nandflash 初始化问题？

guobinname_301 · 发表于 2012-10-30 21:08:17

在 nandflash初始化函数中
int nand_scan (struct mtd_info *mtd, int maxchips)
{
int i, j, nand_maf_id, nand_dev_id, busw;
struct nand_chip *this = mtd->priv;  /* 取出struct nand_chip 结构*/

/* Get buswidth to select the correct functions*/
busw = this->options & NAND_BUSWIDTH_16;

/* check for proper chip_delay setup, set 20us if not */
if (!this->chip_delay)
this->chip_delay = 20;

/* check, if a user supplied command function given */
if (this->cmdfunc == NULL)
this->cmdfunc = nand_command;
这里面有一句if (!this->chip_delay)
this->chip_delay = 20；
chip_delay 成员在这个结构中定义struct nand_chip {
.....
.....
int chip_delay;
.....
}
问题：if (!this->chip_delay)
this->chip_delay = 20;
这个判断语句应该是this指向的chip_delay的值为空或为0 的情况下this->chip_delay = 20。
那程序是如何判断以下成员的值是否为0或为空？？？？
struct nand_chip {
void  __iomem *IO_ADDR_R;
void  __iomem *IO_ADDR_W;

u_char (*read_byte)(struct mtd_info *mtd);
void (*write_byte)(struct mtd_info *mtd, u_char byte);
u16 (*read_word)(struct mtd_info *mtd);
void (*write_word)(struct mtd_info *mtd, u16 word);

void (*write_buf)(struct mtd_info *mtd, const u_char *buf, int len);
void (*read_buf)(struct mtd_info *mtd, u_char *buf, int len);
int (*verify_buf)(struct mtd_info *mtd, const u_char *buf, int len);
void (*select_chip)(struct mtd_info *mtd, int chip);
int (*block_bad)(struct mtd_info *mtd, loff_t ofs, int getchip);
int (*block_markbad)(struct mtd_info *mtd, loff_t ofs);
void (*hwcontrol)(struct mtd_info *mtd, int cmd);
int (*dev_ready)(struct mtd_info *mtd);
void (*cmdfunc)(struct mtd_info *mtd, unsigned command, int column, int page_addr);
int (*waitfunc)(struct mtd_info *mtd, struct nand_chip *this, int state);
int (*calculate_ecc)(struct mtd_info *mtd, const u_char *dat, u_char *ecc_code);
int (*correct_data)(struct mtd_info *mtd, u_char *dat, u_char *read_ecc, u_char *calc_ecc);
void (*enable_hwecc)(struct mtd_info *mtd, int mode);
void (*erase_cmd)(struct mtd_info *mtd, int page);
int (*scan_bbt)(struct mtd_info *mtd);
int eccmode;
int eccsize;
int eccbytes;
int eccsteps;
int chip_delay;
#if 0
spinlock_t chip_lock;
wait_queue_head_t wq;
nand_state_t state;
#endif
int page_shift;
int phys_erase_shift;
int bbt_erase_shift;
int chip_shift;
u_char *data_buf;
u_char *oob_buf;
int oobdirty;
u_char *data_poi;
unsigned int options;
int badblockpos;
int numchips;
unsigned long chipsize;
int pagemask;
int pagebuf;
struct nand_oobinfo *autooob;
uint8_t *bbt;
struct nand_bbt_descr *bbt_td;
struct nand_bbt_descr *bbt_md;
struct nand_bbt_descr *badblock_pattern;
struct nand_hw_control *controller;
void *priv;
};