[PATCH] nand_base: fix regression on nand with 64/128 oob size

Alexander Couzens lynxis at fe80.eu
Sun Mar 12 13:02:32 PDT 2017


41b207a70d3a accidently changed the oob layout for nand when ECC doesn't use
the full available ecc reserved data.
This only affects controllers which use the default large page ops
nand_ooblayout_ecc_lp.

E.g. for davinci:
- nand has 2048 byte page, 64 byte oob
- 3 byte ecc every 512 byte using 1bit hw ecc
- requires 12 byte of oob space for ecc
- old layout reserved 24 byte based on 64 byte oob

Old layout started using byte from offset 40 while new layout
uses the last X bytes so it fits into the end of oob.
Meaning in this example the old layout uses byte 40-51, while
the new layout use byte 52-63.

Signed-off-by: Alexander Couzens <lynxis at fe80.eu>
---
 drivers/mtd/nand/nand_base.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index b0524f8accb6..ba88345fd334 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -112,8 +112,25 @@ static int nand_ooblayout_ecc_lp(struct mtd_info *mtd, int section,
 	if (section)
 		return -ERANGE;
 
+	/* to be compatible with previous layouts
+	 * 64 byte oob must have ecc data at byte 40,
+	 * 128 byte oob must have ecc data at byte 80 */
+	switch (mtd->oobsize) {
+	case 64:
+		oobregion->offset = 40;
+		break;
+	case 128:
+		oobregion->offset = 80;
+		break;
+	default:
+		oobregion->offset = mtd->oobsize - oobregion->length;
+		break;
+	}
+
 	oobregion->length = ecc->total;
-	oobregion->offset = mtd->oobsize - oobregion->length;
+	if (oobregion->offset + oobregion->length > mtd->oobsize) {
+		return -ERANGE;
+	}
 
 	return 0;
 }
-- 
2.12.0




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