/proc/mtd 各参数的含义 -- linux内核

经/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）。

以下是别人的文章：

详细由linux/drivers/mtd下的mtdcore.c文件里的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" ", 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 ");
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);
}

读出来的结果例如以下：
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"

当中size和erasesize的定义在linux/include/linux/mtd下mtd.h文件里的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);
}