diff options
Diffstat (limited to 'Documentation/ABI/testing/sysfs-class-mtd')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-class-mtd | 71 |
1 files changed, 66 insertions, 5 deletions
diff --git a/Documentation/ABI/testing/sysfs-class-mtd b/Documentation/ABI/testing/sysfs-class-mtd index 4d55a188898..1399bb2da3e 100644 --- a/Documentation/ABI/testing/sysfs-class-mtd +++ b/Documentation/ABI/testing/sysfs-class-mtd @@ -14,8 +14,7 @@ Description: The /sys/class/mtd/mtd{0,1,2,3,...} directories correspond to each /dev/mtdX character device. These may represent physical/simulated flash devices, partitions on a flash - device, or concatenated flash devices. They exist regardless - of whether CONFIG_MTD_CHAR is actually enabled. + device, or concatenated flash devices. What: /sys/class/mtd/mtdXro/ Date: April 2009 @@ -23,8 +22,7 @@ KernelVersion: 2.6.29 Contact: linux-mtd@lists.infradead.org Description: These directories provide the corresponding read-only device - nodes for /sys/class/mtd/mtdX/ . They are only created - (for the benefit of udev) if CONFIG_MTD_CHAR is enabled. + nodes for /sys/class/mtd/mtdX/ . What: /sys/class/mtd/mtdX/dev Date: April 2009 @@ -106,7 +104,7 @@ Description: One of the following ASCII strings, representing the device type: - absent, ram, rom, nor, nand, dataflash, ubi, unknown + absent, ram, rom, nor, nand, mlc-nand, dataflash, ubi, unknown What: /sys/class/mtd/mtdX/writesize Date: April 2009 @@ -123,3 +121,66 @@ Description: half page, or a quarter page). In the case of ECC NOR, it is the ECC block size. + +What: /sys/class/mtd/mtdX/ecc_strength +Date: April 2012 +KernelVersion: 3.4 +Contact: linux-mtd@lists.infradead.org +Description: + Maximum number of bit errors that the device is capable of + correcting within each region covering an ECC step (see + ecc_step_size). This will always be a non-negative integer. + + 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() and mtd_read_oob(). 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 operations. + 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; + i.e., devices for which ecc_strength is zero. + +What: /sys/class/mtd/mtdX/ecc_step_size +Date: May 2013 +KernelVersion: 3.10 +Contact: linux-mtd@lists.infradead.org +Description: + The size of a single region covered by ECC, known as the ECC + step. Devices may have several equally sized ECC steps within + each writesize region. + + It will always be a non-negative integer. In the case of + devices lacking any ECC capability, it is 0. |