fs/yaffs2/yaffs_ecc.h

   1 /*
   2  * YAFFS: Yet another Flash File System . A NAND-flash specific file system.
   3  *
   4  * Copyright (C) 2002-2011 Aleph One Ltd.
   5  *   for Toby Churchill Ltd and Brightstar Engineering
   6  *
   7  * Created by Charles Manning <charles@aleph1.co.uk>
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU Lesser General Public License version 2.1 as
  11  * published by the Free Software Foundation.
  12  *
  13  * Note: Only YAFFS headers are LGPL, YAFFS C code is covered by GPL.
  14  */
  15
  16 /*
  17  * This code implements the ECC algorithm used in SmartMedia.
  18  *
  19  * The ECC comprises 22 bits of parity information and is stuffed into 3 bytes.
  20  * The two unused bit are set to 1.
  21  * The ECC can correct single bit errors in a 256-byte page of data.
  22  * Thus, two such ECC blocks are used on a 512-byte NAND page.
  23  *
  24  */
  25
  26 #ifndef __YAFFS_ECC_H__
  27 #define __YAFFS_ECC_H__
  28
  29 struct yaffs_ecc_other {
  30         unsigned char col_parity;
  31         unsigned line_parity;
  32         unsigned line_parity_prime;
  33 };
  34
  35 void yaffs_ecc_calc(const unsigned char *data, unsigned char *ecc);
  36 int yaffs_ecc_correct(unsigned char *data, unsigned char *read_ecc,
  37                       const unsigned char *test_ecc);
  38
  39 void yaffs_ecc_calc_other(const unsigned char *data, unsigned n_bytes,
  40                           struct yaffs_ecc_other *ecc);
  41 int yaffs_ecc_correct_other(unsigned char *data, unsigned n_bytes,
  42                             struct yaffs_ecc_other *read_ecc,
  43                             const struct yaffs_ecc_other *test_ecc);
  44 #endif