From edbc4540e02c201bdd4f4d498ebb6ed517fd36e2 Mon Sep 17 00:00:00 2001 From: Mike Dunn Date: Wed, 25 Apr 2012 12:06:11 -0700 Subject: mtd: driver _read() returns max_bitflips; mtd_read() returns -EUCLEAN MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The drivers' _read() method, absent an error, returns a non-negative integer indicating the maximum number of bit errors that were corrected in any one region comprising an ecc step. MTD returns -EUCLEAN if this is >= bitflip_threshold, 0 otherwise. If bitflip_threshold is zero, the comparison is not made since these devices lack ECC and always return zero in the non-error case (thanks Brian)¹. Note that this is a subtle change to the driver interface. This and the preceding patches in this set were tested with ubi on top of the nandsim and docg4 devices, running the ubi test io_basic from mtd-utils. ¹ http://lists.infradead.org/pipermail/linux-mtd/2012-March/040468.html Signed-off-by: Mike Dunn Acked-by: Robert Jarzmik Acked-by: Brian Norris Ivan Djelic Signed-off-by: Artem Bityutskiy Signed-off-by: David Woodhouse --- Documentation/ABI/testing/sysfs-class-mtd | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'Documentation') diff --git a/Documentation/ABI/testing/sysfs-class-mtd b/Documentation/ABI/testing/sysfs-class-mtd index 78835080856..db1ad7e34fc 100644 --- a/Documentation/ABI/testing/sysfs-class-mtd +++ b/Documentation/ABI/testing/sysfs-class-mtd @@ -167,7 +167,10 @@ Description: block degradation, but high enough to avoid the consequences of a persistent return value of -EUCLEAN on devices where sticky bitflips occur. Note that if bitflip_threshold exceeds - ecc_strength, -EUCLEAN is never returned by the read functions. + ecc_strength, -EUCLEAN is never returned by mtd_read(). + Conversely, if bitflip_threshold is zero, -EUCLEAN is always + returned, absent a hard error. This is generally applicable only to NAND flash devices with ECC - capability. It is ignored on devices lacking ECC capability. + capability. It is ignored on devices lacking ECC capability; + i.e., devices for which ecc_strength is zero. -- cgit v1.2.3-70-g09d2