Move all file operations from libc/aio to fs/aio. These will need to be kernel routines in order to handler issues with using file descriptors on worker thread

9 files changed, 1265 insertions, 0 deletions

diff --git a/nuttx/fs/Kconfig b/nuttx/fs/Kconfig
index 9165814dc..85de5acd6 100644
--- a/nuttx/fs/Kconfig
+++ b/nuttx/fs/Kconfig
@@ -48,6 +48,7 @@ config FS_WRITABLE
 	bool
 	default n
 
+source fs/aio/Kconfig
 source fs/semaphore/Kconfig
 source fs/mqueue/Kconfig
 source fs/shm/Kconfig
diff --git a/nuttx/fs/Makefile b/nuttx/fs/Makefile
index 2d3a97422..92f1a9400 100644
--- a/nuttx/fs/Makefile
+++ b/nuttx/fs/Makefile
@@ -47,6 +47,7 @@ include inode/Make.defs
 include vfs/Make.defs
 include driver/Make.defs
 include dirent/Make.defs
+include aio/Make.defs
 include mmap/Make.defs
 
 # OS resources
diff --git a/nuttx/fs/aio/Make.defs b/nuttx/fs/aio/Make.defs
new file mode 100644
index 000000000..c1d0bea8a
--- /dev/null
+++ b/nuttx/fs/aio/Make.defs
@@ -0,0 +1,46 @@
+############################################################################
+# fs/aio/Make.defs
+#
+#   Copyright (C) 2014 Gregory Nutt. All rights reserved.
+#   Author: Gregory Nutt <gnutt@nuttx.org>
+#
+# 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.
+#
+############################################################################
+
+ifeq ($(CONFIG_LIBC_AIO),y)
+
+# Add the asynchronous I/O C files to the build
+
+CSRCS += aio_cancel.c aio_fsync.c aio_read.c aio_signal.c aio_write.c
+
+# Add the asynchronous I/O directory to the build
+
+DEPPATH += --dep-path aio
+VPATH += :aio
+endif
diff --git a/nuttx/fs/aio/aio.h b/nuttx/fs/aio/aio.h
new file mode 100644
index 000000000..a7a179171
--- /dev/null
+++ b/nuttx/fs/aio/aio.h
@@ -0,0 +1,91 @@
+/****************************************************************************
+ * fs/aio/aio.h
+ *
+ *   Copyright (C) 2014 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * 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 __FS_AIO_AIO_H
+#define __FS_AIO_AIO_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <aio.h>
+#include <nuttx/wqueue.h>
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Types
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Variables
+ ****************************************************************************/
+
+#undef EXTERN
+#if defined(__cplusplus)
+#define EXTERN extern "C"
+extern "C"
+{
+#else
+#define EXTERN extern
+#endif
+
+/****************************************************************************
+ * Public Function Prototypes
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: aio_signal
+ *
+ * Description:
+ *   Signal the client that an I/O has completed.
+ *
+ * Input Parameters:
+ *   aiocbp - Pointer to the asynchronous I/O state structure that includes
+ *            information about how to signal the client
+ *
+ * Returned Value:
+ *   Zero (OK) if the client was successfully signalled.  Otherwise, a
+ *   negated errno value is returned.
+ *
+ ****************************************************************************/
+
+int aio_signal(FAR struct aiocb *aiocbp);
+
+#endif /* __FS_AIO_AIO_H */
diff --git a/nuttx/fs/aio/aio_cancel.c b/nuttx/fs/aio/aio_cancel.c
new file mode 100644
index 000000000..7e6c17d1e
--- /dev/null
+++ b/nuttx/fs/aio/aio_cancel.c
@@ -0,0 +1,167 @@
+/****************************************************************************
+ * fs/aio/aio_cancel.c
+ *
+ *   Copyright (C) 2014 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * 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 <aio.h>
+#include <sched.h>
+#include <assert.h>
+#include <errno.h>
+
+#include <nuttx/wqueue.h>
+
+#include "aio/aio.h"
+
+#ifdef CONFIG_LIBC_AIO
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+/* Configuration ************************************************************/
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Variables
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Variables
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: aio_read
+ *
+ * Description:
+ *   The aio_cancel() function attempts to cancel one or more asynchronous
+ *   I/O requests currently outstanding against file descriptor 'fildes'.
+ *   The aiocbp argument points to the asynchronous I/O control block for
+ *   a particular request to be cancelled..
+ *
+ *   Normal asynchronous notification will occur for asynchronous I/O
+ *   operations that are successfully cancelled. If there are requests that
+ *   cannot be cancelled, then the normal asynchronous completion process
+ *   will take place for those requests when they are completed.
+ *
+ *   For requested operations that are successfully cancelled, the associated
+ *   error status will be set to ECANCELED and the return status will be -1.
+ *   For requested operations that are not successfully cancelled, the aiocbp
+ *   will not be modified by aio_cancel().
+ *
+ * Input Parameters:
+ *   fildes - Not used in this implmentation
+ *   aiocbp - Points to the asynchronous I/O control block for a particular
+ *            request to be cancelled.
+ *
+ * Returned Value:
+ *    The aio_cancel() function will return the value AIO_CANCELED if the
+ *    requested operation(s) were cancelled. The value AIO_NOTCANCELED will
+ *    be returned if at least one of the requested operation(s) cannot be
+ *    cancelled because it is in progress. In this case, the state of the
+ *    other operations, if any, referenced in the call to aio_cancel() is
+ *    not indicated by the return value of aio_cancel(). The application
+ *    may determine the state of affairs for these operations by using
+ *    aio_error(). The value AIO_ALLDONE is returned if all of the
+ *    operations have already completed. Otherwise, the function will return
+ *    -1 and set errno to indicate the error.
+ *
+ * POSIX Compliance
+ *   By standard, this function support the value of NULL for aiocbp.  If
+ *   aiocbp is NULL, then all outstanding cancelable asynchronous I/O
+ *   requests against fildes will be cancelled.  In this implementation,
+ *   nothing is done if aiocbp is NULL and the fildes parameter is always
+ *   ignored.  ENOSYS will be returned.
+ *
+ ****************************************************************************/
+
+int aio_cancel(int fildes, FAR struct aiocb *aiocbp)
+{
+  int status;
+  int ret;
+
+  /* Ignore NULL AIO control blocks (see "POSIX Compliance" above) */
+
+  if (aiocbp)
+    {
+      set_errno(ENOSYS);
+      return ERROR;
+    }
+
+  /* Lock the scheduler so that no I/O events can complete on the worker
+   * thread until we set complete this operation.
+   */
+
+  sched_lock();
+
+  /* Check if the I/O has completed */
+
+  if (aiocbp->aio_result == -EINPROGRESS)
+    {
+      /* No ... attempt to cancel the I/O.  There are two possibilities:  (1)
+       * the work has already been started and is no longer queued, or (2)
+       * the work has not been started and is still in the work queue.  Only
+       * the second case can be cancelled.  work_cancel() will return
+       * -ENOENT in the first case.
+       */
+
+      status = work_cancel(LPWORK, &aiocbp->aio_work);
+      ret = status >= 0 ? AIO_CANCELED : AIO_NOTCANCELED;
+    }
+  else
+    {
+      /* The I/O has already completed */
+
+      ret = AIO_ALLDONE;
+    }
+
+  sched_unlock();
+  return ret;
+}
+
+#endif /* CONFIG_LIBC_AIO */
diff --git a/nuttx/fs/aio/aio_fsync.c b/nuttx/fs/aio/aio_fsync.c
new file mode 100644
index 000000000..f4441d5df
--- /dev/null
+++ b/nuttx/fs/aio/aio_fsync.c
@@ -0,0 +1,228 @@
+/****************************************************************************
+ * fs/aio/aio_fsync.c
+ *
+ *   Copyright (C) 2014 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * 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 <unistd.h>
+#include <aio.h>
+#include <assert.h>
+#include <errno.h>
+#include <debug.h>
+
+#include <nuttx/wqueue.h>
+
+#include "aio/aio.h"
+
+#ifdef CONFIG_LIBC_AIO
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+/* Configuration ************************************************************/
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Variables
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Variables
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: aio_fsync_worker
+ *
+ * Description:
+ *   This function executes on the worker thread and performs the
+ *   asynchronous I/O operation.
+ *
+ * Input Parameters:
+ *   arg - Worker argument.  In this case, a pointer to an instance of
+ *     struct aiocb cast to void *.
+ *
+ * Returned Value:
+ *   None
+ *
+ ****************************************************************************/
+
+static void aio_fsync_worker(FAR void *arg)
+{
+  FAR struct aiocb *aiocbp = (FAR struct aiocb *)arg;
+  DEBUGASSERT(arg);
+  int ret;
+
+  /* Perform the fsync using aio_fildes */
+
+  ret = fsync(aiocbp->aio_fildes);
+  if (ret < 0)
+    {
+      int errcode = get_errno();
+      fdbg("ERROR: fsync failed: %d\n", errode);
+      DEBUGASSERT(errcode > 0);
+      aiocbp->aio_result = -errcode;
+    }
+  else
+    {
+      aiocbp->aio_result = OK;
+    }
+
+  /* Signal the client */
+
+  (void)aio_signal(aiocbp);
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: aio_fsync
+ *
+ * Description:
+ *   The aio_fsync() function asynchronously forces all I/O operations
+ *   associated with the file indicated by the file descriptor aio_fildes
+ *   member of the aiocb structure referenced by the aiocbp argument and
+ *   queued at the time of the call to aio_fsync() to the synchronized
+ *   I/O completion state. The function call will return when the
+ *   synchronization request has been initiated or queued to the file or
+ *   device (even when the data cannot be synchronized immediately).
+ *
+ *   If op is O_DSYNC, all currently queued I/O operations will be
+ *   completed as if by a call to fdatasync(); that is, as defined for
+ *   synchronized I/O data integrity completion. If op is O_SYNC, all
+ *   currently queued I/O operations will be completed as if by a call to
+ *   fsync(); that is, as defined for synchronized I/O file integrity
+ *   completion. If the aio_fsync() function fails, or if the operation
+ *   queued by aio_fsync() fails, then, as for fsync() and fdatasync(),
+ *   outstanding I/O operations are not guaranteed to have been completed.
+ *   [See "POSIX Compliance" below]
+ *
+ *   If aio_fsync() succeeds, then it is only the I/O that was queued at
+ *   the time of the call to aio_fsync() that is guaranteed to be forced
+ *   to the relevant completion state. The completion of subsequent I/O
+ *   on the file descriptor is not guaranteed to be completed in a
+ *   synchronized fashion.
+ *
+ *   The aiocbp argument refers to an asynchronous I/O control block. The
+ *   aiocbp value may be used as an argument to aio_error() and aio_return()
+ *   in order to determine the error status and return status, respectively,
+ *   of the asynchronous operation while it is proceeding. When the request
+ *   is queued, the error status for the operation is [EINPROGRESS]. When
+ *   all data has been successfully transferred, the error status will be
+ *   reset to reflect the success or failure of the operation. If the
+ *   operation does not complete successfully, the error status for the
+ *   operation will be set to indicate the error. The aio_sigevent member
+ *   determines the asynchronous notification to occur when all operations
+ *   have achieved synchronized I/O completion. All other members of the
+ *   structure referenced by aiocbp are ignored. If the control block
+ *   referenced by aiocbp becomes an illegal address prior to asynchronous
+ *   I/O completion, then the behavior is undefined.
+ *
+ *   If the aio_fsync() function fails or aiocbp indicates an error condition,
+ *   data is not guaranteed to have been successfully transferred.
+ *
+ * Input Parameters:
+ *   op     - Should be either O_SYNC or O_DSYNC.  Ignored in this implementation.
+ *   aiocbp - A pointer to an instance of struct aiocb
+ *
+ * Returned Value:
+ *   The aio_fsync() function will return the value 0 if the I/O operation is 
+ *   successfully queued; otherwise, the function will return the value -1 and
+ *   set errno to indicate the error.
+ *
+ *   The aio_fsync() function will fail if:
+ *
+ *     EAGAIN - The requested asynchronous operation was not queued due to
+ *       temporary resource limitations.
+ *     EBADF - The aio_fildes member of the aiocb structure referenced by
+ *       the aiocbp argument is not a valid file descriptor open for writing.
+ *     EINVAL - This implementation does not support synchronized I/O for
+ *       this file.
+ *      EINVAL - A value of op other than O_DSYNC or O_SYNC was specified.
+ *
+ *   In the event that any of the queued I/O operations fail, aio_fsync()
+ *   will return the error condition defined for read() and write(). The
+ *   error is returned in the error status for the asynchronous fsync()
+ *   operation, which can be retrieved using aio_error().
+ *
+ * POSIX Compliance
+ * - NuttX does not currently make any distinction between O_DYSNC and O_SYNC.
+ *   Hence, the 'op' argument is ignored altogether.
+ * - Most errors required in the standard are not detected at this point.
+ *   There are no pre-queuing checks for the validity of the operation.
+ *
+ ****************************************************************************/
+
+int aio_fsync(int op, FAR struct aiocb *aiocbp)
+{
+  int ret;
+
+  DEBUGASSERT(op == O_SYNC /* || op == O_DSYNC */);
+  DEBUGASSERT(aiocbp);
+
+  /* The result -EINPROGRESS means that the transfer has not yet completed */
+
+  aiocbp->aio_result = -EINPROGRESS;
+  aiocbp->aio_priv   = NULL;
+
+  /* Save the ID of the calling, client thread */
+
+  aiocbp->aio_pid = getpid();
+
+  /* Defer the work to the worker thread */
+
+  ret = work_queue(LPWORK, &aiocbp->aio_work, aio_fsync_worker, aiocbp, 0);
+  if (ret < 0)
+    {
+      aiocbp->aio_result = ret;
+      set_errno(ret);
+      return ERROR;
+    }
+
+  return OK;
+}
+
+#endif /* CONFIG_LIBC_AIO */
diff --git a/nuttx/fs/aio/aio_read.c b/nuttx/fs/aio/aio_read.c
new file mode 100644
index 000000000..90c6a024a
--- /dev/null
+++ b/nuttx/fs/aio/aio_read.c
@@ -0,0 +1,276 @@
+/****************************************************************************
+ * fs/aio/aio_read.c
+ *
+ *   Copyright (C) 2014 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * 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 <unistd.h>
+#include <sched.h>
+#include <aio.h>
+#include <assert.h>
+#include <errno.h>
+#include <debug.h>
+
+#include <nuttx/wqueue.h>
+
+#include "aio/aio.h"
+
+#ifdef CONFIG_LIBC_AIO
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+/* Configuration ************************************************************/
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Variables
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Variables
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: aio_read_worker
+ *
+ * Description:
+ *   This function executes on the worker thread and performs the
+ *   asynchronous I/O operation.
+ *
+ * Input Parameters:
+ *   arg - Worker argument.  In this case, a pointer to an instance of
+ *     struct aiocb cast to void *.
+ *
+ * Returned Value:
+ *   None
+ *
+ ****************************************************************************/
+
+static void aio_read_worker(FAR void *arg)
+{
+  FAR struct aiocb *aiocbp = (FAR struct aiocb *)arg;
+  DEBUGASSERT(arg);
+  ssize_t nread;
+
+  /* Perform the read using:
+   *
+   *   aio_fildes  - File descriptor
+   *   aio_buf     - Location of buffer
+   *   aio_nbytes  - Length of transfer
+   *   aio_offset  - File offset
+   */
+
+ nread = pread(aiocbp->aio_fildes, (FAR void *)aiocbp->aio_buf,
+               aiocbp->aio_nbytes, aiocbp->aio_offset);
+
+  /* Set the result of the read */
+
+  if (nread < 0)
+    {
+      int errcode = get_errno();
+      fdbg("ERROR: pread failed: %d\n", errode);
+      DEBUGASSERT(errcode > 0);
+      aiocbp->aio_result = -errcode;
+    }
+  else
+    {
+      aiocbp->aio_result = nread;
+    }
+
+  /* Signal the client */
+
+  (void)aio_signal(aiocbp);
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: aio_read
+ *
+ * Description:
+ *   The aio_read() function reads aiocbp->aio_nbytes from the file
+ *   associated with aiocbp->aio_fildes into the buffer pointed to by
+ *   aiocbp->aio_buf. The function call will return when the read request
+ *   has been initiated or queued to the file or device (even when the data
+ *   cannot be delivered immediately).
+ *
+ *   The aiocbp value may be used as an argument to aio_error() and
+ *   aio_return() in order to determine the error status and return status,
+ *   respectively, of the asynchronous operation while it is proceeding. If
+ *   an error condition is encountered during queuing, the function call
+ *   will return without having initiated or queued the request. The
+ *   requested operation takes place at the absolute position in the file as
+ *   given by aio_offset, as if lseek() were called immediately prior to the
+ *   operation with an offset equal to aio_offset and a whence equal to
+ *   SEEK_SET. After a successful call to enqueue an asynchronous I/O
+ *   operation, the value of the file offset for the file is unspecified.
+ *
+ *   The aiocbp->aio_lio_opcode field will be ignored by aio_read().
+ *
+ *   The aiocbp argument points to an aiocb structure. If the buffer pointed
+ *   to by aiocbp->aio_buf or the control block pointed to by aiocbp becomes
+ *   an illegal address prior to asynchronous I/O completion, then the
+ *   behavior is undefined.
+ *
+ *   Simultaneous asynchronous operations using the same aiocbp produce
+ *   undefined results.
+ *
+ *   For any system action that changes the process memory space while an
+ *   synchronous I/O is outstanding to the address range being changed, the
+ *   result of that action is undefined.
+ *
+ * Input Parameters:
+ *   aiocbp - A pointer to an instance of struct aiocb
+ *
+ * Returned Value:
+ *
+ *   The aio_read() function will return the value zero if the I/O operation
+ *   is successfully queued; otherwise, the function will return the value
+ *   -1 and set errno to indicate the error.  The aio_read() function will
+ *   ail if:
+ *
+ *   EAGAIN - The requested asynchronous I/O operation was not queued due to
+ *     system resource limitations.
+ *
+ *   Each of the following conditions may be detected synchronously at the
+ *   time of the call to aio_read(), or asynchronously. If any of the
+ *   conditions below are detected synchronously, the aio_read() function
+ *   will return -1 and set errno to the corresponding value. If any of the
+ *   conditions below are detected asynchronously, the return status of the
+ *   asynchronous operation is set to -1, and the error status of the
+ *   asynchronous operation is set to the corresponding value.
+ *
+ *   EBADF - The aiocbp->aio_fildes argument is not a valid file descriptor
+ *     open for reading.
+ *   EINVAL - The file offset value implied by aiocbp->aio_offset would be
+ *     invalid, aiocbp->aio_reqprio is not a valid value, or
+ *     aiocbp->aio_nbytes is an invalid value.
+ *
+ *   In the case that the aio_read() successfully queues the I/O operation
+ *   but the operation is subsequently cancelled or encounters an error, the
+ *   return status of the asynchronous operation is one of the values
+ *   normally returned by the read() function call. In addition, the error
+ *   status of the asynchronous operation is set to one of the error
+ *   statuses normally set by the read() function call, or one of the
+ *   following values:
+ *
+ *   EBADF - The aiocbp->aio_fildes argument is not a valid file descriptor
+ *     open for reading.
+ *   ECANCELED - The requested I/O was cancelled before the I/O completed
+ *     due to an explicit aio_cancel() request.
+ *   EINVAL - The file offset value implied by aiocbp->aio_offset would be
+ *     invalid.
+ *
+ * The following condition may be detected synchronously or asynchronously:
+ *
+ *   EOVERFLOW - The file is a regular file, aiobcp->aio_nbytes is greater
+ *     than 0, and the starting offset in aiobcp->aio_offset is before the
+ *     end-of-file and is at or beyond the offset maximum in the open file
+ *     description associated with aiocbp->aio_fildes.
+ *
+ * POSIX Compliance:
+ * - The POSIX specification of asynchronous I/O implies that a thread is
+ *   created for each I/O operation.  The standard requires that if
+ *   prioritized I/O is supported for this file, then the asynchronous
+ *   operation will be submitted at a priority equal to a base scheduling
+ *   priority minus aiocbp->aio_reqprio. If Thread Execution Scheduling is
+ *   not supported, then the base scheduling priority is that of the calling
+ *   thread.
+ *
+ *   My initial gut feeling is the creating a new thread on each asynchronous
+ *   I/O operation would not be a good use of resources in a deeply embedded
+ *   system.  So I decided to execute all asynchronous I/O on a low-priority
+ *   or user-space worker thread.  There are two negative consequences of this
+ *   decision that need to be revisited:
+ *
+ *     1) The worker thread runs at a fixed priority making it impossible to
+ *        meet the POSIX requirement for asynchronous I/O.  That standard
+ *        specifically requires varying priority.
+ *     2) On the worker thread, each I/O will still be performed synchronously,
+ *        one at a time.  This is not a violation of the POSIX requirement,
+ *        but one would think there could be opportunities for concurrent I/O.
+ *
+ *   In reality, in a small embedded system, there will probably only be one
+ *   real file system and, in this case, the I/O will be performed sequentially
+ *   anyway.  Most simple embedded hardware will not support any concurrent
+ *   accesses.
+ *
+ * - Most errors required in the standard are not detected at this point.
+ *   There are no pre-queuing checks for the validity of the operation.
+ *
+ ****************************************************************************/
+
+int aio_read(FAR struct aiocb *aiocbp)
+{
+  int ret;
+
+  DEBUGASSERT(aiocbp);
+
+  /* The result -EINPROGRESS means that the transfer has not yet completed */
+
+  aiocbp->aio_result = -EINPROGRESS;
+  aiocbp->aio_priv   = NULL;
+
+  /* Save the ID of the calling, client thread */
+
+  aiocbp->aio_pid = getpid();
+
+  /* Defer the work to the worker thread */
+
+  ret = work_queue(LPWORK, &aiocbp->aio_work, aio_read_worker, aiocbp, 0);
+  if (ret < 0)
+    {
+      aiocbp->aio_result = ret;
+      set_errno(ret);
+      return ERROR;
+    }
+
+  return OK;
+}
+
+#endif /* CONFIG_LIBC_AIO */
diff --git a/nuttx/fs/aio/aio_signal.c b/nuttx/fs/aio/aio_signal.c
new file mode 100644
index 000000000..60cb0be77
--- /dev/null
+++ b/nuttx/fs/aio/aio_signal.c
@@ -0,0 +1,148 @@
+/****************************************************************************
+ * fs/aio/aio_signal.c
+ *
+ *   Copyright (C) 2014 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * 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 <sched.h>
+#include <signal.h>
+#include <aio.h>
+#include <assert.h>
+#include <errno.h>
+#include <debug.h>
+
+#include "aio/aio.h"
+
+#ifdef CONFIG_LIBC_AIO
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+/* Configuration ************************************************************/
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Variables
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Variables
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+/****************************************************************************
+ * Name: aio_signal
+ *
+ * Description:
+ *   Signal the client that an I/O has completed.
+ *
+ * Input Parameters:
+ *   aiocbp - Pointer to the asynchronous I/O state structure that includes
+ *            information about how to signal the client
+ *
+ * Returned Value:
+ *   Zero (OK) if the client was successfully signalled.  Otherwise, a
+ *   negated errno value is returned.
+ *
+ * Assumptions:
+ *   This function runs only in the context of the worker thread.
+ *
+ ****************************************************************************/
+
+int aio_signal(FAR struct aiocb *aiocbp)
+{
+  int errcode;
+  int status;
+  int ret;
+
+  DEBUGASSERT(aiocbp);
+ 
+  ret = OK; /* Assume success */
+
+  /* Signal the client */
+
+  if (aiocbp->aio_sigevent.sigev_notify == SIGEV_SIGNAL)
+    {
+#ifdef CONFIG_CAN_PASS_STRUCTS
+      status = sigqueue(aiocbp->aio_pid, aiocbp->aio_sigevent.sigev_signo,
+                        aiocbp->aio_sigevent.sigev_value);
+#else
+      status = sigqueue(aiocbp->aio_pid, aiocbp->aio_sigevent.sigev_sign,
+                        aiocbp->aio_sigevent.sigev_value.sival_ptr);
+#endif
+      if (ret < 0)
+        {
+          errcode = get_errno();
+          fdbg("ERROR: sigqueue failed: %d\n", errcode);
+          ret = ERROR;
+        }
+    }
+
+  /* Send the poll signal in any event in case the caller is waiting
+   * on sig_suspend();
+   */
+
+  status = kill(aiocbp->aio_pid, SIGPOLL);
+  if (status && ret == OK)
+    {
+      errcode = get_errno();
+      fdbg("ERROR: kill failed: %d\n", errcode);
+      ret = ERROR;
+    }
+
+  /* Make sure that errno is set correctly on return */
+
+  if (ret < 0)
+    {
+      set_errno(errcode);
+      return ERROR;
+    }
+
+  return OK;
+}
+
+#endif /* CONFIG_LIBC_AIO */
diff --git a/nuttx/fs/aio/aio_write.c b/nuttx/fs/aio/aio_write.c
new file mode 100644
index 000000000..51a470964
--- /dev/null
+++ b/nuttx/fs/aio/aio_write.c
@@ -0,0 +1,307 @@
+/****************************************************************************
+ * fs/aio/aio_write.c
+ *
+ *   Copyright (C) 2014 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * 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 <unistd.h>
+#include <fcntl.h>
+#include <sched.h>
+#include <aio.h>
+#include <assert.h>
+#include <errno.h>
+#include <debug.h>
+
+#include <nuttx/wqueue.h>
+
+#include "aio/aio.h"
+
+#ifdef CONFIG_LIBC_AIO
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+/* Configuration ************************************************************/
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Variables
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Variables
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: aio_write_worker
+ *
+ * Description:
+ *   This function executes on the worker thread and performs the
+ *   asynchronous I/O operation.
+ *
+ * Input Parameters:
+ *   arg - Worker argument.  In this case, a pointer to an instance of
+ *     struct aiocb cast to void *.
+ *
+ * Returned Value:
+ *   None
+ *
+ ****************************************************************************/
+
+static void aio_write_worker(FAR void *arg)
+{
+  FAR struct aiocb *aiocbp = (FAR struct aiocb *)arg;
+  DEBUGASSERT(arg);
+  ssize_t nwritten;
+  int oflags;
+
+  /* Call fcntl(F_GETFL) to get the file open mode. */
+
+  oflags = fcntl(aiocbp->aio_fildes, F_GETFL);
+  if (oflags < 0)
+    {
+      int errcode = get_errno();
+      fdbg("ERROR: fcntl failed: %d\n", errode);
+      aiocbp->aio_result = -errcode;
+    }
+  else
+    {
+      /* Perform the write using:
+       *
+       *   aio_fildes  - File descriptor
+       *   aio_buf     - Location of buffer
+       *   aio_nbytes  - Length of transfer
+       *   aio_offset  - File offset
+       */
+
+      /* Check if O_APPEND is set in the file open flags */
+
+      if ((oflags & O_APPEND) != 0)
+        {
+          /* Append to the current file position */
+
+          nwritten = write(aiocbp->aio_fildes,
+                           (FAR const void *)aiocbp->aio_buf,
+                           aiocbp->aio_nbytes);
+        }
+      else
+        {
+          nwritten = pwrite(aiocbp->aio_fildes,
+                            (FAR const void *)aiocbp->aio_buf,
+                            aiocbp->aio_nbytes,
+                            aiocbp->aio_offset);
+        }
+
+      /* Set the result of the write */
+
+      if (nwritten < 0)
+        {
+          int errcode = get_errno();
+          fdbg("ERROR: write/pwrite failed: %d\n", errode);
+          DEBUGASSERT(errcode > 0);
+          aiocbp->aio_result = -errcode;
+        }
+      else
+        {
+          aiocbp->aio_result = nwritten;
+        }
+    }
+
+  /* Signal the client */
+
+  (void)aio_signal(aiocbp);
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: aio_write
+ *
+ * Description:
+ *   The aio_write() function writes aiocbp->aio_nbytes to the file
+ *   associated with aiocbp->aio_fildes from the buffer pointed to by
+ *   aiocbp->aio_buf. The function call will return when the write request
+ *   has been initiated or queued to the file or device (even when the data
+ *   cannot be delivered immediately).
+ *
+ *   The aiocbp value may be used as an argument to aio_error() and
+ *   aio_return() in order to determine the error status and return status,
+ *   respectively, of the asynchronous operation while it is proceeding.
+ *
+ *   The aiocbp argument points to an aiocb structure. If the buffer pointed
+ *   to by aiocbp->aio_buf or the control block pointed to by aiocbp becomes
+ *   an illegal address prior to asynchronous I/O completion, then the
+ *   behavior is undefined.
+ *
+ *   If O_APPEND is not set for the file descriptor aio_fildes, then the
+ *   requested operation will take place at the absolute position in the file
+ *   as given by aio_offset, as if lseek() were called immediately prior to the
+ *   operation with an offset equal to aio_offset and a whence equal to SEEK_SET.
+ *   If O_APPEND is set for the file descriptor, write operations append to the
+ *   file in the same order as the calls were made. After a successful call to
+ *   enqueue an asynchronous I/O operation, the value of the file offset for the
+ *   file is unspecified.
+ *
+ *   The aiocbp->aio_lio_opcode field will be ignored by aio_write().
+ *
+ *   Simultaneous asynchronous operations using the same aiocbp produce
+ *   undefined results.
+ *
+ *   For any system action that changes the process memory space while an
+ *   synchronous I/O is outstanding to the address range being changed, the
+ *   result of that action is undefined.
+ *
+ * Input Parameters:
+ *   aiocbp - A pointer to an instance of struct aiocb
+ *
+ * Returned Value:
+ *
+ *   The aio_write() function will return the value zero if the I/O operation
+ *   is successfully queued; otherwise, the function will return the value
+ *   -1 and set errno to indicate the error.  The aio_write() function will
+ *   ail if:
+ *
+ *   EAGAIN - The requested asynchronous I/O operation was not queued due to
+ *     system resource limitations.
+ *
+ *   Each of the following conditions may be detected synchronously at the
+ *   time of the call to aio_write(), or asynchronously. If any of the
+ *   conditions below are detected synchronously, the aio_write() function
+ *   will return -1 and set errno to the corresponding value. If any of the
+ *   conditions below are detected asynchronously, the return status of the
+ *   asynchronous operation is set to -1, and the error status of the
+ *   asynchronous operation is set to the corresponding value.
+ *
+ *   EBADF - The aiocbp->aio_fildes argument is not a valid file descriptor
+ *     open for writing.
+ *   EINVAL - The file offset value implied by aiocbp->aio_offset would be
+ *     invalid, aiocbp->aio_reqprio is not a valid value, or
+ *     aiocbp->aio_nbytes is an invalid value.
+ *
+ *   In the case that the aio_write() successfully queues the I/O operation
+ *   but the operation is subsequently cancelled or encounters an error, the
+ *   return status of the asynchronous operation is one of the values
+ *   normally returned by the write() function call. In addition, the error
+ *   status of the asynchronous operation is set to one of the error
+ *   statuses normally set by the write() function call, or one of the
+ *   following values:
+ *
+ *   EBADF - The aiocbp->aio_fildes argument is not a valid file descriptor
+ *     open for writing.
+ *   EINVAL - The file offset value implied by aiocbp->aio_offset would be
+ *     invalid.
+ *   ECANCELED - The requested I/O was cancelled before the I/O completed
+ *     due to an explicit aio_cancel() request.
+ *
+ * The following condition may be detected synchronously or asynchronously:
+ *
+ *   EFBIG - The file is a regular file, aiobcp->aio_nbytes is greater
+ *     than 0, and the starting offset in aiobcp->aio_offset is at or
+ *     beyond the offset maximum in the open file description associated
+ *     with aiocbp->aio_fildes.
+ *
+ * POSIX Compliance:
+ * - The POSIX specification of asynchronous I/O implies that a thread is
+ *   created for each I/O operation.  The standard requires that if
+ *   prioritized I/O is supported for this file, then the asynchronous
+ *   operation will be submitted at a priority equal to a base scheduling
+ *   priority minus aiocbp->aio_reqprio. If Thread Execution Scheduling is
+ *   not supported, then the base scheduling priority is that of the calling
+ *   thread.
+ *
+ *   My initial gut feeling is the creating a new thread on each asynchronous
+ *   I/O operation would not be a good use of resources in a deeply embedded
+ *   system.  So I decided to execute all asynchronous I/O on a low-priority
+ *   or user-space worker thread.  There are two negative consequences of this
+ *   decision that need to be revisited:
+ *
+ *     1) The worker thread runs at a fixed priority making it impossible to
+ *        meet the POSIX requirement for asynchronous I/O.  That standard
+ *        specifically requires varying priority.
+ *     2) On the worker thread, each I/O will still be performed synchronously,
+ *        one at a time.  This is not a violation of the POSIX requirement,
+ *        but one would think there could be opportunities for concurrent I/O.
+ *
+ *   In reality, in a small embedded system, there will probably only be one
+ *   real file system and, in this case, the I/O will be performed sequentially
+ *   anyway.  Most simple embedded hardware will not support any concurrent
+ *   accesses.
+ *
+ * - Most errors required in the standard are not detected at this point.
+ *   There are no pre-queuing checks for the validity of the operation.
+ *
+ ****************************************************************************/
+
+int aio_write(FAR struct aiocb *aiocbp)
+{
+  int ret;
+
+  DEBUGASSERT(aiocbp);
+
+  /* The result -EINPROGRESS means that the transfer has not yet completed */
+
+  aiocbp->aio_result = -EINPROGRESS;
+  aiocbp->aio_priv   = NULL;
+
+  /* Save the ID of the calling, client thread */
+
+  aiocbp->aio_pid = getpid();
+
+  /* Defer the work to the worker thread */
+
+  ret = work_queue(LPWORK, &aiocbp->aio_work, aio_write_worker, aiocbp, 0);
+  if (ret < 0)
+    {
+      aiocbp->aio_result = ret;
+      set_errno(ret);
+      return ERROR;
+    }
+
+  return OK;
+}
+
+#endif /* CONFIG_LIBC_AIO */