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801c135ce7
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>
299 lines
10 KiB
Plaintext
299 lines
10 KiB
Plaintext
# $Id: Kconfig,v 1.11 2005/11/07 11:14:19 gleixner Exp $
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menu "Memory Technology Devices (MTD)"
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config MTD
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tristate "Memory Technology Device (MTD) support"
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help
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Memory Technology Devices are flash, RAM and similar chips, often
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used for solid state file systems on embedded devices. This option
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will provide the generic support for MTD drivers to register
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themselves with the kernel and for potential users of MTD devices
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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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config MTD_DEBUG
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bool "Debugging"
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depends on MTD
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help
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This turns on low-level debugging for the entire MTD sub-system.
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Normally, you should say 'N'.
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config MTD_DEBUG_VERBOSE
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int "Debugging verbosity (0 = quiet, 3 = noisy)"
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depends on MTD_DEBUG
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default "0"
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help
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Determines the verbosity level of the MTD debugging messages.
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config MTD_CONCAT
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tristate "MTD concatenating support"
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depends on MTD
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help
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Support for concatenating several MTD devices into a single
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(virtual) one. This allows you to have -for example- a JFFS(2)
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file system spanning multiple physical flash chips. If unsure,
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say 'Y'.
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config MTD_PARTITIONS
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bool "MTD partitioning support"
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depends on MTD
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help
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If you have a device which needs to divide its flash chip(s) up
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into multiple 'partitions', each of which appears to the user as
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a separate MTD device, you require this option to be enabled. If
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unsure, say 'Y'.
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Note, however, that you don't need this option for the DiskOnChip
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devices. Partitioning on NFTL 'devices' is a different - that's the
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'normal' form of partitioning used on a block device.
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config MTD_REDBOOT_PARTS
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tristate "RedBoot partition table parsing"
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depends on MTD_PARTITIONS
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---help---
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RedBoot is a ROM monitor and bootloader which deals with multiple
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'images' in flash devices by putting a table one of the erase
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blocks on the device, similar to a partition table, which gives
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the offsets, lengths and names of all the images stored in the
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flash.
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If you need code which can detect and parse this table, and register
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MTD 'partitions' corresponding to each image in the table, enable
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this option.
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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
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SA1100 map driver (CONFIG_MTD_SA1100) has an option for this, for
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example.
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config MTD_REDBOOT_DIRECTORY_BLOCK
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int "Location of RedBoot partition table"
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depends on MTD_REDBOOT_PARTS
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default "-1"
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---help---
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This option is the Linux counterpart to the
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CYGNUM_REDBOOT_FIS_DIRECTORY_BLOCK RedBoot compile time
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option.
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The option specifies which Flash sectors holds the RedBoot
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partition table. A zero or positive value gives an absolute
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erase block number. A negative value specifies a number of
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sectors before the end of the device.
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For example "2" means block number 2, "-1" means the last
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block and "-2" means the penultimate block.
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config MTD_REDBOOT_PARTS_UNALLOCATED
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bool "Include unallocated flash regions"
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depends on MTD_REDBOOT_PARTS
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help
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If you need to register each unallocated flash region as a MTD
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'partition', enable this option.
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config MTD_REDBOOT_PARTS_READONLY
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bool "Force read-only for RedBoot system images"
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depends on MTD_REDBOOT_PARTS
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help
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If you need to force read-only for 'RedBoot', 'RedBoot Config' and
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'FIS directory' images, enable this option.
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config MTD_CMDLINE_PARTS
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bool "Command line partition table parsing"
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depends on MTD_PARTITIONS = "y" && MTD = "y"
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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
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SA1100 map driver (CONFIG_MTD_SA1100) has an option for this, for
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example.
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The format for the command line is as follows:
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mtdparts=<mtddef>[;<mtddef]
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<mtddef> := <mtd-id>:<partdef>[,<partdef>]
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<partdef> := <size>[@offset][<name>][ro]
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<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
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<name> := (NAME)
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Due to the way Linux handles the command line, no spaces are
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allowed in the partition definition, including mtd id's and partition
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names.
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Examples:
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1 flash resource (mtd-id "sa1100"), with 1 single writable partition:
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mtdparts=sa1100:-
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Same flash, but 2 named partitions, the first one being read-only:
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mtdparts=sa1100:256k(ARMboot)ro,-(root)
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If unsure, say 'N'.
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config MTD_AFS_PARTS
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tristate "ARM Firmware Suite partition parsing"
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depends on ARM && MTD_PARTITIONS
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---help---
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The ARM Firmware Suite allows the user to divide flash devices into
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multiple 'images'. Each such image has a header containing its name
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and offset/size etc.
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If you need code which can detect and parse these tables, and
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register MTD 'partitions' corresponding to each image detected,
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enable this option.
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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
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'armflash' map driver (CONFIG_MTD_ARMFLASH) does this, for example.
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comment "User Modules And Translation Layers"
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depends on MTD
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config MTD_CHAR
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tristate "Direct char device access to MTD devices"
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depends on MTD
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help
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This provides a character device for each MTD device present in
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the system, allowing the user to read and write directly to the
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memory chips, and also use ioctl() to obtain information about
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the device, or to erase parts of it.
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config MTD_BLKDEVS
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tristate "Common interface to block layer for MTD 'translation layers'"
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depends on MTD && BLOCK
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default n
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config MTD_BLOCK
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tristate "Caching block device access to MTD devices"
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depends on MTD && 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
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as block devices, it is possible to use MTD devices which are based
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on RAM chips in this manner. This block device is a user of MTD
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devices performing that function.
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At the moment, it is also required for the Journalling Flash File
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System(s) to obtain a handle on the MTD device when it's mounted
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(although JFFS and JFFS2 don't actually use any of the functionality
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of the mtdblock device).
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Later, it may be extended to perform read/erase/modify/write cycles
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on flash chips to emulate a smaller block size. Needless to say,
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this is very unsafe, but could be useful for file systems which are
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almost never written to.
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You do not need this option for use with the DiskOnChip devices. For
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those, enable NFTL support (CONFIG_NFTL) instead.
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config MTD_BLOCK_RO
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tristate "Readonly block device access to MTD devices"
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depends on MTD_BLOCK!=y && MTD && BLOCK
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select MTD_BLKDEVS
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help
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This allows you to mount read-only file systems (such as cramfs)
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from an MTD device, without the overhead (and danger) of the caching
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driver.
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You do not need this option for use with the DiskOnChip devices. For
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those, enable NFTL support (CONFIG_NFTL) instead.
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config FTL
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tristate "FTL (Flash Translation Layer) support"
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depends on MTD && 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
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is part of the PCMCIA specification. It uses a kind of pseudo-
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file system on a flash device to emulate a block device with
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512-byte sectors, on top of which you put a 'normal' file system.
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You may find that the algorithms used in this code are patented
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unless you live in the Free World where software patents aren't
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legal - in the USA you are only permitted to use this on PCMCIA
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hardware, although under the terms of the GPL you're obviously
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permitted to copy, modify and distribute the code as you wish. Just
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not use it.
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config NFTL
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tristate "NFTL (NAND Flash Translation Layer) support"
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depends on MTD && 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
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used on M-Systems' DiskOnChip devices. It uses a kind of pseudo-
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file system on a flash device to emulate a block device with
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512-byte sectors, on top of which you put a 'normal' file system.
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You may find that the algorithms used in this code are patented
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unless you live in the Free World where software patents aren't
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legal - in the USA you are only permitted to use this on DiskOnChip
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hardware, although under the terms of the GPL you're obviously
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permitted to copy, modify and distribute the code as you wish. Just
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not use it.
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config NFTL_RW
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bool "Write support for NFTL"
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depends on NFTL
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help
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Support for writing to the NAND Flash Translation Layer, as used
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on the DiskOnChip.
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config INFTL
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tristate "INFTL (Inverse NAND Flash Translation Layer) support"
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depends on MTD && 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
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uses a kind of pseudo-file system on a flash device to emulate
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a block device with 512-byte sectors, on top of which you put
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a 'normal' file system.
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You may find that the algorithms used in this code are patented
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unless you live in the Free World where software patents aren't
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legal - in the USA you are only permitted to use this on DiskOnChip
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hardware, although under the terms of the GPL you're obviously
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permitted to copy, modify and distribute the code as you wish. Just
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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 MTD && 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
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as the Resident Flash Disk (RFD), as used by the Embedded BIOS
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of General Software. There is a blurb at:
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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 MTD && BLOCK
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select MTD_BLKDEVS
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help
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This enables read only access to SmartMedia formatted NAND
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flash. You can mount it with FAT file system.
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source "drivers/mtd/chips/Kconfig"
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source "drivers/mtd/maps/Kconfig"
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source "drivers/mtd/devices/Kconfig"
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source "drivers/mtd/nand/Kconfig"
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source "drivers/mtd/onenand/Kconfig"
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source "drivers/mtd/ubi/Kconfig"
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endmenu
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