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android_kernel_xiaomi_sm8350/drivers/mtd/Kconfig
Artem B. Bityutskiy 801c135ce7 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>
2007-04-27 14:23:33 +03:00

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# $Id: Kconfig,v 1.11 2005/11/07 11:14:19 gleixner Exp $
menu "Memory Technology Devices (MTD)"
config MTD
tristate "Memory Technology Device (MTD) support"
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
them. It will also allow you to select individual drivers for
particular hardware and users of MTD devices. If unsure, say N.
config MTD_DEBUG
bool "Debugging"
depends on MTD
help
This turns on low-level debugging for the entire MTD sub-system.
Normally, you should say 'N'.
config MTD_DEBUG_VERBOSE
int "Debugging verbosity (0 = quiet, 3 = noisy)"
depends on MTD_DEBUG
default "0"
help
Determines the verbosity level of the MTD debugging messages.
config MTD_CONCAT
tristate "MTD concatenating support"
depends on MTD
help
Support for concatenating several MTD devices into a single
(virtual) one. This allows you to have -for example- a JFFS(2)
file system spanning multiple physical flash chips. If unsure,
say 'Y'.
config MTD_PARTITIONS
bool "MTD partitioning support"
depends on MTD
help
If you have a device which needs to divide its flash chip(s) up
into multiple 'partitions', each of which appears to the user as
a separate MTD device, you require this option to be enabled. If
unsure, say 'Y'.
Note, however, that you don't need this option for the DiskOnChip
devices. Partitioning on NFTL 'devices' is a different - that's the
'normal' form of partitioning used on a block device.
config MTD_REDBOOT_PARTS
tristate "RedBoot partition table parsing"
depends on MTD_PARTITIONS
---help---
RedBoot is a ROM monitor and bootloader which deals with multiple
'images' in flash devices by putting a table one of the erase
blocks on the device, similar to a partition table, which gives
the offsets, lengths and names of all the images stored in the
flash.
If you need code which can detect and parse this table, and register
MTD 'partitions' corresponding to each image in the table, enable
this option.
You will still need the parsing functions to be called by the driver
for your particular device. It won't happen automatically. The
SA1100 map driver (CONFIG_MTD_SA1100) has an option for this, for
example.
config MTD_REDBOOT_DIRECTORY_BLOCK
int "Location of RedBoot partition table"
depends on MTD_REDBOOT_PARTS
default "-1"
---help---
This option is the Linux counterpart to the
CYGNUM_REDBOOT_FIS_DIRECTORY_BLOCK RedBoot compile time
option.
The option specifies which Flash sectors holds the RedBoot
partition table. A zero or positive value gives an absolute
erase block number. A negative value specifies a number of
sectors before the end of the device.
For example "2" means block number 2, "-1" means the last
block and "-2" means the penultimate block.
config MTD_REDBOOT_PARTS_UNALLOCATED
bool "Include unallocated flash regions"
depends on MTD_REDBOOT_PARTS
help
If you need to register each unallocated flash region as a MTD
'partition', enable this option.
config MTD_REDBOOT_PARTS_READONLY
bool "Force read-only for RedBoot system images"
depends on MTD_REDBOOT_PARTS
help
If you need to force read-only for 'RedBoot', 'RedBoot Config' and
'FIS directory' images, enable this option.
config MTD_CMDLINE_PARTS
bool "Command line partition table parsing"
depends on MTD_PARTITIONS = "y" && MTD = "y"
---help---
Allow generic configuration of the MTD partition tables via the kernel
command line. Multiple flash resources are supported for hardware where
different kinds of flash memory are available.
You will still need the parsing functions to be called by the driver
for your particular device. It won't happen automatically. The
SA1100 map driver (CONFIG_MTD_SA1100) has an option for this, for
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
<size> := standard linux memsize OR "-" to denote all
remaining space
<name> := (NAME)
Due to the way Linux handles the command line, no spaces are
allowed in the partition definition, including mtd id's and partition
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'.
config MTD_AFS_PARTS
tristate "ARM Firmware Suite partition parsing"
depends on ARM && MTD_PARTITIONS
---help---
The ARM Firmware Suite allows the user to divide flash devices into
multiple 'images'. Each such image has a header containing its name
and offset/size etc.
If you need code which can detect and parse these tables, and
register MTD 'partitions' corresponding to each image detected,
enable this option.
You will still need the parsing functions to be called by the driver
for your particular device. It won't happen automatically. The
'armflash' map driver (CONFIG_MTD_ARMFLASH) does this, for example.
comment "User Modules And Translation Layers"
depends on MTD
config MTD_CHAR
tristate "Direct char device access to MTD devices"
depends on MTD
help
This provides a character device for each MTD device present in
the system, allowing the user to read and write directly to the
memory chips, and also use ioctl() to obtain information about
the device, or to erase parts of it.
config MTD_BLKDEVS
tristate "Common interface to block layer for MTD 'translation layers'"
depends on MTD && BLOCK
default n
config MTD_BLOCK
tristate "Caching block device access to MTD devices"
depends on MTD && BLOCK
select MTD_BLKDEVS
---help---
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"
depends on MTD_BLOCK!=y && MTD && BLOCK
select MTD_BLKDEVS
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"
depends on MTD && BLOCK
select MTD_BLKDEVS
---help---
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"
depends on MTD && BLOCK
select MTD_BLKDEVS
---help---
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"
depends on MTD && BLOCK
select MTD_BLKDEVS
---help---
This provides support for the Inverse NAND Flash Translation
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.
config RFD_FTL
tristate "Resident Flash Disk (Flash Translation Layer) support"
depends on MTD && BLOCK
select MTD_BLKDEVS
---help---
This provides support for the flash translation layer known
as the Resident Flash Disk (RFD), as used by the Embedded BIOS
of General Software. There is a blurb at:
http://www.gensw.com/pages/prod/bios/rfd.htm
config SSFDC
tristate "NAND SSFDC (SmartMedia) read only translation layer"
depends on MTD && BLOCK
select MTD_BLKDEVS
help
This enables read only access to SmartMedia formatted NAND
flash. You can mount it with FAT file system.
source "drivers/mtd/chips/Kconfig"
source "drivers/mtd/maps/Kconfig"
source "drivers/mtd/devices/Kconfig"
source "drivers/mtd/nand/Kconfig"
source "drivers/mtd/onenand/Kconfig"
source "drivers/mtd/ubi/Kconfig"
endmenu
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