MTD - 版本历史

Comcat：/* MTD 上的文件系统 = */

2017-10-30T03:05:09Z

‎MTD 上的文件系统 =

Comcat：/* MTD 上的文件系统 = */

2017-10-30T02:57:13Z

‎MTD 上的文件系统 =

Comcat：/* Overview */

2017-10-30T02:56:37Z

‎Overview

Comcat：/* Architecture */

2017-10-30T02:56:24Z

‎Architecture

Comcat：/* Architecture */

2017-10-30T02:56:13Z

‎Architecture

Comcat：/* MTD hardware device drivers */

2017-10-30T02:56:01Z

‎MTD hardware device drivers

2017年10月30日 (一) 02:55 Comcat

2017-10-30T02:55:00Z

2017年10月30日 (一) 02:53 Comcat

2017-10-30T02:53:28Z

Comcat：以“== Overview == MTD --- Memory Technology Devices 目的在于为 Flash ROM, EEPROM 等设备提供一个统一的接口，亦可将一段RAM虚拟成一个MTD 设...”为内容创建页面

2017-10-30T02:51:57Z

以“== Overview == MTD --- Memory Technology Devices 目的在于为 Flash ROM, EEPROM 等设备提供一个统一的接口，亦可将一段RAM虚拟成一个MTD 设...”为内容创建页面

新页面

== Overview ==

MTD --- Memory Technology Devices

目的在于为 Flash ROM, EEPROM 等设备提供一个统一的接口，亦可将一段RAM虚拟成一个MTD 设备。

MTD 设备与传统设备的区别：

HARD drives MTD device Consists of sectors Consists of eraseblocks Sectors are small (512, 1024 bytes) Eraseblocks are larger (32KB, 128KB) Maintains 2 main operations: read sector and write sector Maintains 3 main operations: read from eraseblock, write to eraseblock, and erase eraseblock Bad sectors are re-mapped and hidden by hardware, at least at modern LBA hard drives Bad eraseblocks are not hidden and should be dealt with in software HDD sectors are devoid of the wear-out property Eraseblocks get worn-out (i.e., bad and unusable) after about 104-105 erase cycles.

 

== Architecture ==

主要分两层：

=== cMTD hardware device drivers ===

Common Flash Interface (CFI) onboard NOR flash
Onboard NAND flash
On-board memory
EEPROM
PCMCIA flash (not CompactFlash but real flash)
M-Systems' DiskOnChip 2000 and Millennium

所有这些设备有一些基本的访问接口： CFI, JEDEC, MAP_ROM, MAP_RAM
最为常见的是 NAND 和 NOR

=== MTD User modules ===

MTD 提供多种访问方式：

Raw character access
Raw block access
Flash Translation Layer (FTL) （将MTD虚拟成一个块设备，则可像块设备一样在上建立文件系统）
NFTL
Journalling Flash File System, v2 (JFFS2)
( JFFS2 provides a filesystem directly on the flash, rather than emulating a block device)

 

2. USB sticks, CompactFlash cards and other removable flash media are not MTD devices. They are block devices. They do contain flash chip inside, but they also contain some translation layer above which emulates block device. This translation layer is implemented in hardware. So for outside world these devices look exactly as hard drives, not like MTD devices.

3. NAND && NOR

NOR 一般实现 CFI 接口，让用户读取其参数。读写擦除数据可以像操作内存一样，其往往映射到一个固定的地址空间，比如： 0x1e00 0000

NAND 的读写则需要通过控制寄存器来操作。

NOR Flash is connected to a address / data bus direct like other memory devices as SRAM etc.
NAND Flash uses a multiplexed I/O Interface with some additional control pins.

NOR flash is a random access device appropriate for code storage application.
NAND flash is a sequential access device appropriate for mass storage applications

NOR Flash can be used for code storage and code execution.
Code stored on NAND Flash can't be executed frome there. It must be loaded into RAM memory and executed from there.

== MTD 上的文件系统 ===

JFFS2 and YAFFS for bare NAND Flash and SmartMediaCards
NTFL for DiskOnChip devices
TRUEFFS from M-Systems for DiskOnChip devices
SmartMedia DOS-FAT as defined by the SSFDC Forum

== Examples ==

<source lang=bash>
root@nec:/root> xxd /dev/mtd4 | head -4
0000000: ffff ffff ffff ffff ffff ffff ffff ffff ................
0000010: ffff ffff ffff ffff ffff ffff ffff ffff ................
0000020: ffff ffff ffff ffff ffff ffff ffff ffff ................
0000030: ffff ffff ffff ffff ffff ffff ffff ffff ................

root@nec:/root> date > /dev/mtd4

root@nec:/root> xxd /dev/mtd4 | head -10
0000000: 5361 7420 4a61 6e20 2031 2030 303a 3137 Sat Jan 1 00:17
0000010: 3a33 3720 474d 5420 3230 3030 0aff ffff :37 GMT 2000....
0000020: ffff ffff ffff ffff ffff ffff ffff ffff ................

Can use the flash_eraseall (mtd-tools) commands to erase a whole MTD partition:
root@nec:/root> flash_eraseall /dev/mtd4
</source>

The mkfs.jffs2 tool is used to create a JFFS2 filesystem image; it populates the image with files from a given directory. For instance, to create a JFFS2 image for a flash partition of 3 MB total size and to populate it with the files from the /tmp/flashtools directory you would use:

<source lang=bash>
# mkfs.jffs2 --pad=3145728 --eraseblock=262144 --root=/tmp/flashtools/ --output image.jffs2

# eraseall /dev/mtd4
Erased 3072 Kibyte @ 0 -- 100% complete.

# dd if=image.jffs2 of=/dev/mtd4 bs=256k
12+0 records in
12+0 records out

# mount -t jffs2 /dev/mtdblock4 /mnt

# df /mnt
Filesystem 1k-blocks Used Available Use% Mounted on
/dev/mtdblock4 3072 2488 584 81% /mnt
</source>

@@ 第23行： / 第23行： @@
 * PCMCIA flash (not CompactFlash but real flash)
 * M-Systems' DiskOnChip 2000 and Millennium
 所有这些设备有一些基本的访问接口： CFI, JEDEC, MAP_ROM, MAP_RAM
@@ 第38行： / 第39行： @@
 * NFTL
 * Journalling Flash File System, v2 (JFFS2)
 JFFS2 provides a filesystem directly on the flash, rather than emulating a block device

@@ 第73行： / 第73行： @@
 <br>
-== MTD 上的文件系统 ===
+== MTD 上的文件系统 ==
 * JFFS2 and YAFFS for bare NAND Flash and SmartMediaCards

@@ 第75行： / 第75行： @@
 == MTD 上的文件系统 ===
-    JFFS2 and YAFFS for bare NAND Flash and SmartMediaCards
+* JFFS2 and YAFFS for bare NAND Flash and SmartMediaCards
-    NTFL for DiskOnChip devices
+* NTFL for DiskOnChip devices
-    TRUEFFS from M-Systems for DiskOnChip devices
+* TRUEFFS from M-Systems for DiskOnChip devices
-    SmartMedia DOS-FAT as defined by the SSFDC Forum
+* SmartMedia DOS-FAT as defined by the SSFDC Forum
 <br>

@@ 第3行： / 第3行： @@
 MTD --- Memory Technology Devices
-目的在于为 Flash ROM, EEPROM 等设备提供一个统一的接口，亦可将一段RAM虚拟成一个MTD 设备。
+目的在于为 Flash ROM, EEPROM 等设备提供一个统一的接口，亦可将一段RAM虚拟成一个MTD 设备
 MTD 设备与传统设备的区别：

@@ 第26行： / 第26行： @@
 所有这些设备有一些基本的访问接口： CFI, JEDEC, MAP_ROM, MAP_RAM
 最为常见的是 NAND 和 NOR
 === MTD User modules ===

@@ 第17行： / 第17行： @@
 === MTD hardware device drivers ===
-    Common Flash Interface (CFI) onboard NOR flash
+* Common Flash Interface (CFI) onboard NOR flash
-    Onboard NAND flash
+* Onboard NAND flash
-    On-board memory
+* On-board memory
-    EEPROM
+* EEPROM
-    PCMCIA flash (not CompactFlash but real flash)
+* PCMCIA flash (not CompactFlash but real flash)
-    M-Systems' DiskOnChip 2000 and Millennium
+* M-Systems' DiskOnChip 2000 and Millennium
 所有这些设备有一些基本的访问接口： CFI, JEDEC, MAP_ROM, MAP_RAM
 最为常见的是 NAND 和 NOR
 === MTD User modules ===

@@ 第32行： / 第32行： @@
 MTD 提供多种访问方式：
-    Raw character access
+* Raw character access
-    Raw block access
+* Raw block access
-    Flash Translation Layer (FTL) （将MTD虚拟成一个块设备，则可像块设备一样在上建立文件系统）
+* Flash Translation Layer (FTL) （将MTD虚拟成一个块设备，则可像块设备一样在上建立文件系统）
-    NFTL
+* NFTL
-    Journalling Flash File System, v2 (JFFS2)
+* Journalling Flash File System, v2 (JFFS2)
-    ( JFFS2 provides a filesystem directly on the flash, rather than emulating a block device)
 <br>
-. USB sticks, CompactFlash cards and other removable flash media are not MTD devices. They are block devices. They do contain flash chip inside, but they also contain some translation layer above which emulates block device. This translation layer is implemented in hardware. So for outside world these devices look exactly as hard drives, not like MTD devices.
+'''NOTE:''' USB sticks, CompactFlash cards and other removable flash media are not MTD devices. They are block devices. They do contain flash chip inside, but they also contain some translation layer above which emulates block device. This translation layer is implemented in hardware. So for outside world these devices look exactly as hard drives, not like MTD devices.
 <br>
@@ 第66行： / 第67行： @@
 Code stored on NAND Flash can't be executed frome there. It must be loaded into RAM memory and executed from there.
 == MTD 上的文件系统 ===
@@ 第74行： / 第76行： @@
      SmartMedia DOS-FAT as defined by the SSFDC Forum
 == Examples ==

@@ 第15行： / 第15行： @@
 主要分两层：
-=== cMTD hardware device drivers ===
+=== MTD hardware device drivers ===
      Common Flash Interface (CFI) onboard NOR flash
@@ 第43行： / 第43行： @@
 . USB sticks, CompactFlash cards and other removable flash media are not MTD devices. They are block devices. They do contain flash chip inside, but they also contain some translation layer above which emulates block device. This translation layer is implemented in hardware. So for outside world these devices look exactly as hard drives, not like MTD devices.
-. NAND && NOR
+<br>
-    NOR 一般实现 CFI 接口，让用户读取其参数。读写擦除数据可以像操作内存一样，其往往映射到一个固定的地址空间，比如： 0x1e00 0000
+NOR flash is a random access device appropriate for code storage application.
-    NAND 的读写则需要通过控制寄存器来操作。
+NAND flash is a sequential access device appropriate for mass storage applications
-    NOR flash is a random access device appropriate for code storage application.
+NOR Flash can be used for code storage and code execution.
-    NAND flash is a sequential access device appropriate for mass storage applications
-    NOR Flash can be used for code storage and code execution.
+Code stored on NAND Flash can't be executed frome there. It must be loaded into RAM memory and executed from there.
-    Code stored on NAND Flash can't be executed frome there. It must be loaded into RAM memory and executed from there.