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;
}