static int nand_read_oob (struct mtd_info *mtd, loff_t from, size_t len,
size_t *retlen, u_char *buf);
static int nand_write (struct mtd_info *mtd, loff_t to, size_t len,
size_t *retlen, const u_char *buf);
static int nand_read_oob (struct mtd_info *mtd, loff_t from, size_t len,
size_t *retlen, u_char *buf);
static int nand_write (struct mtd_info *mtd, loff_t to, size_t len,
size_t *retlen, const u_char *buf);