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。
相关阅读：
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;
}