108 lines
4.5 KiB
Plaintext
108 lines
4.5 KiB
Plaintext
|
# SPDX-License-Identifier: GPL-2.0-only
|
||
|
|
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_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
|