linux-kernel - [PATCH 11/15] MTD: nand: add ->badblockbits to specify the minimum number of bits in bad block byte to consider the block good

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Message-Id: <1266863982-5258-12-git-send-email-maximlevitsky@gmail.com>
Date:	Mon, 22 Feb 2010 20:39:38 +0200
From:	Maxim Levitsky <maximlevitsky@...il.com>
To:	David Woodhouse <dwmw2@...radead.org>
Cc:	linux-mtd <linux-mtd@...ts.infradead.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Alex Dubov <oakad@...oo.com>, joern <joern@...fs.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	<stanley.miao@...driver.com>, Vitaly Wool <vitalywool@...il.com>,
	Maxim Levitsky <maximlevitsky@...il.com>
Subject: [PATCH 11/15] MTD: nand: add ->badblockbits to specify the minimum number of bits in bad block byte to consider the block good

This can be used to protect against bitflips in that field, but now mostly
for smartmedia.

Signed-off-by: Maxim Levitsky <maximlevitsky@...il.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;
 
-- 
1.6.3.3

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