drivers/mtd/ubi/Kconfig

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