diff options
author | Mike Dunn <mikedunn@newsguy.com> | 2012-04-25 21:06:08 +0200 |
---|---|---|
committer | David Woodhouse <David.Woodhouse@intel.com> | 2012-05-14 06:11:39 +0200 |
commit | d062d4ede877fcd2ecc4c6262abad09a6f32950a (patch) | |
tree | 320869428d5aef43b803c4a8131140aabb21c8fb /Documentation/ABI/testing | |
parent | mtd: expose ecc_strength through sysfs (diff) | |
download | linux-d062d4ede877fcd2ecc4c6262abad09a6f32950a.tar.xz linux-d062d4ede877fcd2ecc4c6262abad09a6f32950a.zip |
mtd: bitflip_threshold added to mtd_info and sysfs
An element 'bitflip_threshold' is added to struct mtd_info, and also exposed as
a read/write variable in sysfs. This will be used to determine whether or not
mtd_read() returns -EUCLEAN or 0 (absent a hard error). If the driver leaves it
as zero, mtd will set it to a default value of ecc_strength.
This v2 adds the line that propagates bitflip_threshold from the master to the
partitions - thanks Ivan¹.
¹ http://lists.infradead.org/pipermail/linux-mtd/2012-April/040900.html
Signed-off-by: Mike Dunn <mikedunn@newsguy.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Diffstat (limited to 'Documentation/ABI/testing')
-rw-r--r-- | Documentation/ABI/testing/sysfs-class-mtd | 36 |
1 files changed, 36 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-class-mtd b/Documentation/ABI/testing/sysfs-class-mtd index 43d18180b46e..78835080856a 100644 --- a/Documentation/ABI/testing/sysfs-class-mtd +++ b/Documentation/ABI/testing/sysfs-class-mtd @@ -135,3 +135,39 @@ Description: have multiple ecc steps within each writesize region. In the case of devices lacking any ECC capability, it is 0. + +What: /sys/class/mtd/mtdX/bitflip_threshold +Date: April 2012 +KernelVersion: 3.4 +Contact: linux-mtd@lists.infradead.org +Description: + This allows the user to examine and adjust the criteria by which + mtd returns -EUCLEAN from mtd_read(). If the maximum number of + bit errors that were corrected on any single region comprising + an ecc step (as reported by the driver) equals or exceeds this + value, -EUCLEAN is returned. Otherwise, absent an error, 0 is + returned. Higher layers (e.g., UBI) use this return code as an + indication that an erase block may be degrading and should be + scrutinized as a candidate for being marked as bad. + + The initial value may be specified by the flash device driver. + If not, then the default value is ecc_strength. + + The introduction of this feature brings a subtle change to the + meaning of the -EUCLEAN return code. Previously, it was + interpreted to mean simply "one or more bit errors were + corrected". Its new interpretation can be phrased as "a + dangerously high number of bit errors were corrected on one or + more regions comprising an ecc step". The precise definition of + "dangerously high" can be adjusted by the user with + bitflip_threshold. Users are discouraged from doing this, + however, unless they know what they are doing and have intimate + knowledge of the properties of their device. Broadly speaking, + bitflip_threshold should be low enough to detect genuine erase + 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. + + This is generally applicable only to NAND flash devices with ECC + capability. It is ignored on devices lacking ECC capability. |