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menuconfig MTD_UBI
tristate "Enable UBI - Unsorted block images"
select CRC32
help
UBI is a software layer above MTD layer which admits use 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_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".
comment "UBI debugging options"
config MTD_UBI_CHECK_IO
bool "Check IO operations"
help
When enabled UBI will check if erased blocks are really erased and if areas
written to are empty before writing.
config MTD_UBI_GENERAL_EXTRA_CHECKS
bool "general extra checks"
help
This enables some general extra checks in UBI
endif # MTD_UBI
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