1menu "UBI support" 2 3config 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 15if MTD_UBI 16 17config 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 34config 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 63config 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 84config 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 92config 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 99endif # MTD_UBI 100endmenu # "Enable UBI - Unsorted block images" 101