linux-kernel - [PATCH] mtd: nand: s3c2410: fix bug in s3c2410_nand_correct

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Message-Id: <1460047697-72830-1-git-send-email-zengzhaoxiu@163.com>
Date:	Fri,  8 Apr 2016 00:48:17 +0800
From:	zengzhaoxiu@....com
To:	kgene@...nel.org, k.kozlowski@...sung.com,
	boris.brezillon@...e-electrons.com, richard@....at,
	dwmw2@...radead.org, computersforpeace@...il.com
Cc:	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, linux-mtd@...ts.infradead.org,
	linux-kernel@...r.kernel.org, Zeng Zhaoxiu <zhaoxiu.zeng@...il.com>
Subject: [PATCH] mtd: nand: s3c2410: fix bug in s3c2410_nand_correct_data()

From: Zeng Zhaoxiu <zhaoxiu.zeng@...il.com>

If there is only one bit difference in the ECC, the function should return 1.
The result of "diff0 & ~(1<<fls(diff0))" is equal to diff0, so the function
actually returns -1.

Here, we can use the simple expression "(diff0 & (diff0 - 1)) == 0" to determine
whether the diff0 has only one 1-bit.
---
 drivers/mtd/nand/s3c2410.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/s3c2410.c b/drivers/mtd/nand/s3c2410.c
index 9c9397b..c9698cf 100644
--- a/drivers/mtd/nand/s3c2410.c
+++ b/drivers/mtd/nand/s3c2410.c
@@ -542,7 +542,7 @@ static int s3c2410_nand_correct_data(struct mtd_info *mtd, u_char *dat,
 	diff0 |= (diff1 << 8);
 	diff0 |= (diff2 << 16);
 
-	if ((diff0 & ~(1<<fls(diff0))) == 0)
+	if ((diff0 & (diff0 - 1)) == 0)
 		return 1;
 
 	return -1;
-- 
2.5.5