+++ /dev/null
-/*
- * YAFFS: Yet Another Flash File System. A NAND-flash specific file system.
- *
- * Copyright (C) 2002-2007 Aleph One Ltd.
- * for Toby Churchill Ltd and Brightstar Engineering
- *
- * Created by Charles Manning <charles@aleph1.co.uk>
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- */
-
-/*
- * This code implements the ECC algorithm used in SmartMedia.
- *
- * The ECC comprises 22 bits of parity information and is stuffed into 3 bytes.
- * The two unused bit are set to 1.
- * The ECC can correct single bit errors in a 256-byte page of data. Thus, two such ECC
- * blocks are used on a 512-byte NAND page.
- *
- */
-
-/* Table generated by gen-ecc.c
- * Using a table means we do not have to calculate p1..p4 and p1'..p4'
- * for each byte of data. These are instead provided in a table in bits7..2.
- * Bit 0 of each entry indicates whether the entry has an odd or even parity, and therefore
- * this bytes influence on the line parity.
- */
-
-const char *yaffs_ecc_c_version =
- "$Id: yaffs_ecc.c,v 1.9 2007-02-14 01:09:06 wookey Exp $";
-
-#include "yportenv.h"
-
-#include "yaffs_ecc.h"
-
-static const unsigned char column_parity_table[] = {
- 0x00, 0x55, 0x59, 0x0c, 0x65, 0x30, 0x3c, 0x69,
- 0x69, 0x3c, 0x30, 0x65, 0x0c, 0x59, 0x55, 0x00,
- 0x95, 0xc0, 0xcc, 0x99, 0xf0, 0xa5, 0xa9, 0xfc,
- 0xfc, 0xa9, 0xa5, 0xf0, 0x99, 0xcc, 0xc0, 0x95,
- 0x99, 0xcc, 0xc0, 0x95, 0xfc, 0xa9, 0xa5, 0xf0,
- 0xf0, 0xa5, 0xa9, 0xfc, 0x95, 0xc0, 0xcc, 0x99,
- 0x0c, 0x59, 0x55, 0x00, 0x69, 0x3c, 0x30, 0x65,
- 0x65, 0x30, 0x3c, 0x69, 0x00, 0x55, 0x59, 0x0c,
- 0xa5, 0xf0, 0xfc, 0xa9, 0xc0, 0x95, 0x99, 0xcc,
- 0xcc, 0x99, 0x95, 0xc0, 0xa9, 0xfc, 0xf0, 0xa5,
- 0x30, 0x65, 0x69, 0x3c, 0x55, 0x00, 0x0c, 0x59,
- 0x59, 0x0c, 0x00, 0x55, 0x3c, 0x69, 0x65, 0x30,
- 0x3c, 0x69, 0x65, 0x30, 0x59, 0x0c, 0x00, 0x55,
- 0x55, 0x00, 0x0c, 0x59, 0x30, 0x65, 0x69, 0x3c,
- 0xa9, 0xfc, 0xf0, 0xa5, 0xcc, 0x99, 0x95, 0xc0,
- 0xc0, 0x95, 0x99, 0xcc, 0xa5, 0xf0, 0xfc, 0xa9,
- 0xa9, 0xfc, 0xf0, 0xa5, 0xcc, 0x99, 0x95, 0xc0,
- 0xc0, 0x95, 0x99, 0xcc, 0xa5, 0xf0, 0xfc, 0xa9,
- 0x3c, 0x69, 0x65, 0x30, 0x59, 0x0c, 0x00, 0x55,
- 0x55, 0x00, 0x0c, 0x59, 0x30, 0x65, 0x69, 0x3c,
- 0x30, 0x65, 0x69, 0x3c, 0x55, 0x00, 0x0c, 0x59,
- 0x59, 0x0c, 0x00, 0x55, 0x3c, 0x69, 0x65, 0x30,
- 0xa5, 0xf0, 0xfc, 0xa9, 0xc0, 0x95, 0x99, 0xcc,
- 0xcc, 0x99, 0x95, 0xc0, 0xa9, 0xfc, 0xf0, 0xa5,
- 0x0c, 0x59, 0x55, 0x00, 0x69, 0x3c, 0x30, 0x65,
- 0x65, 0x30, 0x3c, 0x69, 0x00, 0x55, 0x59, 0x0c,
- 0x99, 0xcc, 0xc0, 0x95, 0xfc, 0xa9, 0xa5, 0xf0,
- 0xf0, 0xa5, 0xa9, 0xfc, 0x95, 0xc0, 0xcc, 0x99,
- 0x95, 0xc0, 0xcc, 0x99, 0xf0, 0xa5, 0xa9, 0xfc,
- 0xfc, 0xa9, 0xa5, 0xf0, 0x99, 0xcc, 0xc0, 0x95,
- 0x00, 0x55, 0x59, 0x0c, 0x65, 0x30, 0x3c, 0x69,
- 0x69, 0x3c, 0x30, 0x65, 0x0c, 0x59, 0x55, 0x00,
-};
-
-/* Count the bits in an unsigned char or a U32 */
-
-static int yaffs_CountBits(unsigned char x)
-{
- int r = 0;
- while (x) {
- if (x & 1)
- r++;
- x >>= 1;
- }
- return r;
-}
-
-static int yaffs_CountBits32(unsigned x)
-{
- int r = 0;
- while (x) {
- if (x & 1)
- r++;
- x >>= 1;
- }
- return r;
-}
-
-/* Calculate the ECC for a 256-byte block of data */
-void yaffs_ECCCalculate(const unsigned char *data, unsigned char *ecc)
-{
- unsigned int i;
-
- unsigned char col_parity = 0;
- unsigned char line_parity = 0;
- unsigned char line_parity_prime = 0;
- unsigned char t;
- unsigned char b;
-
- for (i = 0; i < 256; i++) {
- b = column_parity_table[*data++];
- col_parity ^= b;
-
- if (b & 0x01) // odd number of bits in the byte
- {
- line_parity ^= i;
- line_parity_prime ^= ~i;
- }
-
- }
-
- ecc[2] = (~col_parity) | 0x03;
-
- t = 0;
- if (line_parity & 0x80)
- t |= 0x80;
- if (line_parity_prime & 0x80)
- t |= 0x40;
- if (line_parity & 0x40)
- t |= 0x20;
- if (line_parity_prime & 0x40)
- t |= 0x10;
- if (line_parity & 0x20)
- t |= 0x08;
- if (line_parity_prime & 0x20)
- t |= 0x04;
- if (line_parity & 0x10)
- t |= 0x02;
- if (line_parity_prime & 0x10)
- t |= 0x01;
- ecc[1] = ~t;
-
- t = 0;
- if (line_parity & 0x08)
- t |= 0x80;
- if (line_parity_prime & 0x08)
- t |= 0x40;
- if (line_parity & 0x04)
- t |= 0x20;
- if (line_parity_prime & 0x04)
- t |= 0x10;
- if (line_parity & 0x02)
- t |= 0x08;
- if (line_parity_prime & 0x02)
- t |= 0x04;
- if (line_parity & 0x01)
- t |= 0x02;
- if (line_parity_prime & 0x01)
- t |= 0x01;
- ecc[0] = ~t;
-
-#ifdef CONFIG_YAFFS_ECC_WRONG_ORDER
- // Swap the bytes into the wrong order
- t = ecc[0];
- ecc[0] = ecc[1];
- ecc[1] = t;
-#endif
-}
-
-
-/* Correct the ECC on a 256 byte block of data */
-
-int yaffs_ECCCorrect(unsigned char *data, unsigned char *read_ecc,
- const unsigned char *test_ecc)
-{
- unsigned char d0, d1, d2; /* deltas */
-
- d0 = read_ecc[0] ^ test_ecc[0];
- d1 = read_ecc[1] ^ test_ecc[1];
- d2 = read_ecc[2] ^ test_ecc[2];
-
- if ((d0 | d1 | d2) == 0)
- return 0; /* no error */
-
- if (((d0 ^ (d0 >> 1)) & 0x55) == 0x55 &&
- ((d1 ^ (d1 >> 1)) & 0x55) == 0x55 &&
- ((d2 ^ (d2 >> 1)) & 0x54) == 0x54) {
- /* Single bit (recoverable) error in data */
-
- unsigned byte;
- unsigned bit;
-
-#ifdef CONFIG_YAFFS_ECC_WRONG_ORDER
- // swap the bytes to correct for the wrong order
- unsigned char t;
-
- t = d0;
- d0 = d1;
- d1 = t;
-#endif
-
- bit = byte = 0;
-
- if (d1 & 0x80)
- byte |= 0x80;
- if (d1 & 0x20)
- byte |= 0x40;
- if (d1 & 0x08)
- byte |= 0x20;
- if (d1 & 0x02)
- byte |= 0x10;
- if (d0 & 0x80)
- byte |= 0x08;
- if (d0 & 0x20)
- byte |= 0x04;
- if (d0 & 0x08)
- byte |= 0x02;
- if (d0 & 0x02)
- byte |= 0x01;
-
- if (d2 & 0x80)
- bit |= 0x04;
- if (d2 & 0x20)
- bit |= 0x02;
- if (d2 & 0x08)
- bit |= 0x01;
-
- data[byte] ^= (1 << bit);
-
- return 1; /* Corrected the error */
- }
-
- if ((yaffs_CountBits(d0) +
- yaffs_CountBits(d1) +
- yaffs_CountBits(d2)) == 1) {
- /* Reccoverable error in ecc */
-
- read_ecc[0] = test_ecc[0];
- read_ecc[1] = test_ecc[1];
- read_ecc[2] = test_ecc[2];
-
- return 1; /* Corrected the error */
- }
-
- /* Unrecoverable error */
-
- return -1;
-
-}
-
-
-/*
- * ECCxxxOther does ECC calcs on arbitrary n bytes of data
- */
-void yaffs_ECCCalculateOther(const unsigned char *data, unsigned nBytes,
- yaffs_ECCOther * eccOther)
-{
- unsigned int i;
-
- unsigned char col_parity = 0;
- unsigned line_parity = 0;
- unsigned line_parity_prime = 0;
- unsigned char b;
-
- for (i = 0; i < nBytes; i++) {
- b = column_parity_table[*data++];
- col_parity ^= b;
-
- if (b & 0x01) {
- /* odd number of bits in the byte */
- line_parity ^= i;
- line_parity_prime ^= ~i;
- }
-
- }
-
- eccOther->colParity = (col_parity >> 2) & 0x3f;
- eccOther->lineParity = line_parity;
- eccOther->lineParityPrime = line_parity_prime;
-}
-
-int yaffs_ECCCorrectOther(unsigned char *data, unsigned nBytes,
- yaffs_ECCOther * read_ecc,
- const yaffs_ECCOther * test_ecc)
-{
- unsigned char cDelta; /* column parity delta */
- unsigned lDelta; /* line parity delta */
- unsigned lDeltaPrime; /* line parity delta */
- unsigned bit;
-
- cDelta = read_ecc->colParity ^ test_ecc->colParity;
- lDelta = read_ecc->lineParity ^ test_ecc->lineParity;
- lDeltaPrime = read_ecc->lineParityPrime ^ test_ecc->lineParityPrime;
-
- if ((cDelta | lDelta | lDeltaPrime) == 0)
- return 0; /* no error */
-
- if (lDelta == ~lDeltaPrime &&
- (((cDelta ^ (cDelta >> 1)) & 0x15) == 0x15))
- {
- /* Single bit (recoverable) error in data */
-
- bit = 0;
-
- if (cDelta & 0x20)
- bit |= 0x04;
- if (cDelta & 0x08)
- bit |= 0x02;
- if (cDelta & 0x02)
- bit |= 0x01;
-
- if(lDelta >= nBytes)
- return -1;
-
- data[lDelta] ^= (1 << bit);
-
- return 1; /* corrected */
- }
-
- if ((yaffs_CountBits32(lDelta) + yaffs_CountBits32(lDeltaPrime) +
- yaffs_CountBits(cDelta)) == 1) {
- /* Reccoverable error in ecc */
-
- *read_ecc = *test_ecc;
- return 1; /* corrected */
- }
-
- /* Unrecoverable error */
-
- return -1;
-
-}
-
projects / openwrt / openwrt.git / blobdiff