drivers/mtd/ubi/Kconfig

   1 menuconfig MTD_UBI
   2         tristate "Enable UBI - Unsorted block images"
   3         select CRC32
   4         help
   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).
  10
  11 if MTD_UBI
  12
  13 config MTD_UBI_WL_THRESHOLD
  14         int "UBI wear-leveling threshold"
  15         default 4096
  16         range 2 65536
  17         help
  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.
  23
  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).
  29
  30 config MTD_UBI_BEB_LIMIT
  31         int "Maximum expected bad eraseblock count per 1024 eraseblocks"
  32         default 20
  33         range 0 768
  34         help
  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
  38           is ignored.
  39
  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).
  45
  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.
  53
  54           This option can be overridden by the "mtd=" UBI module parameter or
  55           by the "attach" ioctl.
  56
  57           Leave the default value if unsure.
  58
  59 config MTD_UBI_FASTMAP
  60         bool "UBI Fastmap (Experimental feature)"
  61         default n
  62         help
  63            Important: this feature is experimental so far and the on-flash
  64            format for fastmap may change in the next kernel versions
  65
  66            Fastmap is a mechanism which allows attaching an UBI device
  67            in nearly constant time. Instead of scanning the whole MTD device it
  68            only has to locate a checkpoint (called fastmap) on the device.
  69            The on-flash fastmap contains all information needed to attach
  70            the device. Using fastmap makes only sense on large devices where
  71            attaching by scanning takes long. UBI will not automatically install
  72            a fastmap on old images, but you can set the UBI module parameter
  73            fm_autoconvert to 1 if you want so. Please note that fastmap-enabled
  74            images are still usable with UBI implementations without
  75            fastmap support. On typical flash devices the whole fastmap fits
  76            into one PEB. UBI will reserve PEBs to hold two fastmaps.
  77
  78            If in doubt, say "N".
  79
  80 config MTD_UBI_GLUEBI
  81         tristate "MTD devices emulation driver (gluebi)"
  82         help
  83            This option enables gluebi - an additional driver which emulates MTD
  84            devices on top of UBI volumes: for each UBI volumes an MTD device is
  85            created, and all I/O to this MTD device is redirected to the UBI
  86            volume. This is handy to make MTD-oriented software (like JFFS2)
  87            work on top of UBI. Do not enable this unless you use legacy
  88            software.
  89
  90 config MTD_UBI_BLOCK
  91         bool "Read-only block devices on top of UBI volumes"
  92         default n
  93         help
  94            This option enables read-only UBI block devices support. UBI block
  95            devices will be layered on top of UBI volumes, which means that the
  96            UBI driver will transparently handle things like bad eraseblocks and
  97            bit-flips. You can put any block-oriented file system on top of UBI
  98            volumes in read-only mode (e.g., ext4), but it is probably most
  99            practical for read-only file systems, like squashfs.
 100
 101            When selected, this feature will be built in the UBI driver.
 102
 103            If in doubt, say "N".
 104
 105 endif # MTD_UBI