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How to configure the Linux kernel/Device drivers/Memory Technology Devices (MTD)

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Howto configure the Linux kernel / drivers / mtd


$Id: Kconfig,v 1.11 2005/11/07 11:14:19 gleixner Exp $

Memory Technology Devices (MTD)Edit

  • Option: MTD
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) Memory Technology Device (MTD) support
      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.


  • Option: MTD_DEBUG
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) Debugging
    • depends on MTD
      This turns on low-level debugging for the entire MTD sub-system. Normally, you should say 'N'.


  • Option: MTD_DEBUG_VERBOSE
    • Kernel Versions: 2.6.15.6 ...

"Debugging verbosity (0 = quiet, 3 = noisy)"

    • depends on MTD_DEBUG
    • default "0"
      Determines the verbosity level of the MTD debugging messages.


  • Option: MTD_CONCAT
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) MTD concatenating support
    • depends on MTD
      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'.


  • Option: MTD_PARTITIONS
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) MTD partitioning support
    • depends on MTD
      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.


  • Option: MTD_REDBOOT_PARTS
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) RedBoot partition table parsing
    • depends on MTD_PARTITIONS
      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.


  • Option: MTD_REDBOOT_DIRECTORY_BLOCK
    • Kernel Versions: 2.6.15.6 ...

"Location of RedBoot partition table"

    • depends on MTD_REDBOOT_PARTS
    • default "-1"
      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 absolete 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.


  • Option: MTD_REDBOOT_PARTS_UNALLOCATED
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) Include unallocated flash regions
    • depends on MTD_REDBOOT_PARTS
      If you need to register each unallocated flash region as a MTD 'partition', enable this option.


  • Option: MTD_REDBOOT_PARTS_READONLY
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) Force read-only for RedBoot system images
    • depends on MTD_REDBOOT_PARTS
      If you need to force read-only for 'RedBoot', 'RedBoot Config' and 'FIS directory' images, enable this option.


  • Option: MTD_CMDLINE_PARTS
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) Command line partition table parsing
    • depends on MTD_PARTITIONS = "y"
      Allow generic configuration of the MTD paritition 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'.


  • Option: MTD_AFS_PARTS
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) ARM Firmware Suite partition parsing
    • depends on ARM && MTD_PARTITIONS
      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.

"User Modules And Translation Layers"

    • depends on MTD


  • Option: MTD_CHAR
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) Direct char device access to MTD devices
    • depends on MTD
      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.


  • Option: MTD_BLOCK
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) Caching block device access to MTD devices
    • depends on MTD
      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.


  • Option: MTD_BLOCK_RO
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) Readonly block device access to MTD devices
    • depends on MTD_BLOCK!=y && MTD
      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.


  • Option: FTL
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) FTL (Flash Translation Layer) support
    • depends on MTD
      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.


  • Option: NFTL
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) NFTL (NAND Flash Translation Layer) support
    • depends on MTD
      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.


  • Option: NFTL_RW
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) Write support for NFTL
    • depends on NFTL
      Support for writing to the NAND Flash Translation Layer, as used on the DiskOnChip.


  • Option: INFTL
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) INFTL (Inverse NAND Flash Translation Layer) support
    • depends on MTD
      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.


  • Option: RFD_FTL
    • Kernel Versions: 2.6.15.6 ... tristate Resident Flash Disk (Flash Translation Layer) support
    • depends on MTD
      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:
//www.gensw.com/pages/prod/bios/rfd.htm








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