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%08xn", 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 -- disabledn",

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 %#xn",

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-onlyn",

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-onlyn",