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Added asserts on geometry and updated config documentation

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littlefs had an unwritten assumption that the block device's program
size would be a multiple of the read size, and the block size would
be a multiple of the program size. This has already caused confusion
for users. Added a note and assert to catch unexpected geometries
early.

Also found that the prog/erase functions indicated they must return
LFS_ERR_CORRUPT to catch bad blocks. This is no longer true as errors
are found by CRC.
This commit is contained in:
Christopher Haster 2018-01-11 11:56:09 -06:00
parent 472ccc4203
commit c2fab8fabb
2 changed files with 9 additions and 3 deletions
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4
lfs.c
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@ -1926,6 +1926,10 @@ static int lfs_init(lfs_t *lfs, const struct lfs_config *cfg) {
}
}
// check that program and read sizes are multiples of the block size
assert(lfs->cfg->prog_size % lfs->cfg->read_size == 0);
assert(lfs->cfg->block_size % lfs->cfg->prog_size == 0);
// check that the block size is large enough to fit ctz pointers
assert(4*lfs_npw2(0xffffffff / (lfs->cfg->block_size-2*4))
<= lfs->cfg->block_size);

8
lfs.h
View File

@ -99,14 +99,14 @@ struct lfs_config {
// Program a region in a block. The block must have previously
// been erased. Negative error codes are propogated to the user.
// The prog function must return LFS_ERR_CORRUPT if the block should
// be considered bad.
// May return LFS_ERR_CORRUPT if the block should be considered bad.
int (*prog)(const struct lfs_config *c, lfs_block_t block,
lfs_off_t off, const void *buffer, lfs_size_t size);
// Erase a block. A block must be erased before being programmed.
// The state of an erased block is undefined. Negative error codes
// are propogated to the user.
// May return LFS_ERR_CORRUPT if the block should be considered bad.
int (*erase)(const struct lfs_config *c, lfs_block_t block);
// Sync the state of the underlying block device. Negative error codes
@ -121,11 +121,13 @@ struct lfs_config {
// Minimum size of a block program. This determines the size of program
// buffers. This may be larger than the physical program size to improve
// performance by caching more of the block device.
// Must be a multiple of the read size.
lfs_size_t prog_size;
// Size of an erasable block. This does not impact ram consumption and
// may be larger than the physical erase size. However, this should be
// kept small as each file currently takes up an entire block .
// kept small as each file currently takes up an entire block.
// Must be a multiple of the program size.
lfs_size_t block_size;
// Number of erasable blocks on the device.