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| -rw-r--r-- | Documentation/ABI/testing/sysfs-class-mtd | 242 |
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diff --git a/Documentation/ABI/testing/sysfs-class-mtd b/Documentation/ABI/testing/sysfs-class-mtd new file mode 100644 index 0000000000..f77fa4f6d4 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-class-mtd @@ -0,0 +1,242 @@ +What: /sys/class/mtd/ +Date: April 2009 +KernelVersion: 2.6.29 +Contact: linux-mtd@lists.infradead.org +Description: + The mtd/ class subdirectory belongs to the MTD subsystem + (MTD core). + +What: /sys/class/mtd/mtdX/ +Date: April 2009 +KernelVersion: 2.6.29 +Contact: linux-mtd@lists.infradead.org +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. + +What: /sys/class/mtd/mtdXro/ +Date: April 2009 +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/ . + +What: /sys/class/mtd/mtdX/dev +Date: April 2009 +KernelVersion: 2.6.29 +Contact: linux-mtd@lists.infradead.org +Description: + Major and minor numbers of the character device corresponding + to this MTD device (in <major>:<minor> format). This is the + read-write device so <minor> will be even. + +What: /sys/class/mtd/mtdXro/dev +Date: April 2009 +KernelVersion: 2.6.29 +Contact: linux-mtd@lists.infradead.org +Description: + Major and minor numbers of the character device corresponding + to the read-only variant of the MTD device (in + <major>:<minor> format). In this case <minor> will be odd. + +What: /sys/class/mtd/mtdX/erasesize +Date: April 2009 +KernelVersion: 2.6.29 +Contact: linux-mtd@lists.infradead.org +Description: + "Major" erase size for the device. If numeraseregions is + zero, this is the eraseblock size for the entire device. + Otherwise, the MEMGETREGIONCOUNT/MEMGETREGIONINFO ioctls + can be used to determine the actual eraseblock layout. + +What: /sys/class/mtd/mtdX/flags +Date: April 2009 +KernelVersion: 2.6.29 +Contact: linux-mtd@lists.infradead.org +Description: + A hexadecimal value representing the device flags, ORed + together: + + 0x0400: MTD_WRITEABLE - device is writable + 0x0800: MTD_BIT_WRITEABLE - single bits can be flipped + 0x1000: MTD_NO_ERASE - no erase necessary + 0x2000: MTD_POWERUP_LOCK - always locked after reset + +What: /sys/class/mtd/mtdX/name +Date: April 2009 +KernelVersion: 2.6.29 +Contact: linux-mtd@lists.infradead.org +Description: + A human-readable ASCII name for the device or partition. + This will match the name in /proc/mtd . + +What: /sys/class/mtd/mtdX/numeraseregions +Date: April 2009 +KernelVersion: 2.6.29 +Contact: linux-mtd@lists.infradead.org +Description: + For devices that have variable eraseblock sizes, this + provides the total number of erase regions. Otherwise, + it will read back as zero. + +What: /sys/class/mtd/mtdX/oobsize +Date: April 2009 +KernelVersion: 2.6.29 +Contact: linux-mtd@lists.infradead.org +Description: + Number of OOB bytes per page. + +What: /sys/class/mtd/mtdX/size +Date: April 2009 +KernelVersion: 2.6.29 +Contact: linux-mtd@lists.infradead.org +Description: + Total size of the device/partition, in bytes. + +What: /sys/class/mtd/mtdX/type +Date: April 2009 +KernelVersion: 2.6.29 +Contact: linux-mtd@lists.infradead.org +Description: + One of the following ASCII strings, representing the device + type: + + absent, ram, rom, nor, nand, mlc-nand, dataflash, ubi, unknown + +What: /sys/class/mtd/mtdX/writesize +Date: April 2009 +KernelVersion: 2.6.29 +Contact: linux-mtd@lists.infradead.org +Description: + Minimal writable flash unit size. This will always be + a positive integer. + + In the case of NOR flash it is 1 (even though individual + bits can be cleared). + + In the case of NAND flash it is one NAND page (or a + 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. + +What: /sys/class/mtd/mtdX/ecc_failures +Date: June 2014 +KernelVersion: 3.17 +Contact: linux-mtd@lists.infradead.org +Description: + The number of failures reported by this device's ECC. Typically, + these failures are associated with failed read operations. + + It will always be a non-negative integer. In the case of + devices lacking any ECC capability, it is 0. + +What: /sys/class/mtd/mtdX/corrected_bits +Date: June 2014 +KernelVersion: 3.17 +Contact: linux-mtd@lists.infradead.org +Description: + The number of bits that have been corrected by means of the + device's ECC. + + It will always be a non-negative integer. In the case of + devices lacking any ECC capability, it is 0. + +What: /sys/class/mtd/mtdX/bad_blocks +Date: June 2014 +KernelVersion: 3.17 +Contact: linux-mtd@lists.infradead.org +Description: + The number of blocks marked as bad, if any, in this partition. + +What: /sys/class/mtd/mtdX/bbt_blocks +Date: June 2014 +KernelVersion: 3.17 +Contact: linux-mtd@lists.infradead.org +Description: + The number of blocks that are marked as reserved, if any, in + this partition. These are typically used to store the in-flash + bad block table (BBT). + +What: /sys/class/mtd/mtdX/offset +Date: March 2015 +KernelVersion: 4.1 +Contact: linux-mtd@lists.infradead.org +Description: + For a partition, the offset of that partition from the start + of the parent (another partition or a flash device) in bytes. + This attribute is absent on flash devices, so it can be used + to distinguish them from partitions. + +What: /sys/class/mtd/mtdX/oobavail +Date: April 2018 +KernelVersion: 4.16 +Contact: linux-mtd@lists.infradead.org +Description: + Number of bytes available for a client to place data into + the out of band area. |