在上一篇中probe函數中的一個很重要的函數nand_scan函數，現在來說另外一個很重要的函數add_mtd_partitions函數，add_mtd_partitions()會對每一個新建分區建立一個新的mtd_part 結構體，將其加入mtd_ partitions中，並調用add_mtd_device()將此分區作為MTD設備加入mtd_table。成功時返回0，如果分配mtd_part時內存不足，則返回-ENOMEM。
相關閱讀：
Linux下的nandflash驅動分析（1）——基於S3C6410平台 http://www.linuxidc.com/Linux/2012-05/61439.htm
Linux下的nandflash驅動分析（2）——基於S3C6410平台 http://www.linuxidc.com/Linux/2012-05/61544.htm
Linux下的nandflash驅動分析（3）——基於S3C6410平台 http://www.linuxidc.com/Linux/2012-05/61545.htm
1、在說這個函數前，先說下，與這有關的結構體struct mtd_part和struct mtd_partition結構體，如下所示：
mtd_part結構體用於描述分區，其mtd_info結構體成員用於描述本分區
/* Our partition node structure */
struct mtd_part {
struct mtd_info mtd; 分區的信息（大部分由其master決定
struct mtd_info *master; 該分區的主分區
u_int32_t offset; 該分區的偏移地址
int index; 分區號
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 */ 標識字符串
u_int32_t size;/* partition size */ 分區大小
u_int32_t offset;/* offset within the master MTD space */ 主MTD空間內的偏移
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 */
};
現在來看下6410中的定義：
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、下面來看add_mtd_partitions函數，源碼如下：
/*
* 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++) { 主要就是這個循環體，應該是分別添加每個struct mtd_partition結構
slave = add_one_partition(master, parts + i, i, cur_offset);
if (!slave)
return -ENOMEM;
cur_offset = slave->offset + slave->mtd.size;
}
return 0;
}