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menuconfig MTD
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tristate "Memory Technology Device (MTD) support"
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imply NVMEM
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help
Memory Technology Devices are flash, RAM and similar chips, often
used for solid state file systems on embedded devices. This option
will provide the generic support for MTD drivers to register
themselves with the kernel and for potential users of MTD devices
to enumerate the devices which are present and obtain a handle on
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them. It will also allow you to select individual drivers for
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particular hardware and users of MTD devices. If unsure, say N.
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if MTD
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config MTD_TESTS
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tristate "MTD tests support (DANGEROUS)"
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depends on m
help
This option includes various MTD tests into compilation. The tests
should normally be compiled as kernel modules. The modules perform
various checks and verifications when loaded.
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WARNING: some of the tests will ERASE entire MTD device which they
test. Do not use these tests unless you really know what you do.
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config MTD_CMDLINE_PARTS
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tristate "Command line partition table parsing"
depends on MTD
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help
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Allow generic configuration of the MTD partition tables via the kernel
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command line. Multiple flash resources are supported for hardware where
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different kinds of flash memory are available.
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You will still need the parsing functions to be called by the driver
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for your particular device. It won't happen automatically. The
SA1100 map driver (CONFIG_MTD_SA1100) has an option for this, for
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example.
The format for the command line is as follows:
mtdparts=<mtddef>[;<mtddef]
<mtddef> := <mtd-id>:<partdef>[,<partdef>]
<partdef> := <size>[@offset][<name>][ro]
<mtd-id> := unique id used in mapping driver/device
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<size> := standard linux memsize OR "-" to denote all
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remaining space
<name> := (NAME)
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Due to the way Linux handles the command line, no spaces are
allowed in the partition definition, including mtd id's and partition
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names.
Examples:
1 flash resource (mtd-id "sa1100"), with 1 single writable partition:
mtdparts=sa1100:-
Same flash, but 2 named partitions, the first one being read-only:
mtdparts=sa1100:256k(ARMboot)ro,-(root)
If unsure, say 'N'.
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config MTD_OF_PARTS
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tristate "OpenFirmware partitioning information support"
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default y
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depends on OF
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help
This provides a partition parsing function which derives
the partition map from the children of the flash node,
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as described in Documentation/devicetree/bindings/mtd/partition.txt.
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config MTD_AR7_PARTS
tristate "TI AR7 partitioning support"
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help
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TI AR7 partitioning support
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config MTD_BCM63XX_PARTS
tristate "BCM63XX CFE partitioning support"
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depends on BCM63XX || BMIPS_GENERIC || COMPILE_TEST
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select CRC32
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select MTD_PARSER_IMAGETAG
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help
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This provides partition parsing for BCM63xx devices with CFE
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bootloaders.
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config MTD_BCM47XX_PARTS
tristate "BCM47XX partitioning support"
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depends on BCM47XX || ARCH_BCM_5301X
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help
This provides partitions parser for devices based on BCM47xx
boards.
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menu "Partition parsers"
source "drivers/mtd/parsers/Kconfig"
endmenu
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comment "User Modules And Translation Layers"
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#
# MTD block device support is select'ed if needed
#
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config MTD_BLKDEVS
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tristate
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config MTD_BLOCK
tristate "Caching block device access to MTD devices"
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depends on BLOCK
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select MTD_BLKDEVS
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help
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Although most flash chips have an erase size too large to be useful
as block devices, it is possible to use MTD devices which are based
on RAM chips in this manner. This block device is a user of MTD
devices performing that function.
At the moment, it is also required for the Journalling Flash File
System(s) to obtain a handle on the MTD device when it's mounted
(although JFFS and JFFS2 don't actually use any of the functionality
of the mtdblock device).
Later, it may be extended to perform read/erase/modify/write cycles
on flash chips to emulate a smaller block size. Needless to say,
this is very unsafe, but could be useful for file systems which are
almost never written to.
You do not need this option for use with the DiskOnChip devices. For
those, enable NFTL support (CONFIG_NFTL) instead.
config MTD_BLOCK_RO
tristate "Readonly block device access to MTD devices"
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depends on MTD_BLOCK!=y && BLOCK
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select MTD_BLKDEVS
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help
This allows you to mount read-only file systems (such as cramfs)
from an MTD device, without the overhead (and danger) of the caching
driver.
You do not need this option for use with the DiskOnChip devices. For
those, enable NFTL support (CONFIG_NFTL) instead.
config FTL
tristate "FTL (Flash Translation Layer) support"
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depends on BLOCK
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select MTD_BLKDEVS
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help
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This provides support for the original Flash Translation Layer which
is part of the PCMCIA specification. It uses a kind of pseudo-
file system on a flash device to emulate a block device with
512-byte sectors, on top of which you put a 'normal' file system.
You may find that the algorithms used in this code are patented
unless you live in the Free World where software patents aren't
legal - in the USA you are only permitted to use this on PCMCIA
hardware, although under the terms of the GPL you're obviously
permitted to copy, modify and distribute the code as you wish. Just
not use it.
config NFTL
tristate "NFTL (NAND Flash Translation Layer) support"
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depends on BLOCK
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select MTD_BLKDEVS
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help
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This provides support for the NAND Flash Translation Layer which is
used on M-Systems' DiskOnChip devices. It uses a kind of pseudo-
file system on a flash device to emulate a block device with
512-byte sectors, on top of which you put a 'normal' file system.
You may find that the algorithms used in this code are patented
unless you live in the Free World where software patents aren't
legal - in the USA you are only permitted to use this on DiskOnChip
hardware, although under the terms of the GPL you're obviously
permitted to copy, modify and distribute the code as you wish. Just
not use it.
config NFTL_RW
bool "Write support for NFTL"
depends on NFTL
help
Support for writing to the NAND Flash Translation Layer, as used
on the DiskOnChip.
config INFTL
tristate "INFTL (Inverse NAND Flash Translation Layer) support"
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depends on BLOCK
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select MTD_BLKDEVS
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help
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This provides support for the Inverse NAND Flash Translation
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Layer which is used on M-Systems' newer DiskOnChip devices. It
uses a kind of pseudo-file system on a flash device to emulate
a block device with 512-byte sectors, on top of which you put
a 'normal' file system.
You may find that the algorithms used in this code are patented
unless you live in the Free World where software patents aren't
legal - in the USA you are only permitted to use this on DiskOnChip
hardware, although under the terms of the GPL you're obviously
permitted to copy, modify and distribute the code as you wish. Just
not use it.
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config RFD_FTL
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tristate "Resident Flash Disk (Flash Translation Layer) support"
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depends on BLOCK
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select MTD_BLKDEVS
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help
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This provides support for the flash translation layer known
as the Resident Flash Disk (RFD), as used by the Embedded BIOS
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of General Software. There is a blurb at:
http://www.gensw.com/pages/prod/bios/rfd.htm
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config SSFDC
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tristate "NAND SSFDC (SmartMedia) read only translation layer"
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depends on BLOCK
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select MTD_BLKDEVS
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help
This enables read only access to SmartMedia formatted NAND
flash. You can mount it with FAT file system.
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config SM_FTL
tristate "SmartMedia/xD new translation layer"
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depends on BLOCK
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select MTD_BLKDEVS
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select MTD_NAND_ECC_SW_HAMMING
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help
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This enables EXPERIMENTAL R/W support for SmartMedia/xD
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FTL (Flash translation layer).
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Write support is only lightly tested, therefore this driver
isn't recommended to use with valuable data (anyway if you have
valuable data, do backups regardless of software/hardware you
use, because you never know what will eat your data...)
If you only need R/O access, you can use older R/O driver
(CONFIG_SSFDC)
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config MTD_OOPS
tristate "Log panic/oops to an MTD buffer"
help
This enables panic and oops messages to be logged to a circular
buffer in a flash partition where it can be read back at some
later point.
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config MTD_SWAP
tristate "Swap on MTD device support"
depends on MTD && SWAP
select MTD_BLKDEVS
help
Provides volatile block device driver on top of mtd partition
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suitable for swapping. The mapping of written blocks is not saved.
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The driver provides wear leveling by storing erase counter into the
OOB.
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config MTD_PARTITIONED_MASTER
bool "Retain master device when partitioned"
default n
depends on MTD
help
For historical reasons, by default, either a master is present or
several partitions are present, but not both. The concern was that
data listed in multiple partitions was dangerous; however, SCSI does
this and it is frequently useful for applications. This config option
leaves the master in even if the device is partitioned. It also makes
the parent of the partition device be the master device, rather than
what lies behind the master.
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source "drivers/mtd/chips/Kconfig"
source "drivers/mtd/maps/Kconfig"
source "drivers/mtd/devices/Kconfig"
source "drivers/mtd/nand/Kconfig"
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source "drivers/mtd/lpddr/Kconfig"
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source "drivers/mtd/spi-nor/Kconfig"
UBI: Unsorted Block Images
UBI (Latin: "where?") manages multiple logical volumes on a single
flash device, specifically supporting NAND flash devices. UBI provides
a flexible partitioning concept which still allows for wear-levelling
across the whole flash device.
In a sense, UBI may be compared to the Logical Volume Manager
(LVM). Whereas LVM maps logical sector numbers to physical HDD sector
numbers, UBI maps logical eraseblocks to physical eraseblocks.
More information may be found at
http://www.linux-mtd.infradead.org/doc/ubi.html
Partitioning/Re-partitioning
An UBI volume occupies a certain number of erase blocks. This is
limited by a configured maximum volume size, which could also be
viewed as the partition size. Each individual UBI volume's size can
be changed independently of the other UBI volumes, provided that the
sum of all volume sizes doesn't exceed a certain limit.
UBI supports dynamic volumes and static volumes. Static volumes are
read-only and their contents are protected by CRC check sums.
Bad eraseblocks handling
UBI transparently handles bad eraseblocks. When a physical
eraseblock becomes bad, it is substituted by a good physical
eraseblock, and the user does not even notice this.
Scrubbing
On a NAND flash bit flips can occur on any write operation,
sometimes also on read. If bit flips persist on the device, at first
they can still be corrected by ECC, but once they accumulate,
correction will become impossible. Thus it is best to actively scrub
the affected eraseblock, by first copying it to a free eraseblock
and then erasing the original. The UBI layer performs this type of
scrubbing under the covers, transparently to the UBI volume users.
Erase Counts
UBI maintains an erase count header per eraseblock. This frees
higher-level layers (like file systems) from doing this and allows
for centralized erase count management instead. The erase counts are
used by the wear-levelling algorithm in the UBI layer. The algorithm
itself is exchangeable.
Booting from NAND
For booting directly from NAND flash the hardware must at least be
capable of fetching and executing a small portion of the NAND
flash. Some NAND flash controllers have this kind of support. They
usually limit the window to a few kilobytes in erase block 0. This
"initial program loader" (IPL) must then contain sufficient logic to
load and execute the next boot phase.
Due to bad eraseblocks, which may be randomly scattered over the
flash device, it is problematic to store the "secondary program
loader" (SPL) statically. Also, due to bit-flips it may become
corrupted over time. UBI allows to solve this problem gracefully by
storing the SPL in a small static UBI volume.
UBI volumes vs. static partitions
UBI volumes are still very similar to static MTD partitions:
* both consist of eraseblocks (logical eraseblocks in case of UBI
volumes, and physical eraseblocks in case of static partitions;
* both support three basic operations - read, write, erase.
But UBI volumes have the following advantages over traditional
static MTD partitions:
* there are no eraseblock wear-leveling constraints in case of UBI
volumes, so the user should not care about this;
* there are no bit-flips and bad eraseblocks in case of UBI volumes.
So, UBI volumes may be considered as flash devices with relaxed
restrictions.
Where can it be found?
Documentation, kernel code and applications can be found in the MTD
gits.
What are the applications for?
The applications help to create binary flash images for two purposes: pfi
files (partial flash images) for in-system update of UBI volumes, and plain
binary images, with or without OOB data in case of NAND, for a manufacturing
step. Furthermore some tools are/and will be created that allow flash content
analysis after a system has crashed..
Who did UBI?
The original ideas, where UBI is based on, were developed by Andreas
Arnez, Frank Haverkamp and Thomas Gleixner. Josh W. Boyer and some others
were involved too. The implementation of the kernel layer was done by Artem
B. Bityutskiy. The user-space applications and tools were written by Oliver
Lohmann with contributions from Frank Haverkamp, Andreas Arnez, and Artem.
Joern Engel contributed a patch which modifies JFFS2 so that it can be run on
a UBI volume. Thomas Gleixner did modifications to the NAND layer. Alexander
Schmidt made some testing work as well as core functionality improvements.
Signed-off-by: Artem B. Bityutskiy <dedekind@linutronix.de>
Signed-off-by: Frank Haverkamp <haver@vnet.ibm.com>
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source "drivers/mtd/ubi/Kconfig"
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endif # MTD