2 tristate "Enable UBI - Unsorted block images"
5 UBI is a software layer above MTD layer which admits of LVM-like
6 logical volumes on top of MTD devices, hides some complexities of
7 flash chips like wear and bad blocks and provides some other useful
8 capabilities. Please, consult the MTD web site for more details
9 (www.linux-mtd.infradead.org).
13 config MTD_UBI_WL_THRESHOLD
14 int "UBI wear-leveling threshold"
18 This parameter defines the maximum difference between the highest
19 erase counter value and the lowest erase counter value of eraseblocks
20 of UBI devices. When this threshold is exceeded, UBI starts performing
21 wear leveling by means of moving data from eraseblock with low erase
22 counter to eraseblocks with high erase counter.
24 The default value should be OK for SLC NAND flashes, NOR flashes and
25 other flashes which have eraseblock life-cycle 100000 or more.
26 However, in case of MLC NAND flashes which typically have eraseblock
27 life-cycle less than 10000, the threshold should be lessened (e.g.,
28 to 128 or 256, although it does not have to be power of 2).
30 config MTD_UBI_BEB_LIMIT
31 int "Maximum expected bad eraseblock count per 1024 eraseblocks"
35 This option specifies the maximum bad physical eraseblocks UBI
36 expects on the MTD device (per 1024 eraseblocks). If the underlying
37 flash does not admit of bad eraseblocks (e.g. NOR flash), this value
40 NAND datasheets often specify the minimum and maximum NVM (Number of
41 Valid Blocks) for the flashes' endurance lifetime. The maximum
42 expected bad eraseblocks per 1024 eraseblocks then can be calculated
43 as "1024 * (1 - MinNVB / MaxNVB)", which gives 20 for most NANDs
44 (MaxNVB is basically the total count of eraseblocks on the chip).
46 To put it differently, if this value is 20, UBI will try to reserve
47 about 1.9% of physical eraseblocks for bad blocks handling. And that
48 will be 1.9% of eraseblocks on the entire NAND chip, not just the MTD
49 partition UBI attaches. This means that if you have, say, a NAND
50 flash chip admits maximum 40 bad eraseblocks, and it is split on two
51 MTD partitions of the same size, UBI will reserve 40 eraseblocks when
52 attaching a partition.
54 This option can be overridden by the "mtd=" UBI module parameter or
55 by the "attach" ioctl.
57 Leave the default value if unsure.
60 tristate "MTD devices emulation driver (gluebi)"
62 This option enables gluebi - an additional driver which emulates MTD
63 devices on top of UBI volumes: for each UBI volumes an MTD device is
64 created, and all I/O to this MTD device is redirected to the UBI
65 volume. This is handy to make MTD-oriented software (like JFFS2)
66 work on top of UBI. Do not enable this unless you use legacy