linux下的nandflash驱动分析（3）——基于s3c6410平台

在上一篇中probe函数中的一个很重要的函数nand_scan函数，现在来说另外一个很重要的函数add_mtd_partitions函数，add_mtd_partitions()会对每一个新建分区建立一个新的mtd_part 结构体，将其加入mtd_ partitions中，并调用add_mtd_device()将此分区作为MTD设备加入mtd_table。成功时返回0，如果分配mtd_part时内存不足，则返回-ENOMEM。

1、在说这个函数前，先说下，与这有关的结构体struct mtd_part和struct mtd_partition结构体，如下所示：

mtd_part结构体用于描述分区，其mtd_info结构体成员用于描述本分区

/* Our partition node structure */

struct mtd_part {

struct mtd_info mtd; 分区的信息（大部分由其master决定

struct mtd_info *master; 该分区的主分区

u_int32_t offset; 该分区的偏移地址

int index; 分区号

struct list_head list;

int registered;

};

/*

* Partition definition structure:

*

* An array of struct partition is passed along with a MTD object to

* add_mtd_partitions() to create them.

*

* For each partition, these fields are available:

* name: string that will be used to label the partition's MTD device.

* size: the partition size; if defined as MTDPART_SIZ_FULL, the partition

* will extend to the end of the master MTD device.

* offset: absolute starting position within the master MTD device; if

* defined as MTDPART_OFS_APPEND, the partition will start where the

* previous one ended; if MTDPART_OFS_NXTBLK, at the next erase block.

* mask_flags: contains flags that have to be masked (removed) from the

* master MTD flag set for the corresponding MTD partition.

* For example, to force a read-only partition, simply adding

* MTD_WRITEABLE to the mask_flags will do the trick.

*

* Note: writeable partitions require their size and offset be

* erasesize aligned (e.g. use MTDPART_OFS_NEXTBLK).

*/

struct mtd_partition {

char *name;
/* identifier string */ 标识字符串

u_int32_t size;
/* partition size */ 分区大小

u_int32_t offset;
/* offset within the master MTD space */ 主MTD空间内的偏移

u_int32_t mask_flags;
/* master MTD flags to mask out for this partition */

struct nand_ecclayout *ecclayout;
/* out of band layout for this partition (NAND only)*/

struct mtd_info **mtdp;
/* pointer to store the MTD object */

};

现在来看下6410中的定义：

struct mtd_partition s3c_partition_info[] = {

{

.name = "Bootloader",

.offset = 0,

.size = (256*SZ_1K),

.mask_flags = MTD_CAP_NANDFLASH,

},

{

.name = "Kernel",

.offset = (256*SZ_1K),

.size = (4*SZ_1M) - (256*SZ_1K),

.mask_flags = MTD_CAP_NANDFLASH,

},

#if defined(CONFIG_SPLIT_ROOT_FILESYSTEM)

{

.name = "Rootfs",

.offset = (4*SZ_1M),

// .size = (512*SZ_1M),//(48*SZ_1M),

.size = (80*SZ_1M),//(48*SZ_1M),

},

#endif

{

.name = "File System",

.offset = MTDPART_OFS_APPEND,

.size = MTDPART_SIZ_FULL,

}

};

struct s3c_nand_mtd_info s3c_nand_mtd_part_info = {

.chip_nr = 1,

.mtd_part_nr = ARRAY_SIZE(s3c_partition_info),

.partition = s3c_partition_info,

};

2、下面来看add_mtd_partitions函数，源码如下：

/*

* This function, given a master MTD object and a partition table, creates

* and registers slave MTD objects which are bound to the master according to

* the partition definitions.

* (Q: should we register the master MTD object as well?)

*/

int add_mtd_partitions(struct mtd_info *master,

const struct mtd_partition *parts,

int nbparts)

{

struct mtd_part *slave;

u_int32_t cur_offset = 0;

int i;

printk(KERN_NOTICE "Creating %d MTD partitions on \"%s\":\n", nbparts, master->name);

for (i = 0; i < nbparts; i++) { 主要就是这个循环体，应该是分别添加每个struct mtd_partition结构

slave = add_one_partition(master, parts + i, i, cur_offset);

if (!slave)

return -ENOMEM;

cur_offset = slave->offset + slave->mtd.size;

}

return 0;

}

接着看add_one_partition函数，源码如下：

static struct mtd_part *add_one_partition(struct mtd_info *master,

const struct mtd_partition *part, int partno,

u_int32_t cur_offset)

{

struct mtd_part *slave; 新建的struct mtd_part结构

/* allocate the partition structure */

slave = kzalloc(sizeof(*slave), GFP_KERNEL);

if (!slave) {

printk(KERN_ERR"memory allocation error while creating partitions for \"%s\"\n",

master->name);

del_mtd_partitions(master);

return NULL;

}

list_add(&slave->list, &mtd_partitions);

这里有个定义：static LIST_HEAD(mtd_partitions);

/* set up the MTD object for this partition */ 其实下面这么多，基本上都是根据主分区和我们定义的

struct mtd_partition中的信息去初始化新建的分区

slave->mtd.type = master->type;

slave->mtd.flags = master->flags & ~part->mask_flags;

slave->mtd.size = part->size;

slave->mtd.writesize = master->writesize;

slave->mtd.oobsize = master->oobsize;

slave->mtd.oobavail = master->oobavail;

slave->mtd.subpage_sft = master->subpage_sft;

slave->mtd.name = part->name;

slave->mtd.owner = master->owner;

slave->mtd.read = part_read;

slave->mtd.write = part_write;

if (master->panic_write)

slave->mtd.panic_write = part_panic_write;

if (master->point && master->unpoint) {

slave->mtd.point = part_point;

slave->mtd.unpoint = part_unpoint;

}

if (master->read_oob)

slave->mtd.read_oob = part_read_oob;

if (master->write_oob)

slave->mtd.write_oob = part_write_oob;

if (master->read_user_prot_reg)

slave->mtd.read_user_prot_reg = part_read_user_prot_reg;

if (master->read_fact_prot_reg)

slave->mtd.read_fact_prot_reg = part_read_fact_prot_reg;

if (master->write_user_prot_reg)

slave->mtd.write_user_prot_reg = part_write_user_prot_reg;

if (master->lock_user_prot_reg)

slave->mtd.lock_user_prot_reg = part_lock_user_prot_reg;

if (master->get_user_prot_info)

slave->mtd.get_user_prot_info = part_get_user_prot_info;

if (master->get_fact_prot_info)

slave->mtd.get_fact_prot_info = part_get_fact_prot_info;

if (master->sync)

slave->mtd.sync = part_sync;

if (!partno && master->suspend && master->resume) {

slave->mtd.suspend = part_suspend;

slave->mtd.resume = part_resume;

}

if (master->writev)

slave->mtd.writev = part_writev;

if (master->lock)

slave->mtd.lock = part_lock;

if (master->unlock)

slave->mtd.unlock = part_unlock;

if (master->block_isbad)

slave->mtd.block_isbad = part_block_isbad;

if (master->block_markbad)

slave->mtd.block_markbad = part_block_markbad;

slave->mtd.erase = part_erase;

slave->master = master;

slave->offset = part->offset;

slave->index = partno;

if (slave->offset == MTDPART_OFS_APPEND)

slave->offset = cur_offset;

if (slave->offset == MTDPART_OFS_NXTBLK) {

slave->offset = cur_offset;

if ((cur_offset % master->erasesize) != 0) {

/* Round up to next erasesize */

slave->offset = ((cur_offset / master->erasesize) + 1) * master->erasesize;

printk(KERN_NOTICE "Moving partition %d: "

"0x%08x -> 0x%08x\n", partno,

cur_offset, slave->offset);

}

}

if (slave->mtd.size == MTDPART_SIZ_FULL)

slave->mtd.size = master->size - slave->offset;

printk(KERN_NOTICE "0x%08x-0x%08x : \"%s\"\n", slave->offset,

slave->offset + slave->mtd.size, slave->mtd.name);

/* let's do some sanity checks */

if (slave->offset >= master->size) {

/* let's register it anyway to preserve ordering */

slave->offset = 0;

slave->mtd.size = 0;

printk(KERN_ERR"mtd: partition \"%s\" is out of reach -- disabled\n",

part->name);

goto out_register;

}

if (slave->offset + slave->mtd.size > master->size) {

slave->mtd.size = master->size - slave->offset;

printk(KERN_WARNING"mtd: partition \"%s\" extends beyond the end of device \"%s\" -- size truncated to %#x\n",

part->name, master->name, slave->mtd.size);

}

if (master->numeraseregions > 1) {

/* Deal with variable erase size stuff */

int i, max = master->numeraseregions;

u32 end = slave->offset + slave->mtd.size;

struct mtd_erase_region_info *regions = master->eraseregions;

/* Find the first erase regions which is part of this

* partition. */

for (i = 0; i < max && regions[i].offset <= slave->offset; i++)

;

/* The loop searched for the region _behind_ the first one */

i--;

/* Pick biggest erasesize */

for (; i < max && regions[i].offset < end; i++) {

if (slave->mtd.erasesize < regions[i].erasesize) {

slave->mtd.erasesize = regions[i].erasesize;

}

}

BUG_ON(slave->mtd.erasesize == 0);

} else {

/* Single erase size */

slave->mtd.erasesize = master->erasesize;

}

if ((slave->mtd.flags & MTD_WRITEABLE) &&

(slave->offset % slave->mtd.erasesize)) {

/* Doesn't start on a boundary of major erase size */

/* FIXME: Let it be writable if it is on a boundary of

* _minor_ erase size though */

slave->mtd.flags &= ~MTD_WRITEABLE;

printk(KERN_WARNING"mtd: partition \"%s\" doesn't start on an erase block boundary -- force read-only\n",

part->name);

}

if ((slave->mtd.flags & MTD_WRITEABLE) &&

(slave->mtd.size % slave->mtd.erasesize)) {

slave->mtd.flags &= ~MTD_WRITEABLE;

printk(KERN_WARNING"mtd: partition \"%s\" doesn't end on an erase block -- force read-only\n",

part->name);

}

slave->mtd.ecclayout = master->ecclayout;

if (master->block_isbad) {

uint32_t offs = 0;

while (offs < slave->mtd.size) {

if (master->block_isbad(master,

offs + slave->offset))

slave->mtd.ecc_stats.badblocks++;

offs += slave->mtd.erasesize;

}

}

out_register:

if (part->mtdp) {

/* store the object pointer (caller may or may not register it*/

*part->mtdp = &slave->mtd;

slave->registered = 0;

} else {

/* register our partition */

add_mtd_device(&slave->mtd);

slave->registered = 1;

}

return slave;

}

调用add_mtd_device()将此分区作为MTD设备加入mtd_table，其中有定义：

struct mtd_info *mtd_table[MAX_MTD_DEVICES];

3、add_mtd_device函数源码：

/**

* add_mtd_device - register an MTD device

* @mtd: pointer to new MTD device info structure

*

* Add a device to the list of MTD devices present in the system, and

* notify each currently active MTD 'user' of its arrival. Returns

* zero on success or 1 on failure, which currently will only happen

* if the number of present devices exceeds MAX_MTD_DEVICES (i.e. 16)

*/

int add_mtd_device(struct mtd_info *mtd)

{

int i;

BUG_ON(mtd->writesize == 0);

mutex_lock(&mtd_table_mutex);

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

if (!mtd_table[i]) {

struct mtd_notifier *not;

mtd_table[i] = mtd;

mtd->index = i;

mtd->usecount = 0;

/* Some chips always power up locked. Unlock them now */

if ((mtd->flags & MTD_WRITEABLE)

&& (mtd->flags & MTD_POWERUP_LOCK) && mtd->unlock) {

if (mtd->unlock(mtd, 0, mtd->size))

printk(KERN_WARNING

"%s: unlock failed, "

"writes may not work\n",

mtd->name);

}

DEBUG(0, "mtd: Giving out device %d to %s\n",i, mtd->name);

/* No need to get a refcount on the module containing

the notifier, since we hold the mtd_table_mutex */

list_for_each_entry(not, &mtd_notifiers, list)

not->add(mtd);

mutex_unlock(&mtd_table_mutex);

/* We _know_ we aren't being removed, because

our caller is still holding us here. So none

of this try_ nonsense, and no bitching about it

either. :) */

__module_get(THIS_MODULE);

return 0;

}

mutex_unlock(&mtd_table_mutex);

return 1;

}