1# SPDX-License-Identifier: GPL-2.0-only 2menuconfig MTD_UBI 3 tristate "Enable UBI - Unsorted block images" 4 select CRC32 5 help 6 UBI is a software layer above MTD layer which admits use of LVM-like 7 logical volumes on top of MTD devices, hides some complexities of 8 flash chips like wear and bad blocks and provides some other useful 9 capabilities. Please, consult the MTD web site for more details 10 (www.linux-mtd.infradead.org). 11 12if MTD_UBI 13 14config MTD_UBI_WL_THRESHOLD 15 int "UBI wear-leveling threshold" 16 default 4096 17 range 2 65536 18 help 19 This parameter defines the maximum difference between the highest 20 erase counter value and the lowest erase counter value of eraseblocks 21 of UBI devices. When this threshold is exceeded, UBI starts performing 22 wear leveling by means of moving data from eraseblock with low erase 23 counter to eraseblocks with high erase counter. 24 25 The default value should be OK for SLC NAND flashes, NOR flashes and 26 other flashes which have eraseblock life-cycle 100000 or more. 27 However, in case of MLC NAND flashes which typically have eraseblock 28 life-cycle less than 10000, the threshold should be lessened (e.g., 29 to 128 or 256, although it does not have to be power of 2). 30 31config MTD_UBI_BEB_LIMIT 32 int "Maximum expected bad eraseblock count per 1024 eraseblocks" 33 default 20 34 range 0 768 35 help 36 This option specifies the maximum bad physical eraseblocks UBI 37 expects on the MTD device (per 1024 eraseblocks). If the underlying 38 flash does not admit of bad eraseblocks (e.g. NOR flash), this value 39 is ignored. 40 41 NAND datasheets often specify the minimum and maximum NVM (Number of 42 Valid Blocks) for the flashes' endurance lifetime. The maximum 43 expected bad eraseblocks per 1024 eraseblocks then can be calculated 44 as "1024 * (1 - MinNVB / MaxNVB)", which gives 20 for most NANDs 45 (MaxNVB is basically the total count of eraseblocks on the chip). 46 47 To put it differently, if this value is 20, UBI will try to reserve 48 about 1.9% of physical eraseblocks for bad blocks handling. And that 49 will be 1.9% of eraseblocks on the entire NAND chip, not just the MTD 50 partition UBI attaches. This means that if you have, say, a NAND 51 flash chip admits maximum 40 bad eraseblocks, and it is split on two 52 MTD partitions of the same size, UBI will reserve 40 eraseblocks when 53 attaching a partition. 54 55 This option can be overridden by the "mtd=" UBI module parameter or 56 by the "attach" ioctl. 57 58 Leave the default value if unsure. 59 60config MTD_UBI_FASTMAP 61 bool "UBI Fastmap (Experimental feature)" 62 default n 63 help 64 Important: this feature is experimental so far and the on-flash 65 format for fastmap may change in the next kernel versions 66 67 Fastmap is a mechanism which allows attaching an UBI device 68 in nearly constant time. Instead of scanning the whole MTD device it 69 only has to locate a checkpoint (called fastmap) on the device. 70 The on-flash fastmap contains all information needed to attach 71 the device. Using fastmap makes only sense on large devices where 72 attaching by scanning takes long. UBI will not automatically install 73 a fastmap on old images, but you can set the UBI module parameter 74 fm_autoconvert to 1 if you want so. Please note that fastmap-enabled 75 images are still usable with UBI implementations without 76 fastmap support. On typical flash devices the whole fastmap fits 77 into one PEB. UBI will reserve PEBs to hold two fastmaps. 78 79 If in doubt, say "N". 80 81config MTD_UBI_GLUEBI 82 tristate "MTD devices emulation driver (gluebi)" 83 help 84 This option enables gluebi - an additional driver which emulates MTD 85 devices on top of UBI volumes: for each UBI volumes an MTD device is 86 created, and all I/O to this MTD device is redirected to the UBI 87 volume. This is handy to make MTD-oriented software (like JFFS2) 88 work on top of UBI. Do not enable this unless you use legacy 89 software. 90 91config MTD_UBI_BLOCK 92 bool "Read-only block devices on top of UBI volumes" 93 default n 94 depends on BLOCK 95 help 96 This option enables read-only UBI block devices support. UBI block 97 devices will be layered on top of UBI volumes, which means that the 98 UBI driver will transparently handle things like bad eraseblocks and 99 bit-flips. You can put any block-oriented file system on top of UBI 100 volumes in read-only mode (e.g., ext4), but it is probably most 101 practical for read-only file systems, like squashfs. 102 103 When selected, this feature will be built in the UBI driver. 104 105 If in doubt, say "N". 106 107endif # MTD_UBI 108