1.void yaffs_ecc_calc(const unsigned char *data, unsigned char *ecc)//为256B的数据进行校验生成3B的校验位
2.int yaffs_ecc_correct(unsigned char *data, unsigned char *read_ecc,const unsigned char *test_ecc)//没有错误返回0,改正了的错误返回1,不能改能的错误返回-1
3.void yaffs_ecc_calc_other(const unsigned char *data, unsigned n_bytes,struct yaffs_ecc_other *ecc_other)//计算该数据块的任意n_bytes位的ecc值
4.int yaffs_ecc_correct_other(unsigned char *data, unsigned n_bytes,struct yaffs_ecc_other *read_ecc, const struct yaffs_ecc_other *test_ecc)//在读数据时使用,没有错误返回0,改正了的错误返回1,不能改能的错误返回-1
if ((hweight32(delta_line) +
hweight32(delta_line_prime) +
hweight8(delta_col)) == 1) /////////////?????????????????