fat: remove disk_read_sdram API, and move that into the SDFS backend

include/fat.h

@@ -37,14 +37,63 @@ extern "C" {
  * volume.
  */
 typedef struct {
-	///@cond
+    /**
+     * @brief Initialize the underlying device.
+     * 
+     * This function is called at mount time.
+     * 
+     * @return Disk status codes (see fatfs/diskio.h)
+     * @see http://elm-chan.org/fsw/ff/doc/dinit.html
+     */
 	int (*disk_initialize)(void);
+
+    /**
+     * @brief Return the current status of the underlying device.
+     * 
+     * Return the current status of the device. The status can be
+     * a combination of:
+     * 
+     *  * STA_NOINIT: device must be reinitialized
+     *  * STA_NODISK: no medium in the device
+     *  * STA_PROTECT: write protected
+     * 
+     * @return Disk status codes (see fatfs/diskio.h)
+     * @see http://elm-chan.org/fsw/ff/doc/dstat.html
+     */
 	int (*disk_status)(void);
+
+    /**
+     * @brief Read sectors from the underlying device into RDRAM.
+     * 
+     * This function reads sectors from the underlying device into RDRAM.
+     * 
+     * @return Result code (see fatfs/diskio.h)
+     * @see http://elm-chan.org/fsw/ff/doc/dread.html
+     */
 	int (*disk_read)(uint8_t* buff, int64_t sector, int count);
-	int (*disk_read_sdram)(uint8_t* buff, int64_t sector, int count);
+
+    /**
+     * @brief Write sectors from RDRAM to the underlying device.
+     * 
+     * This function writes sectors from RDRAM to the underlying device.
+     * 
+     * @return Result code (see fatfs/diskio.h)
+     * @see http://elm-chan.org/fsw/ff/doc/dwrite.html
+     */
 	int (*disk_write)(const uint8_t* buff, int64_t sector, int count);
+
+    /**
+     * @brief Perform a I/O request on the underlying device.
+     * 
+     * This function performs a I/O request on the underlying device.
+     * FatFs uses this function to perform various operations like
+     * getting the sector count, the sector size, etc. It can be
+     * used to implement custom operations as well.
+     * 
+     * @return Result code (see fatfs/diskio.h)
+     * @see http://elm-chan.org/fsw/ff/doc/dioctl.html
+     */
 	int (*disk_ioctl)(uint8_t cmd, void* buff);
-	///@endcond
 } fat_disk_t;
 
 

src/debug.c

@@ -187,18 +187,27 @@ static int fat_disk_initialize_sd(void)
 
 static int fat_disk_read_sd(uint8_t* buff, int64_t sector, int count)
 {
+	_Static_assert(FF_MIN_SS == 512, "this function assumes sector size == 512");
+	_Static_assert(FF_MAX_SS == 512, "this function assumes sector size == 512");
 	assertf((uint32_t)sector == sector, "unsupported access to SD card > 2 TiB");
-	return cart_card_rd_dram(buff, sector, count) ? RES_ERROR : RES_OK;
-}
 
-static int fat_disk_read_sdram_sd(uint8_t* buff, int64_t sector, int count)
-{
-	assertf((uint32_t)sector == sector, "unsupported access to SD card > 2 TiB");
-	return cart_card_rd_cart(PhysicalAddr(buff), sector, count) ? RES_ERROR : RES_OK;
+	// Check whether the user is requesting a read into RDRAM, or into
+	// the cartridge's SDRAM (that is, a PI-accessible address). We try
+	// to be generic here and not hardcode specific addresses; we assume
+	// libcart will know better than us where the SDRAM is located.
+	if (PhysicalAddr(buff) < 0x00800000)
+		return cart_card_rd_dram(buff, sector, count) ? RES_ERROR : RES_OK;
+	if (io_accessible(PhysicalAddr(buff)))
+		return cart_card_rd_cart(PhysicalAddr(buff), sector, count) ? RES_ERROR : RES_OK;
+
+	return RES_PARERR;
 }
 
+
 static int fat_disk_write_sd(const uint8_t* buff, int64_t sector, int count)
 {
+	_Static_assert(FF_MIN_SS == 512, "this function assumes sector size == 512");
+	_Static_assert(FF_MAX_SS == 512, "this function assumes sector size == 512");
 	assertf((uint32_t)sector == sector, "unsupported access to SD card > 2 TiB");
 	return cart_card_wr_dram(buff, sector, count) ? RES_ERROR : RES_OK;
 }
@@ -208,7 +217,6 @@ static fat_disk_t fat_disk_sd =
 	.disk_initialize = fat_disk_initialize_sd,
 	.disk_status = fat_disk_status_default,
 	.disk_read = fat_disk_read_sd,
-	.disk_read_sdram = fat_disk_read_sdram_sd,
 	.disk_write = fat_disk_write_sd,
 	.disk_ioctl = fat_disk_ioctl_default,
 };

src/fat.c

@@ -30,19 +30,13 @@ DSTATUS disk_status(BYTE pdrv)
 
 DRESULT disk_read(BYTE pdrv, BYTE* buff, LBA_t sector, UINT count)
 {
-	_Static_assert(FF_MIN_SS == 512, "this function assumes sector size == 512");
-	_Static_assert(FF_MAX_SS == 512, "this function assumes sector size == 512");
-	if (fat_disks[pdrv].disk_read && PhysicalAddr(buff) < 0x00800000)
+	if (fat_disks[pdrv].disk_read)
 		return fat_disks[pdrv].disk_read(buff, sector, count);
-	if (fat_disks[pdrv].disk_read_sdram && io_accessible(PhysicalAddr(buff)))
-		return fat_disks[pdrv].disk_read_sdram(buff, sector, count);
 	return RES_PARERR;
 }
 
 DRESULT disk_write(BYTE pdrv, const BYTE* buff, LBA_t sector, UINT count)
 {
-	_Static_assert(FF_MIN_SS == 512, "this function assumes sector size == 512");
-	_Static_assert(FF_MAX_SS == 512, "this function assumes sector size == 512");
 	if (fat_disks[pdrv].disk_write)
 		return fat_disks[pdrv].disk_write(buff, sector, count);
 	return RES_PARERR;