From e47f68587b8255410e79166cbdecae290ca8a84e Mon Sep 17 00:00:00 2001
From: Brian Norris <computersforpeace@gmail.com>
Date: Fri, 22 Jun 2012 16:35:39 -0700
Subject: mtd: check for max_bitflips in mtd_read_oob()
mtd_read_oob() has some unexpected similarities to mtd_read(). For
instance, when ops->datbuf != NULL, nand_base.c might return max_bitflips;
however, when ops->datbuf == NULL, nand_base's code potentially could
return -EUCLEAN (no in-tree drivers do this yet). In any case where the
driver might return max_bitflips, we should translate this into an
appropriate return code using the bitflip_threshold.
Essentially, mtd_read_oob() duplicates the logic from mtd_read().
This prevents users of mtd_read_oob() from receiving a positive return
value (i.e., from max_bitflips) and interpreting it as an unknown error.
Artem: amend comments.
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Reviewed-by: Mike Dunn <mikedunn@newsguy.com>
Reviewed-by: Shmulik Ladkani <shmulik.ladkani@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
---
drivers/mtd/mtdcore.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
(limited to 'drivers')
diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index fcfce24f87d..ec794a72975 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -860,10 +860,22 @@ EXPORT_SYMBOL_GPL(mtd_panic_write);
int mtd_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops)
{
+ int ret_code;
ops->retlen = ops->oobretlen = 0;
if (!mtd->_read_oob)
return -EOPNOTSUPP;
- return mtd->_read_oob(mtd, from, ops);
+ /*
+ * In cases where ops->datbuf != NULL, mtd->_read_oob() has semantics
+ * similar to mtd->_read(), returning a non-negative integer
+ * representing max bitflips. In other cases, mtd->_read_oob() may
+ * return -EUCLEAN. In all cases, perform similar logic to mtd_read().
+ */
+ ret_code = mtd->_read_oob(mtd, from, ops);
+ if (unlikely(ret_code < 0))
+ return ret_code;
+ if (mtd->ecc_strength == 0)
+ return 0; /* device lacks ecc */
+ return ret_code >= mtd->bitflip_threshold ? -EUCLEAN : 0;
}
EXPORT_SYMBOL_GPL(mtd_read_oob);
--
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