--- linux-2.6.27.6/fs/yaffs2/yaffs_ecc.c	1970-01-01 08:00:00.000000000 +0800
+++ linux-2.6.27.6.yaffs/fs/yaffs2/yaffs_ecc.c	2011-05-08 18:01:08.000000000 +0800
@@ -0,0 +1,326 @@
+/*
+ * 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 1.11 2009/03/06 17:20:50 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;
+}
