projects / deliverable / linux.git / blame
| Commit | Line | Data |
|---|---|---|
| 19fe7f1a KC |
1 | What: /sys/class/mtd/ |
| 2 | Date: April 2009 | |
| 3 | KernelVersion: 2.6.29 | |
| 4 | Contact: linux-mtd@lists.infradead.org | |
| 5 | Description: | |
| 6 | The mtd/ class subdirectory belongs to the MTD subsystem | |
| 7 | (MTD core). | |
| 8 | ||
| 9 | What: /sys/class/mtd/mtdX/ | |
| 10 | Date: April 2009 | |
| 11 | KernelVersion: 2.6.29 | |
| 12 | Contact: linux-mtd@lists.infradead.org | |
| 13 | Description: | |
| 14 | The /sys/class/mtd/mtd{0,1,2,3,...} directories correspond | |
| 15 | to each /dev/mtdX character device. These may represent | |
| 16 | physical/simulated flash devices, partitions on a flash | |
| 17 | device, or concatenated flash devices. They exist regardless | |
| 18 | of whether CONFIG_MTD_CHAR is actually enabled. | |
| 19 | ||
| 20 | What: /sys/class/mtd/mtdXro/ | |
| 21 | Date: April 2009 | |
| 22 | KernelVersion: 2.6.29 | |
| 23 | Contact: linux-mtd@lists.infradead.org | |
| 24 | Description: | |
| 25 | These directories provide the corresponding read-only device | |
| 26 | nodes for /sys/class/mtd/mtdX/ . They are only created | |
| 27 | (for the benefit of udev) if CONFIG_MTD_CHAR is enabled. | |
| 28 | ||
| 29 | What: /sys/class/mtd/mtdX/dev | |
| 30 | Date: April 2009 | |
| 31 | KernelVersion: 2.6.29 | |
| 32 | Contact: linux-mtd@lists.infradead.org | |
| 33 | Description: | |
| 34 | Major and minor numbers of the character device corresponding | |
| 35 | to this MTD device (in <major>:<minor> format). This is the | |
| 36 | read-write device so <minor> will be even. | |
| 37 | ||
| 38 | What: /sys/class/mtd/mtdXro/dev | |
| 39 | Date: April 2009 | |
| 40 | KernelVersion: 2.6.29 | |
| 41 | Contact: linux-mtd@lists.infradead.org | |
| 42 | Description: | |
| 43 | Major and minor numbers of the character device corresponding | |
| 44 | to the read-only variant of thie MTD device (in | |
| 45 | <major>:<minor> format). In this case <minor> will be odd. | |
| 46 | ||
| 47 | What: /sys/class/mtd/mtdX/erasesize | |
| 48 | Date: April 2009 | |
| 49 | KernelVersion: 2.6.29 | |
| 50 | Contact: linux-mtd@lists.infradead.org | |
| 51 | Description: | |
| 52 | "Major" erase size for the device. If numeraseregions is | |
| 53 | zero, this is the eraseblock size for the entire device. | |
| 54 | Otherwise, the MEMGETREGIONCOUNT/MEMGETREGIONINFO ioctls | |
| 55 | can be used to determine the actual eraseblock layout. | |
| 56 | ||
| 57 | What: /sys/class/mtd/mtdX/flags | |
| 58 | Date: April 2009 | |
| 59 | KernelVersion: 2.6.29 | |
| 60 | Contact: linux-mtd@lists.infradead.org | |
| 61 | Description: | |
| 62 | A hexadecimal value representing the device flags, ORed | |
| 63 | together: | |
| 64 | ||
| 65 | 0x0400: MTD_WRITEABLE - device is writable | |
| 66 | 0x0800: MTD_BIT_WRITEABLE - single bits can be flipped | |
| 67 | 0x1000: MTD_NO_ERASE - no erase necessary | |
| 68 | 0x2000: MTD_POWERUP_LOCK - always locked after reset | |
| 69 | ||
| 70 | What: /sys/class/mtd/mtdX/name | |
| 71 | Date: April 2009 | |
| 72 | KernelVersion: 2.6.29 | |
| 73 | Contact: linux-mtd@lists.infradead.org | |
| 74 | Description: | |
| 75 | A human-readable ASCII name for the device or partition. | |
| 76 | This will match the name in /proc/mtd . | |
| 77 | ||
| 78 | What: /sys/class/mtd/mtdX/numeraseregions | |
| 79 | Date: April 2009 | |
| 80 | KernelVersion: 2.6.29 | |
| 81 | Contact: linux-mtd@lists.infradead.org | |
| 82 | Description: | |
| 83 | For devices that have variable eraseblock sizes, this | |
| 84 | provides the total number of erase regions. Otherwise, | |
| 85 | it will read back as zero. | |
| 86 | ||
| 87 | What: /sys/class/mtd/mtdX/oobsize | |
| 88 | Date: April 2009 | |
| 89 | KernelVersion: 2.6.29 | |
| 90 | Contact: linux-mtd@lists.infradead.org | |
| 91 | Description: | |
| 92 | Number of OOB bytes per page. | |
| 93 | ||
| 94 | What: /sys/class/mtd/mtdX/size | |
| 95 | Date: April 2009 | |
| 96 | KernelVersion: 2.6.29 | |
| 97 | Contact: linux-mtd@lists.infradead.org | |
| 98 | Description: | |
| 99 | Total size of the device/partition, in bytes. | |
| 100 | ||
| 101 | What: /sys/class/mtd/mtdX/type | |
| 102 | Date: April 2009 | |
| 103 | KernelVersion: 2.6.29 | |
| 104 | Contact: linux-mtd@lists.infradead.org | |
| 105 | Description: | |
| 106 | One of the following ASCII strings, representing the device | |
| 107 | type: | |
| 108 | ||
| 109 | absent, ram, rom, nor, nand, dataflash, ubi, unknown | |
| 110 | ||
| 111 | What: /sys/class/mtd/mtdX/writesize | |
| 112 | Date: April 2009 | |
| 113 | KernelVersion: 2.6.29 | |
| 114 | Contact: linux-mtd@lists.infradead.org | |
| 115 | Description: | |
| 116 | Minimal writable flash unit size. This will always be | |
| 117 | a positive integer. | |
| 118 | ||
| 119 | In the case of NOR flash it is 1 (even though individual | |
| 120 | bits can be cleared). | |
| 121 | ||
| 122 | In the case of NAND flash it is one NAND page (or a | |
| 123 | half page, or a quarter page). | |
| 124 | ||
| 125 | In the case of ECC NOR, it is the ECC block size. | |
| a9b672e8 MD |
126 | |
| 127 | What: /sys/class/mtd/mtdX/ecc_strength | |
| 128 | Date: April 2012 | |
| 129 | KernelVersion: 3.4 | |
| 130 | Contact: linux-mtd@lists.infradead.org | |
| 131 | Description: | |
| 132 | Maximum number of bit errors that the device is capable of | |
| 133 | correcting within each region covering an ecc step. This will | |
| 134 | always be a non-negative integer. Note that some devices will | |
| 135 | have multiple ecc steps within each writesize region. | |
| 136 | ||
| 137 | In the case of devices lacking any ECC capability, it is 0. | |
| d062d4ed MD |
138 | |
| 139 | What: /sys/class/mtd/mtdX/bitflip_threshold | |
| 140 | Date: April 2012 | |
| 141 | KernelVersion: 3.4 | |
| 142 | Contact: linux-mtd@lists.infradead.org | |
| 143 | Description: | |
| 144 | This allows the user to examine and adjust the criteria by which | |
| 021796b8 MD |
145 | mtd returns -EUCLEAN from mtd_read() and mtd_read_oob(). If the |
| 146 | maximum number of bit errors that were corrected on any single | |
| 147 | region comprising an ecc step (as reported by the driver) equals | |
| 148 | or exceeds this value, -EUCLEAN is returned. Otherwise, absent | |
| 149 | an error, 0 is returned. Higher layers (e.g., UBI) use this | |
| 150 | return code as an indication that an erase block may be | |
| 151 | degrading and should be scrutinized as a candidate for being | |
| 152 | marked as bad. | |
| d062d4ed MD |
153 | |
| 154 | The initial value may be specified by the flash device driver. | |
| 155 | If not, then the default value is ecc_strength. | |
| 156 | ||
| 157 | The introduction of this feature brings a subtle change to the | |
| 158 | meaning of the -EUCLEAN return code. Previously, it was | |
| 159 | interpreted to mean simply "one or more bit errors were | |
| 160 | corrected". Its new interpretation can be phrased as "a | |
| 161 | dangerously high number of bit errors were corrected on one or | |
| 162 | more regions comprising an ecc step". The precise definition of | |
| 163 | "dangerously high" can be adjusted by the user with | |
| 164 | bitflip_threshold. Users are discouraged from doing this, | |
| 165 | however, unless they know what they are doing and have intimate | |
| 166 | knowledge of the properties of their device. Broadly speaking, | |
| 167 | bitflip_threshold should be low enough to detect genuine erase | |
| 168 | block degradation, but high enough to avoid the consequences of | |
| 169 | a persistent return value of -EUCLEAN on devices where sticky | |
| 170 | bitflips occur. Note that if bitflip_threshold exceeds | |
| 021796b8 | 171 | ecc_strength, -EUCLEAN is never returned by the read operations. |
| edbc4540 MD |
172 | Conversely, if bitflip_threshold is zero, -EUCLEAN is always |
| 173 | returned, absent a hard error. | |
| d062d4ed MD |
174 | |
| 175 | This is generally applicable only to NAND flash devices with ECC | |
| edbc4540 MD |
176 | capability. It is ignored on devices lacking ECC capability; |
| 177 | i.e., devices for which ecc_strength is zero. |