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    Subject[PATCH 08/29] Staging: yaffs2: yaffs_ecc: Add files
    Date
    Adding files to yaffs2 directory.

    Signed-off-by: Tracey Dent <tdent48227@gmail.com>
    ---
    drivers/staging/yaffs2/yaffs_ecc.c | 323 ++++++++++++++++++++++++++++++++++++
    drivers/staging/yaffs2/yaffs_ecc.h | 44 +++++
    2 files changed, 367 insertions(+), 0 deletions(-)
    create mode 100644 drivers/staging/yaffs2/yaffs_ecc.c
    create mode 100644 drivers/staging/yaffs2/yaffs_ecc.h

    diff --git a/drivers/staging/yaffs2/yaffs_ecc.c b/drivers/staging/yaffs2/yaffs_ecc.c
    new file mode 100644
    index 0000000..35f8747
    --- /dev/null
    +++ b/drivers/staging/yaffs2/yaffs_ecc.c
    @@ -0,0 +1,323 @@
    +/*
    + * YAFFS: Yet Another Flash File System. A NAND-flash specific file system.
    + *
    + * Copyright (C) 2002-2010 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.
    + */
    +
    +#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_count_bits(unsigned char x)
    +{
    + int r = 0;
    + while (x) {
    + if (x & 1)
    + r++;
    + x >>= 1;
    + }
    + return r;
    +}
    +
    +static int yaffs_count_bits32(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_ecc_cacl(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_ecc_correct(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_count_bits(d0) +
    + yaffs_count_bits(d1) +
    + yaffs_count_bits(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_ecc_calc_other(const unsigned char *data, unsigned n_bytes,
    + yaffs_ecc_other *ecc_other)
    +{
    + unsigned int i;
    +
    + unsigned char col_parity = 0;
    + unsigned line_parity = 0;
    + unsigned line_parity_prime = 0;
    + unsigned char b;
    +
    + for (i = 0; i < n_bytes; 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_other->col_parity = (col_parity >> 2) & 0x3f;
    + ecc_other->line_parity = line_parity;
    + ecc_other->line_parity_prime = line_parity_prime;
    +}
    +
    +int yaffs_ecc_correct_other(unsigned char *data, unsigned n_bytes,
    + yaffs_ecc_other *read_ecc,
    + const yaffs_ecc_other *test_ecc)
    +{
    + unsigned char delta_col; /* column parity delta */
    + unsigned delta_line; /* line parity delta */
    + unsigned delta_line_prime; /* line parity delta */
    + unsigned bit;
    +
    + delta_col = read_ecc->col_parity ^ test_ecc->col_parity;
    + delta_line = read_ecc->line_parity ^ test_ecc->line_parity;
    + delta_line_prime = read_ecc->line_parity_prime ^ test_ecc->line_parity_prime;
    +
    + if ((delta_col | delta_line | delta_line_prime) == 0)
    + return 0; /* no error */
    +
    + if (delta_line == ~delta_line_prime &&
    + (((delta_col ^ (delta_col >> 1)) & 0x15) == 0x15)) {
    + /* Single bit (recoverable) error in data */
    +
    + bit = 0;
    +
    + if (delta_col & 0x20)
    + bit |= 0x04;
    + if (delta_col & 0x08)
    + bit |= 0x02;
    + if (delta_col & 0x02)
    + bit |= 0x01;
    +
    + if (delta_line >= n_bytes)
    + return -1;
    +
    + data[delta_line] ^= (1 << bit);
    +
    + return 1; /* corrected */
    + }
    +
    + if ((yaffs_count_bits32(delta_line) + yaffs_count_bits32(delta_line_prime) +
    + yaffs_count_bits(delta_col)) == 1) {
    + /* Reccoverable error in ecc */
    +
    + *read_ecc = *test_ecc;
    + return 1; /* corrected */
    + }
    +
    + /* Unrecoverable error */
    +
    + return -1;
    +}
    diff --git a/drivers/staging/yaffs2/yaffs_ecc.h b/drivers/staging/yaffs2/yaffs_ecc.h
    new file mode 100644
    index 0000000..f505ab5
    --- /dev/null
    +++ b/drivers/staging/yaffs2/yaffs_ecc.h
    @@ -0,0 +1,44 @@
    +/*
    + * YAFFS: Yet another Flash File System . A NAND-flash specific file system.
    + *
    + * Copyright (C) 2002-2010 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 Lesser General Public License version 2.1 as
    + * published by the Free Software Foundation.
    + *
    + * Note: Only YAFFS headers are LGPL, YAFFS C code is covered by GPL.
    + */
    +
    +/*
    + * 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.
    + *
    + */
    +
    +#ifndef __YAFFS_ECC_H__
    +#define __YAFFS_ECC_H__
    +
    +typedef struct {
    + unsigned char col_parity;
    + unsigned line_parity;
    + unsigned line_parity_prime;
    +} yaffs_ecc_other;
    +
    +void yaffs_ecc_cacl(const unsigned char *data, unsigned char *ecc);
    +int yaffs_ecc_correct(unsigned char *data, unsigned char *read_ecc,
    + const unsigned char *test_ecc);
    +
    +void yaffs_ecc_calc_other(const unsigned char *data, unsigned n_bytes,
    + yaffs_ecc_other *ecc);
    +int yaffs_ecc_correct_other(unsigned char *data, unsigned n_bytes,
    + yaffs_ecc_other *read_ecc,
    + const yaffs_ecc_other *test_ecc);
    +#endif
    --
    1.7.3.2.146.gca209


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