Commit e47f6858 authored by Brian Norris's avatar Brian Norris Committed by David Woodhouse

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: default avatarBrian Norris <>
Reviewed-by: default avatarMike Dunn <>
Reviewed-by: default avatarShmulik Ladkani <>
Signed-off-by: default avatarArtem Bityutskiy <>
Signed-off-by: default avatarDavid Woodhouse <>
parent 8bb8b85f
......@@ -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 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;
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