--- /dev/null
+menuconfig MTD_UBI
+ tristate "Enable UBI - Unsorted block images"
+ select CRC32
+ help
+ UBI is a software layer above MTD layer which admits of LVM-like
+ logical volumes on top of MTD devices, hides some complexities of
+ flash chips like wear and bad blocks and provides some other useful
+ capabilities. Please, consult the MTD web site for more details
+ (www.linux-mtd.infradead.org).
+
+if MTD_UBI
+
+config MTD_UBI_WL_THRESHOLD
+ int "UBI wear-leveling threshold"
+ default 4096
+ range 2 65536
+ help
+ This parameter defines the maximum difference between the highest
+ erase counter value and the lowest erase counter value of eraseblocks
+ of UBI devices. When this threshold is exceeded, UBI starts performing
+ wear leveling by means of moving data from eraseblock with low erase
+ counter to eraseblocks with high erase counter.
+
+ The default value should be OK for SLC NAND flashes, NOR flashes and
+ other flashes which have eraseblock life-cycle 100000 or more.
+ However, in case of MLC NAND flashes which typically have eraseblock
+ life-cycle less than 10000, the threshold should be lessened (e.g.,
+ to 128 or 256, although it does not have to be power of 2).
+
+config MTD_UBI_BEB_LIMIT
+ int "Maximum expected bad eraseblock count per 1024 eraseblocks"
+ default 20
+ range 0 768
+ help
+ This option specifies the maximum bad physical eraseblocks UBI
+ expects on the MTD device (per 1024 eraseblocks). If the underlying
+ flash does not admit of bad eraseblocks (e.g. NOR flash), this value
+ is ignored.
+
+ NAND datasheets often specify the minimum and maximum NVM (Number of
+ Valid Blocks) for the flashes' endurance lifetime. The maximum
+ expected bad eraseblocks per 1024 eraseblocks then can be calculated
+ as "1024 * (1 - MinNVB / MaxNVB)", which gives 20 for most NANDs
+ (MaxNVB is basically the total count of eraseblocks on the chip).
+
+ To put it differently, if this value is 20, UBI will try to reserve
+ about 1.9% of physical eraseblocks for bad blocks handling. And that
+ will be 1.9% of eraseblocks on the entire NAND chip, not just the MTD
+ partition UBI attaches. This means that if you have, say, a NAND
+ flash chip admits maximum 40 bad eraseblocks, and it is split on two
+ MTD partitions of the same size, UBI will reserve 40 eraseblocks when
+ attaching a partition.
+
+ This option can be overridden by the "mtd=" UBI module parameter or
+ by the "attach" ioctl.
+
+ Leave the default value if unsure.
+
+config MTD_UBI_FASTMAP
+ bool "UBI Fastmap (Experimental feature)"
+ default n
+ help
+ Important: this feature is experimental so far and the on-flash
+ format for fastmap may change in the next kernel versions
+
+ Fastmap is a mechanism which allows attaching an UBI device
+ in nearly constant time. Instead of scanning the whole MTD device it
+ only has to locate a checkpoint (called fastmap) on the device.
+ The on-flash fastmap contains all information needed to attach
+ the device. Using fastmap makes only sense on large devices where
+ attaching by scanning takes long. UBI will not automatically install
+ a fastmap on old images, but you can set the UBI module parameter
+ fm_autoconvert to 1 if you want so. Please note that fastmap-enabled
+ images are still usable with UBI implementations without
+ fastmap support. On typical flash devices the whole fastmap fits
+ into one PEB. UBI will reserve PEBs to hold two fastmaps.
+
+ If in doubt, say "N".
+
+config MTD_UBI_GLUEBI
+ tristate "MTD devices emulation driver (gluebi)"
+ help
+ This option enables gluebi - an additional driver which emulates MTD
+ devices on top of UBI volumes: for each UBI volumes an MTD device is
+ created, and all I/O to this MTD device is redirected to the UBI
+ volume. This is handy to make MTD-oriented software (like JFFS2)
+ work on top of UBI. Do not enable this unless you use legacy
+ software.
+
+config MTD_UBI_BLOCK
+ bool "Read-only block devices on top of UBI volumes"
+ default n
+ depends on BLOCK
+ help
+ This option enables read-only UBI block devices support. UBI block
+ devices will be layered on top of UBI volumes, which means that the
+ UBI driver will transparently handle things like bad eraseblocks and
+ bit-flips. You can put any block-oriented file system on top of UBI
+ volumes in read-only mode (e.g., ext4), but it is probably most
+ practical for read-only file systems, like squashfs.
+
+ When selected, this feature will be built in the UBI driver.
+
+ If in doubt, say "N".
+
+endif # MTD_UBI
Code Review / kvmfornfv.git / blobdiff