| 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. They exist regardless |
| of whether CONFIG_MTD_CHAR is actually enabled. |
| |
| 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/ . They are only created |
| (for the benefit of udev) if CONFIG_MTD_CHAR is enabled. |
| |
| 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 thie 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, 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. This will |
| always be a non-negative integer. Note that some devices will |
| 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() 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. |
