modifier bits
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+static inline uint8_t usbhost_mapscancode(uint8_t scancode, uint8_t modifier)
+{
+#ifndef CONFIG_HIDKBD_RAWSCANCODES
+  /* Range check */
+
+  if (scancode >= USBHID_NUMSCANCODES)
+    {
+      return 0;
+    }
+
+  /* Is either shift key pressed? */
+
+  if ((modifier & (USBHID_MODIFER_LSHIFT|USBHID_MODIFER_RSHIFT)) != 0)
+    {
+      return ucmap[scancode];
+    }
+  else
+    {
+      return lcmap[scancode];
+    }
+#else
+  return scancode;
+#endif
+}
+
+/****************************************************************************
+ * Name: usbhost_kbdpoll
+ *
+ * Description:
+ *   Periodically check for new keyboard data.
+ *
+ * Input Parameters:
+ *   arg - A reference to the class instance to be destroyed.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+static int usbhost_kbdpoll(int argc, char *argv[])
+{
+  FAR struct usbhost_state_s *priv;
+  FAR struct usb_ctrlreq_s   *ctrlreq;
+#ifndef CONFIG_HIDKBD_NODEBOUNCE
+  uint8_t                     lastkey[6] = {0, 0, 0, 0, 0, 0};
+#endif
+#if defined(CONFIG_DEBUG_USB) && defined(CONFIG_DEBUG_VERBOSE)
+  unsigned int                npolls = 0;
+#endif
+  unsigned int                nerrors;
+  int                         ret;
+
+  uvdbg("Started\n");
+
+  /* Synchronize with the start-up logic.  Get the private instance, re-start
+   * the start-up logic, and wait a bit to make sure that all of the class
+   * creation logic has a chance to run to completion.
+   *
+   * NOTE: that the reference count is incremented here.  Therefore, we know
+   * that the driver data structure will remain stable while this thread is
+   * running.
+   */
+
+   priv = g_priv;
+   DEBUGASSERT(priv != NULL);
+ 
+   priv->polling = true;
+   priv->crefs++;
+   usbhost_givesem(&g_syncsem);
+   sleep(1);
+  
+  /* Loop here until the device is disconnected */
+
+  uvdbg("Entering poll loop\n");
+  while (!priv->disconnected)
+    {
+      /* Make sure that we have exclusive access to the private data
+       * structure. There may now be other tasks with the character driver
+       * open and actively trying to interact with the class driver.
+       */
+
+      usbhost_takesem(&priv->exclsem);
+
+      /* Format the HID report request:
+       *
+       *   bmRequestType 10100001
+       *   bRequest      GET_REPORT (0x01)
+       *   wValue        Report Type and Report Index
+       *   wIndex        Interface Number
+       *   wLength       Descriptor Length
+       *   Data          Descriptor Data
+       */
+
+      ctrlreq       = (struct usb_ctrlreq_s *)priv->tbuffer;
+      ctrlreq->type = USB_REQ_DIR_IN|USB_REQ_TYPE_CLASS|USB_REQ_RECIPIENT_INTERFACE;
+      ctrlreq->req  = USBHID_REQUEST_GETREPORT;
+
+      usbhost_putle16(ctrlreq->value, (USBHID_REPORTTYPE_INPUT << 8));
+      usbhost_putle16(ctrlreq->index, priv->ifno);
+      usbhost_putle16(ctrlreq->len,   sizeof(struct usbhid_kbdreport_s));
+
+      /* Send HID report request */
+
+      ret = DRVR_CTRLIN(priv->drvr, ctrlreq, priv->tbuffer);
+      usbhost_givesem(&priv->exclsem);
+
+      /* Check for errors -- Bail if an excessive number of errors
+       * are encountered.
+       */
+
+      if (ret != OK)
+        {
+          nerrors++;
+          udbg("ERROR: GETREPORT/INPUT, DRVR_CTRLIN returned: %d/%d\n",
+               ret, nerrors);
+
+          if (nerrors > 200)
+            {
+              udbg("Too many errors... aborting: %d\n", nerrors);
+              break;
+            }
+        }
+
+      /* The report was received correctly.  But ignore the keystrokes if no
+       * task has opened the driver.
+       */
+
+      else if (priv->open)
+        {
+          struct usbhid_kbdreport_s *rpt = (struct usbhid_kbdreport_s *)priv->tbuffer;
+          unsigned int               head;
+          unsigned int               tail;
+          uint8_t                    ascii;
+          int                        i;
+
+          /* Add the newly received keystrokes to our internal buffer */
+
+          usbhost_takesem(&priv->exclsem);
+          head = priv->headndx;
+          tail = priv->tailndx;
+
+          for (i = 0; i < 6; i++)
+            {
+              /* Is this key pressed?  But not pressed last time?
+               * HID spec: "The order of keycodes in array fields has no
+               * significance. Order determination is done by the host
+               * software comparing the contents of the previous report to
+               * the current report. If two or more keys are reported in
+               * one report, their order is indeterminate. Keyboards may
+               * buffer events that would have otherwise resulted in
+               * multiple event in a single report.
+               *
+               * "'Repeat Rate' and 'Delay Before First Repeat' are
+               * implemented by the host and not in the keyboard (this
+               * means the BIOS in legacy mode). The host may use the
+               * device report rate and the number of reports to determine
+               * how long a key is being held down. Alternatively, the host
+               * may use its own clock or the idle request for the timing
+               * of these features."
+               */
+
+              if (rpt->key[i] != USBHID_KBDUSE_NONE
+#ifndef CONFIG_HIDKBD_NODEBOUNCE
+                 && rpt->key[i] != lastkey[i]
+#endif
+                 )
+                {
+                  /* Yes.. Add it to the buffer. */
+
+                  /* Map the keyboard scancode to a printable ASCII
+                   * character.  There is no support here for function keys
+                   * or cursor controls in this version of the driver.
+                   */
+
+                  ascii = usbhost_mapscancode(rpt->key[i], rpt->modifier);
+                  uvdbg("Key %d: %02x ASCII:%c modifier: %02x\n",
+                         i, rpt->key[i], ascii ? ascii : ' ', rpt->modifier);
+
+                  /* Zero at this point means that the key does not map to a
+                   * printable character.
+                   */
+
+                  if (ascii != 0)
+                    {
+                      /* Handle control characters.  Zero after this means
+                       * a valid, NUL character.
+                       */
+
+                      if ((rpt->modifier & (USBHID_MODIFER_LCTRL|USBHID_MODIFER_RCTRL)) != 0)
+                        {
+                          ascii &= 0x1f;
+                        }
+ 
+                      /* Copy the next keyboard character into the user
+                       * buffer.
+                       */
+
+                      priv->kbdbuffer[head] = ascii;
+
+                      /* Increment the head index */
+
+                      if (++head >= CONFIG_HIDKBD_BUFSIZE)
+                        {
+                          head = 0;
+                        }
+
+                      /* If the buffer is full, then increment the tail
+                       * index to make space.  Is it better to lose old
+                       * keystrokes or new?
+                       */
+
+                      if (tail == head)
+                       {
+                          if (++tail >= CONFIG_HIDKBD_BUFSIZE)
+                            {
+                              tail = 0;
+                            }
+                        }
+                    }
+                }
+              /* Save the scancode (or lack thereof) for key debouncing on
+               * next keyboard report.
+               */
+
+#ifndef CONFIG_HIDKBD_NODEBOUNCE
+              lastkey[i] = rpt->key[i];
+#endif
+            }
+
+          /* Did we just transition from no data available to data available? */
+
+          if (head != tail && priv->headndx == priv->tailndx)
+            {
+              /* Yes.. Is there a thread waiting for keyboard data now? */
+
+              if (priv->waiting)
+                {
+                  /* Yes.. wake it up */
+
+                  usbhost_givesem(&priv->waitsem);
+                  priv->waiting = false;
+                }
+
+              /* And wake up any threads waiting for the POLLIN event */
+
+              usbhost_pollnotify(priv);
+            }
+
+          /* Update the head/tail indices */
+
+          priv->headndx = head;
+          priv->tailndx = tail;
+          usbhost_givesem(&priv->exclsem);
+        }
+
+      /* If USB debug is on, then provide some periodic indication that
+       * polling is still happening.
+       */
+
+#if defined(CONFIG_DEBUG_USB) && defined(CONFIG_DEBUG_VERBOSE)
+      npolls++;
+      if ((npolls & 31) == 0)
+        {
+          udbg("Still polling: %d\n", npolls);
+        }
+#endif
+      /* Wait for the required amount (or until a signal is received).  We
+       * will wake up when either the delay elapses or we are signalled that
+       * the device has been disconnected.
+       */
+
+      usleep(CONFIG_HIDKBD_POLLUSEC);
+    }
+
+  /* We get here when the driver is removed.. or when too many errors have
+   * been encountered.
+   *
+   * Make sure that we have exclusive access to the private data structure.
+   * There may now be other tasks with the character driver open and actively
+   * trying to interact with the class driver.
+   */
+
+  usbhost_takesem(&priv->exclsem);
+
+  /* Indicate that we are no longer running and decrement the reference
+   * count help by this thread.  If there are no other users of the class,
+   * we can destroy it now.  Otherwise, we have to wait until the all
+   * of the file descriptors are closed.
+   */
+ 
+  udbg("Keyboard removed, polling halted\n");
+  priv->polling = false;
+  if (--priv->crefs < 2)
+    {
+      /* Destroy the instance (while we hold the semaphore!) */
+ 
+      usbhost_destroy(priv);
+    }
+  else
+    {
+      /* No, we will destroy the driver instance when it is finally closed */
+
+      usbhost_givesem(&priv->exclsem);
+    }
+  return 0;
+}
+
+/****************************************************************************
+ * Name: usbhost_cfgdesc
+ *
+ * Description:
+ *   This function implements the connect() method of struct
+ *   usbhost_class_s.  This method is a callback into the class
+ *   implementation.  It is used to provide the device's configuration
+ *   descriptor to the class so that the class may initialize properly
+ *
+ * Input Parameters:
+ *   priv - The USB host class instance.
+ *   configdesc - A pointer to a uint8_t buffer container the configuration descripor.
+ *   desclen - The length in bytes of the configuration descriptor.
+ *   funcaddr - The USB address of the function containing the endpoint that EP0
+ *     controls
+ *
+ * Returned Values:
+ *   On success, zero (OK) is returned. On a failure, a negated errno value is
+ *   returned indicating the nature of the failure
+ *
+ * Assumptions:
+ *   This function will *not* be called from an interrupt handler.
+ *
+ ****************************************************************************/
+
+static inline int usbhost_cfgdesc(FAR struct usbhost_state_s *priv,
+                                  FAR const uint8_t *configdesc, int desclen,
+                                  uint8_t funcaddr)
+{
+  FAR struct usb_cfgdesc_s *cfgdesc;
+  FAR struct usb_desc_s *desc;
+  FAR struct usbhost_epdesc_s epindesc;
+  FAR struct usbhost_epdesc_s epoutdesc;
+  int remaining;
+  uint8_t found = 0;
+  bool done = false;
+  int ret;
+
+  DEBUGASSERT(priv != NULL && 
+              configdesc != NULL &&
+              desclen >= sizeof(struct usb_cfgdesc_s));
+  
+  /* Verify that we were passed a configuration descriptor */
+
+  cfgdesc = (FAR struct usb_cfgdesc_s *)configdesc;
+  if (cfgdesc->type != USB_DESC_TYPE_CONFIG)
+    {
+      return -EINVAL;
+    }
+
+  /* Get the total length of the configuration descriptor (little endian).
+   * It might be a good check to get the number of interfaces here too.
+  */
+
+  remaining = (int)usbhost_getle16(cfgdesc->totallen);
+
+  /* Skip to the next entry descriptor */
+
+  configdesc += cfgdesc->len;
+  remaining  -= cfgdesc->len;
+
+  /* Loop where there are more dscriptors to examine */
+
+  while (remaining >= sizeof(struct usb_desc_s) && !done)
+    {
+      /* What is the next descriptor? */
+
+      desc = (FAR struct usb_desc_s *)configdesc;
+      switch (desc->type)
+        {
+        /* Interface descriptor. We really should get the number of endpoints
+         * from this descriptor too.
+         */
+
+        case USB_DESC_TYPE_INTERFACE:
+          {
+            FAR struct usb_ifdesc_s *ifdesc = (FAR struct usb_ifdesc_s *)configdesc;
+ 
+            uvdbg("Interface descriptor\n");
+            DEBUGASSERT(remaining >= USB_SIZEOF_IFDESC);
+
+            /* Did we already find what we needed from a preceding interface? */
+
+            if ((found & USBHOST_RQDFOUND) == USBHOST_RQDFOUND)
+              {
+                /* Yes.. then break out of the loop and use the preceding
+                 * interface.
+                 */
+
+                done       = true;
+              }
+            else
+              {
+                /* Otherwise, save the interface number and discard any
+                 * endpoints previously found
+                 */
+
+                priv->ifno = ifdesc->ifno;
+                found      = USBHOST_IFFOUND;
+              }
+          }
+          break;
+
+        /* HID descriptor */
+
+        case USBHID_DESCTYPE_HID:
+            uvdbg("HID descriptor\n");
+            break;
+
+        /* Endpoint descriptor.  We expect one or two interrupt endpoints,
+         * a required IN endpoint and an optional OUT endpoint.
+         */
+
+        case USB_DESC_TYPE_ENDPOINT:
+          {
+            FAR struct usb_epdesc_s *epdesc = (FAR struct usb_epdesc_s *)configdesc;
+
+            uvdbg("Endpoint descriptor\n");
+            DEBUGASSERT(remaining >= USB_SIZEOF_EPDESC);
+
+            /* Check for an interrupt endpoint. */
+
+            if ((epdesc->attr & USB_EP_ATTR_XFERTYPE_MASK) == USB_EP_ATTR_XFER_INT)
+              {
+                /* Yes.. it is a interrupt endpoint.  IN or OUT? */
+
+                if (USB_ISEPOUT(epdesc->addr))
+                  {
+                    /* It is an interrupt OUT endpoint.  There not be more than one
+                     * interrupt OUT endpoint.
+                     */
+
+                    if ((found & USBHOST_EPOUTFOUND) != 0)
+                      {
+                        /* Oops.. more than one endpoint.  We don't know what to do with this. */
+
+                        return -EINVAL;
+                      }
+                    found |= USBHOST_EPOUTFOUND;
+
+                    /* Save the interrupt OUT endpoint information */
+
+                    epoutdesc.addr         = epdesc->addr & USB_EP_ADDR_NUMBER_MASK;
+                    epoutdesc.in           = false;
+                    epoutdesc.funcaddr     = funcaddr;
+                    epoutdesc.xfrtype      = USB_EP_ATTR_XFER_INT;
+                    epoutdesc.interval     = epdesc->interval;
+                    epoutdesc.mxpacketsize = usbhost_getle16(epdesc->mxpacketsize);
+                    uvdbg("Interrupt OUT EP addr:%d mxpacketsize:%d\n",
+                          epoutdesc.addr, epoutdesc.mxpacketsize);
+                  }
+                else
+                  {
+                    /* It is an interrupt IN endpoint.  There should be only
+                     * one interrupt IN endpoint.
+                     */
+
+                    if ((found & USBHOST_EPINFOUND) != 0)
+                      {
+                        /* Oops.. more than one endpint.  We don't know what
+                         * to do with this.
+                         */
+
+                        return -EINVAL;
+                      }
+                    found |= USBHOST_EPINFOUND;
+
+                    /* Save the interrupt IN endpoint information */
+                    
+                    epindesc.addr         = epdesc->addr & USB_EP_ADDR_NUMBER_MASK;
+                    epindesc.in           = 1;
+                    epindesc.funcaddr     = funcaddr;
+                    epindesc.xfrtype      = USB_EP_ATTR_XFER_INT;
+                    epindesc.interval     = epdesc->interval;
+                    epindesc.mxpacketsize = usbhost_getle16(epdesc->mxpacketsize);
+                    uvdbg("Interrupt IN EP addr:%d mxpacketsize:%d\n",
+                          epindesc.addr, epindesc.mxpacketsize);
+                  }
+              }
+          }
+          break;
+
+        /* Other descriptors are just ignored for now */
+
+        default:
+          uvdbg("Other descriptor: %d\n", desc->type);
+          break;
+        }
+
+      /* What we found everything that we are going to find? */
+
+      if (found == USBHOST_ALLFOUND)
+        {
+          /* Yes.. then break out of the loop and use the preceding interface */
+
+          done = true;
+        }
+
+      /* Increment the address of the next descriptor */
+ 
+      configdesc += desc->len;
+      remaining  -= desc->len;
+    }
+
+  /* Sanity checking... did we find all of things that we need? */
+    
+  if ((found & USBHOST_RQDFOUND) != USBHOST_RQDFOUND)
+    {
+      ulldbg("ERROR: Found IF:%s EPIN:%s\n",
+             (found & USBHOST_IFFOUND) != 0  ? "YES" : "NO",
+             (found & USBHOST_EPINFOUND) != 0 ? "YES" : "NO");
+      return -EINVAL;
+    }
+
+  /* We are good... Allocate the endpoints.  First, the required interrupt
+   * IN endpoint.
+   */
+
+  ret = DRVR_EPALLOC(priv->drvr, &epindesc, &priv->epin);
+  if (ret != OK)
+    {
+      udbg("ERROR: Failed to allocate interrupt IN endpoint\n");
+      return ret;
+    }
+
+  /* Then the optional interrupt OUT endpoint */
+
+  ullvdbg("Found EPOOUT:%s\n",
+         (found & USBHOST_EPOUTFOUND) != 0 ? "YES" : "NO");
+
+  if ((found & USBHOST_EPOUTFOUND) != 0)
+    {
+      ret = DRVR_EPALLOC(priv->drvr, &epoutdesc, &priv->epout);
+      if (ret != OK)
+        {
+          udbg("ERROR: Failed to allocate interrupt OUT endpoint\n");
+          (void)DRVR_EPFREE(priv->drvr, priv->epin);
+          return ret;
+        }
+    }
+
+  ullvdbg("Endpoints allocated\n");
+  return OK;
+}
+
+/****************************************************************************
+ * Name: usbhost_devinit
+ *
+ * Description:
+ *   The USB device has been successfully connected.  This completes the
+ *   initialization operations.  It is first called after the
+ *   configuration descriptor has been received.
+ *
+ *   This function is called from the connect() method.  This function always
+ *   executes on the thread of the caller of connect().
+ *
+ * Input Parameters:
+ *   priv - A reference to the class instance.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+static inline int usbhost_devinit(FAR struct usbhost_state_s *priv)
+{
+  char devname[DEV_NAMELEN];
+  int ret;
+
+  /* Set aside a transfer buffer for exclusive use by the keyboard class driver */
+
+  ret = usbhost_tdalloc(priv);
+  if (ret != OK)
+    {
+      udbg("ERROR: Failed to allocate transfer buffer\n");
+      return ret;
+    }
+
+  /* Increment the reference count.  This will prevent usbhost_destroy() from
+   * being called asynchronously if the device is removed.
+   */
+
+  priv->crefs++;
+  DEBUGASSERT(priv->crefs == 2);
+
+  /* Start a worker task to poll the USB device.  It would be nice to used the
+   * the NuttX worker thread to do this, but this task needs to wait for events
+   * and activities on the worker thread should not involve significant waiting.
+   * Having a dedicated thread is more efficient in this sense, but requires more
+   * memory resources, primarily for the dedicated stack (CONFIG_HIDKBD_STACKSIZE).
+   */
+
+  uvdbg("user_start: Start poll task\n");
+
+  /* The inputs to a task started by task_create() are very awkard for this
+   * purpose.  They are really designed for command line tasks (argc/argv). So
+   * the following is kludge pass binary data when the keyboard poll task
+   * is started.
+   *
+   * First, make sure we have exclusive access to g_priv (what is the likelihood
+   * of this being used?  About zero, but we protect it anyway).
+   */
+
+  usbhost_takesem(&g_exclsem);
+  g_priv = priv;
+
+#ifndef CONFIG_CUSTOM_STACK
+  priv->pollpid = task_create("usbhost", CONFIG_HIDKBD_DEFPRIO,
+                              CONFIG_HIDKBD_STACKSIZE,
+                              (main_t)usbhost_kbdpoll, (const char **)NULL);
+#else
+  priv->pollpid = task_create("usbhost", CONFIG_HIDKBD_DEFPRIO,
+                              (main_t)usbhost_kbdpoll, (const char **)NULL);
+#endif
+  if (priv->pollpid == ERROR)
+    {
+      /* Failed to started the poll thread... probably due to memory resources */
+
+      usbhost_givesem(&g_exclsem);
+      ret = -ENOMEM;
+      goto errout;
+    }
+
+  /* Now wait for the poll task to get properly initialized */
+
+  usbhost_takesem(&g_syncsem);
+  usbhost_givesem(&g_exclsem);
+
+  /* Register the driver */
+
+  uvdbg("Register driver\n");
+  usbhost_mkdevname(priv, devname);
+  ret = register_driver(devname, &usbhost_fops, 0666, priv);
+
+  /* We now have to be concerned about asynchronous modification of crefs
+   * because the driver has been registerd.
+   */
+
+errout:
+  usbhost_takesem(&priv->exclsem);
+  priv->crefs--;
+  usbhost_givesem(&priv->exclsem);
+  return ret;
+}
+
+/****************************************************************************
+ * Name: usbhost_getle16
+ *
+ * Description:
+ *   Get a (possibly unaligned) 16-bit little endian value.
+ *
+ * Input Parameters:
+ *   val - A pointer to the first byte of the little endian value.
+ *
+ * Returned Values:
+ *   A uint16_t representing the whole 16-bit integer value
+ *
+ ****************************************************************************/
+
+static inline uint16_t usbhost_getle16(const uint8_t *val)
+{
+  return (uint16_t)val[1] << 8 | (uint16_t)val[0];
+}
+
+/****************************************************************************
+ * Name: usbhost_putle16
+ *
+ * Description:
+ *   Put a (possibly unaligned) 16-bit little endian value.
+ *
+ * Input Parameters:
+ *   dest - A pointer to the first byte to save the little endian value.
+ *   val - The 16-bit value to be saved.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+static void usbhost_putle16(uint8_t *dest, uint16_t val)
+{
+  dest[0] = val & 0xff; /* Little endian means LS byte first in byte stream */
+  dest[1] = val >> 8;
+}
+
+/****************************************************************************
+ * Name: usbhost_getle32
+ *
+ * Description:
+ *   Get a (possibly unaligned) 32-bit little endian value.
+ *
+ * Input Parameters:
+ *   dest - A pointer to the first byte to save the big endian value.
+ *   val - The 32-bit value to be saved.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+static inline uint32_t usbhost_getle32(const uint8_t *val)
+{
+ /* Little endian means LS halfword first in byte stream */
+
+  return (uint32_t)usbhost_getle16(&val[2]) << 16 | (uint32_t)usbhost_getle16(val);
+}
+
+/****************************************************************************
+ * Name: usbhost_putle32
+ *
+ * Description:
+ *   Put a (possibly unaligned) 32-bit little endian value.
+ *
+ * Input Parameters:
+ *   dest - A pointer to the first byte to save the little endian value.
+ *   val - The 32-bit value to be saved.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+static void usbhost_putle32(uint8_t *dest, uint32_t val)
+{
+  /* Little endian means LS halfword first in byte stream */
+
+  usbhost_putle16(dest, (uint16_t)(val & 0xffff));
+  usbhost_putle16(dest+2, (uint16_t)(val >> 16));
+}
+
+/****************************************************************************
+ * Name: usbhost_tdalloc
+ *
+ * Description:
+ *   Allocate transfer buffer memory.
+ *
+ * Input Parameters:
+ *   priv - A reference to the class instance.
+ *
+ * Returned Values:
+ *   On sucess, zero (OK) is returned.  On failure, an negated errno value
+ *   is returned to indicate the nature of the failure.
+ *
+ ****************************************************************************/
+
+static inline int usbhost_tdalloc(FAR struct usbhost_state_s *priv)
+{
+  DEBUGASSERT(priv && priv->tbuffer == NULL);
+  return DRVR_ALLOC(priv->drvr, &priv->tbuffer, &priv->tbuflen);
+}
+
+/****************************************************************************
+ * Name: usbhost_tdfree
+ *
+ * Description:
+ *   Free transfer buffer memory.
+ *
+ * Input Parameters:
+ *   priv - A reference to the class instance.
+ *
+ * Returned Values:
+ *   On sucess, zero (OK) is returned.  On failure, an negated errno value
+ *   is returned to indicate the nature of the failure.
+ *
+ ****************************************************************************/
+
+static inline int usbhost_tdfree(FAR struct usbhost_state_s *priv)
+{
+  int result = OK;
+  DEBUGASSERT(priv);
+
+  if (priv->tbuffer)
+    {
+      DEBUGASSERT(priv->drvr);
+      result         = DRVR_FREE(priv->drvr, priv->tbuffer);
+      priv->tbuffer = NULL;
+      priv->tbuflen = 0;
+    }
+  return result;
+}
+
+/****************************************************************************
+ * struct usbhost_registry_s methods
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: usbhost_create
+ *
+ * Description:
+ *   This function implements the create() method of struct usbhost_registry_s. 
+ *   The create() method is a callback into the class implementation.  It is
+ *   used to (1) create a new instance of the USB host class state and to (2)
+ *   bind a USB host driver "session" to the class instance.  Use of this
+ *   create() method will support environments where there may be multiple
+ *   USB ports and multiple USB devices simultaneously connected.
+ *
+ * Input Parameters:
+ *   drvr - An instance of struct usbhost_driver_s that the class
+ *     implementation will "bind" to its state structure and will
+ *     subsequently use to communicate with the USB host driver.
+ *   id - In the case where the device supports multiple base classes,
+ *     subclasses, or protocols, this specifies which to configure for.
+ *
+ * Returned Values:
+ *   On success, this function will return a non-NULL instance of struct
+ *   usbhost_class_s that can be used by the USB host driver to communicate
+ *   with the USB host class.  NULL is returned on failure; this function
+ *   will fail only if the drvr input parameter is NULL or if there are
+ *   insufficient resources to create another USB host class instance.
+ *
+ ****************************************************************************/
+
+static FAR struct usbhost_class_s *usbhost_create(FAR struct usbhost_driver_s *drvr,
+                                                  FAR const struct usbhost_id_s *id)
+{
+  FAR struct usbhost_state_s *priv;
+
+  /* Allocate a USB host class instance */
+
+  priv = usbhost_allocclass();
+  if (priv)
+    {
+      /* Initialize the allocated storage class instance */
+
+      memset(priv, 0, sizeof(struct usbhost_state_s));
+
+      /* Assign a device number to this class instance */
+
+      if (usbhost_allocdevno(priv) == OK)
+        {
+         /* Initialize class method function pointers */
+
+          priv->class.connect      = usbhost_connect;
+          priv->class.disconnected = usbhost_disconnected;
+
+          /* The initial reference count is 1... One reference is held by the driver */
+
+          priv->crefs              = 1;
+
+          /* Initialize semaphores */
+
+          sem_init(&priv->exclsem, 0, 1);
+          sem_init(&priv->waitsem, 0, 0);
+
+          /* Bind the driver to the storage class instance */
+
+          priv->drvr               = drvr;
+
+          /* Return the instance of the USB keyboard class driver */
+ 
+          return &priv->class;
+        }
+    }
+
+  /* An error occurred. Free the allocation and return NULL on all failures */
+
+  if (priv)
+    {
+      usbhost_freeclass(priv);
+    }
+  return NULL;
+}
+
+/****************************************************************************
+ * struct usbhost_class_s methods
+ ****************************************************************************/
+/****************************************************************************
+ * Name: usbhost_connect
+ *
+ * Description:
+ *   This function implements the connect() method of struct
+ *   usbhost_class_s.  This method is a callback into the class
+ *   implementation.  It is used to provide the device's configuration
+ *   descriptor to the class so that the class may initialize properly
+ *
+ * Input Parameters:
+ *   class - The USB host class entry previously obtained from a call to create().
+ *   configdesc - A pointer to a uint8_t buffer container the configuration descripor.
+ *   desclen - The length in bytes of the configuration descriptor.
+ *   funcaddr - The USB address of the function containing the endpoint that EP0
+ *     controls
+ *
+ * Returned Values:
+ *   On success, zero (OK) is returned. On a failure, a negated errno value is
+ *   returned indicating the nature of the failure
+ *
+ *   NOTE that the class instance remains valid upon return with a failure.  It is
+ *   the responsibility of the higher level enumeration logic to call
+ *   CLASS_DISCONNECTED to free up the class driver resources.
+ *
+ * Assumptions:
+ *   - This function will *not* be called from an interrupt handler.
+ *   - If this function returns an error, the USB host controller driver
+ *     must call to DISCONNECTED method to recover from the error
+ *
+ ****************************************************************************/
+
+static int usbhost_connect(FAR struct usbhost_class_s *class,
+                           FAR const uint8_t *configdesc, int desclen,
+                           uint8_t funcaddr)
+{
+  FAR struct usbhost_state_s *priv = (FAR struct usbhost_state_s *)class;
+  int ret;
+
+  DEBUGASSERT(priv != NULL && 
+              configdesc != NULL &&
+              desclen >= sizeof(struct usb_cfgdesc_s));
+
+  /* Parse the configuration descriptor to get the endpoints */
+
+  ret = usbhost_cfgdesc(priv, configdesc, desclen, funcaddr);
+  if (ret != OK)
+    {
+      udbg("usbhost_cfgdesc() failed: %d\n", ret);
+    }
+  else
+    {
+      /* Now configure the device and register the NuttX driver */
+
+      ret = usbhost_devinit(priv);
+      if (ret != OK)
+        {
+          udbg("usbhost_devinit() failed: %d\n", ret);
+        }
+    }
+ 
+  /* ERROR handling:  Do nothing. If we return and error during connection,
+   * the driver is required to call the DISCONNECT method.  Possibilities:
+   *
+   * - Failure occurred before the kbdpoll task was started successfully.
+   *   In this case, the disconnection will have to be handled on the worker
+   *   task.
+   * - Failure occured after the kbdpoll task was started succesffuly.  In
+   *   this case, the disconnetion can be performed on the kbdpoll thread.
+   */
+
+  return ret;
+}
+
+/****************************************************************************
+ * Name: usbhost_disconnected
+ *
+ * Description:
+ *   This function implements the disconnected() method of struct
+ *   usbhost_class_s.  This method is a callback into the class
+ *   implementation.  It is used to inform the class that the USB device has
+ *   been disconnected.
+ *
+ * Input Parameters:
+ *   class - The USB host class entry previously obtained from a call to
+ *     create().
+ *
+ * Returned Values:
+ *   On success, zero (OK) is returned. On a failure, a negated errno value
+ *   is returned indicating the nature of the failure
+ *
+ * Assumptions:
+ *   This function may be called from an interrupt handler.
+ *
+ ****************************************************************************/
+
+static int usbhost_disconnected(struct usbhost_class_s *class)
+{
+  FAR struct usbhost_state_s *priv = (FAR struct usbhost_state_s *)class;
+
+  DEBUGASSERT(priv != NULL);
+
+  /* Set an indication to any users of the keyboard device that the device
+   * is no longer available.
+   */
+
+  priv->disconnected = true;
+  ullvdbg("Disconnected\n");
+
+  /* Is there a thread waiting for keyboard data that will never come? */
+
+  if (priv->waiting)
+    {
+      /* Yes.. wake it up */
+
+      usbhost_givesem(&priv->waitsem);
+      priv->waiting = false;
+    }
+
+  /* Possibilities:
+   *
+   * - Failure occurred before the kbdpoll task was started successfully.
+   *   In this case, the disconnection will have to be handled on the worker
+   *   task.
+   * - Failure occured after the kbdpoll task was started succesffuly.  In
+   *   this case, the disconnetion can be performed on the kbdpoll thread.
+   */
+
+  if (priv->polling)
+    {
+      /* The polling task is still alive. Signal the keyboard polling task. 
+       * When that task wakes up, it will decrement the reference count and,
+       * perhaps, destroy the class instance.  Then it will exit.
+       */
+
+      (void)kill(priv->pollpid, SIGALRM);
+    }
+  else
+    {
+      /* In the case where the failure occurs before the polling task was
+       * started.  Now what?  We are probably executing from an interrupt
+       * handler here.  We will use the worker thread.  This is kind of
+       * wasteful and begs for a re-design.
+       */
+
+      DEBUGASSERT(priv->work.worker == NULL);
+      (void)work_queue(&priv->work, usbhost_destroy, priv, 0);
+    }
+
+  return OK;
+}
+
+/****************************************************************************
+ * Character driver methods
+ ****************************************************************************/
+/****************************************************************************
+ * Name: usbhost_open
+ *
+ * Description:
+ *   Standard character driver open method.
+ *
+ ****************************************************************************/
+
+static int usbhost_open(FAR struct file *filep)
+{
+  FAR struct inode           *inode;
+  FAR struct usbhost_state_s *priv;
+  irqstate_t flags;
+  int ret;
+
+  uvdbg("Entry\n");
+  DEBUGASSERT(filep && filep->f_inode);
+  inode = filep->f_inode;
+  priv  = inode->i_private;
+
+  /* Make sure that we have exclusive access to the private data structure */
+
+  DEBUGASSERT(priv && priv->crefs > 0 && priv->crefs < USBHOST_MAX_CREFS);
+  usbhost_takesem(&priv->exclsem);
+
+  /* Check if the keyboard device is still connected.  We need to disable
+   * interrupts momentarily to assure that there are no asynchronous disconnect
+   * events.
+   */
+
+  flags = irqsave();
+  if (priv->disconnected)
+    {
+      /* No... the driver is no longer bound to the class.  That means that
+       * the USB storage device is no longer connected.  Refuse any further
+       * attempts to open the driver.
+       */
+
+      ret = -ENODEV;
+    }
+  else
+    {
+      /* Otherwise, just increment the reference count on the driver */
+
+      priv->crefs++;
+      priv->open = true;
+      ret        = OK;
+    }
+  irqrestore(flags);
+
+  usbhost_givesem(&priv->exclsem);
+  return ret;
+}
+
+/****************************************************************************
+ * Name: usbhost_close
+ *
+ * Description:
+ *   Standard character driver close method.
+ *
+ ****************************************************************************/
+
+static int usbhost_close(FAR struct file *filep)
+{
+  FAR struct inode           *inode;
+  FAR struct usbhost_state_s *priv;
+
+  uvdbg("Entry\n");
+  DEBUGASSERT(filep && filep->f_inode);
+  inode = filep->f_inode;
+  priv  = inode->i_private;
+
+  /* Decrement the reference count on the driver */
+
+  DEBUGASSERT(priv->crefs > 1);
+  usbhost_takesem(&priv->exclsem);
+  priv->crefs--;
+
+  /* Is this the last reference (other than the one held by the USB host
+   * controller driver)
+   */
+ 
+  if (priv->crefs <= 1)
+    {
+      irqstate_t flags;
+
+      /* Yes.. then the driver is no longer open */
+
+      priv->open    = false;
+      priv->headndx = 0;
+      priv->tailndx = 0;
+
+      /* We need to disable interrupts momentarily to assure that there are
+       * no asynchronous disconnect events.
+       */
+
+      flags = irqsave();
+
+      /* Check if the USB keyboard device is still connected.  If the device is
+       * no longer connected, then unregister the driver and free the driver
+       * class instance.
+       */
+
+      if (priv->disconnected)
+        {
+          /* Destroy the class instance (we can't use priv after this; we can't
+           * 'give' the semapore)
+           */
+
+          usbhost_destroy(priv);
+          irqrestore(flags);
+          return OK;
+        }
+      irqrestore(flags);
+    }
+ 
+  usbhost_givesem(&priv->exclsem);
+  return OK;
+}
+
+/****************************************************************************
+ * Name: usbhost_read
+ *
+ * Description:
+ *   Standard character driver read method.
+ *
+ ****************************************************************************/
+
+static ssize_t usbhost_read(FAR struct file *filep, FAR char *buffer, size_t len)
+{
+  FAR struct inode           *inode;
+  FAR struct usbhost_state_s *priv;
+  size_t                      nbytes;
+  unsigned int                tail;
+  int                         ret;
+
+  uvdbg("Entry\n");
+  DEBUGASSERT(filep && filep->f_inode && buffer);
+  inode = filep->f_inode;
+  priv  = inode->i_private;
+
+  /* Make sure that we have exclusive access to the private data structure */
+
+  DEBUGASSERT(priv && priv->crefs > 0 && priv->crefs < USBHOST_MAX_CREFS);
+  usbhost_takesem(&priv->exclsem);
+
+  /* Check if the keyboard is still connected.  We need to disable interrupts
+   * momentarily to assure that there are no asynchronous disconnect events.
+   */
+
+  if (priv->disconnected)
+    {
+      /* No... the driver is no longer bound to the class.  That means that
+       * the USB keybaord is no longer connected.  Refuse any further attempts
+       * to access the driver.
+       */
+
+      ret = -ENODEV;
+    }
+  else
+    {
+      /* Is there keyboard data now? */
+
+      while (priv->tailndx == priv->headndx)
+        {
+          /* No.. were we open non-blocking? */
+
+          if (filep->f_oflags & O_NONBLOCK)
+            {
+              /* Yes.. then return a failure */
+
+              ret = -EAGAIN;
+              goto errout;
+            }
+
+          /* Wait for data to be available */
+
+          uvdbg("Waiting...\n");
+          priv->waiting = true;
+          usbhost_givesem(&priv->exclsem);
+          usbhost_takesem(&priv->waitsem);
+          usbhost_takesem(&priv->exclsem);
+
+          /* Did the keyboard become disconnected while we were waiting */
+
+          if (priv->disconnected)
+            {
+              ret = -ENODEV;
+              goto errout;
+            }
+        }
+
+      /* Read data from our internal buffer of received characters */
+ 
+      for (tail  = priv->tailndx, nbytes = 0;
+           tail != priv->headndx && nbytes < len;
+           nbytes++)
+        {
+           /* Copy the next keyboard character into the user buffer */
+
+           *buffer++ = priv->kbdbuffer[tail];
+
+           /* Handle wrap-around of the tail index */
+
+           if (++tail >= CONFIG_HIDKBD_BUFSIZE)
+             {
+               tail = 0;
+             }
+        }
+      ret = nbytes;
+
+      /* Update the tail index (pehaps marking the buffer empty) */
+
+      priv->tailndx = tail;
+    }
+
+errout:
+  usbhost_givesem(&priv->exclsem);
+  return (ssize_t)ret;
+}
+
+/****************************************************************************
+ * Name: usbhost_write
+ *
+ * Description:
+ *   Standard character driver write method.
+ *
+ ****************************************************************************/
+
+static ssize_t usbhost_write(FAR struct file *filep, FAR const char *buffer, size_t len)
+{
+  /* We won't try to write to the keyboard */
+
+  return -ENOSYS;
+}
+
+/****************************************************************************
+ * Name: usbhost_poll
+ *
+ * Description:
+ *   Standard character driver poll method.
+ *
+ ****************************************************************************/
+
+#ifndef CONFIG_DISABLE_POLL
+static int usbhost_poll(FAR struct file *filep, FAR struct pollfd *fds,
+                        bool setup)
+{
+  FAR struct inode           *inode;
+  FAR struct usbhost_state_s *priv;
+  int                         ret = OK;
+  int                         i;
+
+  uvdbg("Entry\n");
+  DEBUGASSERT(filep && filep->f_inode && fds);
+  inode = filep->f_inode;
+  priv  = inode->i_private;
+
+  /* Make sure that we have exclusive access to the private data structure */
+
+  DEBUGASSERT(priv);
+  usbhost_takesem(&priv->exclsem);
+
+  /* Check if the keyboard is still connected.  We need to disable interrupts
+   * momentarily to assure that there are no asynchronous disconnect events.
+   */
+
+  if (priv->disconnected)
+    {
+      /* No... the driver is no longer bound to the class.  That means that
+       * the USB keybaord is no longer connected.  Refuse any further attempts
+       * to access the driver.
+       */
+
+      ret = -ENODEV;
+    }
+  else if (setup)
+    {
+      /* This is a request to set up the poll.  Find an availableslot for
+       * the poll structure reference
+       */
+
+      for (i = 0; i < CONFIG_HIDKBD_NPOLLWAITERS; i++)
+        {
+          /* Find an available slot */
+
+          if (!priv->fds[i])
+            {
+              /* Bind the poll structure and this slot */
+
+              priv->fds[i] = fds;
+              fds->priv    = &priv->fds[i];
+              break;
+            }
+        }
+
+      if (i >= CONFIG_HIDKBD_NPOLLWAITERS)
+        {
+          fds->priv    = NULL;
+          ret          = -EBUSY;
+          goto errout;
+        }
+
+      /* Should we immediately notify on any of the requested events? Notify
+       * the POLLIN event if there is buffered keyboard data.
+       */
+
+      if (priv->headndx != priv->tailndx)
+        {
+          usbhost_pollnotify(priv);
+        }
+    }
+  else
+    {
+      /* This is a request to tear down the poll. */
+
+      struct pollfd **slot = (struct pollfd **)fds->priv;
+      DEBUGASSERT(slot);
+
+      /* Remove all memory of the poll setup */
+
+      *slot                = NULL;
+      fds->priv            = NULL;
+    }
+
+errout:
+  sem_post(&priv->exclsem);
+  return ret;
+}
+#endif
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: usbhost_kbdinit
+ *
+ * Description:
+ *   Initialize the USB storage HID keyboard class driver.  This function
+ *   should be called be platform-specific code in order to initialize and
+ *   register support for the USB host HID keyboard class device.
+ *
+ * Input Parameters:
+ *   None
+ *
+ * Returned Values:
+ *   On success this function will return zero (OK);  A negated errno value
+ *   will be returned on failure.
+ *
+ ****************************************************************************/
+
+int usbhost_kbdinit(void)
+{
+  /* Perform any one-time initialization of the class implementation */
+
+  sem_init(&g_exclsem, 0, 1);
+  sem_init(&g_syncsem, 0, 0);
+
+  /* Advertise our availability to support (certain) devices */
+
+  return usbhost_registerclass(&g_skeleton);
+}
+
+#endif /* CONFIG_USBHOST)&& !CONFIG_USBHOST_INT_DISABLE && CONFIG_NFILE_DESCRIPTORS */
+
+
diff --git a/nuttx/drivers/usbhost/usbhost_registerclass.c b/nuttx/drivers/usbhost/usbhost_registerclass.c
new file mode 100644
index 000000000..76ef511af
--- /dev/null
+++ b/nuttx/drivers/usbhost/usbhost_registerclass.c
@@ -0,0 +1,117 @@
+/****************************************************************************
+ * drivers/usbhost/usbhost_registerclass.c
+ *
+ *   Copyright (C) 2010 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/types.h>
+#include <errno.h>
+#include <debug.h>
+
+#include <arch/irq.h>
+#include <nuttx/usb/usbhost.h>
+
+#include "usbhost_registry.h"
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: usbhost_registerclass
+ *
+ * Description:
+ *   Register a USB host class implementation.  The caller provides an
+ *   instance of struct usbhost_registry_s that contains all of the
+ *   information that will be needed later to (1) associate the USB host
+ *   class implementation with a connected USB device, and (2) to obtain and
+ *   bind a struct usbhost_class_s instance for the device.
+ *
+ * Input Parameters:
+ *   class - An write-able instance of struct usbhost_registry_s that will be
+ *     maintained in a registry.
+ *
+ * Returned Values:
+ *   On success, this function will return zero (OK).  Otherwise, a negated
+ *   errno value is returned.
+ *
+ ****************************************************************************/
+
+int usbhost_registerclass(struct usbhost_registry_s *class)
+{
+  irqstate_t flags;
+
+  uvdbg("Registering class:%p nids:%d\n", class, class->nids);
+
+  /* g_classregistry is a singly-linkedlist of class ID information added by
+   * calls to usbhost_registerclass().  Since this list is accessed from USB
+   * host controller interrupt handling logic, accesses to this list must be
+   * protected by disabling interrupts.
+   */
+
+  flags = irqsave();
+
+  /* Add the new class ID info to the head of the list */
+
+  class->flink    = g_classregistry;
+  g_classregistry = class;
+
+  irqrestore(flags);
+  return OK;
+}
+
diff --git a/nuttx/drivers/usbhost/usbhost_registry.c b/nuttx/drivers/usbhost/usbhost_registry.c
new file mode 100644
index 000000000..56c03e2dc
--- /dev/null
+++ b/nuttx/drivers/usbhost/usbhost_registry.c
@@ -0,0 +1,80 @@
+/****************************************************************************
+ * drivers/usbhost/usbhost_registry.c
+ *
+ *   Copyright (C) 2010 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <nuttx/usb/usbhost.h>
+
+#include "usbhost_registry.h"
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Data
+ ****************************************************************************/
+
+/* g_classregistry is a singly-linkedlist of class ID information added by
+ * calls to usbhost_registerclass().  Since this list is accessed from USB
+ * host controller interrupt handling logic, accesses to this list must be
+ * protected by disabling interrupts.
+ */
+
+struct usbhost_registry_s *g_classregistry;
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
diff --git a/nuttx/drivers/usbhost/usbhost_registry.h b/nuttx/drivers/usbhost/usbhost_registry.h
new file mode 100644
index 000000000..63436af5d
--- /dev/null
+++ b/nuttx/drivers/usbhost/usbhost_registry.h
@@ -0,0 +1,87 @@
+/****************************************************************************
+ * drivers/usbhost/usbdev_registry.h
+ *
+ *   Copyright (C) 2010 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#ifndef __DRIVERS_USBHOST_USBHOST_REGISTRY_H
+#define __DRIVERS_USBHOST_USBHOST_REGISTRY_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <nuttx/usb/usbhost.h>
+
+/****************************************************************************
+ * Definitions
+ ****************************************************************************/
+
+/* Configuration ************************************************************/
+
+/****************************************************************************
+ * Public Types
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Data
+ ****************************************************************************/
+
+#undef EXTERN
+#if defined(__cplusplus)
+#  define EXTERN extern "C"
+extern "C"
+{
+#else
+#  define EXTERN extern
+#endif
+
+/* g_classregistry is a singly-linkedlist of class ID information added by
+ * calls to usbhost_registerclass().  Since this list is accessed from USB
+ * host controller interrupt handling logic, accesses to this list must be
+ * protected by disabling interrupts.
+ */
+
+EXTERN struct usbhost_registry_s *g_classregistry;
+
+/************************************************************************************
+ * Public Function Prototypes
+ ************************************************************************************/
+
+#undef EXTERN
+#if defined(__cplusplus)
+}
+#endif
+
+#endif /* #define __DRIVERS_USBHOST_USBHOST_REGISTRY_H */
diff --git a/nuttx/drivers/usbhost/usbhost_skeleton.c b/nuttx/drivers/usbhost/usbhost_skeleton.c
new file mode 100644
index 000000000..206b347c5
--- /dev/null
+++ b/nuttx/drivers/usbhost/usbhost_skeleton.c
@@ -0,0 +1,1060 @@
+/****************************************************************************
+ * drivers/usbhost/usbhost_skeleton.c
+ *
+ *   Copyright (C) 2011 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <semaphore.h>
+#include <assert.h>
+#include <errno.h>
+#include <debug.h>
+
+#include <nuttx/kmalloc.h>
+#include <nuttx/fs.h>
+#include <nuttx/arch.h>
+#include <nuttx/wqueue.h>
+
+#include <nuttx/usb/usb.h>
+#include <nuttx/usb/usbhost.h>
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/* Configuration ************************************************************/
+
+#ifndef CONFIG_SCHED_WORKQUEUE
+#  warning "Worker thread support is required (CONFIG_SCHED_WORKQUEUE)"
+#endif
+
+/* Driver support ***********************************************************/
+/* This format is used to construct the /dev/skel[n] device driver path.  It
+ * defined here so that it will be used consistently in all places.
+ */
+
+#define DEV_FORMAT          "/dev/skel%c"
+#define DEV_NAMELEN         12
+
+/* Used in usbhost_cfgdesc() */
+
+#define USBHOST_IFFOUND     0x01
+#define USBHOST_BINFOUND    0x02
+#define USBHOST_BOUTFOUND   0x04
+#define USBHOST_ALLFOUND    0x07
+
+#define USBHOST_MAX_CREFS   0x7fff
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+/* This structure contains the internal, private state of the USB host class
+ * driver.
+ */
+
+struct usbhost_state_s
+{
+  /* This is the externally visible portion of the state */
+
+  struct usbhost_class_s  class;
+
+  /* This is an instance of the USB host driver bound to this class instance */
+
+  struct usbhost_driver_s *drvr;
+
+  /* The remainder of the fields are provide to the class driver */
+  
+  char                    devchar;      /* Character identifying the /dev/skel[n] device */
+  volatile bool           disconnected; /* TRUE: Device has been disconnected */
+  uint8_t                 ifno;         /* Interface number */
+  int16_t                 crefs;        /* Reference count on the driver instance */
+  sem_t                   exclsem;      /* Used to maintain mutual exclusive access */
+  struct work_s           work;         /* For interacting with the worker thread */
+  FAR uint8_t            *tbuffer;      /* The allocated transfer buffer */
+  size_t                  tbuflen;      /* Size of the allocated transfer buffer */
+  usbhost_ep_t            epin;         /* IN endpoint */
+  usbhost_ep_t            epout;        /* OUT endpoint */
+};
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+/* Semaphores */
+
+static void usbhost_takesem(sem_t *sem);
+#define usbhost_givesem(s) sem_post(s);
+
+/* Memory allocation services */
+
+static inline FAR struct usbhost_state_s *usbhost_allocclass(void);
+static inline void usbhost_freeclass(FAR struct usbhost_state_s *class);
+
+/* Device name management */
+
+static int usbhost_allocdevno(FAR struct usbhost_state_s *priv);
+static void usbhost_freedevno(FAR struct usbhost_state_s *priv);
+static inline void usbhost_mkdevname(FAR struct usbhost_state_s *priv, char *devname);
+
+/* Worker thread actions */
+
+static void usbhost_destroy(FAR void *arg);
+
+/* Helpers for usbhost_connect() */
+
+static inline int usbhost_cfgdesc(FAR struct usbhost_state_s *priv,
+                                  FAR const uint8_t *configdesc, int desclen,
+                                  uint8_t funcaddr);
+static inline int usbhost_devinit(FAR struct usbhost_state_s *priv);
+
+/* (Little Endian) Data helpers */
+
+static inline uint16_t usbhost_getle16(const uint8_t *val);
+static inline void usbhost_putle16(uint8_t *dest, uint16_t val);
+static inline uint32_t usbhost_getle32(const uint8_t *val);
+static void usbhost_putle32(uint8_t *dest, uint32_t val);
+
+/* Transfer descriptor memory management */
+
+static inline int usbhost_talloc(FAR struct usbhost_state_s *priv);
+static inline int usbhost_tfree(FAR struct usbhost_state_s *priv);
+
+/* struct usbhost_registry_s methods */
+ 
+static struct usbhost_class_s *usbhost_create(FAR struct usbhost_driver_s *drvr,
+                                              FAR const struct usbhost_id_s *id);
+
+/* struct usbhost_class_s methods */
+
+static int usbhost_connect(FAR struct usbhost_class_s *class,
+                           FAR const uint8_t *configdesc, int desclen,
+                           uint8_t funcaddr);
+static int usbhost_disconnected(FAR struct usbhost_class_s *class);
+
+/* Driver methods -- depend upon the type of NuttX driver interface exported */
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/* This structure provides the registry entry ID informatino that will  be 
+ * used to associate the USB class driver to a connected USB device.
+ */
+
+static const const struct usbhost_id_s g_id =
+{
+  0,  /* base -- Must be one of the USB_CLASS_* definitions in usb.h */
+  0,  /* subclass -- depends on the device */
+  0,  /* proto -- depends on the device    */
+  0,  /* vid      */
+  0   /* pid      */
+};
+
+/* This is the USB host storage class's registry entry */
+
+static struct usbhost_registry_s g_skeleton =
+{
+  NULL,                   /* flink    */
+  usbhost_create,         /* create   */
+  1,                      /* nids     */
+  &g_id                   /* id[]     */
+};
+
+/* This is a bitmap that is used to allocate device names /dev/skela-z. */
+
+static uint32_t g_devinuse;
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: usbhost_takesem
+ *
+ * Description:
+ *   This is just a wrapper to handle the annoying behavior of semaphore
+ *   waits that return due to the receipt of a signal.
+ *
+ ****************************************************************************/
+
+static void usbhost_takesem(sem_t *sem)
+{
+  /* Take the semaphore (perhaps waiting) */
+
+  while (sem_wait(sem) != 0)
+    {
+      /* The only case that an error should occr here is if the wait was
+       * awakened by a signal.
+       */
+
+      ASSERT(errno == EINTR);
+    }
+}
+
+/****************************************************************************
+ * Name: usbhost_allocclass
+ *
+ * Description:
+ *   This is really part of the logic that implements the create() method
+ *   of struct usbhost_registry_s.  This function allocates memory for one
+ *   new class instance.
+ *
+ * Input Parameters:
+ *   None
+ *
+ * Returned Values:
+ *   On success, this function will return a non-NULL instance of struct
+ *   usbhost_class_s.  NULL is returned on failure; this function will
+ *   will fail only if there are insufficient resources to create another
+ *   USB host class instance.
+ *
+ ****************************************************************************/
+
+static inline FAR struct usbhost_state_s *usbhost_allocclass(void)
+{
+  FAR struct usbhost_state_s *priv;
+
+  DEBUGASSERT(!up_interrupt_context());
+  priv = (FAR struct usbhost_state_s *)kmalloc(sizeof(struct usbhost_state_s));
+  uvdbg("Allocated: %p\n", priv);;
+  return priv;
+}
+
+/****************************************************************************
+ * Name: usbhost_freeclass
+ *
+ * Description:
+ *   Free a class instance previously allocated by usbhost_allocclass().
+ *
+ * Input Parameters:
+ *   class - A reference to the class instance to be freed.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+static inline void usbhost_freeclass(FAR struct usbhost_state_s *class)
+{
+  DEBUGASSERT(class != NULL);
+
+  /* Free the class instance (perhaps calling sched_free() in case we are
+   * executing from an interrupt handler.
+   */
+
+  uvdbg("Freeing: %p\n", class);;
+  kfree(class);
+}
+
+/****************************************************************************
+ * Name: Device name management
+ *
+ * Description:
+ *   Some tiny functions to coordinate management of device names.
+ *
+ ****************************************************************************/
+
+static int usbhost_allocdevno(FAR struct usbhost_state_s *priv)
+{
+  irqstate_t flags;
+  int devno;
+
+  flags = irqsave();
+  for (devno = 0; devno < 26; devno++)
+    {
+      uint32_t bitno = 1 << devno;
+      if ((g_devinuse & bitno) == 0)
+        {
+          g_devinuse |= bitno;
+          priv->devchar = 'a' + devno;
+          irqrestore(flags);
+          return OK;
+        }
+    }
+
+  irqrestore(flags);
+  return -EMFILE;
+}
+
+static void usbhost_freedevno(FAR struct usbhost_state_s *priv)
+{
+  int devno = 'a' - priv->devchar;
+
+  if (devno >= 0 && devno < 26)
+    {
+      irqstate_t flags = irqsave();
+      g_devinuse &= ~(1 << devno);
+      irqrestore(flags);
+    }
+}
+
+static inline void usbhost_mkdevname(FAR struct usbhost_state_s *priv, char *devname)
+{
+  (void)snprintf(devname, DEV_NAMELEN, DEV_FORMAT, priv->devchar);
+}
+
+/****************************************************************************
+ * Name: usbhost_destroy
+ *
+ * Description:
+ *   The USB device has been disconnected and the refernce count on the USB
+ *   host class instance has gone to 1.. Time to destroy the USB host class
+ *   instance.
+ *
+ * Input Parameters:
+ *   arg - A reference to the class instance to be destroyed.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+static void usbhost_destroy(FAR void *arg)
+{
+  FAR struct usbhost_state_s *priv = (FAR struct usbhost_state_s *)arg;
+
+  DEBUGASSERT(priv != NULL);
+  uvdbg("crefs: %d\n", priv->crefs);
+ 
+  /* Unregister the driver */
+
+  /* Release the device name used by this connection */
+
+  usbhost_freedevno(priv);
+
+  /* Free the endpoints */
+
+  /* Free any transfer buffers */
+
+  /* Destroy the semaphores */
+
+  /* Disconnect the USB host device */
+
+  DRVR_DISCONNECT(priv->drvr);
+
+  /* And free the class instance.  Hmmm.. this may execute on the worker
+   * thread and the work structure is part of what is getting freed.  That
+   * should be okay because once the work contained is removed from the
+   * queue, it should not longer be accessed by the worker thread.
+   */
+
+  usbhost_freeclass(priv);
+}
+
+/****************************************************************************
+ * Name: usbhost_cfgdesc
+ *
+ * Description:
+ *   This function implements the connect() method of struct
+ *   usbhost_class_s.  This method is a callback into the class
+ *   implementation.  It is used to provide the device's configuration
+ *   descriptor to the class so that the class may initialize properly
+ *
+ * Input Parameters:
+ *   priv - The USB host class instance.
+ *   configdesc - A pointer to a uint8_t buffer container the configuration descripor.
+ *   desclen - The length in bytes of the configuration descriptor.
+ *   funcaddr - The USB address of the function containing the endpoint that EP0
+ *     controls
+ *
+ * Returned Values:
+ *   On success, zero (OK) is returned. On a failure, a negated errno value is
+ *   returned indicating the nature of the failure
+ *
+ * Assumptions:
+ *   This function will *not* be called from an interrupt handler.
+ *
+ ****************************************************************************/
+
+static inline int usbhost_cfgdesc(FAR struct usbhost_state_s *priv,
+                                  FAR const uint8_t *configdesc, int desclen,
+                                  uint8_t funcaddr)
+{
+  FAR struct usb_cfgdesc_s *cfgdesc;
+  FAR struct usb_desc_s *desc;
+  FAR struct usbhost_epdesc_s bindesc;
+  FAR struct usbhost_epdesc_s boutdesc;
+  int remaining;
+  uint8_t found = 0;
+  int ret;
+
+  DEBUGASSERT(priv != NULL && 
+              configdesc != NULL &&
+              desclen >= sizeof(struct usb_cfgdesc_s));
+  
+  /* Verify that we were passed a configuration descriptor */
+
+  cfgdesc = (FAR struct usb_cfgdesc_s *)configdesc;
+  if (cfgdesc->type != USB_DESC_TYPE_CONFIG)
+    {
+      return -EINVAL;
+    }
+
+  /* Get the total length of the configuration descriptor (little endian).
+   * It might be a good check to get the number of interfaces here too.
+  */
+
+  remaining = (int)usbhost_getle16(cfgdesc->totallen);
+
+  /* Skip to the next entry descriptor */
+
+  configdesc += cfgdesc->len;
+  remaining  -= cfgdesc->len;
+
+  /* Loop where there are more dscriptors to examine */
+
+  while (remaining >= sizeof(struct usb_desc_s))
+    {
+      /* What is the next descriptor? */
+
+      desc = (FAR struct usb_desc_s *)configdesc;
+      switch (desc->type)
+        {
+        /* Interface descriptor. We really should get the number of endpoints
+         * from this descriptor too.
+         */
+
+        case USB_DESC_TYPE_INTERFACE:
+          {
+            FAR struct usb_ifdesc_s *ifdesc = (FAR struct usb_ifdesc_s *)configdesc;
+ 
+            uvdbg("Interface descriptor\n");
+            DEBUGASSERT(remaining >= USB_SIZEOF_IFDESC);
+
+            /* Save the interface number and mark ONLY the interface found */
+
+            priv->ifno = ifdesc->ifno;
+            found      = USBHOST_IFFOUND;
+          }
+          break;
+
+        /* Endpoint descriptor.  Here, we expect two bulk endpoints, an IN
+         * and an OUT.
+         */
+
+        case USB_DESC_TYPE_ENDPOINT:
+          {
+            FAR struct usb_epdesc_s *epdesc = (FAR struct usb_epdesc_s *)configdesc;
+
+            uvdbg("Endpoint descriptor\n");
+            DEBUGASSERT(remaining >= USB_SIZEOF_EPDESC);
+
+            /* Check for a bulk endpoint. */
+
+            if ((epdesc->attr & USB_EP_ATTR_XFERTYPE_MASK) == USB_EP_ATTR_XFER_BULK)
+              {
+                /* Yes.. it is a bulk endpoint.  IN or OUT? */
+
+                if (USB_ISEPOUT(epdesc->addr))
+                  {
+                    /* It is an OUT bulk endpoint.  There should be only one
+                     * bulk OUT endpoint.
+                     */
+
+                    if ((found & USBHOST_BOUTFOUND) != 0)
+                      {
+                        /* Oops.. more than one endpoint.  We don't know
+                         * what to do with this.
+                         */
+
+                        return -EINVAL;
+                      }
+                    found |= USBHOST_BOUTFOUND;
+
+                    /* Save the bulk OUT endpoint information */
+
+                    boutdesc.addr         = epdesc->addr & USB_EP_ADDR_NUMBER_MASK;
+                    boutdesc.in           = false;
+                    boutdesc.funcaddr     = funcaddr;
+                    boutdesc.xfrtype      = USB_EP_ATTR_XFER_BULK;
+                    boutdesc.interval     = epdesc->interval;
+                    boutdesc.mxpacketsize = usbhost_getle16(epdesc->mxpacketsize);
+                    uvdbg("Bulk OUT EP addr:%d mxpacketsize:%d\n",
+                          boutdesc.addr, boutdesc.mxpacketsize);
+                  }
+                else
+                  {
+                    /* It is an IN bulk endpoint.  There should be only one
+                     * bulk IN endpoint.
+                     */
+
+                    if ((found & USBHOST_BINFOUND) != 0)
+                      {
+                        /* Oops.. more than one endpoint.  We don't know
+                         * what to do with this.
+                         */
+
+                        return -EINVAL;
+                      }
+                    found |= USBHOST_BINFOUND;
+
+                    /* Save the bulk IN endpoint information */
+                    
+                    bindesc.addr         = epdesc->addr & USB_EP_ADDR_NUMBER_MASK;
+                    bindesc.in           = 1;
+                    bindesc.funcaddr     = funcaddr;
+                    bindesc.xfrtype      = USB_EP_ATTR_XFER_BULK;
+                    bindesc.interval     = epdesc->interval;
+                    bindesc.mxpacketsize = usbhost_getle16(epdesc->mxpacketsize);
+                    uvdbg("Bulk IN EP addr:%d mxpacketsize:%d\n",
+                          bindesc.addr, bindesc.mxpacketsize);
+                  }
+              }
+          }
+          break;
+
+        /* Other descriptors are just ignored for now */
+
+        default:
+          break;
+        }
+
+      /* If we found everything we need with this interface, then break out
+       * of the loop early.
+       */
+
+      if (found == USBHOST_ALLFOUND)
+        {
+          break;
+        }
+
+      /* Increment the address of the next descriptor */
+ 
+      configdesc += desc->len;
+      remaining  -= desc->len;
+    }
+
+  /* Sanity checking... did we find all of things that we need? */
+    
+  if (found != USBHOST_ALLFOUND)
+    {
+      ulldbg("ERROR: Found IF:%s BIN:%s BOUT:%s\n",
+             (found & USBHOST_IFFOUND) != 0  ? "YES" : "NO",
+             (found & USBHOST_BINFOUND) != 0 ? "YES" : "NO",
+             (found & USBHOST_BOUTFOUND) != 0 ? "YES" : "NO");
+      return -EINVAL;
+    }
+
+  /* We are good... Allocate the endpoints */
+
+  ret = DRVR_EPALLOC(priv->drvr, &boutdesc, &priv->epout);
+  if (ret != OK)
+    {
+      udbg("ERROR: Failed to allocate Bulk OUT endpoint\n");
+      return ret;
+    }
+
+  ret = DRVR_EPALLOC(priv->drvr, &bindesc, &priv->epin);
+  if (ret != OK)
+    {
+      udbg("ERROR: Failed to allocate Bulk IN endpoint\n");
+      (void)DRVR_EPFREE(priv->drvr, priv->epout);
+      return ret;
+    }
+
+  ullvdbg("Endpoints allocated\n");
+  return OK;
+}
+
+/****************************************************************************
+ * Name: usbhost_devinit
+ *
+ * Description:
+ *   The USB device has been successfully connected.  This completes the
+ *   initialization operations.  It is first called after the
+ *   configuration descriptor has been received.
+ *
+ *   This function is called from the connect() method.  This function always
+ *   executes on the thread of the caller of connect().
+ *
+ * Input Parameters:
+ *   priv - A reference to the class instance.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+static inline int usbhost_devinit(FAR struct usbhost_state_s *priv)
+{
+  int ret = OK;
+
+  /* Set aside a transfer buffer for exclusive use by the class driver */
+
+  /* Increment the reference count.  This will prevent usbhost_destroy() from
+   * being called asynchronously if the device is removed.
+   */
+
+  priv->crefs++;
+  DEBUGASSERT(priv->crefs == 2);
+
+  /* Configure the device */
+
+  /* Register the driver */
+
+  if (ret == OK)
+    {
+      char devname[DEV_NAMELEN];
+
+      uvdbg("Register block driver\n");
+      usbhost_mkdevname(priv, devname);
+      // ret = register_blockdriver(devname, &g_bops, 0, priv);
+    }
+
+  /* Check if we successfully initialized. We now have to be concerned
+   * about asynchronous modification of crefs because the block
+   * driver has been registerd.
+   */
+
+  if (ret == OK)
+    {
+      usbhost_takesem(&priv->exclsem);
+      DEBUGASSERT(priv->crefs >= 2);
+
+      /* Handle a corner case where (1) open() has been called so the
+       * reference count is > 2, but the device has been disconnected.
+       * In this case, the class instance needs to persist until close()
+       * is called.
+       */
+
+      if (priv->crefs <= 2 && priv->disconnected)
+        {
+          /* We don't have to give the semaphore because it will be
+           * destroyed when usb_destroy is called.
+           */
+  
+          ret = -ENODEV;
+        }
+      else
+        {
+          /* Ready for normal operation as a block device driver */
+
+          uvdbg("Successfully initialized\n");
+          priv->crefs--;
+          usbhost_givesem(&priv->exclsem);
+        }
+    }
+
+  return ret;
+}
+
+/****************************************************************************
+ * Name: usbhost_getle16
+ *
+ * Description:
+ *   Get a (possibly unaligned) 16-bit little endian value.
+ *
+ * Input Parameters:
+ *   val - A pointer to the first byte of the little endian value.
+ *
+ * Returned Values:
+ *   A uint16_t representing the whole 16-bit integer value
+ *
+ ****************************************************************************/
+
+static inline uint16_t usbhost_getle16(const uint8_t *val)
+{
+  return (uint16_t)val[1] << 8 | (uint16_t)val[0];
+}
+
+/****************************************************************************
+ * Name: usbhost_putle16
+ *
+ * Description:
+ *   Put a (possibly unaligned) 16-bit little endian value.
+ *
+ * Input Parameters:
+ *   dest - A pointer to the first byte to save the little endian value.
+ *   val - The 16-bit value to be saved.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+static void usbhost_putle16(uint8_t *dest, uint16_t val)
+{
+  dest[0] = val & 0xff; /* Little endian means LS byte first in byte stream */
+  dest[1] = val >> 8;
+}
+
+/****************************************************************************
+ * Name: usbhost_getle32
+ *
+ * Description:
+ *   Get a (possibly unaligned) 32-bit little endian value.
+ *
+ * Input Parameters:
+ *   dest - A pointer to the first byte to save the big endian value.
+ *   val - The 32-bit value to be saved.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+static inline uint32_t usbhost_getle32(const uint8_t *val)
+{
+ /* Little endian means LS halfword first in byte stream */
+
+  return (uint32_t)usbhost_getle16(&val[2]) << 16 | (uint32_t)usbhost_getle16(val);
+}
+
+/****************************************************************************
+ * Name: usbhost_putle32
+ *
+ * Description:
+ *   Put a (possibly unaligned) 32-bit little endian value.
+ *
+ * Input Parameters:
+ *   dest - A pointer to the first byte to save the little endian value.
+ *   val - The 32-bit value to be saved.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+static void usbhost_putle32(uint8_t *dest, uint32_t val)
+{
+  /* Little endian means LS halfword first in byte stream */
+
+  usbhost_putle16(dest, (uint16_t)(val & 0xffff));
+  usbhost_putle16(dest+2, (uint16_t)(val >> 16));
+}
+
+/****************************************************************************
+ * Name: usbhost_talloc
+ *
+ * Description:
+ *   Allocate transfer buffer memory.
+ *
+ * Input Parameters:
+ *   priv - A reference to the class instance.
+ *
+ * Returned Values:
+ *   On sucess, zero (OK) is returned.  On failure, an negated errno value
+ *   is returned to indicate the nature of the failure.
+ *
+ ****************************************************************************/
+
+static inline int usbhost_talloc(FAR struct usbhost_state_s *priv)
+{
+  DEBUGASSERT(priv && priv->tbuffer == NULL);
+  return DRVR_ALLOC(priv->drvr, &priv->tbuffer, &priv->tbuflen);
+}
+
+/****************************************************************************
+ * Name: usbhost_tfree
+ *
+ * Description:
+ *   Free transfer buffer memory.
+ *
+ * Input Parameters:
+ *   priv - A reference to the class instance.
+ *
+ * Returned Values:
+ *   On sucess, zero (OK) is returned.  On failure, an negated errno value
+ *   is returned to indicate the nature of the failure.
+ *
+ ****************************************************************************/
+
+static inline int usbhost_tfree(FAR struct usbhost_state_s *priv)
+{
+  int result = OK;
+  DEBUGASSERT(priv);
+
+  if (priv->tbuffer)
+    {
+      DEBUGASSERT(priv->drvr);
+      result         = DRVR_FREE(priv->drvr, priv->tbuffer);
+      priv->tbuffer = NULL;
+      priv->tbuflen = 0;
+    }
+  return result;
+}
+
+/****************************************************************************
+ * struct usbhost_registry_s methods
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: usbhost_create
+ *
+ * Description:
+ *   This function implements the create() method of struct usbhost_registry_s. 
+ *   The create() method is a callback into the class implementation.  It is
+ *   used to (1) create a new instance of the USB host class state and to (2)
+ *   bind a USB host driver "session" to the class instance.  Use of this
+ *   create() method will support environments where there may be multiple
+ *   USB ports and multiple USB devices simultaneously connected.
+ *
+ * Input Parameters:
+ *   drvr - An instance of struct usbhost_driver_s that the class
+ *     implementation will "bind" to its state structure and will
+ *     subsequently use to communicate with the USB host driver.
+ *   id - In the case where the device supports multiple base classes,
+ *     subclasses, or protocols, this specifies which to configure for.
+ *
+ * Returned Values:
+ *   On success, this function will return a non-NULL instance of struct
+ *   usbhost_class_s that can be used by the USB host driver to communicate
+ *   with the USB host class.  NULL is returned on failure; this function
+ *   will fail only if the drvr input parameter is NULL or if there are
+ *   insufficient resources to create another USB host class instance.
+ *
+ ****************************************************************************/
+
+static FAR struct usbhost_class_s *usbhost_create(FAR struct usbhost_driver_s *drvr,
+                                                  FAR const struct usbhost_id_s *id)
+{
+  FAR struct usbhost_state_s *priv;
+
+  /* Allocate a USB host class instance */
+
+  priv = usbhost_allocclass();
+  if (priv)
+    {
+      /* Initialize the allocated storage class instance */
+
+      memset(priv, 0, sizeof(struct usbhost_state_s));
+
+      /* Assign a device number to this class instance */
+
+      if (usbhost_allocdevno(priv) == OK)
+        {
+         /* Initialize class method function pointers */
+
+          priv->class.connect      = usbhost_connect;
+          priv->class.disconnected = usbhost_disconnected;
+
+          /* The initial reference count is 1... One reference is held by the driver */
+
+          priv->crefs              = 1;
+
+          /* Initialize semphores (this works okay in the interrupt context) */
+
+          sem_init(&priv->exclsem, 0, 1);
+
+          /* Bind the driver to the storage class instance */
+
+          priv->drvr               = drvr;
+
+          /* Return the instance of the USB class driver */
+ 
+          return &priv->class;
+        }
+    }
+
+  /* An error occurred. Free the allocation and return NULL on all failures */
+
+  if (priv)
+    {
+      usbhost_freeclass(priv);
+    }
+  return NULL;
+}
+
+/****************************************************************************
+ * struct usbhost_class_s methods
+ ****************************************************************************/
+/****************************************************************************
+ * Name: usbhost_connect
+ *
+ * Description:
+ *   This function implements the connect() method of struct
+ *   usbhost_class_s.  This method is a callback into the class
+ *   implementation.  It is used to provide the device's configuration
+ *   descriptor to the class so that the class may initialize properly
+ *
+ * Input Parameters:
+ *   class - The USB host class entry previously obtained from a call to create().
+ *   configdesc - A pointer to a uint8_t buffer container the configuration descripor.
+ *   desclen - The length in bytes of the configuration descriptor.
+ *   funcaddr - The USB address of the function containing the endpoint that EP0
+ *     controls
+ *
+ * Returned Values:
+ *   On success, zero (OK) is returned. On a failure, a negated errno value is
+ *   returned indicating the nature of the failure
+ *
+ *   NOTE that the class instance remains valid upon return with a failure.  It is
+ *   the responsibility of the higher level enumeration logic to call
+ *   CLASS_DISCONNECTED to free up the class driver resources.
+ *
+ * Assumptions:
+ *   - This function will *not* be called from an interrupt handler.
+ *   - If this function returns an error, the USB host controller driver
+ *     must call to DISCONNECTED method to recover from the error
+ *
+ ****************************************************************************/
+
+static int usbhost_connect(FAR struct usbhost_class_s *class,
+                           FAR const uint8_t *configdesc, int desclen,
+                           uint8_t funcaddr)
+{
+  FAR struct usbhost_state_s *priv = (FAR struct usbhost_state_s *)class;
+  int ret;
+
+  DEBUGASSERT(priv != NULL && 
+              configdesc != NULL &&
+              desclen >= sizeof(struct usb_cfgdesc_s));
+
+  /* Parse the configuration descriptor to get the endpoints */
+
+  ret = usbhost_cfgdesc(priv, configdesc, desclen, funcaddr);
+  if (ret != OK)
+    {
+      udbg("usbhost_cfgdesc() failed: %d\n", ret);
+    }
+  else
+    {
+      /* Now configure the device and register the NuttX driver */
+
+      ret = usbhost_devinit(priv);
+      if (ret != OK)
+        {
+          udbg("usbhost_devinit() failed: %d\n", ret);
+        }
+    }
+ 
+  return ret;
+}
+
+/****************************************************************************
+ * Name: usbhost_disconnected
+ *
+ * Description:
+ *   This function implements the disconnected() method of struct
+ *   usbhost_class_s.  This method is a callback into the class
+ *   implementation.  It is used to inform the class that the USB device has
+ *   been disconnected.
+ *
+ * Input Parameters:
+ *   class - The USB host class entry previously obtained from a call to
+ *     create().
+ *
+ * Returned Values:
+ *   On success, zero (OK) is returned. On a failure, a negated errno value
+ *   is returned indicating the nature of the failure
+ *
+ * Assumptions:
+ *   This function may be called from an interrupt handler.
+ *
+ ****************************************************************************/
+
+static int usbhost_disconnected(struct usbhost_class_s *class)
+{
+  FAR struct usbhost_state_s *priv = (FAR struct usbhost_state_s *)class;
+  irqstate_t flags;
+
+  DEBUGASSERT(priv != NULL);
+
+  /* Set an indication to any users of the device that the device is no
+   * longer available.
+   */
+
+  flags              = irqsave();
+  priv->disconnected = true;
+
+  /* Now check the number of references on the class instance.  If it is one,
+   * then we can free the class instance now.  Otherwise, we will have to
+   * wait until the holders of the references free them by closing the
+   * block driver.
+   */
+
+  ullvdbg("crefs: %d\n", priv->crefs);
+  if (priv->crefs == 1)
+    {
+      /* Destroy the class instance.  If we are executing from an interrupt
+       * handler, then defer the destruction to the worker thread.
+       * Otherwise, destroy the instance now.
+       */
+
+      if (up_interrupt_context())
+        {
+          /* Destroy the instance on the worker thread. */
+
+          uvdbg("Queuing destruction: worker %p->%p\n", priv->work.worker, usbhost_destroy);
+          DEBUGASSERT(priv->work.worker == NULL);
+          (void)work_queue(&priv->work, usbhost_destroy, priv, 0);
+       }
+      else
+        {
+          /* Do the work now */
+
+          usbhost_destroy(priv);
+        }
+    }
+
+  irqrestore(flags);  
+  return OK;
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: usbhost_skelinit
+ *
+ * Description:
+ *   Initialize the USB class driver.  This function should be called
+ *   be platform-specific code in order to initialize and register support
+ *   for the USB host class device.
+ *
+ * Input Parameters:
+ *   None
+ *
+ * Returned Values:
+ *   On success this function will return zero (OK);  A negated errno value
+ *   will be returned on failure.
+ *
+ ****************************************************************************/
+
+int usbhost_skelinit(void)
+{
+  /* Perform any one-time initialization of the class implementation */
+
+  /* Advertise our availability to support (certain) devices */
+
+  return usbhost_registerclass(&g_skeleton);
+}
diff --git a/nuttx/drivers/usbhost/usbhost_storage.c b/nuttx/drivers/usbhost/usbhost_storage.c
new file mode 100644
index 000000000..8f5864b6d
--- /dev/null
+++ b/nuttx/drivers/usbhost/usbhost_storage.c
@@ -0,0 +1,2233 @@
+/****************************************************************************
+ * drivers/usbhost/usbhost_storage.c
+ *
+ *   Copyright (C) 2010-2011 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <semaphore.h>
+#include <assert.h>
+#include <errno.h>
+#include <debug.h>
+
+#include <nuttx/kmalloc.h>
+#include <nuttx/fs.h>
+#include <nuttx/arch.h>
+#include <nuttx/wqueue.h>
+#include <nuttx/scsi.h>
+
+#include <nuttx/usb/usb.h>
+#include <nuttx/usb/usbhost.h>
+#include <nuttx/usb/storage.h>
+
+/* Don't compile if prerequisites are not met */
+
+#if defined(CONFIG_USBHOST) && !defined(CONFIG_USBHOST_BULK_DISABLE) && \
+   !defined(CONFIG_DISABLE_MOUNTPOINT) && CONFIG_NFILE_DESCRIPTORS > 0
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/* Configuration ************************************************************/
+
+#ifndef CONFIG_SCHED_WORKQUEUE
+#  warning "Worker thread support is required (CONFIG_SCHED_WORKQUEUE)"
+#endif
+
+/* If the create() method is called by the USB host device driver from an
+ * interrupt handler, then it will be unable to call kmalloc() in order to
+ * allocate a new class instance.  If the create() method is called from the
+ * interrupt level, then class instances must be pre-allocated.
+ */
+
+#ifndef CONFIG_USBHOST_NPREALLOC
+#  define CONFIG_USBHOST_NPREALLOC 0
+#endif
+
+#if CONFIG_USBHOST_NPREALLOC > 26
+#  error "Currently limited to 26 devices /dev/sda-z"
+#endif
+
+/* Driver support ***********************************************************/
+/* This format is used to construct the /dev/sd[n] device driver path.  It
+ * defined here so that it will be used consistently in all places.
+ */
+
+#define DEV_FORMAT          "/dev/sd%c"
+#define DEV_NAMELEN         10
+
+/* Used in usbhost_connect() */
+
+#define USBHOST_IFFOUND     0x01
+#define USBHOST_BINFOUND    0x02
+#define USBHOST_BOUTFOUND   0x04
+#define USBHOST_ALLFOUND    0x07
+
+#define USBHOST_MAX_RETRIES 100
+#define USBHOST_MAX_CREFS   0x7fff
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+/* This structure contains the internal, private state of the USB host mass
+ * storage class.
+ */
+
+struct usbhost_state_s
+{
+  /* This is the externally visible portion of the state */
+
+  struct usbhost_class_s  class;
+
+  /* This is an instance of the USB host driver bound to this class instance */
+
+  struct usbhost_driver_s *drvr;
+
+  /* The remainder of the fields are provide to the mass storage class */
+  
+  char                    sdchar;       /* Character identifying the /dev/sd[n] device */
+  volatile bool           disconnected; /* TRUE: Device has been disconnected */
+  uint8_t                 ifno;         /* Interface number */
+  int16_t                 crefs;        /* Reference count on the driver instance */
+  uint16_t                blocksize;    /* Block size of USB mass storage device */
+  uint32_t                nblocks;      /* Number of blocks on the USB mass storage device */
+  sem_t                   exclsem;      /* Used to maintain mutual exclusive access */
+  struct work_s           work;         /* For interacting with the worker thread */
+  FAR uint8_t            *tbuffer;      /* The allocated transfer buffer */
+  size_t                  tbuflen;      /* Size of the allocated transfer buffer */
+  usbhost_ep_t            bulkin;       /* Bulk IN endpoint */
+  usbhost_ep_t            bulkout;      /* Bulk OUT endpoint */
+};
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+/* Semaphores */
+
+static void usbhost_takesem(sem_t *sem);
+#define usbhost_givesem(s) sem_post(s);
+
+/* Memory allocation services */
+
+static inline FAR struct usbhost_state_s *usbhost_allocclass(void);
+static inline void usbhost_freeclass(FAR struct usbhost_state_s *class);
+
+/* Device name management */
+
+static int usbhost_allocdevno(FAR struct usbhost_state_s *priv);
+static void usbhost_freedevno(FAR struct usbhost_state_s *priv);
+static inline void usbhost_mkdevname(FAR struct usbhost_state_s *priv, char *devname);
+
+/* CBW/CSW debug helpers */
+
+#if defined(CONFIG_DEBUG_USB) && defined(CONFIG_DEBUG_VERBOSE)
+static void usbhost_dumpcbw(FAR struct usbstrg_cbw_s *cbw);
+static void usbhost_dumpcsw(FAR struct usbstrg_csw_s *csw);
+#else
+#  define usbhost_dumpcbw(cbw);
+#  define usbhost_dumpcsw(csw);
+#endif
+
+/* CBW helpers */
+
+static inline void usbhost_requestsensecbw(FAR struct usbstrg_cbw_s *cbw);
+static inline void usbhost_testunitreadycbw(FAR struct usbstrg_cbw_s *cbw);
+static inline void usbhost_readcapacitycbw(FAR struct usbstrg_cbw_s *cbw);
+static inline void usbhost_inquirycbw (FAR struct usbstrg_cbw_s *cbw);
+static inline void usbhost_readcbw (size_t startsector, uint16_t blocksize,
+                                    unsigned int nsectors,
+                                    FAR struct usbstrg_cbw_s *cbw);
+static inline void usbhost_writecbw(size_t startsector, uint16_t blocksize,
+                                    unsigned int nsectors,
+                                    FAR struct usbstrg_cbw_s *cbw);
+/* Command helpers */
+
+static inline int usbhost_maxlunreq(FAR struct usbhost_state_s *priv);
+static inline int usbhost_testunitready(FAR struct usbhost_state_s *priv);
+static inline int usbhost_requestsense(FAR struct usbhost_state_s *priv);
+static inline int usbhost_readcapacity(FAR struct usbhost_state_s *priv);
+static inline int usbhost_inquiry(FAR struct usbhost_state_s *priv);
+
+/* Worker thread actions */
+
+static void usbhost_destroy(FAR void *arg);
+
+/* Helpers for usbhost_connect() */
+
+static inline int usbhost_cfgdesc(FAR struct usbhost_state_s *priv,
+                                  FAR const uint8_t *configdesc, int desclen,
+                                  uint8_t funcaddr);
+static inline int usbhost_initvolume(FAR struct usbhost_state_s *priv);
+
+/* (Little Endian) Data helpers */
+
+static inline uint16_t usbhost_getle16(const uint8_t *val);
+static inline uint16_t usbhost_getbe16(const uint8_t *val);
+static inline void usbhost_putle16(uint8_t *dest, uint16_t val);
+static inline void usbhost_putbe16(uint8_t *dest, uint16_t val);
+static inline uint32_t usbhost_getle32(const uint8_t *val);
+static inline uint32_t usbhost_getbe32(const uint8_t *val);
+static void usbhost_putle32(uint8_t *dest, uint32_t val);
+static void usbhost_putbe32(uint8_t *dest, uint32_t val);
+
+/* Transfer descriptor memory management */
+
+static inline int usbhost_talloc(FAR struct usbhost_state_s *priv);
+static inline int usbhost_tfree(FAR struct usbhost_state_s *priv);
+static FAR struct usbstrg_cbw_s *usbhost_cbwalloc(FAR struct usbhost_state_s *priv);
+
+/* struct usbhost_registry_s methods */
+ 
+static struct usbhost_class_s *usbhost_create(FAR struct usbhost_driver_s *drvr,
+                                              FAR const struct usbhost_id_s *id);
+
+/* struct usbhost_class_s methods */
+
+static int usbhost_connect(FAR struct usbhost_class_s *class,
+                           FAR const uint8_t *configdesc, int desclen,
+                           uint8_t funcaddr);
+static int usbhost_disconnected(FAR struct usbhost_class_s *class);
+
+/* struct block_operations methods */
+
+static int usbhost_open(FAR struct inode *inode);
+static int usbhost_close(FAR struct inode *inode);
+static ssize_t usbhost_read(FAR struct inode *inode, FAR unsigned char *buffer,
+                            size_t startsector, unsigned int nsectors);
+#ifdef CONFIG_FS_WRITABLE
+static ssize_t usbhost_write(FAR struct inode *inode,
+                             FAR const unsigned char *buffer, size_t startsector,
+                             unsigned int nsectors);
+#endif
+static int usbhost_geometry(FAR struct inode *inode,
+                            FAR struct geometry *geometry);
+static int usbhost_ioctl(FAR struct inode *inode, int cmd,
+                         unsigned long arg);
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/* This structure provides the registry entry ID informatino that will  be 
+ * used to associate the USB host mass storage class to a connected USB
+ * device.
+ */
+
+static const const struct usbhost_id_s g_id =
+{
+  USB_CLASS_MASS_STORAGE, /* base     */
+  USBSTRG_SUBCLASS_SCSI,  /* subclass */
+  USBSTRG_PROTO_BULKONLY, /* proto    */
+  0,                      /* vid      */
+  0                       /* pid      */
+};
+
+/* This is the USB host storage class's registry entry */
+
+static struct usbhost_registry_s g_storage =
+{
+  NULL,                   /* flink    */
+  usbhost_create,         /* create   */
+  1,                      /* nids     */
+  &g_id                   /* id[]     */
+};
+
+/* Block driver operations.  This is the interface exposed to NuttX by the
+ * class that permits it to behave like a block driver.
+ */
+
+static const struct block_operations g_bops =
+{
+  usbhost_open,           /* open     */
+  usbhost_close,          /* close    */
+  usbhost_read,           /* read     */
+#ifdef CONFIG_FS_WRITABLE
+  usbhost_write,          /* write    */
+#else
+  NULL,                   /* write    */
+#endif
+  usbhost_geometry,       /* geometry */
+  usbhost_ioctl           /* ioctl    */
+};
+
+/* This is an array of pre-allocated USB host storage class instances */
+
+#if CONFIG_USBHOST_NPREALLOC > 0
+static struct usbhost_state_s g_prealloc[CONFIG_USBHOST_NPREALLOC];
+#endif
+
+/* This is a list of free, pre-allocated USB host storage class instances */
+
+#if CONFIG_USBHOST_NPREALLOC > 0
+static struct usbhost_state_s *g_freelist;
+#endif
+
+/* This is a bitmap that is used to allocate device names /dev/sda-z. */
+
+static uint32_t g_devinuse;
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: usbhost_takesem
+ *
+ * Description:
+ *   This is just a wrapper to handle the annoying behavior of semaphore
+ *   waits that return due to the receipt of a signal.
+ *
+ ****************************************************************************/
+
+static void usbhost_takesem(sem_t *sem)
+{
+  /* Take the semaphore (perhaps waiting) */
+
+  while (sem_wait(sem) != 0)
+    {
+      /* The only case that an error should occr here is if the wait was
+       * awakened by a signal.
+       */
+
+      ASSERT(errno == EINTR);
+    }
+}
+
+/****************************************************************************
+ * Name: usbhost_allocclass
+ *
+ * Description:
+ *   This is really part of the logic that implements the create() method
+ *   of struct usbhost_registry_s.  This function allocates memory for one
+ *   new class instance.
+ *
+ * Input Parameters:
+ *   None
+ *
+ * Returned Values:
+ *   On success, this function will return a non-NULL instance of struct
+ *   usbhost_class_s.  NULL is returned on failure; this function will
+ *   will fail only if there are insufficient resources to create another
+ *   USB host class instance.
+ *
+ ****************************************************************************/
+
+#if CONFIG_USBHOST_NPREALLOC > 0
+static inline FAR struct usbhost_state_s *usbhost_allocclass(void)
+{
+  struct usbhost_state_s *priv;
+  irqstate_t flags;
+
+  /* We may be executing from an interrupt handler so we need to take one of
+   * our pre-allocated class instances from the free list.
+   */
+
+  flags = irqsave();
+  priv = g_freelist;
+  if (priv)
+    {
+      g_freelist        = priv->class.flink;
+      priv->class.flink = NULL;
+    }
+  irqrestore(flags);
+  ullvdbg("Allocated: %p\n", priv);;
+  return priv;
+}
+#else
+static inline FAR struct usbhost_state_s *usbhost_allocclass(void)
+{
+  FAR struct usbhost_state_s *priv;
+
+  /* We are not executing from an interrupt handler so we can just call
+   * kmalloc() to get memory for the class instance.
+   */
+
+  DEBUGASSERT(!up_interrupt_context());
+  priv = (FAR struct usbhost_state_s *)kmalloc(sizeof(struct usbhost_state_s));
+  uvdbg("Allocated: %p\n", priv);;
+  return priv;
+}
+#endif
+
+/****************************************************************************
+ * Name: usbhost_freeclass
+ *
+ * Description:
+ *   Free a class instance previously allocated by usbhost_allocclass().
+ *
+ * Input Parameters:
+ *   class - A reference to the class instance to be freed.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+#if CONFIG_USBHOST_NPREALLOC > 0
+static inline void usbhost_freeclass(FAR struct usbhost_state_s *class)
+{
+  irqstate_t flags;
+  DEBUGASSERT(class != NULL);
+
+  ullvdbg("Freeing: %p\n", class);;
+
+  /* Just put the pre-allocated class structure back on the freelist */
+
+  flags = irqsave();
+  class->class.flink = g_freelist;
+  g_freelist = class;
+  irqrestore(flags);  
+}
+#else
+static inline void usbhost_freeclass(FAR struct usbhost_state_s *class)
+{
+  DEBUGASSERT(class != NULL);
+
+  /* Free the class instance (calling sched_free() in case we are executing
+   * from an interrupt handler.
+   */
+
+  uvdbg("Freeing: %p\n", class);;
+  kfree(class);
+}
+#endif
+
+/****************************************************************************
+ * Name: Device name management
+ *
+ * Description:
+ *   Some tiny functions to coordinate management of mass storage device names.
+ *
+ ****************************************************************************/
+
+static int usbhost_allocdevno(FAR struct usbhost_state_s *priv)
+{
+  irqstate_t flags;
+  int devno;
+
+  flags = irqsave();
+  for (devno = 0; devno < 26; devno++)
+    {
+      uint32_t bitno = 1 << devno;
+      if ((g_devinuse & bitno) == 0)
+        {
+          g_devinuse |= bitno;
+          priv->sdchar = 'a' + devno;
+          irqrestore(flags);
+          return OK;
+        }
+    }
+
+  irqrestore(flags);
+  return -EMFILE;
+}
+
+static void usbhost_freedevno(FAR struct usbhost_state_s *priv)
+{
+  int devno = 'a' - priv->sdchar;
+
+  if (devno >= 0 && devno < 26)
+    {
+      irqstate_t flags = irqsave();
+      g_devinuse &= ~(1 << devno);
+      irqrestore(flags);
+    }
+}
+
+static inline void usbhost_mkdevname(FAR struct usbhost_state_s *priv, char *devname)
+{
+  (void)snprintf(devname, DEV_NAMELEN, DEV_FORMAT, priv->sdchar);
+}
+
+/****************************************************************************
+ * Name: CBW/CSW debug helpers
+ *
+ * Description:
+ *   The following functions are helper functions used to dump CBWs and CSWs.
+ *
+ * Input Parameters:
+ *   cbw/csw - A reference to the CBW/CSW to dump.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+#if defined(CONFIG_DEBUG_USB) && defined(CONFIG_DEBUG_VERBOSE)
+static void usbhost_dumpcbw(FAR struct usbstrg_cbw_s *cbw)
+{
+  int i;
+
+  uvdbg("CBW:\n");
+  uvdbg("  signature: %08x\n", usbhost_getle32(cbw->signature));
+  uvdbg("  tag:       %08x\n", usbhost_getle32(cbw->tag));
+  uvdbg("  datlen:    %08x\n", usbhost_getle32(cbw->datlen));
+  uvdbg("  flags:     %02x\n", cbw->flags);
+  uvdbg("  lun:       %02x\n", cbw->lun);
+  uvdbg("  cdblen:    %02x\n", cbw->cdblen);
+
+  uvdbg("CDB:\n");
+  for (i = 0; i < cbw->cdblen; i += 8)
+    {
+      uvdbg("  %02x %02x %02x %02x %02x %02x %02x %02x\n",
+            cbw->cdb[i],   cbw->cdb[i+1], cbw->cdb[i+2], cbw->cdb[i+3],
+            cbw->cdb[i+4], cbw->cdb[i+5], cbw->cdb[i+6], cbw->cdb[i+7]);
+    }
+}
+
+static void usbhost_dumpcsw(FAR struct usbstrg_csw_s *csw)
+{
+  uvdbg("CSW:\n");
+  uvdbg("  signature: %08x\n", usbhost_getle32(csw->signature));
+  uvdbg("  tag:       %08x\n", usbhost_getle32(csw->tag));
+  uvdbg("  residue:   %08x\n", usbhost_getle32(csw->residue));
+  uvdbg("  status:    %02x\n", csw->status);
+}
+#endif
+
+/****************************************************************************
+ * Name: CBW helpers
+ *
+ * Description:
+ *   The following functions are helper functions used to format CBWs.
+ *
+ * Input Parameters:
+ *   cbw - A reference to allocated and initialized CBW to be built.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+static inline void usbhost_requestsensecbw(FAR struct usbstrg_cbw_s *cbw)
+{
+  FAR struct scsicmd_requestsense_s *reqsense;
+
+  /* Format the CBW */
+
+  usbhost_putle32(cbw->datlen, SCSIRESP_FIXEDSENSEDATA_SIZEOF);
+  cbw->flags         = USBSTRG_CBWFLAG_IN;
+  cbw->cdblen        = SCSICMD_REQUESTSENSE_SIZEOF;
+
+  /* Format the CDB */
+
+  reqsense           = (FAR struct scsicmd_requestsense_s *)cbw->cdb;
+  reqsense->opcode   = SCSI_CMD_REQUESTSENSE;
+  reqsense->alloclen = SCSIRESP_FIXEDSENSEDATA_SIZEOF;
+
+  usbhost_dumpcbw(cbw);
+}
+
+static inline void usbhost_testunitreadycbw(FAR struct usbstrg_cbw_s *cbw)
+{
+  /* Format the CBW */
+
+  cbw->cdblen = SCSICMD_TESTUNITREADY_SIZEOF;
+
+  /* Format the CDB */
+
+  cbw->cdb[0] = SCSI_CMD_TESTUNITREADY;
+
+  usbhost_dumpcbw(cbw);
+}
+
+static inline void usbhost_readcapacitycbw(FAR struct usbstrg_cbw_s *cbw)
+{
+  FAR struct scsicmd_readcapacity10_s *rcap10;
+
+  /* Format the CBW */
+
+  usbhost_putle32(cbw->datlen, SCSIRESP_READCAPACITY10_SIZEOF);
+  cbw->flags     = USBSTRG_CBWFLAG_IN;
+  cbw->cdblen    = SCSICMD_READCAPACITY10_SIZEOF;
+
+  /* Format the CDB */
+
+  rcap10         = (FAR struct scsicmd_readcapacity10_s *)cbw->cdb;
+  rcap10->opcode = SCSI_CMD_READCAPACITY10;
+
+  usbhost_dumpcbw(cbw);
+}
+
+static inline void usbhost_inquirycbw (FAR struct usbstrg_cbw_s *cbw)
+{
+  FAR struct scscicmd_inquiry_s *inq;
+
+  /* Format the CBW */
+
+  usbhost_putle32(cbw->datlen, SCSIRESP_INQUIRY_SIZEOF);
+  cbw->flags    = USBSTRG_CBWFLAG_IN;
+  cbw->cdblen   = SCSICMD_INQUIRY_SIZEOF;
+
+  /* Format the CDB */
+
+  inq           = (FAR struct scscicmd_inquiry_s *)cbw->cdb;
+  inq->opcode   = SCSI_CMD_INQUIRY;
+  usbhost_putbe16(inq->alloclen, SCSIRESP_INQUIRY_SIZEOF);
+
+  usbhost_dumpcbw(cbw);
+}
+
+static inline void
+usbhost_readcbw (size_t startsector, uint16_t blocksize,
+                 unsigned int nsectors, FAR struct usbstrg_cbw_s *cbw)
+{
+  FAR struct scsicmd_read10_s *rd10;
+
+  /* Format the CBW */
+
+  usbhost_putle32(cbw->datlen, blocksize * nsectors);
+  cbw->flags   = USBSTRG_CBWFLAG_IN;
+  cbw->cdblen  = SCSICMD_READ10_SIZEOF;
+
+  /* Format the CDB */
+
+  rd10 = (FAR struct scsicmd_read10_s *)cbw->cdb;
+  rd10->opcode = SCSI_CMD_READ10;
+  usbhost_putbe32(rd10->lba, startsector);
+  usbhost_putbe16(rd10->xfrlen, nsectors);
+
+  usbhost_dumpcbw(cbw);
+}
+
+static inline void
+usbhost_writecbw(size_t startsector, uint16_t blocksize,
+                 unsigned int nsectors, FAR struct usbstrg_cbw_s *cbw)
+{
+  FAR struct scsicmd_write10_s *wr10;
+
+  /* Format the CBW */
+
+  usbhost_putle32(cbw->datlen, blocksize * nsectors);
+  cbw->cdblen  = SCSICMD_WRITE10_SIZEOF;
+
+  /* Format the CDB */
+
+  wr10 = (FAR struct scsicmd_write10_s *)cbw->cdb;
+  wr10->opcode = SCSI_CMD_WRITE10;
+  usbhost_putbe32(wr10->lba, startsector);
+  usbhost_putbe16(wr10->xfrlen, nsectors);
+
+  usbhost_dumpcbw(cbw);
+}
+
+/****************************************************************************
+ * Name: Command helpers
+ *
+ * Description:
+ *   The following functions are helper functions used to send commands.
+ *
+ * Input Parameters:
+ *   priv - A reference to the class instance.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+static inline int usbhost_maxlunreq(FAR struct usbhost_state_s *priv)
+{
+  FAR struct usb_ctrlreq_s *req = (FAR struct usb_ctrlreq_s *)priv->tbuffer;
+  DEBUGASSERT(priv && priv->tbuffer);
+  int ret;
+
+  /* Request maximum logical unit number.  NOTE: On an IN transaction, The
+   * req and buffer pointers passed to DRVR_CTRLIN may refer to the same
+   * allocated memory.
+   */
+
+  uvdbg("Request maximum logical unit number\n");
+  memset(req, 0, sizeof(struct usb_ctrlreq_s));
+  req->type    = USB_DIR_IN|USB_REQ_TYPE_CLASS|USB_REQ_RECIPIENT_INTERFACE;
+  req->req     = USBSTRG_REQ_GETMAXLUN;
+  usbhost_putle16(req->len, 1);
+
+  ret = DRVR_CTRLIN(priv->drvr, req, priv->tbuffer);
+  if (ret != OK)
+    {
+      /* Devices that do not support multiple LUNs may stall this command.
+       * On a failure, a single LUN is assumed.
+       */
+
+      *(priv->tbuffer) = 0;
+    }
+  return OK;
+}
+
+static inline int usbhost_testunitready(FAR struct usbhost_state_s *priv)
+{
+  FAR struct usbstrg_cbw_s *cbw;
+  int result;
+
+  /* Initialize a CBW (re-using the allocated transfer buffer) */
+ 
+  cbw = usbhost_cbwalloc(priv);
+  if (!cbw)
+    {
+      udbg("ERROR: Failed to create CBW\n");
+      return -ENOMEM;
+    }
+  
+  /* Construct and send the CBW */
+ 
+  usbhost_testunitreadycbw(cbw);
+  result = DRVR_TRANSFER(priv->drvr, priv->bulkout,
+                        (uint8_t*)cbw, USBSTRG_CBW_SIZEOF);
+  if (result == OK)
+    {
+      /* Receive the CSW */
+
+      result = DRVR_TRANSFER(priv->drvr, priv->bulkin,
+                             priv->tbuffer, USBSTRG_CSW_SIZEOF);
+      if (result == OK)
+        {
+          usbhost_dumpcsw((FAR struct usbstrg_csw_s *)priv->tbuffer);
+        }
+    }
+  return result;
+}
+
+static inline int usbhost_requestsense(FAR struct usbhost_state_s *priv)
+{
+  FAR struct usbstrg_cbw_s *cbw;
+  int result;
+
+  /* Initialize a CBW (re-using the allocated transfer buffer) */
+ 
+  cbw = usbhost_cbwalloc(priv);
+  if (!cbw)
+    {
+      udbg("ERROR: Failed to create CBW\n");
+      return -ENOMEM;
+    }
+
+  /* Construct and send the CBW */
+ 
+  usbhost_requestsensecbw(cbw);
+  result = DRVR_TRANSFER(priv->drvr, priv->bulkout,
+                        (uint8_t*)cbw, USBSTRG_CBW_SIZEOF);
+  if (result == OK)
+    {
+      /* Receive the sense data response */
+
+      result = DRVR_TRANSFER(priv->drvr, priv->bulkin,
+                             priv->tbuffer, SCSIRESP_FIXEDSENSEDATA_SIZEOF);
+      if (result == OK)
+        {
+          /* Receive the CSW */
+
+          result = DRVR_TRANSFER(priv->drvr, priv->bulkin,
+                                 priv->tbuffer, USBSTRG_CSW_SIZEOF);
+          if (result == OK)
+            {
+              usbhost_dumpcsw((FAR struct usbstrg_csw_s *)priv->tbuffer);
+            }
+        }
+    }
+
+  return result;
+}
+
+static inline int usbhost_readcapacity(FAR struct usbhost_state_s *priv)
+{
+  FAR struct usbstrg_cbw_s *cbw;
+  FAR struct scsiresp_readcapacity10_s *resp;
+  int result;
+
+  /* Initialize a CBW (re-using the allocated transfer buffer) */
+ 
+  cbw = usbhost_cbwalloc(priv);
+  if (!cbw)
+    {
+      udbg("ERROR: Failed to create CBW\n");
+      return -ENOMEM;
+    }
+
+  /* Construct and send the CBW */
+ 
+  usbhost_readcapacitycbw(cbw);
+  result = DRVR_TRANSFER(priv->drvr, priv->bulkout,
+                        (uint8_t*)cbw, USBSTRG_CBW_SIZEOF);
+  if (result == OK)
+    {
+      /* Receive the read capacity CBW IN response */
+
+      result = DRVR_TRANSFER(priv->drvr, priv->bulkin,
+                             priv->tbuffer, SCSIRESP_READCAPACITY10_SIZEOF);
+      if (result == OK)
+        {
+          /* Save the capacity information */
+
+          resp            = (FAR struct scsiresp_readcapacity10_s *)priv->tbuffer;
+          priv->nblocks   = usbhost_getbe32(resp->lba) + 1;
+          priv->blocksize = usbhost_getbe32(resp->blklen);
+
+          /* Receive the CSW */
+
+          result = DRVR_TRANSFER(priv->drvr, priv->bulkin,
+                                 priv->tbuffer, USBSTRG_CSW_SIZEOF);
+          if (result == OK)
+            {
+              usbhost_dumpcsw((FAR struct usbstrg_csw_s *)priv->tbuffer);
+            }
+        }
+    }
+
+  return result;
+}
+
+static inline int usbhost_inquiry(FAR struct usbhost_state_s *priv)
+{
+  FAR struct usbstrg_cbw_s *cbw;
+  FAR struct scsiresp_inquiry_s *resp;
+  int result;
+
+  /* Initialize a CBW (re-using the allocated transfer buffer) */
+ 
+  cbw = usbhost_cbwalloc(priv);
+  if (!cbw)
+    {
+      udbg("ERROR: Failed to create CBW\n");
+      return -ENOMEM;
+    }
+
+  /* Construct and send the CBW */
+ 
+  usbhost_inquirycbw(cbw);
+  result = DRVR_TRANSFER(priv->drvr, priv->bulkout,
+                         (uint8_t*)cbw, USBSTRG_CBW_SIZEOF);
+  if (result == OK)
+    {
+      /* Receive the CBW IN response */
+
+      result = DRVR_TRANSFER(priv->drvr, priv->bulkin,
+                             priv->tbuffer, SCSIRESP_INQUIRY_SIZEOF);
+      if (result == OK)
+        {
+          /* TODO: If USB debug is enabled, dump the response data here */
+
+          resp = (FAR struct scsiresp_inquiry_s *)priv->tbuffer;
+
+          /* Receive the CSW */
+
+          result = DRVR_TRANSFER(priv->drvr, priv->bulkin,
+                                 priv->tbuffer, USBSTRG_CSW_SIZEOF);
+          if (result == OK)
+            {
+              usbhost_dumpcsw((FAR struct usbstrg_csw_s *)priv->tbuffer);
+            }
+        }
+    }
+
+  return result;
+}
+
+/****************************************************************************
+ * Name: usbhost_destroy
+ *
+ * Description:
+ *   The USB mass storage device has been disconnected and the refernce count
+ *   on the USB host class instance has gone to 1.. Time to destroy the USB
+ *   host class instance.
+ *
+ * Input Parameters:
+ *   arg - A reference to the class instance to be destroyed.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+static void usbhost_destroy(FAR void *arg)
+{
+  FAR struct usbhost_state_s *priv = (FAR struct usbhost_state_s *)arg;
+  char devname[DEV_NAMELEN];
+
+  DEBUGASSERT(priv != NULL);
+  uvdbg("crefs: %d\n", priv->crefs);
+ 
+  /* Unregister the block driver */
+
+  usbhost_mkdevname(priv, devname);
+  (void)unregister_blockdriver(devname);
+
+  /* Release the device name used by this connection */
+
+  usbhost_freedevno(priv);
+
+  /* Free the bulk endpoints */
+
+  if (priv->bulkout)
+    {
+      DRVR_EPFREE(priv->drvr, priv->bulkout);
+    }
+
+  if (priv->bulkin)
+    {
+      DRVR_EPFREE(priv->drvr, priv->bulkin);
+    }
+
+  /* Free any transfer buffers */
+
+  usbhost_tfree(priv);
+
+  /* Destroy the semaphores */
+
+  sem_destroy(&priv->exclsem);
+
+  /* Disconnect the USB host device */
+
+  DRVR_DISCONNECT(priv->drvr);
+
+  /* And free the class instance.  Hmmm.. this may execute on the worker
+   * thread and the work structure is part of what is getting freed.  That
+   * should be okay because once the work contained is removed from the
+   * queue, it should not longer be accessed by the worker thread.
+   */
+
+  usbhost_freeclass(priv);
+}
+
+/****************************************************************************
+ * Name: usbhost_cfgdesc
+ *
+ * Description:
+ *   This function implements the connect() method of struct
+ *   usbhost_class_s.  This method is a callback into the class
+ *   implementation.  It is used to provide the device's configuration
+ *   descriptor to the class so that the class may initialize properly
+ *
+ * Input Parameters:
+ *   priv - The USB host class instance.
+ *   configdesc - A pointer to a uint8_t buffer container the configuration descripor.
+ *   desclen - The length in bytes of the configuration descriptor.
+ *   funcaddr - The USB address of the function containing the endpoint that EP0
+ *     controls
+ *
+ * Returned Values:
+ *   On success, zero (OK) is returned. On a failure, a negated errno value is
+ *   returned indicating the nature of the failure
+ *
+ * Assumptions:
+ *   This function will *not* be called from an interrupt handler.
+ *
+ ****************************************************************************/
+
+static inline int usbhost_cfgdesc(FAR struct usbhost_state_s *priv,
+                                  FAR const uint8_t *configdesc, int desclen,
+                                  uint8_t funcaddr)
+{
+  FAR struct usb_cfgdesc_s *cfgdesc;
+  FAR struct usb_desc_s *desc;
+  FAR struct usbhost_epdesc_s bindesc;
+  FAR struct usbhost_epdesc_s boutdesc;
+  int remaining;
+  uint8_t found = 0;
+  int ret;
+
+  DEBUGASSERT(priv != NULL && 
+              configdesc != NULL &&
+              desclen >= sizeof(struct usb_cfgdesc_s));
+  
+  /* Verify that we were passed a configuration descriptor */
+
+  cfgdesc = (FAR struct usb_cfgdesc_s *)configdesc;
+  if (cfgdesc->type != USB_DESC_TYPE_CONFIG)
+    {
+      return -EINVAL;
+    }
+
+  /* Get the total length of the configuration descriptor (little endian).
+   * It might be a good check to get the number of interfaces here too.
+  */
+
+  remaining = (int)usbhost_getle16(cfgdesc->totallen);
+
+  /* Skip to the next entry descriptor */
+
+  configdesc += cfgdesc->len;
+  remaining  -= cfgdesc->len;
+
+  /* Loop where there are more dscriptors to examine */
+
+  while (remaining >= sizeof(struct usb_desc_s))
+    {
+      /* What is the next descriptor? */
+
+      desc = (FAR struct usb_desc_s *)configdesc;
+      switch (desc->type)
+        {
+        /* Interface descriptor. We really should get the number of endpoints
+         * from this descriptor too.
+         */
+
+        case USB_DESC_TYPE_INTERFACE:
+          {
+            FAR struct usb_ifdesc_s *ifdesc = (FAR struct usb_ifdesc_s *)configdesc;
+ 
+            uvdbg("Interface descriptor\n");
+            DEBUGASSERT(remaining >= USB_SIZEOF_IFDESC);
+
+            /* Save the interface number and mark ONLY the interface found */
+
+            priv->ifno = ifdesc->ifno;
+            found      = USBHOST_IFFOUND;
+          }
+          break;
+
+        /* Endpoint descriptor.  We expect two bulk endpoints, an IN and an
+         * OUT.
+         */
+
+        case USB_DESC_TYPE_ENDPOINT:
+          {
+            FAR struct usb_epdesc_s *epdesc = (FAR struct usb_epdesc_s *)configdesc;
+
+            uvdbg("Endpoint descriptor\n");
+            DEBUGASSERT(remaining >= USB_SIZEOF_EPDESC);
+
+            /* Check for a bulk endpoint.  We only support the bulk-only
+             * protocol so I suppose anything else should really be an error.
+             */
+
+            if ((epdesc->attr & USB_EP_ATTR_XFERTYPE_MASK) == USB_EP_ATTR_XFER_BULK)
+              {
+                /* Yes.. it is a bulk endpoint.  IN or OUT? */
+
+                if (USB_ISEPOUT(epdesc->addr))
+                  {
+                    /* It is an OUT bulk endpoint.  There should be only one
+                     * bulk OUT endpoint.
+                     */
+
+                    if ((found & USBHOST_BOUTFOUND) != 0)
+                      {
+                        /* Oops.. more than one endpoint.  We don't know
+                         * what to do with this.
+                         */
+
+                        return -EINVAL;
+                      }
+                    found |= USBHOST_BOUTFOUND;
+
+                    /* Save the bulk OUT endpoint information */
+
+                    boutdesc.addr         = epdesc->addr & USB_EP_ADDR_NUMBER_MASK;
+                    boutdesc.in           = false;
+                    boutdesc.funcaddr     = funcaddr;
+                    boutdesc.xfrtype      = USB_EP_ATTR_XFER_BULK;
+                    boutdesc.interval     = epdesc->interval;
+                    boutdesc.mxpacketsize = usbhost_getle16(epdesc->mxpacketsize);
+                    uvdbg("Bulk OUT EP addr:%d mxpacketsize:%d\n",
+                          boutdesc.addr, boutdesc.mxpacketsize);
+                  }
+                else
+                  {
+                    /* It is an IN bulk endpoint.  There should be only one
+                     * bulk IN endpoint.
+                     */
+
+                    if ((found & USBHOST_BINFOUND) != 0)
+                      {
+                        /* Oops.. more than one endpoint.  We don't know
+                         * what to do with this.
+                         */
+
+                        return -EINVAL;
+                      }
+                    found |= USBHOST_BINFOUND;
+
+                    /* Save the bulk IN endpoint information */
+                    
+                    bindesc.addr         = epdesc->addr & USB_EP_ADDR_NUMBER_MASK;
+                    bindesc.in           = 1;
+                    bindesc.funcaddr     = funcaddr;
+                    bindesc.xfrtype      = USB_EP_ATTR_XFER_BULK;
+                    bindesc.interval     = epdesc->interval;
+                    bindesc.mxpacketsize = usbhost_getle16(epdesc->mxpacketsize);
+                    uvdbg("Bulk IN EP addr:%d mxpacketsize:%d\n",
+                          bindesc.addr, bindesc.mxpacketsize);
+                  }
+              }
+          }
+          break;
+
+        /* Other descriptors are just ignored for now */
+
+        default:
+          break;
+        }
+
+      /* If we found everything we need with this interface, then break out
+       * of the loop early.
+       */
+
+      if (found == USBHOST_ALLFOUND)
+        {
+          break;
+        }
+
+      /* Increment the address of the next descriptor */
+ 
+      configdesc += desc->len;
+      remaining  -= desc->len;
+    }
+
+  /* Sanity checking... did we find all of things that we need? Hmmm..  I wonder..
+   * can we work read-only or write-only if only one bulk endpoint found?
+   */
+    
+  if (found != USBHOST_ALLFOUND)
+    {
+      ulldbg("ERROR: Found IF:%s BIN:%s BOUT:%s\n",
+             (found & USBHOST_IFFOUND) != 0  ? "YES" : "NO",
+             (found & USBHOST_BINFOUND) != 0 ? "YES" : "NO",
+             (found & USBHOST_BOUTFOUND) != 0 ? "YES" : "NO");
+      return -EINVAL;
+    }
+
+  /* We are good... Allocate the endpoints */
+
+  ret = DRVR_EPALLOC(priv->drvr, &boutdesc, &priv->bulkout);
+  if (ret != OK)
+    {
+      udbg("ERROR: Failed to allocate Bulk OUT endpoint\n");
+      return ret;
+    }
+
+  ret = DRVR_EPALLOC(priv->drvr, &bindesc, &priv->bulkin);
+  if (ret != OK)
+    {
+      udbg("ERROR: Failed to allocate Bulk IN endpoint\n");
+      (void)DRVR_EPFREE(priv->drvr, priv->bulkout);
+      return ret;
+    }
+
+  ullvdbg("Endpoints allocated\n");
+  return OK;
+}
+
+/****************************************************************************
+ * Name: usbhost_initvolume
+ *
+ * Description:
+ *   The USB mass storage device has been successfully connected.  This
+ *   completes the initialization operations.  It is first called after the
+ *   configuration descriptor has been received.
+ *
+ *   This function is called from the connect() method.  This function always
+ *   executes on the thread of the caller of connect().
+ *
+ * Input Parameters:
+ *   priv - A reference to the class instance.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+static inline int usbhost_initvolume(FAR struct usbhost_state_s *priv)
+{
+  FAR struct usbstrg_csw_s *csw;
+  unsigned int retries;
+  int ret = OK;
+
+  DEBUGASSERT(priv != NULL);
+
+  /* Set aside a transfer buffer for exclusive use by the mass storage driver */
+
+  ret = usbhost_talloc(priv);
+  if (ret != OK)
+    {
+      udbg("ERROR: Failed to allocate transfer buffer\n");
+      return ret;
+    }
+
+  /* Increment the reference count.  This will prevent usbhost_destroy() from
+   * being called asynchronously if the device is removed.
+   */
+
+  priv->crefs++;
+  DEBUGASSERT(priv->crefs == 2);
+
+  /* Request the maximum logical unit number */
+
+  uvdbg("Get max LUN\n");
+  ret = usbhost_maxlunreq(priv);
+
+  /* Wait for the unit to be ready */
+
+  for (retries = 0; retries < USBHOST_MAX_RETRIES && ret == OK; retries++)
+    {
+      uvdbg("Test unit ready, retries=%d\n", retries);
+
+      /* Send TESTUNITREADY to see the unit is ready */
+      
+      ret = usbhost_testunitready(priv);
+      if (ret == OK)
+        {
+          /* Is the unit is ready */
+
+          csw = (FAR struct usbstrg_csw_s *)priv->tbuffer;
+          if (csw->status == 0)
+            {
+              /* Yes... break out of the loop */
+
+              break;
+            }
+
+          /* No.. Request mode sense information.  The REQUEST SENSE command
+           * is sent only "to clear interlocked unit attention conditions."
+           * The returned status is ignored here.
+           */
+
+          uvdbg("Request sense\n");
+          ret = usbhost_requestsense(priv);
+        }
+    }
+
+  /* Did the unit become ready?  Did an error occur? Or did we time out? */
+
+  if (retries >= USBHOST_MAX_RETRIES)
+    {
+      udbg("ERROR: Timeout!\n");
+      ret = -ETIMEDOUT;
+    }
+
+  if (ret == OK)
+    {
+      /* Get the capacity of the volume */
+
+      uvdbg("Read capacity\n");
+      ret = usbhost_readcapacity(priv);
+      if (ret == OK)
+        {
+          /* Check the CSW for errors */
+
+          csw = (FAR struct usbstrg_csw_s *)priv->tbuffer;
+          if (csw->status != 0)
+            {
+              udbg("ERROR: CSW status error: %d\n", csw->status);
+              ret = -ENODEV;
+            }
+        }
+    }
+
+  /* Get information about the volume */
+
+  if (ret == OK)
+    {
+      /* Inquiry */
+
+      uvdbg("Inquiry\n");
+      ret = usbhost_inquiry(priv);
+      if (ret == OK)
+        {
+          /* Check the CSW for errors */
+
+          csw = (FAR struct usbstrg_csw_s *)priv->tbuffer;
+          if (csw->status != 0)
+            {
+              udbg("ERROR: CSW status error: %d\n", csw->status);
+              ret = -ENODEV;
+            }
+        }
+    }
+
+  /* Register the block driver */
+
+  if (ret == OK)
+    {
+      char devname[DEV_NAMELEN];
+
+      uvdbg("Register block driver\n");
+      usbhost_mkdevname(priv, devname);
+      ret = register_blockdriver(devname, &g_bops, 0, priv);
+    }
+
+  /* Check if we successfully initialized. We now have to be concerned
+   * about asynchronous modification of crefs because the block
+   * driver has been registerd.
+   */
+
+  if (ret == OK)
+    {
+      usbhost_takesem(&priv->exclsem);
+      DEBUGASSERT(priv->crefs >= 2);
+
+      /* Decrement the reference count */
+
+      priv->crefs--;
+
+      /* Handle a corner case where (1) open() has been called so the
+       * reference count was > 2, but the device has been disconnected.
+       * In this case, the class instance needs to persist until close()
+       * is called.
+       */
+
+      if (priv->crefs <= 1 && priv->disconnected)
+        {
+          /* The will cause the enumeration logic to disconnect
+           * the class driver.
+           */
+
+          ret = -ENODEV;
+        }
+
+      /* Release the semaphore... there is a race condition here.
+       * Decrementing the reference count and releasing the semaphore
+       * allows usbhost_destroy() to execute (on the worker thread);
+       * the class driver instance could get destoryed before we are
+       * ready to handle it!
+       */
+
+       usbhost_givesem(&priv->exclsem);
+    }
+
+  return ret;
+}
+
+/****************************************************************************
+ * Name: usbhost_getle16
+ *
+ * Description:
+ *   Get a (possibly unaligned) 16-bit little endian value.
+ *
+ * Input Parameters:
+ *   val - A pointer to the first byte of the little endian value.
+ *
+ * Returned Values:
+ *   A uint16_t representing the whole 16-bit integer value
+ *
+ ****************************************************************************/
+
+static inline uint16_t usbhost_getle16(const uint8_t *val)
+{
+  return (uint16_t)val[1] << 8 | (uint16_t)val[0];
+}
+
+/****************************************************************************
+ * Name: usbhost_getbe16
+ *
+ * Description:
+ *   Get a (possibly unaligned) 16-bit big endian value.
+ *
+ * Input Parameters:
+ *   val - A pointer to the first byte of the big endian value.
+ *
+ * Returned Values:
+ *   A uint16_t representing the whole 16-bit integer value
+ *
+ ****************************************************************************/
+
+static inline uint16_t usbhost_getbe16(const uint8_t *val)
+{
+  return (uint16_t)val[0] << 8 | (uint16_t)val[1];
+}
+
+/****************************************************************************
+ * Name: usbhost_putle16
+ *
+ * Description:
+ *   Put a (possibly unaligned) 16-bit little endian value.
+ *
+ * Input Parameters:
+ *   dest - A pointer to the first byte to save the little endian value.
+ *   val - The 16-bit value to be saved.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+static void usbhost_putle16(uint8_t *dest, uint16_t val)
+{
+  dest[0] = val & 0xff; /* Little endian means LS byte first in byte stream */
+  dest[1] = val >> 8;
+}
+
+/****************************************************************************
+ * Name: usbhost_putbe16
+ *
+ * Description:
+ *   Put a (possibly unaligned) 16-bit big endian value.
+ *
+ * Input Parameters:
+ *   dest - A pointer to the first byte to save the big endian value.
+ *   val - The 16-bit value to be saved.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+static void usbhost_putbe16(uint8_t *dest, uint16_t val)
+{
+  dest[0] = val >> 8; /* Big endian means MS byte first in byte stream */
+  dest[1] = val & 0xff;
+}
+
+/****************************************************************************
+ * Name: usbhost_getle32
+ *
+ * Description:
+ *   Get a (possibly unaligned) 32-bit little endian value.
+ *
+ * Input Parameters:
+ *   dest - A pointer to the first byte to save the big endian value.
+ *   val - The 32-bit value to be saved.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+static inline uint32_t usbhost_getle32(const uint8_t *val)
+{
+ /* Little endian means LS halfword first in byte stream */
+
+  return (uint32_t)usbhost_getle16(&val[2]) << 16 | (uint32_t)usbhost_getle16(val);
+}
+
+/****************************************************************************
+ * Name: usbhost_getbe32
+ *
+ * Description:
+ *   Get a (possibly unaligned) 32-bit big endian value.
+ *
+ * Input Parameters:
+ *   dest - A pointer to the first byte to save the big endian value.
+ *   val - The 32-bit value to be saved.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+static inline uint32_t usbhost_getbe32(const uint8_t *val)
+{
+  /* Big endian means MS halfword first in byte stream */
+
+  return (uint32_t)usbhost_getbe16(val) << 16 | (uint32_t)usbhost_getbe16(&val[2]);
+}
+
+/****************************************************************************
+ * Name: usbhost_putle32
+ *
+ * Description:
+ *   Put a (possibly unaligned) 32-bit little endian value.
+ *
+ * Input Parameters:
+ *   dest - A pointer to the first byte to save the little endian value.
+ *   val - The 32-bit value to be saved.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+static void usbhost_putle32(uint8_t *dest, uint32_t val)
+{
+  /* Little endian means LS halfword first in byte stream */
+
+  usbhost_putle16(dest, (uint16_t)(val & 0xffff));
+  usbhost_putle16(dest+2, (uint16_t)(val >> 16));
+}
+
+/****************************************************************************
+ * Name: usbhost_putbe32
+ *
+ * Description:
+ *   Put a (possibly unaligned) 32-bit big endian value.
+ *
+ * Input Parameters:
+ *   dest - A pointer to the first byte to save the big endian value.
+ *   val - The 32-bit value to be saved.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+static void usbhost_putbe32(uint8_t *dest, uint32_t val)
+{
+  /* Big endian means MS halfword first in byte stream */
+
+  usbhost_putbe16(dest, (uint16_t)(val >> 16));
+  usbhost_putbe16(dest+2, (uint16_t)(val & 0xffff));
+}
+
+/****************************************************************************
+ * Name: usbhost_talloc
+ *
+ * Description:
+ *   Allocate transfer buffer memory.
+ *
+ * Input Parameters:
+ *   priv - A reference to the class instance.
+ *
+ * Returned Values:
+ *   On sucess, zero (OK) is returned.  On failure, an negated errno value
+ *   is returned to indicate the nature of the failure.
+ *
+ ****************************************************************************/
+
+static inline int usbhost_talloc(FAR struct usbhost_state_s *priv)
+{
+  DEBUGASSERT(priv && priv->tbuffer == NULL);
+  return DRVR_ALLOC(priv->drvr, &priv->tbuffer, &priv->tbuflen);
+}
+
+/****************************************************************************
+ * Name: usbhost_tfree
+ *
+ * Description:
+ *   Free transfer buffer memory.
+ *
+ * Input Parameters:
+ *   priv - A reference to the class instance.
+ *
+ * Returned Values:
+ *   On sucess, zero (OK) is returned.  On failure, an negated errno value
+ *   is returned to indicate the nature of the failure.
+ *
+ ****************************************************************************/
+
+static inline int usbhost_tfree(FAR struct usbhost_state_s *priv)
+{
+  int result = OK;
+  DEBUGASSERT(priv);
+
+  if (priv->tbuffer)
+    {
+      DEBUGASSERT(priv->drvr);
+      result         = DRVR_FREE(priv->drvr, priv->tbuffer);
+      priv->tbuffer = NULL;
+      priv->tbuflen = 0;
+    }
+  return result;
+}
+
+/****************************************************************************
+ * Name: usbhost_cbwalloc
+ *
+ * Description:
+ *   Initialize a CBW (re-using the allocated transfer buffer). Upon
+ *   successful return, the CBW is cleared and has the CBW signature in place.
+ *
+ * Input Parameters:
+ *   priv - A reference to the class instance.
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+static FAR struct usbstrg_cbw_s *usbhost_cbwalloc(FAR struct usbhost_state_s *priv)
+{
+  FAR struct usbstrg_cbw_s *cbw = NULL;
+
+  DEBUGASSERT(priv->tbuffer && priv->tbuflen >= sizeof(struct usbstrg_cbw_s))
+
+  /* Intialize the CBW sructure */
+
+  cbw = (FAR struct usbstrg_cbw_s *)priv->tbuffer;
+  memset(cbw, 0, sizeof(struct usbstrg_cbw_s));
+  usbhost_putle32(cbw->signature, USBSTRG_CBW_SIGNATURE);
+  return cbw;
+}
+
+/****************************************************************************
+ * struct usbhost_registry_s methods
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: usbhost_create
+ *
+ * Description:
+ *   This function implements the create() method of struct usbhost_registry_s. 
+ *   The create() method is a callback into the class implementation.  It is
+ *   used to (1) create a new instance of the USB host class state and to (2)
+ *   bind a USB host driver "session" to the class instance.  Use of this
+ *   create() method will support environments where there may be multiple
+ *   USB ports and multiple USB devices simultaneously connected.
+ *
+ * Input Parameters:
+ *   drvr - An instance of struct usbhost_driver_s that the class
+ *     implementation will "bind" to its state structure and will
+ *     subsequently use to communicate with the USB host driver.
+ *   id - In the case where the device supports multiple base classes,
+ *     subclasses, or protocols, this specifies which to configure for.
+ *
+ * Returned Values:
+ *   On success, this function will return a non-NULL instance of struct
+ *   usbhost_class_s that can be used by the USB host driver to communicate
+ *   with the USB host class.  NULL is returned on failure; this function
+ *   will fail only if the drvr input parameter is NULL or if there are
+ *   insufficient resources to create another USB host class instance.
+ *
+ ****************************************************************************/
+
+static FAR struct usbhost_class_s *usbhost_create(FAR struct usbhost_driver_s *drvr,
+                                                  FAR const struct usbhost_id_s *id)
+{
+  FAR struct usbhost_state_s *priv;
+
+  /* Allocate a USB host mass storage class instance */
+
+  priv = usbhost_allocclass();
+  if (priv)
+    {
+      /* Initialize the allocated storage class instance */
+
+      memset(priv, 0, sizeof(struct usbhost_state_s));
+
+      /* Assign a device number to this class instance */
+
+      if (usbhost_allocdevno(priv) == OK)
+        {
+         /* Initialize class method function pointers */
+
+          priv->class.connect      = usbhost_connect;
+          priv->class.disconnected = usbhost_disconnected;
+
+          /* The initial reference count is 1... One reference is held by the driver */
+
+          priv->crefs              = 1;
+
+          /* Initialize semphores (this works okay in the interrupt context) */
+
+          sem_init(&priv->exclsem, 0, 1);
+
+          /* Bind the driver to the storage class instance */
+
+          priv->drvr               = drvr;
+
+          /* NOTE: We do not yet know the geometry of the USB mass storage device */
+ 
+          /* Return the instance of the USB mass storage class */
+ 
+          return &priv->class;
+        }
+    }
+
+  /* An error occurred. Free the allocation and return NULL on all failures */
+
+  if (priv)
+    {
+      usbhost_freeclass(priv);
+    }
+  return NULL;
+}
+
+/****************************************************************************
+ * struct usbhost_class_s methods
+ ****************************************************************************/
+/****************************************************************************
+ * Name: usbhost_connect
+ *
+ * Description:
+ *   This function implements the connect() method of struct
+ *   usbhost_class_s.  This method is a callback into the class
+ *   implementation.  It is used to provide the device's configuration
+ *   descriptor to the class so that the class may initialize properly
+ *
+ * Input Parameters:
+ *   class - The USB host class entry previously obtained from a call to create().
+ *   configdesc - A pointer to a uint8_t buffer container the configuration descripor.
+ *   desclen - The length in bytes of the configuration descriptor.
+ *   funcaddr - The USB address of the function containing the endpoint that EP0
+ *     controls
+ *
+ * Returned Values:
+ *   On success, zero (OK) is returned. On a failure, a negated errno value is
+ *   returned indicating the nature of the failure
+ *
+ *   NOTE that the class instance remains valid upon return with a failure.  It is
+ *   the responsibility of the higher level enumeration logic to call
+ *   CLASS_DISCONNECTED to free up the class driver resources.
+ *
+ * Assumptions:
+ *   - This function will *not* be called from an interrupt handler.
+ *   - If this function returns an error, the USB host controller driver
+ *     must call to DISCONNECTED method to recover from the error
+ *
+ ****************************************************************************/
+
+static int usbhost_connect(FAR struct usbhost_class_s *class,
+                           FAR const uint8_t *configdesc, int desclen,
+                           uint8_t funcaddr)
+{
+  FAR struct usbhost_state_s *priv = (FAR struct usbhost_state_s *)class;
+  int ret;
+
+  DEBUGASSERT(priv != NULL && 
+              configdesc != NULL &&
+              desclen >= sizeof(struct usb_cfgdesc_s));
+
+  /* Parse the configuration descriptor to get the bulk I/O endpoints */
+
+  ret = usbhost_cfgdesc(priv, configdesc, desclen, funcaddr);
+  if (ret != OK)
+    {
+      udbg("usbhost_cfgdesc() failed: %d\n", ret);
+    }
+  else
+    {
+      /* Now configure the LUNs and register the block driver(s) */
+
+      ret = usbhost_initvolume(priv);
+      if (ret != OK)
+        {
+          udbg("usbhost_initvolume() failed: %d\n", ret);
+        }
+    }
+ 
+  return ret;
+}
+
+/****************************************************************************
+ * Name: usbhost_disconnected
+ *
+ * Description:
+ *   This function implements the disconnected() method of struct
+ *   usbhost_class_s.  This method is a callback into the class
+ *   implementation.  It is used to inform the class that the USB device has
+ *   been disconnected.
+ *
+ * Input Parameters:
+ *   class - The USB host class entry previously obtained from a call to
+ *     create().
+ *
+ * Returned Values:
+ *   On success, zero (OK) is returned. On a failure, a negated errno value
+ *   is returned indicating the nature of the failure
+ *
+ * Assumptions:
+ *   This function may be called from an interrupt handler.
+ *
+ ****************************************************************************/
+
+static int usbhost_disconnected(struct usbhost_class_s *class)
+{
+  FAR struct usbhost_state_s *priv = (FAR struct usbhost_state_s *)class;
+  irqstate_t flags;
+
+  DEBUGASSERT(priv != NULL);
+
+  /* Set an indication to any users of the mass storage device that the device
+   * is no longer available.
+   */
+
+  flags              = irqsave();
+  priv->disconnected = true;
+
+  /* Now check the number of references on the class instance.  If it is one,
+   * then we can free the class instance now.  Otherwise, we will have to
+   * wait until the holders of the references free them by closing the
+   * block driver.
+   */
+
+  ullvdbg("crefs: %d\n", priv->crefs);
+  if (priv->crefs == 1)
+    {
+      /* Destroy the class instance.  If we are executing from an interrupt
+       * handler, then defer the destruction to the worker thread.
+       * Otherwise, destroy the instance now.
+       */
+
+      if (up_interrupt_context())
+        {
+          /* Destroy the instance on the worker thread. */
+
+          uvdbg("Queuing destruction: worker %p->%p\n", priv->work.worker, usbhost_destroy);
+          DEBUGASSERT(priv->work.worker == NULL);
+          (void)work_queue(&priv->work, usbhost_destroy, priv, 0);
+       }
+      else
+        {
+          /* Do the work now */
+
+          usbhost_destroy(priv);
+        }
+    }
+
+  irqrestore(flags);  
+  return OK;
+}
+
+/****************************************************************************
+ * struct block_operations methods
+ ****************************************************************************/
+/****************************************************************************
+ * Name: usbhost_open
+ *
+ * Description: Open the block device
+ *
+ ****************************************************************************/
+
+static int usbhost_open(FAR struct inode *inode)
+{
+  FAR struct usbhost_state_s *priv;
+  irqstate_t flags;
+  int ret;
+
+  uvdbg("Entry\n");
+  DEBUGASSERT(inode && inode->i_private);
+  priv = (FAR struct usbhost_state_s *)inode->i_private;
+
+  /* Make sure that we have exclusive access to the private data structure */
+
+  DEBUGASSERT(priv->crefs > 0 && priv->crefs < USBHOST_MAX_CREFS);
+  usbhost_takesem(&priv->exclsem);
+
+  /* Check if the mass storage device is still connected.  We need to disable
+   * interrupts momentarily to assure that there are no asynchronous disconnect
+   * events.
+   */
+
+  flags = irqsave();
+  if (priv->disconnected)
+    {
+      /* No... the block driver is no longer bound to the class.  That means that
+       * the USB storage device is no longer connected.  Refuse any further
+       * attempts to open the driver.
+       */
+
+      ret = -ENODEV;
+    }
+  else
+    {
+      /* Otherwise, just increment the reference count on the driver */
+
+      priv->crefs++;
+      ret = OK;
+    }
+  irqrestore(flags);
+
+  usbhost_givesem(&priv->exclsem);
+  return ret;
+}
+
+/****************************************************************************
+ * Name: usbhost_close
+ *
+ * Description: close the block device
+ *
+ ****************************************************************************/
+
+static int usbhost_close(FAR struct inode *inode)
+{
+  FAR struct usbhost_state_s *priv;
+  irqstate_t flags;
+
+  uvdbg("Entry\n");
+  DEBUGASSERT(inode && inode->i_private);
+  priv = (FAR struct usbhost_state_s *)inode->i_private;
+
+  /* Decrement the reference count on the block driver */
+
+  DEBUGASSERT(priv->crefs > 1);
+  usbhost_takesem(&priv->exclsem);
+  priv->crefs--;
+
+  /* Release the semaphore.  The following operations when crefs == 1 are
+   * safe because we know that there is no outstanding open references to
+   * the block driver.
+   */
+
+  usbhost_givesem(&priv->exclsem);
+
+  /* We need to disable interrupts momentarily to assure that there are
+   * no asynchronous disconnect events.
+   */
+
+  flags = irqsave();
+
+  /* Check if the USB mass storage device is still connected.  If the
+   * storage device is not connected and the reference count just
+   * decremented to one, then unregister the block driver and free
+   * the class instance.
+   */
+
+  if (priv->crefs <= 1 && priv->disconnected)
+    {
+      /* Destroy the class instance */
+
+      DEBUGASSERT(priv->crefs == 1);
+      usbhost_destroy(priv);
+    }
+
+  irqrestore(flags);
+  return OK;
+}
+
+/****************************************************************************
+ * Name: usbhost_read
+ *
+ * Description:
+ *   Read the specified numer of sectors from the read-ahead buffer or from
+ *   the physical device.
+ *
+ ****************************************************************************/
+
+static ssize_t usbhost_read(FAR struct inode *inode, unsigned char *buffer,
+                            size_t startsector, unsigned int nsectors)
+{
+  FAR struct usbhost_state_s *priv;
+  ssize_t ret = 0;
+  int result;
+
+  DEBUGASSERT(inode && inode->i_private);
+  priv = (FAR struct usbhost_state_s *)inode->i_private;
+  uvdbg("startsector: %d nsectors: %d sectorsize: %d\n",
+        startsector, nsectors, priv->blocksize);
+
+  /* Check if the mass storage device is still connected */
+
+  if (priv->disconnected)
+    {
+      /* No... the block driver is no longer bound to the class.  That means that
+       * the USB storage device is no longer connected.  Refuse any attempt to read
+       * from the device.
+       */
+
+      ret = -ENODEV;
+    }
+  else if (nsectors > 0)
+    {
+      FAR struct usbstrg_cbw_s *cbw;
+
+      usbhost_takesem(&priv->exclsem);
+
+      /* Assume allocation failure */
+
+      ret = -ENOMEM;
+
+      /* Initialize a CBW (re-using the allocated transfer buffer) */
+ 
+      cbw = usbhost_cbwalloc(priv);
+      if (cbw)
+        {
+          /* Assume some device failure */
+
+          ret = -ENODEV;
+
+          /* Construct and send the CBW */
+ 
+          usbhost_readcbw(startsector, priv->blocksize, nsectors, cbw);
+          result = DRVR_TRANSFER(priv->drvr, priv->bulkout,
+                                 (uint8_t*)cbw, USBSTRG_CBW_SIZEOF);
+          if (result == OK)
+            {
+              /* Receive the user data */
+
+              result = DRVR_TRANSFER(priv->drvr, priv->bulkin,
+                                     buffer, priv->blocksize * nsectors);
+              if (result == OK)
+                {
+                  /* Receive the CSW */
+
+                  result = DRVR_TRANSFER(priv->drvr, priv->bulkin,
+                                         priv->tbuffer, USBSTRG_CSW_SIZEOF);
+                  if (result == OK)
+                    {
+                      FAR struct usbstrg_csw_s *csw;
+
+                      /* Check the CSW status */
+
+                      csw = (FAR struct usbstrg_csw_s *)priv->tbuffer;
+                      if (csw->status == 0)
+                        {
+                          ret = nsectors;
+                        }
+                    }
+                }
+            }
+        }
+
+      usbhost_givesem(&priv->exclsem);
+    }
+
+  /* On success, return the number of blocks read */
+
+  return ret;
+}
+
+/****************************************************************************
+ * Name: usbhost_write
+ *
+ * Description:
+ *   Write the specified number of sectors to the write buffer or to the
+ *   physical device.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_FS_WRITABLE
+static ssize_t usbhost_write(FAR struct inode *inode, const unsigned char *buffer,
+                           size_t startsector, unsigned int nsectors)
+{
+  FAR struct usbhost_state_s *priv;
+  ssize_t ret;
+  int result;
+
+  uvdbg("sector: %d nsectors: %d sectorsize: %d\n");
+  DEBUGASSERT(inode && inode->i_private);
+  priv = (FAR struct usbhost_state_s *)inode->i_private;
+
+  /* Check if the mass storage device is still connected */
+
+  if (priv->disconnected)
+    {
+      /* No... the block driver is no longer bound to the class.  That means that
+       * the USB storage device is no longer connected.  Refuse any attempt to
+       * write to the device.
+       */
+
+      ret = -ENODEV;
+    }
+  else
+    {
+      FAR struct usbstrg_cbw_s *cbw;
+
+      usbhost_takesem(&priv->exclsem);
+
+     /* Assume allocation failure */
+
+      ret = -ENOMEM;
+
+      /* Initialize a CBW (re-using the allocated transfer buffer) */
+ 
+      cbw = usbhost_cbwalloc(priv);
+      if (cbw)
+        {
+          /* Assume some device failure */
+
+          ret = -ENODEV;
+
+          /* Construct and send the CBW */
+ 
+          usbhost_writecbw(startsector, priv->blocksize, nsectors, cbw);
+          result = DRVR_TRANSFER(priv->drvr, priv->bulkout,
+                                 (uint8_t*)cbw, USBSTRG_CBW_SIZEOF);
+          if (result == OK)
+            {
+              /* Send the user data */
+
+              result = DRVR_TRANSFER(priv->drvr, priv->bulkout,
+                                     (uint8_t*)buffer, priv->blocksize * nsectors);
+              if (result == OK)
+                {
+                  /* Receive the CSW */
+
+                  result = DRVR_TRANSFER(priv->drvr, priv->bulkin,
+                                         priv->tbuffer, USBSTRG_CSW_SIZEOF);
+                  if (result == OK)
+                    {
+                      FAR struct usbstrg_csw_s *csw;
+
+                      /* Check the CSW status */
+
+                      csw = (FAR struct usbstrg_csw_s *)priv->tbuffer;
+                      if (csw->status == 0)
+                        {
+                          ret = nsectors;
+                        }
+                    }
+                }
+            }
+        }
+
+      usbhost_givesem(&priv->exclsem);
+    }
+
+  /* On success, return the number of blocks written */
+
+  return ret;
+}
+#endif
+
+/****************************************************************************
+ * Name: usbhost_geometry
+ *
+ * Description: Return device geometry
+ *
+ ****************************************************************************/
+
+static int usbhost_geometry(FAR struct inode *inode, struct geometry *geometry)
+{
+  FAR struct usbhost_state_s *priv;
+  int ret = -EINVAL;
+
+  uvdbg("Entry\n");
+  DEBUGASSERT(inode && inode->i_private);
+
+  /* Check if the mass storage device is still connected */
+
+  priv = (FAR struct usbhost_state_s *)inode->i_private;
+  if (priv->disconnected)
+    {
+      /* No... the block driver is no longer bound to the class.  That means that
+       * the USB storage device is no longer connected.  Refuse to return any
+       * geometry info.
+       */
+
+      ret = -ENODEV;
+    }
+  else if (geometry)
+    {
+      /* Return the geometry of the USB mass storage device */
+
+      usbhost_takesem(&priv->exclsem);
+
+      geometry->geo_available     = true;
+      geometry->geo_mediachanged  = false;
+#ifdef CONFIG_FS_WRITABLE
+      geometry->geo_writeenabled  = true;
+#else
+      geometry->geo_writeenabled  = false;
+#endif
+      geometry->geo_nsectors      = priv->nblocks;
+      geometry->geo_sectorsize    = priv->blocksize;
+      usbhost_givesem(&priv->exclsem);
+
+      uvdbg("nsectors: %ld sectorsize: %d\n",
+             (long)geometry->geo_nsectors, geometry->geo_sectorsize);
+
+      ret = OK;
+    }
+
+  return ret;
+}
+
+/****************************************************************************
+ * Name: usbhost_ioctl
+ *
+ * Description: Return device geometry
+ *
+ ****************************************************************************/
+
+static int usbhost_ioctl(FAR struct inode *inode, int cmd, unsigned long arg)
+{
+  FAR struct usbhost_state_s *priv;
+  int ret;
+
+  uvdbg("Entry\n");
+  DEBUGASSERT(inode && inode->i_private);
+  priv  = (FAR struct usbhost_state_s *)inode->i_private;
+
+  /* Check if the mass storage device is still connected */
+
+  if (priv->disconnected)
+    {
+      /* No... the block driver is no longer bound to the class.  That means that
+       * the USB storage device is no longer connected.  Refuse to process any
+       * ioctl commands.
+       */
+
+      ret = -ENODEV;
+    }
+  else
+    {
+      /* Process the IOCTL by command */
+
+      usbhost_takesem(&priv->exclsem);
+      switch (cmd)
+        {
+        /* Add support for ioctl commands here */
+
+        default:
+          ret = -ENOTTY;
+          break;
+        }
+      usbhost_givesem(&priv->exclsem);
+    }
+  return ret;
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: usbhost_storageinit
+ *
+ * Description:
+ *   Initialize the USB host storage class.  This function should be called
+ *   be platform-specific code in order to initialize and register support
+ *   for the USB host storage class.
+ *
+ * Input Parameters:
+ *   None
+ *
+ * Returned Values:
+ *   On success this function will return zero (OK);  A negated errno value
+ *   will be returned on failure.
+ *
+ ****************************************************************************/
+
+int usbhost_storageinit(void)
+{
+  /* If we have been configured to use pre-allocated storage class instances,
+   * then place all of the pre-allocated USB host storage class instances
+   * into a free list.
+   */
+
+#if CONFIG_USBHOST_NPREALLOC > 0
+  int i;
+
+  g_freelist = NULL;
+  for (i = 0; i < CONFIG_USBHOST_NPREALLOC; i++)
+    {
+      struct usbhost_state_s *class = &g_prealloc[i];
+      class->class.flink = g_freelist;
+      g_freelist         = class;
+    }
+#endif
+
+  /* Advertise our availability to support (certain) mass storage devices */
+
+  return usbhost_registerclass(&g_storage);
+}
+
+#endif  /* CONFIG_USBHOST && !CONFIG_USBHOST_BULK_DISABLE && !CONFIG_DISABLE_MOUNTPOINT && CONFIG_NFILE_DESCRIPTORS > 0 */