mtd: do not assume oobsize is power of 2 (305b93f1) · Commits · 戴 / test

Previous generations of MTDs all used OOB sizes that were powers of 2, (e.g., 64, 128). However, newer generations of flash, especially NAND, use irregular OOB sizes that are not powers of 2 (e.g., 218, 224, 448). This means we cannot use masks like "mtd->oobsize - 1" to assume that we will get a proper bitmask for OOB operations. These masks are really only intended to hide the "page" portion of the offset, leaving any OOB offset intact, so a masking with the writesize (which *is* always a power of 2) is valid and makes more sense. This has been tested for read/write of NAND devices (nanddump/nandwrite) using nandsim and actual NAND flash. Signed-off-by:

Brian Norris <computersforpeace@gmail.com> Signed-off-by:

Artem Bityutskiy <artem.bityutskiy@intel.com>

drivers/mtd/mtdchar.c

+4 −4

Original line number	Diff line number	Diff line
		@@ -410,7 +410,7 @@ static int mtd_do_writeoob(struct file file, struct mtd_info mtd,
		return ret;

		ops.ooblen = length;
		ops.ooboffs = start & (mtd->oobsize - 1);
		ops.ooboffs = start & (mtd->writesize - 1);
		ops.datbuf = NULL;
		ops.mode = MTD_OOB_PLACE;

		@@ -421,7 +421,7 @@ static int mtd_do_writeoob(struct file file, struct mtd_info mtd,
		if (IS_ERR(ops.oobbuf))
		return PTR_ERR(ops.oobbuf);

		start &= ~((uint64_t)mtd->oobsize - 1);
		start &= ~((uint64_t)mtd->writesize - 1);
		ret = mtd->write_oob(mtd, start, &ops);

		if (ops.oobretlen > 0xFFFFFFFFU)
		@@ -452,7 +452,7 @@ static int mtd_do_readoob(struct mtd_info *mtd, uint64_t start,
		return ret;

		ops.ooblen = length;
		ops.ooboffs = start & (mtd->oobsize - 1);
		ops.ooboffs = start & (mtd->writesize - 1);
		ops.datbuf = NULL;
		ops.mode = MTD_OOB_PLACE;

		@@ -463,7 +463,7 @@ static int mtd_do_readoob(struct mtd_info *mtd, uint64_t start,
		if (!ops.oobbuf)
		return -ENOMEM;

		start &= ~((uint64_t)mtd->oobsize - 1);
		start &= ~((uint64_t)mtd->writesize - 1);
		ret = mtd->read_oob(mtd, start, &ops);

		if (put_user(ops.oobretlen, retp))

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