Commit d7904619 authored by Miquel Raynal's avatar Miquel Raynal
Browse files

mtd: rawnand: Add nand_extract_bits() 



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: default avatarMiquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: default avatarBoris Brezillon <boris.brezillon@collabora.com>
Link: https://lore.kernel.org/linux-mtd/20200519074549.23673-5-miquel.raynal@bootlin.com
parent 0651ed50

drivers/mtd/nand/raw/nand_base.c

+44 −0
Original line number Diff line number Diff line
@@ -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

include/linux/mtd/rawnand.h

+4 −0
Original line number Diff line number Diff line
@@ -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

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