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Memory technology devices linux

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Содержание
  1. Memory technology devices linux
  2. Design aims
  3. News
  4. Memory technology devices linux
  5. Devices and partitions
  6. Devices
  7. Partitions
  8. NAND simulator
  9. MTD Utilities
  10. flash_erase
  11. nanddump
  12. nandwrite
  13. mtdpart
  14. Programming Interfaces
  15. ioctl ABI
  16. libmtd
  17. Kernel API
  18. Reading

Memory technology devices linux

Memory Technology Devices

Design aims

We’re working on a generic Linux subsystem for memory devices, especially Flash devices.

The aim of the system is to make it simple to provide a driver for new hardware, by providing a generic interface between the hardware drivers and the upper layers of the system.

Hardware drivers need to know nothing about the storage formats used, such as FTL, FFS2, etc., but will only need to provide simple routines for read, write and erase. Presentation of the device’s contents to the user in an appropriate form will be handled by the upper layers of the system.

News

  • 07 Oct 2022: mtd-utils version 2.1.5 is out — see the release announcement
  • 06 Jan 2022: mtd-utils version 2.1.4 is out — see the release announcement
  • 25 Jul 2021: mtd-utils version 2.1.3 is out — see the release announcement
  • 13 Jul 2020: mtd-utils version 2.1.2 is out — see the release announcement
  • 21 Jul 2019: mtd-utils version 2.1.1 is out — see the release announcement
  • 19 Mar 2019: mtd-utils version 2.1.0 is out — see the release announcement
  • 16 Apr 2018: mtd-utils version 2.0.2 is out — see the release announcement
  • 24 Aug 2017: mtd-utils version 2.0.1 is out — see the release announcement
  • 22 Dec 2016: mtd-utils version 2.0.0 is out — see the release announcement
  • 03 Aug 2015: mtd-utils version 1.5.2 is out — see the release announcement
  • 19 Aug 2011: mtd-utils version 1.4.6 is out — this is just a bug-fix release which fixes » mtdinfo -a » breakage
  • 19 Aug 2011: ubifs back-port trees for kernels 2.6.28-2.6.31 are no longer maintained
  • 25 Jun 2011: mtd-utils version 1.4.5 is out
  • 29 May 2011: CONFIG_MTD_PARTITIONS was removed by Jamie Iles.
  • 20 May 2011: UBIFS now can fixup free space to work around the «dumb flasher» issue, see here.
  • 08 Apr 2011: UBIFS does not check data CRC by default starting from linux kernel version 2.6.39 , see here
  • 02 Apr 2011: mtd-utils version 1.4.4 is out (» flash_eraseall -j» bug fixed)
  • 28 Mar 2011: Software BCH ECC library merged upstream
  • 28 Mar 2011: Swap on top of MTD device ( mtdswap driver) merged upstream
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Memory technology devices linux

The Memory Technology Devices (MTD) subsystem provides a common interface to many types of raw flash storage devices. It includes facilities for partioning flash, erasing flash, and managing bad blocks.

Devices and partitions

The mtdinfo command, provided as part of the mtd-utils distribution, displays all available MTD devices and partitions:

$ mtdinfo Count of MTD devices: 5 Present MTD devices: mtd0, mtd1, mtd2, mtd3, mtd4 Sysfs interface supported: yes 
$ mtdinfo /dev/mtd0 mtd0 Name: NAND 128MiB 1,8V 8-bit Type: nand Eraseblock size: 16384 bytes, 16.0 KiB Amount of eraseblocks: 8192 (134217728 bytes, 128.0 MiB) Minimum input/output unit size: 512 bytes Sub-page size: 256 bytes OOB size: 16 bytes Character device major/minor: 90:0 Bad blocks are allowed: true Device is writable: true

Like many such userspace tools, mtdinfo is a thin wrapper around the MTD sysfs interface in /sys/class/mtd .

Devices

Most mtd-utils commands take a /dev/mtdX device node as an argument.

You can read/write directly from/to /dev/mtdX devices, but there are complications:

  • reads can be any size, but writes must be a multiple of the device’s minimum write size (as reported by /sys/class/mtd/mtdX/writesize )
  • blocks must be erased before they can be written
  • on NAND devices, reading from or writing to a bad block may produce unexpected results

For these reasons, the [mtd-utils utilities](#MTD Utilities) are often used for flash I/O.

Partitions

MTD allows flash devices to be carved into partitions. Several on-flash partition table formats are supported, as well as partitions defined on the kernel command line or in the device tree.

NAND simulator

MTD includes a NAND simulator module ( nandsim ) that attaches a virtual MTD device:

$ modprobe nandsim $ mtdinfo -a Count of MTD devices: 1 Present MTD devices: mtd0 Sysfs interface supported: yes mtd0 Name: NAND simulator partition 0 Type: nand Eraseblock size: 16384 bytes, 16.0 KiB Amount of eraseblocks: 8192 (134217728 bytes, 128.0 MiB) Minimum input/output unit size: 512 bytes Sub-page size: 256 bytes OOB size: 16 bytes Character device major/minor: 90:0 Bad blocks are allowed: true Device is writable: true

MTD Utilities

MTD includes a suite of userspace tools, distributed as mtd-utils.

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flash_erase

The flash_erase utility erases the data and out-of-band areas of a device, partition, or range of blocks:

$ flash_erase /dev/mtd0 0 0 Erasing 16 Kibyte @ 7ffc000 -- 100 % complete

Reading an erased flash returns all-ones:

$ dd if=/dev/mtd0 bs=512 count=1 | hd 00000000 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |. | * 00000200

nanddump

The nanddump utility dumps the contents of an MTD device, skipping any bad blocks that it encounters:

$ nanddump /dev/mtd0 -f nand.img ECC failed: 0 ECC corrected: 0 Number of bad blocks: 0 Number of bbt blocks: 0 Block size 16384, page size 512, OOB size 16 Dumping data starting at 0x00000000 and ending at 0x08000000.

It can optionally dump out-of-band data and bad blocks.

nandwrite

The nandwrite utility copies a source file to an MTD device, skipping any bad blocks that it encounters:

$ sudo nandwrite /dev/mtd0 nand.img Writing data to block 0 at offset 0x0 Writing data to block 1 at offset 0x4000 Writing data to block 2 at offset 0x8000 Writing data to block 3 at offset 0xc000 .

mtdpart

The mtdpart utility adds and deletes MTD partitions (but does not update the on-flash partition table):

$ mtdinfo Count of MTD devices: 2 Present MTD devices: mtd0, mtd1 Sysfs interface supported: yes $ sudo mtdpart del /dev/mtd0 1 $ mtdinfo Count of MTD devices: 1 Present MTD devices: mtd0 Sysfs interface supported: yes $ sudo mtdpart add /dev/mtd0 ubi 0 1048576 $ mtdinfo Count of MTD devices: 2 Present MTD devices: mtd0, mtd1 Sysfs interface supported: yes $ mtdinfo /dev/mtd1 mtd1 Name: ubi Type: nand Eraseblock size: 16384 bytes, 16.0 KiB Amount of eraseblocks: 64 (1048576 bytes, 1024.0 KiB) Minimum input/output unit size: 512 bytes Sub-page size: 256 bytes OOB size: 16 bytes Character device major/minor: 90:2 Bad blocks are allowed: true Device is writable: true

Programming Interfaces

ioctl ABI

Behind the scenes, the mtd-utils commands interact with the MTD subsystem via an ioctl interface:

/* Get basic MTD characteristics info (better to use sysfs) */ #define MEMGETINFO _IOR('M', 1, struct mtd_info_user) /* Erase segment of MTD */ #define MEMERASE _IOW('M', 2, struct erase_info_user) /* Write out-of-band data from MTD */ #define MEMWRITEOOB _IOWR('M', 3, struct mtd_oob_buf) /* Read out-of-band data from MTD */ #define MEMREADOOB _IOWR('M', 4, struct mtd_oob_buf) /* Lock a chip (for MTD that supports it) */ #define MEMLOCK _IOW('M', 5, struct erase_info_user) /* Unlock a chip (for MTD that supports it) */ #define MEMUNLOCK _IOW('M', 6, struct erase_info_user) /* Check if chip is locked (for MTD that supports it) */ #define MEMISLOCKED _IOR('M', 23, struct erase_info_user) /* Check if an eraseblock is bad */ #define MEMGETBADBLOCK _IOW('M', 11, __kernel_loff_t) /* Mark an eraseblock as bad */ #define MEMSETBADBLOCK _IOW('M', 12, __kernel_loff_t) /* * Most generic write interface; can write in-band and/or out-of-band in various * modes (see "struct mtd_write_req") */ #define MEMWRITE _IOWR('M', 24, struct mtd_write_req)

libmtd

The mtd-utils source builds a static library (libmtd.a) that wraps the MTD ioctls in a tidy API, e.g., mtd_mark_bad() :

/** * mtd_mark_bad - mark an eraseblock as bad. * @mtd: MTD device description object * @fd: MTD device node file descriptor * @eb: eraseblock to mark as bad * * This function marks eraseblock @eb as bad. Returns %0 in case of success and * %-1 in case of failure. */ int mtd_mark_bad(const struct mtd_dev_info *mtd, int fd, int eb);

Sadly, libmtd.a is not included in the mtd-utils binary distribution.

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Kernel API

Higher layer kernel subsystems (flash filesytems, UBI) interact with raw flash via the MTD API defined in include/linux/mtd/mtd.h, including:

int mtd_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf); int mtd_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen, const u_char *buf); int mtd_erase(struct mtd_info *mtd, struct erase_info *instr); int mtd_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops); int mtd_write_oob(struct mtd_info *mtd, loff_t to, struct mtd_oob_ops *ops);

Device drivers register MTD devices with the MTD core via mtd_device_register() .

Reading

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