drivers/mtd/mtdblock.c

Source file repositories/reference/linux-study-clean/drivers/mtd/mtdblock.c

File Facts

System
Linux kernel
Corpus path
drivers/mtd/mtdblock.c
Extension
.c
Size
8965 bytes
Lines
362
Domain
Driver Families
Bucket
drivers/mtd
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

struct mtdblk_dev {
	struct mtd_blktrans_dev mbd;
	int count;
	struct mutex cache_mutex;
	unsigned char *cache_data;
	unsigned long cache_offset;
	unsigned int cache_size;
	enum { STATE_EMPTY, STATE_CLEAN, STATE_DIRTY } cache_state;
};

/*
 * Cache stuff...
 *
 * Since typical flash erasable sectors are much larger than what Linux's
 * buffer cache can handle, we must implement read-modify-write on flash
 * sectors for each block write requests.  To avoid over-erasing flash sectors
 * and to speed things up, we locally cache a whole flash sector while it is
 * being written to until a different sector is required.
 */

static int erase_write (struct mtd_info *mtd, unsigned long pos,
			unsigned int len, const char *buf)
{
	struct erase_info erase;
	size_t retlen;
	int ret;

	/*
	 * First, let's erase the flash block.
	 */
	erase.addr = pos;
	erase.len = len;

	ret = mtd_erase(mtd, &erase);
	if (ret) {
		printk (KERN_WARNING "mtdblock: erase of region [0x%lx, 0x%x] "
				     "on \"%s\" failed\n",
			pos, len, mtd->name);
		return ret;
	}

	/*
	 * Next, write the data to flash.
	 */

	ret = mtd_write(mtd, pos, len, &retlen, buf);
	if (ret)
		return ret;
	if (retlen != len)
		return -EIO;
	return 0;
}


static int write_cached_data (struct mtdblk_dev *mtdblk)
{
	struct mtd_info *mtd = mtdblk->mbd.mtd;
	int ret;

	if (mtdblk->cache_state != STATE_DIRTY)
		return 0;

	pr_debug("mtdblock: writing cached data for \"%s\" "
			"at 0x%lx, size 0x%x\n", mtd->name,
			mtdblk->cache_offset, mtdblk->cache_size);

	ret = erase_write (mtd, mtdblk->cache_offset,
			   mtdblk->cache_size, mtdblk->cache_data);

	/*
	 * Here we could arguably set the cache state to STATE_CLEAN.
	 * However this could lead to inconsistency since we will not
	 * be notified if this content is altered on the flash by other
	 * means.  Let's declare it empty and leave buffering tasks to
	 * the buffer cache instead.
	 *
	 * If this cache_offset points to a bad block, data cannot be
	 * written to the device. Clear cache_state to avoid writing to
	 * bad blocks repeatedly.
	 */
	if (ret == 0 || ret == -EIO)
		mtdblk->cache_state = STATE_EMPTY;
	return ret;
}


static int do_cached_write (struct mtdblk_dev *mtdblk, unsigned long pos,
			    int len, const char *buf)
{
	struct mtd_info *mtd = mtdblk->mbd.mtd;

Annotation

Implementation Notes