1What: /sys/class/mtd/ 2Date: April 2009 3KernelVersion: 2.6.29 4Contact: linux-mtd@lists.infradead.org 5Description: 6 The mtd/ class subdirectory belongs to the MTD subsystem 7 (MTD core). 8 9What: /sys/class/mtd/mtdX/ 10Date: April 2009 11KernelVersion: 2.6.29 12Contact: linux-mtd@lists.infradead.org 13Description: 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. 18 19What: /sys/class/mtd/mtdXro/ 20Date: April 2009 21KernelVersion: 2.6.29 22Contact: linux-mtd@lists.infradead.org 23Description: 24 These directories provide the corresponding read-only device 25 nodes for /sys/class/mtd/mtdX/ . 26 27What: /sys/class/mtd/mtdX/dev 28Date: April 2009 29KernelVersion: 2.6.29 30Contact: linux-mtd@lists.infradead.org 31Description: 32 Major and minor numbers of the character device corresponding 33 to this MTD device (in <major>:<minor> format). This is the 34 read-write device so <minor> will be even. 35 36What: /sys/class/mtd/mtdXro/dev 37Date: April 2009 38KernelVersion: 2.6.29 39Contact: linux-mtd@lists.infradead.org 40Description: 41 Major and minor numbers of the character device corresponding 42 to the read-only variant of the MTD device (in 43 <major>:<minor> format). In this case <minor> will be odd. 44 45What: /sys/class/mtd/mtdX/erasesize 46Date: April 2009 47KernelVersion: 2.6.29 48Contact: linux-mtd@lists.infradead.org 49Description: 50 "Major" erase size for the device. If numeraseregions is 51 zero, this is the eraseblock size for the entire device. 52 Otherwise, the MEMGETREGIONCOUNT/MEMGETREGIONINFO ioctls 53 can be used to determine the actual eraseblock layout. 54 55What: /sys/class/mtd/mtdX/flags 56Date: April 2009 57KernelVersion: 2.6.29 58Contact: linux-mtd@lists.infradead.org 59Description: 60 A hexadecimal value representing the device flags, ORed 61 together: 62 63 0x0400: MTD_WRITEABLE - device is writable 64 0x0800: MTD_BIT_WRITEABLE - single bits can be flipped 65 0x1000: MTD_NO_ERASE - no erase necessary 66 0x2000: MTD_POWERUP_LOCK - always locked after reset 67 68What: /sys/class/mtd/mtdX/name 69Date: April 2009 70KernelVersion: 2.6.29 71Contact: linux-mtd@lists.infradead.org 72Description: 73 A human-readable ASCII name for the device or partition. 74 This will match the name in /proc/mtd . 75 76What: /sys/class/mtd/mtdX/numeraseregions 77Date: April 2009 78KernelVersion: 2.6.29 79Contact: linux-mtd@lists.infradead.org 80Description: 81 For devices that have variable eraseblock sizes, this 82 provides the total number of erase regions. Otherwise, 83 it will read back as zero. 84 85What: /sys/class/mtd/mtdX/oobsize 86Date: April 2009 87KernelVersion: 2.6.29 88Contact: linux-mtd@lists.infradead.org 89Description: 90 Number of OOB bytes per page. 91 92What: /sys/class/mtd/mtdX/size 93Date: April 2009 94KernelVersion: 2.6.29 95Contact: linux-mtd@lists.infradead.org 96Description: 97 Total size of the device/partition, in bytes. 98 99What: /sys/class/mtd/mtdX/type 100Date: April 2009 101KernelVersion: 2.6.29 102Contact: linux-mtd@lists.infradead.org 103Description: 104 One of the following ASCII strings, representing the device 105 type: 106 107 absent, ram, rom, nor, nand, mlc-nand, dataflash, ubi, unknown 108 109What: /sys/class/mtd/mtdX/writesize 110Date: April 2009 111KernelVersion: 2.6.29 112Contact: linux-mtd@lists.infradead.org 113Description: 114 Minimal writable flash unit size. This will always be 115 a positive integer. 116 117 In the case of NOR flash it is 1 (even though individual 118 bits can be cleared). 119 120 In the case of NAND flash it is one NAND page (or a 121 half page, or a quarter page). 122 123 In the case of ECC NOR, it is the ECC block size. 124 125What: /sys/class/mtd/mtdX/ecc_strength 126Date: April 2012 127KernelVersion: 3.4 128Contact: linux-mtd@lists.infradead.org 129Description: 130 Maximum number of bit errors that the device is capable of 131 correcting within each region covering an ECC step (see 132 ecc_step_size). This will always be a non-negative integer. 133 134 In the case of devices lacking any ECC capability, it is 0. 135 136What: /sys/class/mtd/mtdX/bitflip_threshold 137Date: April 2012 138KernelVersion: 3.4 139Contact: linux-mtd@lists.infradead.org 140Description: 141 This allows the user to examine and adjust the criteria by which 142 mtd returns -EUCLEAN from mtd_read() and mtd_read_oob(). If the 143 maximum number of bit errors that were corrected on any single 144 region comprising an ecc step (as reported by the driver) equals 145 or exceeds this value, -EUCLEAN is returned. Otherwise, absent 146 an error, 0 is returned. Higher layers (e.g., UBI) use this 147 return code as an indication that an erase block may be 148 degrading and should be scrutinized as a candidate for being 149 marked as bad. 150 151 The initial value may be specified by the flash device driver. 152 If not, then the default value is ecc_strength. 153 154 The introduction of this feature brings a subtle change to the 155 meaning of the -EUCLEAN return code. Previously, it was 156 interpreted to mean simply "one or more bit errors were 157 corrected". Its new interpretation can be phrased as "a 158 dangerously high number of bit errors were corrected on one or 159 more regions comprising an ecc step". The precise definition of 160 "dangerously high" can be adjusted by the user with 161 bitflip_threshold. Users are discouraged from doing this, 162 however, unless they know what they are doing and have intimate 163 knowledge of the properties of their device. Broadly speaking, 164 bitflip_threshold should be low enough to detect genuine erase 165 block degradation, but high enough to avoid the consequences of 166 a persistent return value of -EUCLEAN on devices where sticky 167 bitflips occur. Note that if bitflip_threshold exceeds 168 ecc_strength, -EUCLEAN is never returned by the read operations. 169 Conversely, if bitflip_threshold is zero, -EUCLEAN is always 170 returned, absent a hard error. 171 172 This is generally applicable only to NAND flash devices with ECC 173 capability. It is ignored on devices lacking ECC capability; 174 i.e., devices for which ecc_strength is zero. 175 176What: /sys/class/mtd/mtdX/ecc_step_size 177Date: May 2013 178KernelVersion: 3.10 179Contact: linux-mtd@lists.infradead.org 180Description: 181 The size of a single region covered by ECC, known as the ECC 182 step. Devices may have several equally sized ECC steps within 183 each writesize region. 184 185 It will always be a non-negative integer. In the case of 186 devices lacking any ECC capability, it is 0. 187 188What: /sys/class/mtd/mtdX/ecc_failures 189Date: June 2014 190KernelVersion: 3.17 191Contact: linux-mtd@lists.infradead.org 192Description: 193 The number of failures reported by this device's ECC. Typically, 194 these failures are associated with failed read operations. 195 196 It will always be a non-negative integer. In the case of 197 devices lacking any ECC capability, it is 0. 198 199What: /sys/class/mtd/mtdX/corrected_bits 200Date: June 2014 201KernelVersion: 3.17 202Contact: linux-mtd@lists.infradead.org 203Description: 204 The number of bits that have been corrected by means of the 205 device's ECC. 206 207 It will always be a non-negative integer. In the case of 208 devices lacking any ECC capability, it is 0. 209 210What: /sys/class/mtd/mtdX/bad_blocks 211Date: June 2014 212KernelVersion: 3.17 213Contact: linux-mtd@lists.infradead.org 214Description: 215 The number of blocks marked as bad, if any, in this partition. 216 217What: /sys/class/mtd/mtdX/bbt_blocks 218Date: June 2014 219KernelVersion: 3.17 220Contact: linux-mtd@lists.infradead.org 221Description: 222 The number of blocks that are marked as reserved, if any, in 223 this partition. These are typically used to store the in-flash 224 bad block table (BBT). 225 226What: /sys/class/mtd/mtdX/offset 227Date: March 2015 228KernelVersion: 4.1 229Contact: linux-mtd@lists.infradead.org 230Description: 231 For a partition, the offset of that partition from the start 232 of the parent (another partition or a flash device) in bytes. 233 This attribute is absent on flash devices, so it can be used 234 to distinguish them from partitions. 235 236What: /sys/class/mtd/mtdX/oobavail 237Date: April 2018 238KernelVersion: 4.16 239Contact: linux-mtd@lists.infradead.org 240Description: 241 Number of bytes available for a client to place data into 242 the out of band area. 243