Add support for configurable block size on AT24 EEPROM driver

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@4076 42af7a65-404d-4744-a932-0658087f49c3

2 files changed, 432 insertions, 350 deletions

diff --git a/nuttx/ChangeLog b/nuttx/ChangeLog
index 6c9af7dcb..9186808f3 100644
--- a/nuttx/ChangeLog
+++ b/nuttx/ChangeLog
@@ -2188,4 +2188,7 @@
 	* fs/nxffs/nxffs_write.c and nxffs_pack.c:  Fix an error that can occur
 	  when attempt to write to FLASH volume that is completely full but
 	  has no value inodes on it.
-
+	* drivers/mtd/at24xx.c:  Now supports a configurable block size that
+	  supports using "clusters" of AT24 pages as blocks.  This allows bigger
+	  block sizes and more efficient use of FLASH when the AT24 is used to
+	  support a file system (such as NXFFS).
diff --git a/nuttx/drivers/mtd/at24xx.c b/nuttx/drivers/mtd/at24xx.c
index 2aa116d83..50a6ab913 100644
--- a/nuttx/drivers/mtd/at24xx.c
+++ b/nuttx/drivers/mtd/at24xx.c
@@ -1,349 +1,428 @@
-/************************************************************************************

- * drivers/mtd/at24xx.c

- * Driver for I2C-based at24cxx EEPROM(at24c32,at24c64,at24c128,at24c256)

- *

- *   Copyright (C) 2011 Li Zhuoyi. All rights reserved.

- *   Author: Li Zhuoyi <lzyy.cn@gmail.com>

- *   History: 0.1 2011-08-20 initial version

- *

- * Derived from drivers/mtd/m25px.c

- *

- *   Copyright (C) 2009-2011 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 <stdint.h>

-#include <stdbool.h>

-#include <stdlib.h>

-#include <errno.h>

-#include <debug.h>

-

-#include <nuttx/kmalloc.h>

-#include <nuttx/ioctl.h>

-#include <nuttx/i2c.h>

-#include <nuttx/mtd.h>

-

-#ifdef CONFIG_MTD_AT24XX

-

-/************************************************************************************

- * Pre-processor Definitions

- ************************************************************************************/

-#ifndef CONFIG_AT24XX_SIZE

-#define CONFIG_AT24XX_SIZE     64

-#endif

-#ifndef CONFIG_AT24XX_ADDR

-#define CONFIG_AT24XX_ADDR     0x50

-#endif

-

-#if CONFIG_AT24XX_SIZE == 32

-#define AT24XX_NPAGES     128

-#define AT24XX_PAGESIZE   32

-#elif CONFIG_AT24XX_SIZE == 64

-#define AT24XX_NPAGES     256

-#define AT24XX_PAGESIZE   32

-#elif CONFIG_AT24XX_SIZE == 128

-#define AT24XX_NPAGES     256

-#define AT24XX_PAGESIZE   64

-#elif CONFIG_AT24XX_SIZE == 256

-#define AT24XX_NPAGES     512

-#define AT24XX_PAGESIZE   64

-#endif

-

-/************************************************************************************

- * Private Types

- ************************************************************************************/

-

-/* This type represents the state of the MTD device.  The struct mtd_dev_s

- * must appear at the beginning of the definition so that you can freely

- * cast between pointers to struct mtd_dev_s and struct at24c_dev_s.

- */

-

-struct at24c_dev_s

-{

-    struct mtd_dev_s mtd;      /* MTD interface */

-    FAR struct i2c_dev_s *dev; /* Saved I2C interface instance */

-    uint8_t addr;

-    uint16_t pagesize;         /* 32,63 */

-    uint16_t npages;           /* 128,256,512,1024 */

-};

-

-/************************************************************************************

- * Private Function Prototypes

- ************************************************************************************/

-

-/* MTD driver methods */

-

-static int at24c_erase(FAR struct mtd_dev_s *dev, off_t startblock, size_t nblocks);

-static ssize_t at24c_bread(FAR struct mtd_dev_s *dev, off_t startblock,size_t nblocks, FAR uint8_t *buf);

-static ssize_t at24c_bwrite(FAR struct mtd_dev_s *dev, off_t startblock,size_t nblocks, FAR const uint8_t *buf);

-static ssize_t at24c_read(FAR struct mtd_dev_s *dev, off_t offset, size_t nbytes,FAR uint8_t *buffer);

-static int at24c_ioctl(FAR struct mtd_dev_s *dev, int cmd, unsigned long arg);

-

-/************************************************************************************

- * Private Data

- ************************************************************************************/

-static struct at24c_dev_s g_at24c =

-{

-    .addr  = CONFIG_AT24XX_ADDR,

-    .pagesize = AT24XX_PAGESIZE,

-    .npages = AT24XX_NPAGES,

-};

-

-/************************************************************************************

- * Private Functions

- ************************************************************************************/

-

-static int at24c_eraseall(FAR struct at24c_dev_s *priv)

-{

-    int blocksleft = priv->pagesize;

-    int startblock = 0;

-    uint8_t buf[66];

-    memset(&buf[2],0xff,priv->pagesize);

-    I2C_SETADDRESS(priv->dev,priv->addr,7);

-    I2C_SETFREQUENCY(priv->dev,100000);

-    while (blocksleft-- > 0)

-    {

-        uint16_t offset=startblock*priv->pagesize;

-        buf[1]=offset&0xff;

-        buf[0]=(offset>>8)&0xff;

-

-        while (I2C_WRITE(priv->dev,buf,2)<0)

-        {

-            usleep(1000);

-        }

-        I2C_WRITE(priv->dev, buf, priv->pagesize+2);

-        startblock++;

-    }

-    return OK;

-}

-

-/************************************************************************************

- * Name: at24c_erase

- ************************************************************************************/

-

-static int at24c_erase(FAR struct mtd_dev_s *dev, off_t startblock, size_t nblocks)

-{

-    /*

-     * EEprom need not erase

-     */

-    return (int)nblocks;

-}

-

-/************************************************************************************

- * Name: at24c_bread

- ************************************************************************************/

-

-static ssize_t at24c_bread(FAR struct mtd_dev_s *dev, off_t startblock, size_t nblocks,

-                           FAR uint8_t *buffer)

-{

-    FAR struct at24c_dev_s *priv = (FAR struct at24c_dev_s *)dev;

-    size_t blocksleft = nblocks;

-

-    fvdbg("startblock: %08lx nblocks: %d\n", (long)startblock, (int)nblocks);

-

-    if (startblock >= priv->npages)

-    {

-        return 0;

-    }

-

-    if (startblock + nblocks > priv->npages)

-    {

-        nblocks = priv->npages - startblock;

-    }

-

-    I2C_SETADDRESS(priv->dev,priv->addr,7);

-    I2C_SETFREQUENCY(priv->dev,100000);

-    int tail;

-    while (blocksleft-- > 0)

-    {

-        uint16_t offset=startblock*priv->pagesize;

-        uint8_t buf[2];

-        buf[1]=offset&0xff;

-        buf[0]=(offset>>8)&0xff;

-        while (I2C_WRITE(priv->dev,buf,2)<0)

-        {

-            fvdbg("wait\n");

-            usleep(1000);

-        }

-        I2C_READ(priv->dev, buffer,priv->pagesize);

-        startblock++;

-        buffer+=priv->pagesize;

-    }

-    return nblocks;

-}

-

-/************************************************************************************

- * Name: at24c_bwrite

- ************************************************************************************/

-

-static ssize_t at24c_bwrite(FAR struct mtd_dev_s *dev, off_t startblock, size_t nblocks,

-                            FAR const uint8_t *buffer)

-{

-    FAR struct at24c_dev_s *priv = (FAR struct at24c_dev_s *)dev;

-    size_t blocksleft = nblocks;

-    uint8_t buf[66];

-

-    if (startblock >= priv->npages)

-    {

-        return 0;

-    }

-

-    if (startblock + nblocks > priv->npages)

-    {

-        nblocks = priv->npages - startblock;

-    }

-

-

-    fvdbg("startblock: %08lx nblocks: %d\n", (long)startblock, (int)nblocks);

-    I2C_SETADDRESS(priv->dev,priv->addr,7);

-    I2C_SETFREQUENCY(priv->dev,100000);

-    while (blocksleft-- > 0)

-    {

-        uint16_t offset=startblock*priv->pagesize;

-        while (I2C_WRITE(priv->dev,(uint8_t *)&offset,2)<0)

-        {

-            fvdbg("wait\n");

-            usleep(1000);

-        }

-        buf[1]=offset&0xff;

-        buf[0]=(offset>>8)&0xff;

-        memcpy(&buf[2],buffer,priv->pagesize);

-

-        I2C_WRITE(priv->dev, buf, priv->pagesize+2);

-        startblock++;

-        buffer+=priv->pagesize;

-    }

-    return nblocks;

-}

-

-/************************************************************************************

- * Name: at24c_ioctl

- ************************************************************************************/

-

-static int at24c_ioctl(FAR struct mtd_dev_s *dev, int cmd, unsigned long arg)

-{

-    FAR struct at24c_dev_s *priv = (FAR struct at24c_dev_s *)dev;

-    int ret = -EINVAL; /* Assume good command with bad parameters */

-

-    fvdbg("cmd: %d \n", cmd);

-

-    switch (cmd)

-    {

-    case MTDIOC_GEOMETRY:

-    {

-        FAR struct mtd_geometry_s *geo = (FAR struct mtd_geometry_s *)((uintptr_t)arg);

-        if (geo)

-        {

-            /* Populate the geometry structure with information need to know

-             * the capacity and how to access the device.

-             *

-             * NOTE: that the device is treated as though it where just an array

-             * of fixed size blocks.  That is most likely not true, but the client

-             * will expect the device logic to do whatever is necessary to make it

-             * appear so.

-             */

-

-            geo->blocksize    = priv->pagesize;

-            geo->erasesize    = priv->pagesize;

-            geo->neraseblocks = priv->npages;

-            ret               = OK;

-

-            fvdbg("blocksize: %d erasesize: %d neraseblocks: %d\n",

-                  geo->blocksize, geo->erasesize, geo->neraseblocks);

-        }

-    }

-    break;

-

-    case MTDIOC_BULKERASE:

-        ret=at24c_eraseall(priv);

-        break;

-

-    case MTDIOC_XIPBASE:

-    default:

-        ret = -ENOTTY; /* Bad command */

-        break;

-    }

-

-    return ret;

-}

-

-/************************************************************************************

- * Public Functions

- ************************************************************************************/

-

-/************************************************************************************

- * Name: at24c_initialize

- *

- * Description:

- *   Create an initialize MTD device instance.  MTD devices are not registered

- *   in the file system, but are created as instances that can be bound to

- *   other functions (such as a block or character driver front end).

- *

- ************************************************************************************/

-

-FAR struct mtd_dev_s *at24c_initialize(FAR struct i2c_dev_s *dev)

-{

-    FAR struct at24c_dev_s *priv;

-    int ret;

-

-    fvdbg("dev: %p\n", dev);

-

-    /* Allocate a state structure (we allocate the structure instead of using

-     * a fixed, static allocation so that we can handle multiple FLASH devices.

-     * The current implementation would handle only one FLASH part per SPI

-     * device (only because of the SPIDEV_FLASH definition) and so would have

-     * to be extended to handle multiple FLASH parts on the same SPI bus.

-     */

-

-    priv = &g_at24c;

-    if (priv)

-    {

-        /* Initialize the allocated structure */

-

-        priv->mtd.erase  = at24c_erase;

-        priv->mtd.bread  = at24c_bread;

-        priv->mtd.bwrite = at24c_bwrite;

-        priv->mtd.ioctl  = at24c_ioctl;

-        priv->dev        = dev;

-    }

-    /* Return the implementation-specific state structure as the MTD device */

-    fvdbg("Return %p\n", priv);

-    return (FAR struct mtd_dev_s *)priv;

-}

-

-#endif

+/************************************************************************************
+ * drivers/mtd/at24xx.c
+ * Driver for I2C-based at24cxx EEPROM(at24c32,at24c64,at24c128,at24c256)
+ *
+ *   Copyright (C) 2011 Li Zhuoyi. All rights reserved.
+ *   Author: Li Zhuoyi <lzyy.cn@gmail.com>
+ *   History: 0.1 2011-08-20 initial version
+ *
+ *   2011-11-1 Added support for larger MTD block sizes: Hal Glenn <hglenn@2g-eng.com>
+ *
+ * Derived from drivers/mtd/m25px.c
+ *
+ *   Copyright (C) 2009-2011 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 <sys/types.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+#include <debug.h>
+
+#include <nuttx/kmalloc.h>
+#include <nuttx/ioctl.h>
+#include <nuttx/i2c.h>
+#include <nuttx/mtd.h>
+
+#ifdef CONFIG_MTD_AT24XX
+
+/************************************************************************************
+ * Pre-processor Definitions
+ ************************************************************************************/
+
+/* As a minimum, the size of the AT24 part and its 7-bit I2C address are required. */
+
+#ifndef CONFIG_AT24XX_SIZE
+#  warning "Assuming AT24 size 64"
+#  define CONFIG_AT24XX_SIZE 64
+#endif
+#ifndef CONFIG_AT24XX_ADDR
+#  warning "Assuming AT24 address of 0x50"
+#  define CONFIG_AT24XX_ADDR 0x50
+#endif
+
+/* Get the part configuration based on the size configuration */
+
+#if CONFIG_AT24XX_SIZE == 32
+#  define AT24XX_NPAGES     128
+#  define AT24XX_PAGESIZE   32
+#elif CONFIG_AT24XX_SIZE == 48
+#  define AT24XX_NPAGES     192
+#  define AT24XX_PAGESIZE   32
+#elif CONFIG_AT24XX_SIZE == 64
+#  define AT24XX_NPAGES     256
+#  define AT24XX_PAGESIZE   32
+#elif CONFIG_AT24XX_SIZE == 128
+#  define AT24XX_NPAGES     256
+#  define AT24XX_PAGESIZE   64
+#elif CONFIG_AT24XX_SIZE == 256
+#  define AT24XX_NPAGES     512
+#  define AT24XX_PAGESIZE   64
+#endif
+
+/* For applications where a file system is used on the AT24, the tiny page sizes
+ * will result in very inefficient FLASH usage.  In such cases, it is better if
+ * blocks are comprised of "clusters" of pages so that the file system block
+ * size is, say, 256 or 512 bytes.  In any event, the block size *must* be an
+ * even multiple of the pages.
+ */
+
+#ifndef CONFIG_AT24XX_MTD_BLOCKSIZE
+#  warning "Assuming driver block size is the same as the FLASH page size"
+#  define CONFIG_AT24XX_MTD_BLOCKSIZE AT24XX_PAGESIZE
+#endif
+
+/************************************************************************************
+ * Private Types
+ ************************************************************************************/
+
+/* This type represents the state of the MTD device.  The struct mtd_dev_s
+ * must appear at the beginning of the definition so that you can freely
+ * cast between pointers to struct mtd_dev_s and struct at24c_dev_s.
+ */
+
+struct at24c_dev_s
+{
+  struct mtd_dev_s      mtd;      /* MTD interface */
+  FAR struct i2c_dev_s *dev;      /* Saved I2C interface instance */
+  uint8_t               addr;     /* I2C address */
+  uint16_t              pagesize; /* 32, 63 */
+  uint16_t              npages;   /* 128, 256, 512, 1024 */
+};
+
+/************************************************************************************
+ * Private Function Prototypes
+ ************************************************************************************/
+
+/* MTD driver methods */
+
+static int at24c_erase(FAR struct mtd_dev_s *dev, off_t startblock, size_t nblocks);
+static ssize_t at24c_bread(FAR struct mtd_dev_s *dev, off_t startblock,
+                           size_t nblocks, FAR uint8_t *buf);
+static ssize_t at24c_bwrite(FAR struct mtd_dev_s *dev, off_t startblock,
+                            size_t nblocks, FAR const uint8_t *buf);
+static ssize_t at24c_read(FAR struct mtd_dev_s *dev, off_t offset,
+                          size_t nbytes,FAR uint8_t *buffer);
+static int at24c_ioctl(FAR struct mtd_dev_s *dev, int cmd, unsigned long arg);
+
+/************************************************************************************
+ * Private Data
+ ************************************************************************************/
+
+/* At present, only a signal AT24 part is supported.  In this case, a statically
+ * allocated state structure may be used.
+ */
+
+static struct at24c_dev_s g_at24c;
+
+/************************************************************************************
+ * Private Functions
+ ************************************************************************************/
+
+static int at24c_eraseall(FAR struct at24c_dev_s *priv)
+{
+  int startblock = 0;
+  uint8_t buf[AT24XX_PAGESIZE + 2];
+
+  memset(&buf[2],0xff,priv->pagesize);
+  I2C_SETADDRESS(priv->dev,priv->addr,7);
+  I2C_SETFREQUENCY(priv->dev,100000);
+
+  for (startblock = 0; startblock < priv->npages; startblock++)
+    {
+      uint16_t offset = startblock * priv->pagesize;
+      buf[1] = offset & 0xff;
+      buf[0] = (offset >> 8) & 0xff;
+
+      while (I2C_WRITE(priv->dev, buf, 2) < 0)
+        {
+          usleep(1000);
+        }
+      I2C_WRITE(priv->dev, buf, priv->pagesize + 2);
+    }
+
+  return OK;
+}
+
+/************************************************************************************
+ * Name: at24c_erase
+ ************************************************************************************/
+
+static int at24c_erase(FAR struct mtd_dev_s *dev, off_t startblock, size_t nblocks)
+{
+  /* EEprom need not erase */
+
+  return (int)nblocks;
+}
+
+/************************************************************************************
+ * Name: at24c_bread
+ ************************************************************************************/
+
+static ssize_t at24c_bread(FAR struct mtd_dev_s *dev, off_t startblock,
+                           size_t nblocks, FAR uint8_t *buffer)
+{
+  FAR struct at24c_dev_s *priv = (FAR struct at24c_dev_s *)dev;
+  size_t blocksleft;
+
+#if CONFIG_AT24XX_MTD_BLOCKSIZE > AT24XX_PAGESIZE
+  startblock *= CONFIG_AT24XX_MTD_BLOCKSIZE / AT24XX_PAGESIZE;
+  nblocks    *= CONFIG_AT24XX_MTD_BLOCKSIZE / AT24XX_PAGESIZE;
+#endif
+  blocksleft  = nblocks;
+
+  fvdbg("startblock: %08lx nblocks: %d\n", (long)startblock, (int)nblocks);
+
+  if (startblock >= priv->npages)
+    {
+      return 0;
+    }
+
+  if (startblock + nblocks > priv->npages)
+    {
+      nblocks = priv->npages - startblock;
+    }
+
+  I2C_SETADDRESS(priv->dev,priv->addr,7);
+  I2C_SETFREQUENCY(priv->dev,100000);
+
+  while (blocksleft-- > 0)
+    {
+      uint16_t offset = startblock * priv->pagesize;
+      uint8_t buf[2];
+      buf[1] = offset & 0xff;
+      buf[0] = (offset >> 8) & 0xff;
+
+      while (I2C_WRITE(priv->dev, buf, 2) < 0)
+        {
+          fvdbg("wait\n");
+          usleep(1000);
+        }
+
+      I2C_READ(priv->dev, buffer, priv->pagesize);
+      startblock++;
+      buffer += priv->pagesize;
+    }
+
+#if CONFIG_AT24XX_MTD_BLOCKSIZE > AT24XX_PAGESIZE
+  return nblocks / (CONFIG_AT24XX_MTD_BLOCKSIZE / AT24XX_PAGESIZE);
+#else
+  return nblocks;
+#endif
+}
+
+/************************************************************************************
+ * Name: at24c_bwrite
+ *
+ * Operates on MTD block's and translates to FLASH pages
+ *
+ ************************************************************************************/
+
+static ssize_t at24c_bwrite(FAR struct mtd_dev_s *dev, off_t startblock, size_t nblocks,
+                            FAR const uint8_t *buffer)
+{
+  FAR struct at24c_dev_s *priv = (FAR struct at24c_dev_s *)dev;
+  size_t blocksleft;
+  uint8_t buf[AT24XX_PAGESIZE+2];
+
+#if CONFIG_AT24XX_MTD_BLOCKSIZE > AT24XX_PAGESIZE
+  startblock *= CONFIG_AT24XX_MTD_BLOCKSIZE / AT24XX_PAGESIZE;
+  nblocks    *= CONFIG_AT24XX_MTD_BLOCKSIZE / AT24XX_PAGESIZE;
+#endif
+  blocksleft  = nblocks;
+
+  if (startblock >= priv->npages)
+    {
+      return 0;
+    }
+
+  if (startblock + nblocks > priv->npages)
+    {
+      nblocks = priv->npages - startblock;
+    }
+
+  fvdbg("startblock: %08lx nblocks: %d\n", (long)startblock, (int)nblocks);
+  I2C_SETADDRESS(priv->dev, priv->addr, 7);
+  I2C_SETFREQUENCY(priv->dev, 100000);
+
+  while (blocksleft-- > 0)
+    {
+      uint16_t offset = startblock * priv->pagesize;
+      while (I2C_WRITE(priv->dev, (uint8_t *)&offset, 2) < 0)
+        {
+          fvdbg("wait\n");
+          usleep(1000);
+        }
+
+      buf[1] = offset & 0xff;
+      buf[0] = (offset >> 8) & 0xff;
+      memcpy(&buf[2], buffer, priv->pagesize);
+
+      I2C_WRITE(priv->dev, buf, priv->pagesize + 2);
+      startblock++;
+      buffer += priv->pagesize;
+    }
+
+#if CONFIG_AT24XX_MTD_BLOCKSIZE > AT24XX_PAGESIZE
+  return nblocks /(CONFIG_AT24XX_MTD_BLOCKSIZE / AT24XX_PAGESIZE);
+#else
+  return nblocks;
+#endif
+}
+
+/************************************************************************************
+ * Name: at24c_ioctl
+ ************************************************************************************/
+
+static int at24c_ioctl(FAR struct mtd_dev_s *dev, int cmd, unsigned long arg)
+{
+  FAR struct at24c_dev_s *priv = (FAR struct at24c_dev_s *)dev;
+  int ret = -EINVAL; /* Assume good command with bad parameters */
+
+  fvdbg("cmd: %d \n", cmd);
+
+  switch (cmd)
+    {
+      case MTDIOC_GEOMETRY:
+        {
+         FAR struct mtd_geometry_s *geo = (FAR struct mtd_geometry_s *)((uintptr_t)arg);
+          if (geo)
+            {
+              /* Populate the geometry structure with information need to know
+               * the capacity and how to access the device.
+               *
+               * NOTE: that the device is treated as though it where just an array
+               * of fixed size blocks.  That is most likely not true, but the client
+               * will expect the device logic to do whatever is necessary to make it
+               * appear so.
+               *
+               * blocksize:
+               *   May be user defined. The block size for the at24XX devices may be
+               *   larger than the page size in order to better support file systems.
+               *   The read and write functions translate BLOCKS to pages for the
+               *   small flash devices
+               * erasesize:
+               *   It has to be at least as big as the blocksize, bigger serves no
+               *   purpose.
+               * neraseblocks
+               *   Note that the device size is in kb, so * 1024 / 8 for bytes
+               */
+
+#if CONFIG_AT24XX_MTD_BLOCKSIZE > AT24XX_PAGESIZE
+              geo->blocksize    = CONFIG_AT24XX_MTD_BLOCKSIZE;
+              geo->erasesize    = geo->blocksize;
+              geo->neraseblocks = CONFIG_AT24XX_SIZE * (1024/8) / geo->erasesize;
+#else
+              geo->blocksize    = priv->pagesize;
+              geo->erasesize    = priv->pagesize;
+              geo->neraseblocks = priv->npages;
+#endif
+              ret               = OK;
+
+              fvdbg("blocksize: %d erasesize: %d neraseblocks: %d\n",
+                    geo->blocksize, geo->erasesize, geo->neraseblocks);
+            }
+        }
+        break;
+
+      case MTDIOC_BULKERASE:
+        ret=at24c_eraseall(priv);
+        break;
+
+      case MTDIOC_XIPBASE:
+      default:
+        ret = -ENOTTY; /* Bad command */
+        break;
+    }
+
+  return ret;
+}
+
+/************************************************************************************
+ * Public Functions
+ ************************************************************************************/
+
+/************************************************************************************
+ * Name: at24c_initialize
+ *
+ * Description:
+ *   Create an initialize MTD device instance.  MTD devices are not registered
+ *   in the file system, but are created as instances that can be bound to
+ *   other functions (such as a block or character driver front end).
+ *
+ ************************************************************************************/
+
+FAR struct mtd_dev_s *at24c_initialize(FAR struct i2c_dev_s *dev)
+{
+  FAR struct at24c_dev_s *priv;
+
+  fvdbg("dev: %p\n", dev);
+
+  /* Allocate a state structure (we allocate the structure instead of using
+   * a fixed, static allocation so that we can handle multiple FLASH devices.
+   * The current implementation would handle only one FLASH part per I2C
+   * device (only because of the SPIDEV_FLASH definition) and so would have
+   * to be extended to handle multiple FLASH parts on the same I2C bus.
+   */
+
+  priv = &g_at24c;
+  if (priv)
+    {
+      /* Initialize the allocated structure */
+ 
+      priv->addr       = CONFIG_AT24XX_ADDR;
+      priv->pagesize   = AT24XX_PAGESIZE;
+      priv->npages     = AT24XX_NPAGES;
+
+      priv->mtd.erase  = at24c_erase;
+      priv->mtd.bread  = at24c_bread;
+      priv->mtd.bwrite = at24c_bwrite;
+      priv->mtd.ioctl  = at24c_ioctl;
+      priv->dev        = dev;
+    }
+
+  /* Return the implementation-specific state structure as the MTD device */
+
+  fvdbg("Return %p\n", priv);
+  return (FAR struct mtd_dev_s *)priv;
+}
+
+#endif