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mtd: rawnand: Add nand_extract_bits()

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There are cases where ECC bytes are not byte-aligned. Indeed, BCH
implies using a number of ECC bits, which are not always a multiple of
8. We then need a helper like nand_extract_bits() to extract these
syndromes from a buffer.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://lore.kernel.org/linux-mtd/20200519074549.23673-5-miquel.raynal@bootlin.com
This commit is contained in:
Miquel Raynal 2020-05-19 09:45:45 +02:00
parent 0651ed5082
commit d7904619ea
2 changed files with 48 additions and 0 deletions
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44
drivers/mtd/nand/raw/nand_base.c
View File

@ -274,6 +274,50 @@ static int check_offs_len(struct nand_chip *chip, loff_t ofs, uint64_t len)
return ret;
}
/**
* nand_extract_bits - Copy unaligned bits from one buffer to another one
* @dst: destination buffer
* @dst_off: bit offset at which the writing starts
* @src: source buffer
* @src_off: bit offset at which the reading starts
* @nbits: number of bits to copy from @src to @dst
*
* Copy bits from one memory region to another (overlap authorized).
*/
void nand_extract_bits(u8 *dst, unsigned int dst_off, const u8 *src,
unsigned int src_off, unsigned int nbits)
{
unsigned int tmp, n;
dst += dst_off / 8;
dst_off %= 8;
src += src_off / 8;
src_off %= 8;
while (nbits) {
n = min3(8 - dst_off, 8 - src_off, nbits);
tmp = (*src >> src_off) & GENMASK(n - 1, 0);
*dst &= ~GENMASK(n - 1 + dst_off, dst_off);
*dst |= tmp << dst_off;
dst_off += n;
if (dst_off >= 8) {
dst++;
dst_off -= 8;
}
src_off += n;
if (src_off >= 8) {
src++;
src_off -= 8;
}
nbits -= n;
}
}
EXPORT_SYMBOL_GPL(nand_extract_bits);
/**
* nand_select_target() - Select a NAND target (A.K.A. die)
* @chip: NAND chip object

4
include/linux/mtd/rawnand.h
View File

@ -1414,6 +1414,10 @@ int nand_gpio_waitrdy(struct nand_chip *chip, struct gpio_desc *gpiod,
void nand_select_target(struct nand_chip *chip, unsigned int cs);
void nand_deselect_target(struct nand_chip *chip);
/* Bitops */
void nand_extract_bits(u8 *dst, unsigned int dst_off, const u8 *src,
unsigned int src_off, unsigned int nbits);
/**
* nand_get_data_buf() - Get the internal page buffer
* @chip: NAND chip object