* GNU GPL License. The rest is simply to convert the disk on chip
* syndrom into a standard syndom.
*
- * Author: Fabrice Bellard (fabrice.bellard@netgem.com)
+ * Author: Fabrice Bellard (fabrice.bellard@netgem.com)
* Copyright (C) 2000 Netgem S.A.
*
- * $Id: docecc.c,v 1.5 2003/05/21 15:15:06 dwmw2 Exp $
+ * $Id: docecc.c,v 1.7 2005/11/07 11:14:25 gleixner Exp $
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
#include <linux/mtd/mtd.h>
#include <linux/mtd/doc2000.h>
+#define DEBUG_ECC 0
/* need to undef it (from asm/termbits.h) */
#undef B0
a(0) + a(1) @ + a(2) @^2 + ... + a(m-1) @^(m-1)
we consider the integer "i" whose binary representation with a(0) being LSB
and a(m-1) MSB is (a(0),a(1),...,a(m-1)) and locate the entry
- "index_of[i]". Now, @^index_of[i] is that element whose polynomial
+ "index_of[i]". Now, @^index_of[i] is that element whose polynomial
representation is (a(0),a(1),a(2),...,a(m-1)).
NOTE:
The element alpha_to[2^m-1] = 0 always signifying that the
Similarily, the element index_of[0] = A0 always signifying
that the power of alpha which has the polynomial representation
(0,0,...,0) is "infinity".
-
+
*/
static void
* are written back. NOTE! This array must be at least NN-KK elements long.
* The corrected data are written in eras_val[]. They must be xor with the data
* to retrieve the correct data : data[erase_pos[i]] ^= erase_val[i] .
- *
+ *
* First "no_eras" erasures are declared by the calling program. Then, the
* maximum # of errors correctable is t_after_eras = floor((NN-KK-no_eras)/2).
* If the number of channel errors is not greater than "t_after_eras" the
* */
static int
eras_dec_rs(dtype Alpha_to[NN + 1], dtype Index_of[NN + 1],
- gf bb[NN - KK + 1], gf eras_val[NN-KK], int eras_pos[NN-KK],
+ gf bb[NN - KK + 1], gf eras_val[NN-KK], int eras_pos[NN-KK],
int no_eras)
{
int deg_lambda, el, deg_omega;
count = 0;
goto finish;
}
-
+
for(i=1;i<=NN-KK;i++){
s[i] = bb[0];
}
if(bb[j] == 0)
continue;
tmp = Index_of[bb[j]];
-
+
for(i=1;i<=NN-KK;i++)
s[i] ^= Alpha_to[modnn(tmp + (B0+i-1)*PRIM*j)];
}
tmp = modnn(tmp + 2 * KK * (B0+i-1)*PRIM);
s[i] = tmp;
}
-
+
CLEAR(&lambda[1],NN-KK);
lambda[0] = 1;
lambda[j] ^= Alpha_to[modnn(u + tmp)];
}
}
-#if DEBUG >= 1
+#if DEBUG_ECC >= 1
/* Test code that verifies the erasure locator polynomial just constructed
Needed only for decoder debugging. */
-
+
/* find roots of the erasure location polynomial */
for(i=1;i<=no_eras;i++)
reg[i] = Index_of[lambda[i]];
count = -1;
goto finish;
}
-#if DEBUG >= 2
+#if DEBUG_ECC >= 2
printf("\n Erasure positions as determined by roots of Eras Loc Poly:\n");
for (i = 0; i < count; i++)
printf("%d ", loc[i]);
}
for(i=0;i<NN-KK+1;i++)
b[i] = Index_of[lambda[i]];
-
+
/*
* Begin Berlekamp-Massey algorithm to determine error+erasure
* locator polynomial
omega[i] = Index_of[tmp];
}
omega[NN-KK] = A0;
-
+
/*
* Compute error values in poly-form. num1 = omega(inv(X(l))), num2 =
* inv(X(l))**(B0-1) and den = lambda_pr(inv(X(l))) all in poly-form
}
num2 = Alpha_to[modnn(root[j] * (B0 - 1) + NN)];
den = 0;
-
+
/* lambda[i+1] for i even is the formal derivative lambda_pr of lambda[i] */
for (i = min(deg_lambda,NN-KK-1) & ~1; i >= 0; i -=2) {
if(lambda[i+1] != A0)
den ^= Alpha_to[modnn(lambda[i+1] + i * root[j])];
}
if (den == 0) {
-#if DEBUG >= 1
+#if DEBUG_ECC >= 1
printf("\n ERROR: denominator = 0\n");
#endif
/* Convert to dual- basis */
/* The sector bytes are packed into NB_DATA MM bits words */
#define NB_DATA (((SECTOR_SIZE + 1) * 8 + 6) / MM)
-/*
+/*
* Correct the errors in 'sector[]' by using 'ecc1[]' which is the
* content of the feedback shift register applyied to the sector and
* the ECC. Return the number of errors corrected (and correct them in
- * sector), or -1 if error
+ * sector), or -1 if error
*/
int doc_decode_ecc(unsigned char sector[SECTOR_SIZE], unsigned char ecc1[6])
{
Alpha_to = kmalloc((NN + 1) * sizeof(dtype), GFP_KERNEL);
if (!Alpha_to)
return -1;
-
+
Index_of = kmalloc((NN + 1) * sizeof(dtype), GFP_KERNEL);
if (!Index_of) {
kfree(Alpha_to);
bb[2] = ((ecc1[2] & 0xf0) >> 4) | ((ecc1[3] & 0x3f) << 4);
bb[3] = ((ecc1[3] & 0xc0) >> 6) | ((ecc1[0] & 0xff) << 2);
- nb_errors = eras_dec_rs(Alpha_to, Index_of, bb,
+ nb_errors = eras_dec_rs(Alpha_to, Index_of, bb,
error_val, error_pos, 0);
if (nb_errors <= 0)
goto the_end;
can be modified since pos is even */
index = (pos >> 3) ^ 1;
bitpos = pos & 7;
- if ((index >= 0 && index < SECTOR_SIZE) ||
+ if ((index >= 0 && index < SECTOR_SIZE) ||
index == (SECTOR_SIZE + 1)) {
val = error_val[i] >> (2 + bitpos);
parity ^= val;
bitpos = (bitpos + 10) & 7;
if (bitpos == 0)
bitpos = 8;
- if ((index >= 0 && index < SECTOR_SIZE) ||
+ if ((index >= 0 && index < SECTOR_SIZE) ||
index == (SECTOR_SIZE + 1)) {
val = error_val[i] << (8 - bitpos);
parity ^= val;
}
}
}
-
+
/* use parity to test extra errors */
if ((parity & 0xff) != 0)
nb_errors = -1;
git://git.onelab.eu / linux-2.6.git / blobdiff