1menuconfig 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 11if MTD_UBI 12 13config 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 30config 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 59config 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 80config 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 90config MTD_UBI_BLOCK 91 bool "Read-only block devices on top of UBI volumes" 92 default n 93 depends on BLOCK 94 help 95 This option enables read-only UBI block devices support. UBI block 96 devices will be layered on top of UBI volumes, which means that the 97 UBI driver will transparently handle things like bad eraseblocks and 98 bit-flips. You can put any block-oriented file system on top of UBI 99 volumes in read-only mode (e.g., ext4), but it is probably most 100 practical for read-only file systems, like squashfs. 101 102 When selected, this feature will be built in the UBI driver. 103 104 If in doubt, say "N". 105 106endif # MTD_UBI 107