yaffs: Improve debug chunk erased checking, change refreshPeriod

[yaffs2.git] / yaffs_ecc.c

diff --git a/yaffs_ecc.c b/yaffs_ecc.c
index 59f3ed9cd118cffb98371b827605f282ac79b40a..da6145aac27a1c3f8a583ea009ca70aecc9e1f79 100644 (file)
--- a/yaffs_ecc.c
+++ b/yaffs_ecc.c
@@ -1,27 +1,25 @@
 /*
- * YAFFS: Yet another FFS. A NAND-flash specific file system. 
+ * YAFFS: Yet Another Flash File System. A NAND-flash specific file system.
  *
- * yaffs_ecc.c: ECC generation/correction algorithms.
- *
- * Copyright (C) 2002 Aleph One Ltd.
+ * 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.
+ * 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.
-  *
-  */
+/*
+ * 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'
@@ -30,9 +28,6 @@
  * this bytes influence on the line parity.
  */
 
-const char *yaffs_ecc_c_version =
-    "$Id: yaffs_ecc.c,v 1.6 2005-08-11 02:51:49 charles Exp $";
-
 #include "yportenv.h"
 
 #include "yaffs_ecc.h"
@@ -111,12 +106,10 @@ void yaffs_ECCCalculate(const unsigned char *data, unsigned char *ecc)
                b = column_parity_table[*data++];
                col_parity ^= b;
 
-               if (b & 0x01)   // odd number of bits in the byte
-               {
+               if (b & 0x01) {         /* odd number of bits in the byte */
                        line_parity ^= i;
                        line_parity_prime ^= ~i;
                }
-
        }
 
        ecc[2] = (~col_parity) | 0x03;
@@ -160,7 +153,7 @@ void yaffs_ECCCalculate(const unsigned char *data, unsigned char *ecc)
        ecc[0] = ~t;
 
 #ifdef CONFIG_YAFFS_ECC_WRONG_ORDER
-       // Swap the bytes into the wrong order
+       /* Swap the bytes into the wrong order */
        t = ecc[0];
        ecc[0] = ecc[1];
        ecc[1] = t;
@@ -191,7 +184,7 @@ int yaffs_ECCCorrect(unsigned char *data, unsigned char *read_ecc,
                unsigned bit;
 
 #ifdef CONFIG_YAFFS_ECC_WRONG_ORDER
-               // swap the bytes to correct for the wrong order
+               /* swap the bytes to correct for the wrong order */
                unsigned char t;
 
                t = d0;
@@ -230,8 +223,8 @@ int yaffs_ECCCorrect(unsigned char *data, unsigned char *read_ecc,
                return 1; /* Corrected the error */
        }
 
-       if ((yaffs_CountBits(d0) + 
-            yaffs_CountBits(d1) + 
+       if ((yaffs_CountBits(d0) +
+            yaffs_CountBits(d1) +
             yaffs_CountBits(d2)) ==  1) {
                /* Reccoverable error in ecc */
 
@@ -241,7 +234,7 @@ int yaffs_ECCCorrect(unsigned char *data, unsigned char *read_ecc,
 
                return 1; /* Corrected the error */
        }
-       
+
        /* Unrecoverable error */
 
        return -1;
@@ -253,7 +246,7 @@ int yaffs_ECCCorrect(unsigned char *data, unsigned char *read_ecc,
  * ECCxxxOther does ECC calcs on arbitrary n bytes of data
  */
 void yaffs_ECCCalculateOther(const unsigned char *data, unsigned nBytes,
-                            yaffs_ECCOther * eccOther)
+                               yaffs_ECCOther *eccOther)
 {
        unsigned int i;
 
@@ -280,8 +273,8 @@ void yaffs_ECCCalculateOther(const unsigned char *data, unsigned nBytes,
 }
 
 int yaffs_ECCCorrectOther(unsigned char *data, unsigned nBytes,
-                         yaffs_ECCOther * read_ecc,
-                         const yaffs_ECCOther * test_ecc)
+                       yaffs_ECCOther *read_ecc,
+                       const yaffs_ECCOther *test_ecc)
 {
        unsigned char cDelta;   /* column parity delta */
        unsigned lDelta;        /* line parity delta */
@@ -295,8 +288,8 @@ int yaffs_ECCCorrectOther(unsigned char *data, unsigned nBytes,
        if ((cDelta | lDelta | lDeltaPrime) == 0)
                return 0; /* no error */
 
-       if (lDelta == ~lDeltaPrime && (((cDelta ^ (cDelta >> 1)) & 0x15) == 0x15))
-       {
+       if (lDelta == ~lDeltaPrime &&
+           (((cDelta ^ (cDelta >> 1)) & 0x15) == 0x15)) {
                /* Single bit (recoverable) error in data */
 
                bit = 0;
@@ -308,13 +301,16 @@ int yaffs_ECCCorrectOther(unsigned char *data, unsigned nBytes,
                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) {
+                       yaffs_CountBits(cDelta)) == 1) {
                /* Reccoverable error in ecc */
 
                *read_ecc = *test_ecc;
@@ -324,6 +320,4 @@ int yaffs_ECCCorrectOther(unsigned char *data, unsigned nBytes,
        /* Unrecoverable error */
 
        return -1;
-
 }
-