1、在上一篇的probe函数中，在那个很大的for循环中出现了，对NAND的厂商，设备号，是MLC或SLC进行判断，这些是怎样进行的呢？
相关阅读：
其实这些都是在NAND芯片中定义的，我们只需按对应的时序读出这些信息，就可以进行判断，看下面这个图（摘于一个NAND芯片手册）：
2、上一篇中，nand_scan(s3c_mtd, 1)函数没有细说，这一篇说下这个函数，源码如下：
/**
* nand_scan - [NAND Interface] Scan for the NAND device
* @mtd: MTD device structure
* @maxchips: Number of chips to scan for
*
* This fills out all the uninitialized function pointers
* with the defaults.
* The flash ID is read and the mtd/chip structures are
* filled with the appropriate values.
* The mtd->owner field must be set to the module of the caller
*
*/
int nand_scan(struct mtd_info *mtd, int maxchips)
{
int ret;
/* Many callers got this wrong, so check for it for a while... */
if (!mtd->owner && caller_is_module()) {
printk(KERN_CRIT "nand_scan() called with NULL mtd->owner!\n");
BUG();
}
ret = nand_scan_ident(mtd, maxchips);
if (!ret) 如果上面的函数成功，这执行nand_scan_tail函数。这个函数的分析，看下面：
ret = nand_scan_tail(mtd);
return ret;
}
主要就是上面那个函数：nand_scan_ident，源码如下：
/**
* nand_scan_ident - [NAND Interface] Scan for the NAND device
* @mtd: MTD device structure
* @maxchips: Number of chips to scan for
*
* This is the first phase of the normal nand_scan() function. It
* reads the flash ID and sets up MTD fields accordingly.
*
* The mtd->owner field must be set to the module of the caller.
*/
int nand_scan_ident(struct mtd_info *mtd, int maxchips)
{
int i, busw, nand_maf_id;
struct nand_chip *chip = mtd->priv; 得到struct nand_chip结构体
struct nand_flash_dev *type;
/* Get buswidth to select the correct functions */
busw = chip->options & NAND_BUSWIDTH_16; 和数据宽度有关，看下面这个图：
/* Set the default functions */ 根据数据宽度设置默认函数：
nand_set_defaults(chip, busw);此函数源码如下：
/*
* Set default functions
*/
static void nand_set_defaults(struct nand_chip *chip, int busw)
{
/* check for proper chip_delay setup, set 20us if not */
if (!chip->chip_delay)
chip->chip_delay = 20;
/* check, if a user supplied command function given */
if (chip->cmdfunc == NULL)
chip->cmdfunc = nand_command;
/* check, if a user supplied wait function given */
if (chip->waitfunc == NULL)
chip->waitfunc = nand_wait;
if (!chip->select_chip)
chip->select_chip = nand_select_chip;
if (!chip->read_byte)
chip->read_byte = busw nand_read_byte16 : nand_read_byte;
if (!chip->read_word)
chip->read_word = nand_read_word;
if (!chip->block_bad)
chip->block_bad = nand_block_bad;
if (!chip->block_markbad)
chip->block_markbad = nand_default_block_markbad;
if (!chip->write_buf)
chip->write_buf = busw nand_write_buf16 : nand_write_buf;
if (!chip->read_buf)
chip->read_buf = busw nand_read_buf16 : nand_read_buf;
if (!chip->verify_buf)
chip->verify_buf = busw nand_verify_buf16 : nand_verify_buf;
if (!chip->scan_bbt)
chip->scan_bbt = nand_default_bbt;
if (!chip->controller) {
chip->controller = &chip->hwcontrol;
spin_lock_init(&chip->controller->lock);
init_waitqueue_head(&chip->controller->wq);
}
}
/* Read the flash type */ 读取NAND芯片的信息，并进行一些结构体成员的赋值
type = nand_get_flash_type(mtd, chip, busw, &nand_maf_id);
if (IS_ERR(type)) {
printk(KERN_WARNING "No NAND device found!!!\n");
chip->select_chip(mtd, -1);
return PTR_ERR(type);
}
/* Check for a chip array */ 和多芯片有关
for (i = 1; i < maxchips; i++) {
chip->select_chip(mtd, i);
/* See comment in nand_get_flash_type for reset */
chip->cmdfunc(mtd, NAND_CMD_RESET, -1, -1);
/* Send the command for reading device ID */
chip->cmdfunc(mtd, NAND_CMD_READID, 0x00, -1);
/* Read manufacturer and device IDs */
if (nand