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.
18
19 What: /sys/class/mtd/mtdXro/
20 Date: April 2009
21 KernelVersion: 2.6.29
22 Contact: linux-mtd@lists.infradead.org
23 Description:
24 These directories provide the corresponding read-only device
25 nodes for /sys/class/mtd/mtdX/ .
26
27 What: /sys/class/mtd/mtdX/dev
28 Date: April 2009
29 KernelVersion: 2.6.29
30 Contact: linux-mtd@lists.infradead.org
31 Description:
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
36 What: /sys/class/mtd/mtdXro/dev
37 Date: April 2009
38 KernelVersion: 2.6.29
39 Contact: linux-mtd@lists.infradead.org
40 Description:
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
45 What: /sys/class/mtd/mtdX/erasesize
46 Date: April 2009
47 KernelVersion: 2.6.29
48 Contact: linux-mtd@lists.infradead.org
49 Description:
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
55 What: /sys/class/mtd/mtdX/flags
56 Date: April 2009
57 KernelVersion: 2.6.29
58 Contact: linux-mtd@lists.infradead.org
59 Description:
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
68 What: /sys/class/mtd/mtdX/name
69 Date: April 2009
70 KernelVersion: 2.6.29
71 Contact: linux-mtd@lists.infradead.org
72 Description:
73 A human-readable ASCII name for the device or partition.
74 This will match the name in /proc/mtd .
75
76 What: /sys/class/mtd/mtdX/numeraseregions
77 Date: April 2009
78 KernelVersion: 2.6.29
79 Contact: linux-mtd@lists.infradead.org
80 Description:
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
85 What: /sys/class/mtd/mtdX/oobsize
86 Date: April 2009
87 KernelVersion: 2.6.29
88 Contact: linux-mtd@lists.infradead.org
89 Description:
90 Number of OOB bytes per page.
91
92 What: /sys/class/mtd/mtdX/size
93 Date: April 2009
94 KernelVersion: 2.6.29
95 Contact: linux-mtd@lists.infradead.org
96 Description:
97 Total size of the device/partition, in bytes.
98
99 What: /sys/class/mtd/mtdX/type
100 Date: April 2009
101 KernelVersion: 2.6.29
102 Contact: linux-mtd@lists.infradead.org
103 Description:
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
109 What: /sys/class/mtd/mtdX/writesize
110 Date: April 2009
111 KernelVersion: 2.6.29
112 Contact: linux-mtd@lists.infradead.org
113 Description:
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
125 What: /sys/class/mtd/mtdX/ecc_strength
126 Date: April 2012
127 KernelVersion: 3.4
128 Contact: linux-mtd@lists.infradead.org
129 Description:
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
136 What: /sys/class/mtd/mtdX/bitflip_threshold
137 Date: April 2012
138 KernelVersion: 3.4
139 Contact: linux-mtd@lists.infradead.org
140 Description:
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
176 What: /sys/class/mtd/mtdX/ecc_step_size
177 Date: May 2013
178 KernelVersion: 3.10
179 Contact: linux-mtd@lists.infradead.org
180 Description:
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
188 What: /sys/class/mtd/mtdX/ecc_failures
189 Date: June 2014
190 KernelVersion: 3.17
191 Contact: linux-mtd@lists.infradead.org
192 Description:
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
199 What: /sys/class/mtd/mtdX/corrected_bits
200 Date: June 2014
201 KernelVersion: 3.17
202 Contact: linux-mtd@lists.infradead.org
203 Description:
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
210 What: /sys/class/mtd/mtdX/bad_blocks
211 Date: June 2014
212 KernelVersion: 3.17
213 Contact: linux-mtd@lists.infradead.org
214 Description:
215 The number of blocks marked as bad, if any, in this partition.
216
217 What: /sys/class/mtd/mtdX/bbt_blocks
218 Date: June 2014
219 KernelVersion: 3.17
220 Contact: linux-mtd@lists.infradead.org
221 Description:
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
226 What: /sys/class/mtd/mtdX/offset
227 Date: March 2015
228 KernelVersion: 4.1
229 Contact: linux-mtd@lists.infradead.org
230 Description:
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
236 What: /sys/class/mtd/mtdX/oobavail
237 Date: April 2018
238 KernelVersion: 4.16
239 Contact: linux-mtd@lists.infradead.org
240 Description:
241 Number of bytes available for a client to place data into
242 the out of band area.
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