mtd: nand: add ->badblockbits for minimum number of set bits in bad block byte

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Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=e0b58d0a7005cd4b9c7fa4694a437a2d86719c13
Commit:     e0b58d0a7005cd4b9c7fa4694a437a2d86719c13
Parent:     b64d39d8b03fea88417d53715ccbebf71d4dcc9f
Author:     Maxim Levitsky <maximlevitsky at gmail.com>
AuthorDate: Mon Feb 22 20:39:38 2010 +0200
Committer:  David Woodhouse <David.Woodhouse at intel.com>
CommitDate: Fri Feb 26 18:02:07 2010 +0000

    mtd: nand: add ->badblockbits for minimum number of set bits in bad block byte
    
    This can be used to protect against bitflips in that field, but now mostly
    for smartmedia.
    
    Signed-off-by: Maxim Levitsky <maximlevitsky at gmail.com>
    Signed-off-by: David Woodhouse <David.Woodhouse at intel.com>
---
 drivers/mtd/nand/nand_base.c |   13 +++++++++----
 include/linux/mtd/nand.h     |    1 +
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index 51dfea1..ba29a29 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -364,14 +364,18 @@ static int nand_block_bad(struct mtd_info *mtd, loff_t ofs, int getchip)
 		bad = cpu_to_le16(chip->read_word(mtd));
 		if (chip->badblockpos & 0x1)
 			bad >>= 8;
-		if ((bad & 0xFF) != 0xff)
-			res = 1;
+		else
+			bad &= 0xFF;
 	} else {
 		chip->cmdfunc(mtd, NAND_CMD_READOOB, chip->badblockpos, page);
-		if (chip->read_byte(mtd) != 0xff)
-			res = 1;
+		bad = chip->read_byte(mtd);
 	}
 
+	if (likely(chip->badblockbits == 8))
+		res = bad != 0xFF;
+	else
+		res = hweight8(bad) < chip->badblockbits;
+
 	if (getchip)
 		nand_release_device(mtd);
 
@@ -2884,6 +2888,7 @@ static struct nand_flash_dev *nand_get_flash_type(struct mtd_info *mtd,
 	/* Set the bad block position */
 	chip->badblockpos = mtd->writesize > 512 ?
 		NAND_LARGE_BADBLOCK_POS : NAND_SMALL_BADBLOCK_POS;
+	chip->badblockbits = 8;
 
 	/* Get chip options, preserve non chip based options */
 	chip->options &= ~NAND_CHIPOPTIONS_MSK;
diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
index 48bc2c5..f2d4a1a 100644
--- a/include/linux/mtd/nand.h
+++ b/include/linux/mtd/nand.h
@@ -401,6 +401,7 @@ struct nand_chip {
 	int		subpagesize;
 	uint8_t		cellinfo;
 	int		badblockpos;
+	int		badblockbits;
 
 	flstate_t	state;