通过/proc虚拟文件系统读取MTD分区表：cat /proc/mtd

mtd .name = raspi, .size = 0x00400000 (4M) .erasesize = 0x00010000 (64K).numeraseregions = 0

Creating 6 MTD partitions on "raspi":

0x00000000-0x00400000 : "ALL"

0x00000000-0x00030000 : "Bootloader"

0x00030000-0x00040000 : "Config"

0x00040000-0x00050000 : "Factory"

0x00050000-0x00360000 : "Kernel"

0x00360000-0x003b0000 : "DATA"

通过这个结构体可知size是本mtd分区的最大字节数空间，erasesize是本分区的最小擦除字节数空间(块大小，linux的flash是以块为擦除单位的)。

下面是别人的文章：

具体由linux/drivers/mtd下的mtdcore.c文件中的mtd_read_proc函数来实现：

static inline int mtd_proc_info (char *buf, int i)

{

struct mtd_info *this = mtd_table[i];

if (!this)

return 0;

return sprintf(buf, "mtd%d: %8.8x %8.8x \"%s\"\n", i, this->size,

this->erasesize, this->name);

}

static int mtd_read_proc (char *page, char **start, off_t off, int count,

int *eof, void *data_unused)

{

int len, l, i;

off_t begin = 0;

mutex_lock(&mtd_table_mutex);

len = sprintf(page, "dev: size erasesize name\n");

for (i=0; i< MAX_MTD_DEVICES; i++) {

l = mtd_proc_info(page + len, i);

len += l;

if (len+begin > off+count)

goto done;

if (len+begin < off) {

begin += len;

len = 0;

}

}

*eof = 1;

done:

mutex_unlock(&mtd_table_mutex);

if (off >= len+begin)

return 0;

*start = page + (off-begin);

return ((count < begin+len-off) ? count : begin+len-off);

}

读出来的结果如下：

dev: size erasesize name

mtd0: 01000000 00020000 "boot"

mtd1: 01000000 00020000 "setting"

mtd2: 02000000 00020000 "rootfs"

mtd3: 0be00000 00020000 "home"

mtd4: 00200000 00020000 "storage"

mtd5: 00040000 00010000 "u-boot"

mtd6: 00040000 00010000 "others"

其中size和erasesize的定义在linux/include/linux/mtd下mtd.h文件中的struct mtd_info结构体定义：

struct mtd_info {

u_char type;

u_int32_t flags;

u_int32_t size; // Total size of the MTD

/* "Major" erase size for the device. users may take this

* to be the only erase size available, or may use the more detailed

* information below if they desire

*/

u_int32_t erasesize;

/* Minimal writable flash unit size. In case of NOR flash it is 1 (even

* though individual bits can be cleared), in case of NAND flash it is

* one NAND page (or half, or one-fourths of it), in case of ECC-ed NOR

* it is of ECC block size, etc. It is illegal to have writesize = 0.

* Any driver registering a struct mtd_info must ensure a writesize of

* 1 or larger.

*/

u_int32_t writesize;

u_int32_t oobsize; // Amount of OOB data per block (e.g. 16)

u_int32_t oobavail; // Available OOB bytes per block

// Kernel-only stuff starts here.

char *name;

int index;

/* ecc layout structure pointer - read only ! */

struct nand_ecclayout *ecclayout;

/* Data for variable erase regions. If numeraseregions is zero,

* it means that the whole device has erasesize as given above.

*/

int numeraseregions;

struct mtd_erase_region_info *eraseregions;

int (*erase) (struct mtd_info *mtd, struct erase_info *instr);

/* This stuff for eXecute-In-Place */

int (*point) (struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char **mtdbuf);

/* We probably shouldn't allow XIP if the unpoint isn't a NULL */

void (*unpoint) (struct mtd_info *mtd, u_char * addr, loff_t from, size_t len);

int (*read) (struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf);

int (*write) (struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen, const u_char *buf);

int (*read_oob) (struct mtd_info *mtd, loff_t from,

struct mtd_oob_ops *ops);

int (*write_oob) (struct mtd_info *mtd, loff_t to,

struct mtd_oob_ops *ops);

/*

* Methods to access the protection register area, present in some

* flash devices. The user data is one time programmable but the

* factory data is read only.

*/

int (*get_fact_prot_info) (struct mtd_info *mtd, struct otp_info *buf, size_t len);

int (*read_fact_prot_reg) (struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf);

int (*get_user_prot_info) (struct mtd_info *mtd, struct otp_info *buf, size_t len);

int (*read_user_prot_reg) (struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf);

int (*write_user_prot_reg) (struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf);

int (*lock_user_prot_reg) (struct mtd_info *mtd, loff_t from, size_t len);

/* kvec-based read/write methods.

NB: The 'count' parameter is the number of _vectors_, each of

which contains an (ofs, len) tuple.

*/

int (*writev) (struct mtd_info *mtd, const struct kvec *vecs, unsigned long count, loff_t to, size_t *retlen);

/* Sync */

void (*sync) (struct mtd_info *mtd);

/* Chip-supported device locking */

int (*lock) (struct mtd_info *mtd, loff_t ofs, size_t len);

int (*unlock) (struct mtd_info *mtd, loff_t ofs, size_t len);

/* Power Management functions */

int (*suspend) (struct mtd_info *mtd);

void (*resume) (struct mtd_info *mtd);

/* Bad block management functions */

int (*block_isbad) (struct mtd_info *mtd, loff_t ofs);

int (*block_markbad) (struct mtd_info *mtd, loff_t ofs);

struct notifier_block reboot_notifier; /* default mode before reboot */

/* ECC status information */

struct mtd_ecc_stats ecc_stats;

/* Subpage shift (NAND) */

int subpage_sft;

void *priv;

struct module *owner;

int usecount;

/* If the driver is something smart, like UBI, it may need to maintain * its own reference counting. The below functions are only for driver. * The driver may register its callbacks. These callbacks are not * supposed to be called by MTD users */ int (*get_device) (struct mtd_info *mtd); void (*put_device) (struct mtd_info *mtd); }