6 files changed, 87 insertions, 7 deletions
diff --git a/nuttx/ChangeLog b/nuttx/ChangeLog
index f1780c323..f56e14c04 100644
--- a/nuttx/ChangeLog
+++ b/nuttx/ChangeLog
@@ -3309,4 +3309,10 @@
 	  by Kate).
 	* arch/avr/src: Fixes from AVR32 build errors that have crept in
 	  over the time; incorporated Kconfig for AVR3 (Richard Cochran).
+	* fs/fat and include/nuttx/fs/fat.h: The FAT file system allocates
+	  memory for sector I/O buffers used to exchange data with the
+	  configured block driver.  In some contexts, the block driver may
+	  require DMA-capable memory.  If CONFIG_FAT_DMAMEMORY is defined,
+	  then the FAT FS will use platform-provided DMA memory allocators
+	  to allocate the block driver I/O buffers.
 
diff --git a/nuttx/fs/fat/Kconfig b/nuttx/fs/fat/Kconfig
index fed054b5b..1de613ce4 100644
--- a/nuttx/fs/fat/Kconfig
+++ b/nuttx/fs/fat/Kconfig
@@ -41,9 +41,26 @@ config FAT_MAXFNAME
 config FS_FATTIME
 	bool "FAT timestamps"
 	default n
-	---help---	
+	---help---
 		Support FAT date and time. NOTE:  There is not
 		much sense in supporting FAT date and time unless you have a
 		hardware RTC or other way to get the time and date.
 
+config FAT_DMAMEMORY
+	bool "DMA memory allocator"
+	default n
+	---help---
+		The FAT file system allocates two I/O buffers for data transfer, each
+		are the size of one device sector.  One of the buffers is allocated
+		once for each FAT volume that is mounted; the other buffers are
+		allocated each time a FAT file is opened.
+
+		Some hardware, however, may require special DMA-capable memory in
+		order to perform the the transfers.  If FAT_DMAMEMORY is defined
+		then the architecture-specific hardware must provide the funtions
+		fat_dma_alloc() and fat_dma_free():  fat_dmalloc() will allocate
+		DMA-capable memory of the specified size; fat_dmafree() is the
+		corresponding function that will be called to free the DMA-capable
+		memory.
+
 endif
diff --git a/nuttx/fs/fat/fs_fat32.c b/nuttx/fs/fat/fs_fat32.c
index 7b7ce1f5f..60622e2f7 100644
--- a/nuttx/fs/fat/fs_fat32.c
+++ b/nuttx/fs/fat/fs_fat32.c
@@ -302,7 +302,7 @@ static int fat_open(FAR struct file *filep, const char *relpath,
 
   /* Create a file buffer to support partial sector accesses */
 
-  ff->ff_buffer = (uint8_t*)kmalloc(fs->fs_hwsectorsize);
+  ff->ff_buffer = (uint8_t*)fat_io_alloc(fs->fs_hwsectorsize);
   if (!ff->ff_buffer)
     {
       ret = -ENOMEM;
@@ -405,7 +405,7 @@ static int fat_close(FAR struct file *filep)
 
   if (ff->ff_buffer)
     {
-      kfree(ff->ff_buffer);
+      fat_io_free(ff->ff_buffer);
     }
 
   /* Then free the file structure itself. */
@@ -1651,8 +1651,9 @@ static int fat_unbind(void *handle, FAR struct inode **blkdriver)
 
       if (fs->fs_buffer)
         {
-          kfree(fs->fs_buffer);
+          fat_io_free(fs->fs_buffer);
         }
+
       kfree(fs);
     }
 
diff --git a/nuttx/fs/fat/fs_fat32.h b/nuttx/fs/fat/fs_fat32.h
index 5b82ff701..c7fa5219c 100644
--- a/nuttx/fs/fat/fs_fat32.h
+++ b/nuttx/fs/fat/fs_fat32.h
@@ -48,6 +48,7 @@
 #include <semaphore.h>
 #include <time.h>
 
+#include <nuttx/kmalloc.h>
 #include <nuttx/fs/dirent.h>
 
 /****************************************************************************
@@ -677,6 +678,33 @@
 #endif
 
 /****************************************************************************
+ * Name: fat_io_alloc and fat_io_free
+ *
+ * Description:
+ *   The FAT file system allocates two I/O buffers for data transfer, each
+ *   are the size of one device sector.  One of the buffers is allocated
+ *   once for each FAT volume that is mounted; the other buffers are
+ *   allocated each time a FAT file is opened.
+ *
+ *   Some hardware, however, may require special DMA-capable memory in
+ *   order to perform the the transfers.  If CONFIG_FAT_DMAMEMORY is defined
+ *   then the architecture-specific hardware must provide the funtions
+ *   fat_dma_alloc() and fat_dma_free() as prototyped below:  fat_dmalloc()
+ *   will allocate DMA-capable memory of the specified size; fat_dmafree()
+ *   is the corresponding function that will be called to free the DMA-
+ *   capable memory.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_FAT_DMAMEMORY
+#  define fat_io_alloc(s) fat_dma_alloc(s)
+#  define fat_io_free(s)  fat_dma_free(s)
+#else
+#  define fat_io_alloc(s) kmalloc(s)
+#  define fat_io_free(s)  kfree(s)
+#endif
+
+/****************************************************************************
  * Public Types
  ****************************************************************************/
 
diff --git a/nuttx/fs/fat/fs_fat32util.c b/nuttx/fs/fat/fs_fat32util.c
index b88046d79..f8f5ef495 100644
--- a/nuttx/fs/fat/fs_fat32util.c
+++ b/nuttx/fs/fat/fs_fat32util.c
@@ -542,7 +542,7 @@ int fat_mount(struct fat_mountpt_s *fs, bool writeable)
 
   /* Allocate a buffer to hold one hardware sector */
 
-  fs->fs_buffer = (uint8_t*)kmalloc(fs->fs_hwsectorsize);
+  fs->fs_buffer = (uint8_t*)fat_io_alloc(fs->fs_hwsectorsize);
   if (!fs->fs_buffer)
     {
       ret = -ENOMEM;
@@ -668,7 +668,7 @@ int fat_mount(struct fat_mountpt_s *fs, bool writeable)
   return OK;
 
  errout_with_buffer:
-  kfree(fs->fs_buffer);
+  fat_io_free(fs->fs_buffer);
   fs->fs_buffer = 0;
  errout:
   fs->fs_mounted = false;
diff --git a/nuttx/include/nuttx/fs/fat.h b/nuttx/include/nuttx/fs/fat.h
index f69bd8571..3ae0fbee2 100644
--- a/nuttx/include/nuttx/fs/fat.h
+++ b/nuttx/include/nuttx/fs/fat.h
@@ -75,11 +75,39 @@ extern "C" {
 #define EXTERN extern
 #endif
 
-/* Non-standard functions to get and set FAT file/directory attributes */
+/****************************************************************************
+ * Name: fat_getattrib and fat_setattrib
+ *
+ * Description:
+ *   Non-standard functions to get and set FAT file/directory attributes
+ *
+ ****************************************************************************/
 
 EXTERN int fat_getattrib(const char *path, fat_attrib_t *attrib);
 EXTERN int fat_setattrib(const char *path, fat_attrib_t setbits, fat_attrib_t clearbits);
 
+/****************************************************************************
+ * Name: fat_dma_alloc and fat_dma_free
+ *
+ * Description:
+ *   The FAT file system allocates two I/O buffers for data transfer, each
+ *   are the size of one device sector.  One of the buffers is allocated
+ *   once for each FAT volume that is mounted; the other buffers are
+ *   allocated each time a FAT file is opened.
+ *
+ *   Some hardware, however, may require special DMA-capable memory in
+ *   order to perform the the transfers.  If CONFIG_FAT_DMAMEMORY is defined
+ *   then the architecture-specific hardware must provide the funtions
+ *   fat_dma_alloc() and fat_dma_free() as prototyped below:  fat_dmalloc()
+ *   will allocate DMA-capable memory of the specified size; fat_dmafree()
+ *   is the corresponding function that will be called to free the DMA-
+ *   capable memory.
+ *
+ ****************************************************************************/
+
+EXTERN FAR void *fat_dma_alloc(size_t size);
+EXTERN void fat_dma_free(FAR void *memory);
+
 #undef EXTERN
 #ifdef __cplusplus
 }