forked from Minki/linux
021796b892
The -EUCLEAN return value applies to mtd_read_oob() as well as mtd_read(), but only mtd_read() was mentioned in the blurd on bitflip_threshold in the ABI documentation. 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>
178 lines
6.1 KiB
Plaintext
178 lines
6.1 KiB
Plaintext
What: /sys/class/mtd/
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Date: April 2009
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KernelVersion: 2.6.29
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Contact: linux-mtd@lists.infradead.org
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Description:
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The mtd/ class subdirectory belongs to the MTD subsystem
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(MTD core).
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What: /sys/class/mtd/mtdX/
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Date: April 2009
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KernelVersion: 2.6.29
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Contact: linux-mtd@lists.infradead.org
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Description:
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The /sys/class/mtd/mtd{0,1,2,3,...} directories correspond
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to each /dev/mtdX character device. These may represent
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physical/simulated flash devices, partitions on a flash
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device, or concatenated flash devices. They exist regardless
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of whether CONFIG_MTD_CHAR is actually enabled.
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What: /sys/class/mtd/mtdXro/
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Date: April 2009
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KernelVersion: 2.6.29
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Contact: linux-mtd@lists.infradead.org
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Description:
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These directories provide the corresponding read-only device
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nodes for /sys/class/mtd/mtdX/ . They are only created
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(for the benefit of udev) if CONFIG_MTD_CHAR is enabled.
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What: /sys/class/mtd/mtdX/dev
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Date: April 2009
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KernelVersion: 2.6.29
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Contact: linux-mtd@lists.infradead.org
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Description:
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Major and minor numbers of the character device corresponding
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to this MTD device (in <major>:<minor> format). This is the
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read-write device so <minor> will be even.
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What: /sys/class/mtd/mtdXro/dev
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Date: April 2009
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KernelVersion: 2.6.29
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Contact: linux-mtd@lists.infradead.org
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Description:
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Major and minor numbers of the character device corresponding
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to the read-only variant of thie MTD device (in
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<major>:<minor> format). In this case <minor> will be odd.
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What: /sys/class/mtd/mtdX/erasesize
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Date: April 2009
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KernelVersion: 2.6.29
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Contact: linux-mtd@lists.infradead.org
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Description:
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"Major" erase size for the device. If numeraseregions is
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zero, this is the eraseblock size for the entire device.
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Otherwise, the MEMGETREGIONCOUNT/MEMGETREGIONINFO ioctls
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can be used to determine the actual eraseblock layout.
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What: /sys/class/mtd/mtdX/flags
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Date: April 2009
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KernelVersion: 2.6.29
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Contact: linux-mtd@lists.infradead.org
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Description:
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A hexadecimal value representing the device flags, ORed
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together:
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0x0400: MTD_WRITEABLE - device is writable
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0x0800: MTD_BIT_WRITEABLE - single bits can be flipped
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0x1000: MTD_NO_ERASE - no erase necessary
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0x2000: MTD_POWERUP_LOCK - always locked after reset
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What: /sys/class/mtd/mtdX/name
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Date: April 2009
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KernelVersion: 2.6.29
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Contact: linux-mtd@lists.infradead.org
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Description:
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A human-readable ASCII name for the device or partition.
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This will match the name in /proc/mtd .
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What: /sys/class/mtd/mtdX/numeraseregions
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Date: April 2009
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KernelVersion: 2.6.29
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Contact: linux-mtd@lists.infradead.org
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Description:
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For devices that have variable eraseblock sizes, this
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provides the total number of erase regions. Otherwise,
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it will read back as zero.
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What: /sys/class/mtd/mtdX/oobsize
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Date: April 2009
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KernelVersion: 2.6.29
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Contact: linux-mtd@lists.infradead.org
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Description:
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Number of OOB bytes per page.
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What: /sys/class/mtd/mtdX/size
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Date: April 2009
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KernelVersion: 2.6.29
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Contact: linux-mtd@lists.infradead.org
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Description:
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Total size of the device/partition, in bytes.
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What: /sys/class/mtd/mtdX/type
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Date: April 2009
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KernelVersion: 2.6.29
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Contact: linux-mtd@lists.infradead.org
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Description:
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One of the following ASCII strings, representing the device
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type:
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absent, ram, rom, nor, nand, dataflash, ubi, unknown
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What: /sys/class/mtd/mtdX/writesize
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Date: April 2009
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KernelVersion: 2.6.29
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Contact: linux-mtd@lists.infradead.org
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Description:
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Minimal writable flash unit size. This will always be
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a positive integer.
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In the case of NOR flash it is 1 (even though individual
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bits can be cleared).
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In the case of NAND flash it is one NAND page (or a
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half page, or a quarter page).
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In the case of ECC NOR, it is the ECC block size.
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What: /sys/class/mtd/mtdX/ecc_strength
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Date: April 2012
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KernelVersion: 3.4
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Contact: linux-mtd@lists.infradead.org
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Description:
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Maximum number of bit errors that the device is capable of
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correcting within each region covering an ecc step. This will
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always be a non-negative integer. Note that some devices will
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have multiple ecc steps within each writesize region.
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In the case of devices lacking any ECC capability, it is 0.
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What: /sys/class/mtd/mtdX/bitflip_threshold
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Date: April 2012
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KernelVersion: 3.4
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Contact: linux-mtd@lists.infradead.org
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Description:
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This allows the user to examine and adjust the criteria by which
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mtd returns -EUCLEAN from mtd_read() and mtd_read_oob(). If the
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maximum number of bit errors that were corrected on any single
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region comprising an ecc step (as reported by the driver) equals
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or exceeds this value, -EUCLEAN is returned. Otherwise, absent
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an error, 0 is returned. Higher layers (e.g., UBI) use this
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return code as an indication that an erase block may be
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degrading and should be scrutinized as a candidate for being
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marked as bad.
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The initial value may be specified by the flash device driver.
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If not, then the default value is ecc_strength.
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The introduction of this feature brings a subtle change to the
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meaning of the -EUCLEAN return code. Previously, it was
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interpreted to mean simply "one or more bit errors were
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corrected". Its new interpretation can be phrased as "a
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dangerously high number of bit errors were corrected on one or
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more regions comprising an ecc step". The precise definition of
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"dangerously high" can be adjusted by the user with
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bitflip_threshold. Users are discouraged from doing this,
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however, unless they know what they are doing and have intimate
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knowledge of the properties of their device. Broadly speaking,
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bitflip_threshold should be low enough to detect genuine erase
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block degradation, but high enough to avoid the consequences of
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a persistent return value of -EUCLEAN on devices where sticky
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bitflips occur. Note that if bitflip_threshold exceeds
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ecc_strength, -EUCLEAN is never returned by the read operations.
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Conversely, if bitflip_threshold is zero, -EUCLEAN is always
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returned, absent a hard error.
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This is generally applicable only to NAND flash devices with ECC
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capability. It is ignored on devices lacking ECC capability;
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i.e., devices for which ecc_strength is zero.
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