drivers/mtd/ubi/Kconfig

   1 menu "UBI support"
   2
   3 config MTD_UBI
   4         bool "Enable UBI - Unsorted block images"
   5         select CRC32
   6         help
   7           UBI is a software layer above MTD layer which admits of LVM-like
   8           logical volumes on top of MTD devices, hides some complexities of
   9           flash chips like wear and bad blocks and provides some other useful
  10           capabilities. Please, consult the MTD web site for more details
  11           (www.linux-mtd.infradead.org).
  12
  13 if MTD_UBI
  14
  15 config MTD_UBI_WL_THRESHOLD
  16         int "UBI wear-leveling threshold"
  17         default 4096
  18         range 2 65536
  19         help
  20           This parameter defines the maximum difference between the highest
  21           erase counter value and the lowest erase counter value of eraseblocks
  22           of UBI devices. When this threshold is exceeded, UBI starts performing
  23           wear leveling by means of moving data from eraseblock with low erase
  24           counter to eraseblocks with high erase counter.
  25
  26           The default value should be OK for SLC NAND flashes, NOR flashes and
  27           other flashes which have eraseblock life-cycle 100000 or more.
  28           However, in case of MLC NAND flashes which typically have eraseblock
  29           life-cycle less than 10000, the threshold should be lessened (e.g.,
  30           to 128 or 256, although it does not have to be power of 2).
  31
  32 config MTD_UBI_BEB_LIMIT
  33         int "Maximum expected bad eraseblock count per 1024 eraseblocks"
  34         default 20
  35         range 0 768
  36         help
  37           This option specifies the maximum bad physical eraseblocks UBI
  38           expects on the MTD device (per 1024 eraseblocks). If the underlying
  39           flash does not admit of bad eraseblocks (e.g. NOR flash), this value
  40           is ignored.
  41
  42           NAND datasheets often specify the minimum and maximum NVM (Number of
  43           Valid Blocks) for the flashes' endurance lifetime. The maximum
  44           expected bad eraseblocks per 1024 eraseblocks then can be calculated
  45           as "1024 * (1 - MinNVB / MaxNVB)", which gives 20 for most NANDs
  46           (MaxNVB is basically the total count of eraseblocks on the chip).
  47
  48           To put it differently, if this value is 20, UBI will try to reserve
  49           about 1.9% of physical eraseblocks for bad blocks handling. And that
  50           will be 1.9% of eraseblocks on the entire NAND chip, not just the MTD
  51           partition UBI attaches. This means that if you have, say, a NAND
  52           flash chip admits maximum 40 bad eraseblocks, and it is split on two
  53           MTD partitions of the same size, UBI will reserve 40 eraseblocks when
  54           attaching a partition.
  55
  56           This option can be overridden by the "mtd=" UBI module parameter or
  57           by the "attach" ioctl.
  58
  59           Leave the default value if unsure.
  60
  61 config MTD_UBI_FASTMAP
  62         bool "UBI Fastmap (Experimental feature)"
  63         default n
  64         help
  65            Important: this feature is experimental so far and the on-flash
  66            format for fastmap may change in the next kernel versions
  67
  68            Fastmap is a mechanism which allows attaching an UBI device
  69            in nearly constant time. Instead of scanning the whole MTD device it
  70            only has to locate a checkpoint (called fastmap) on the device.
  71            The on-flash fastmap contains all information needed to attach
  72            the device. Using fastmap makes only sense on large devices where
  73            attaching by scanning takes long. UBI will not automatically install
  74            a fastmap on old images, but you can set the UBI module parameter
  75            fm_autoconvert to 1 if you want so. Please note that fastmap-enabled
  76            images are still usable with UBI implementations without
  77            fastmap support. On typical flash devices the whole fastmap fits
  78            into one PEB. UBI will reserve PEBs to hold two fastmaps.
  79
  80            If in doubt, say "N".
  81
  82 config MTD_UBI_FASTMAP_AUTOCONVERT
  83         int "enable UBI Fastmap autoconvert"
  84         depends on MTD_UBI_FASTMAP
  85         default 0
  86         help
  87           Set this parameter to enable fastmap automatically on images
  88           without a fastmap.
  89
  90 config MTD_UBI_FM_DEBUG
  91         int "Enable UBI fastmap debug"
  92         depends on MTD_UBI_FASTMAP
  93         default 0
  94         help
  95           Enable UBI fastmap debug
  96
  97 endif # MTD_UBI
  98 endmenu # "Enable UBI - Unsorted block images"