1menu "UBI support" 2 3config 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 13if MTD_UBI 14 15config 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 32config 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 61config 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 82config 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 90config 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 97endif # MTD_UBI 98endmenu # "Enable UBI - Unsorted block images" 99