drivers/mtd_sdmmc: remove MTD_DRIVER_FLAG_DIRECT_WRITE

[fabian18]

Contribution description

Removing MTD_DRIVER_FLAG_DIRECT_WRITE for mtd_sdmmc_driver as the MTD driver does not expect to have no dev->work_area.

RIOT/drivers/mtd_sdmmc/mtd_sdmmc.c

Lines 99 to 129 in e8be6ee

	static int mtd_sdmmc_write_page(mtd_dev_t *dev, const void *buff, uint32_t page,
	uint32_t offset, uint32_t size)
	{
	mtd_sdmmc_t *mtd_sd = (mtd_sdmmc_t*)dev;
	DEBUG("mtd_sdmmc_write_page: page:%" PRIu32 " offset:%" PRIu32 " size:%" PRIu32 "\n",
	page, offset, size);
	if (offset || size % SDMMC_SDHC_BLOCK_SIZE) {
	#if IS_USED(MODULE_MTD_WRITE_PAGE)
	if (dev->work_area == NULL) {
	DEBUG("mtd_sdmmc_write_page: no work area\n");
	return -ENOTSUP;
	}
	if (sdmmc_read_blocks(mtd_sd->sdmmc, page, SDMMC_SDHC_BLOCK_SIZE,
	1, dev->work_area, NULL)) {
	return -EIO;
	}
	size = MIN(size, SDMMC_SDHC_BLOCK_SIZE - offset);
	DEBUG("mtd_sdmmc_write_page: write %" PRIu32 " bytes at offset %" PRIu32 "\n",
	size, offset);
	memcpy((uint8_t *)dev->work_area + offset, buff, size);
	if (sdmmc_write_blocks(mtd_sd->sdmmc, page, SDMMC_SDHC_BLOCK_SIZE,
	1, dev->work_area, NULL)) {
	return -EIO;
	}
	#else
	return -ENOTSUP;
	#endif

The work area is only allocated when the flag is not set.

RIOT/drivers/mtd/mtd.c

Lines 77 to 84 in e8be6ee

	#ifdef MODULE_MTD_WRITE_PAGE
	if ((mtd->driver->flags & MTD_DRIVER_FLAG_DIRECT_WRITE) == 0) {
	mtd->work_area = malloc(mtd->pages_per_sector * mtd->page_size);
	if (mtd->work_area == NULL) {
	res = -ENOMEM;
	}
	}
	#endif

Testing procedure

Custom board with an eMMC. I can craete a fatfs filesystem on it with:

ifneq (,$(filter mtd,$(USEMODULE)))
  USEMODULE += mtd_write_page
  USEMODULE += mtd_sdmmc_default
  USEMODULE += sdmmc_mmc
endif

ifneq (,$(filter vfs_default,$(USEMODULE)))
  USEMODULE += fatfs_vfs
  USEMODULE += mtd
endif

Issues/PRs references

[benpicco]

MTD_DRIVER_FLAG_DIRECT_WRITE is still correct - you don't need to erase a sector to write it.
I do wonder how fatfs does unaligned writes though, mtd_diskio.c always operates on whole pages.