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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /lib/reed_solomon/reed_solomon.c
downloadlinux-sh-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.gz
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
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+/*
+ * lib/reed_solomon/rslib.c
+ *
+ * Overview:
+ * Generic Reed Solomon encoder / decoder library
+ *
+ * Copyright (C) 2004 Thomas Gleixner (tglx@linutronix.de)
+ *
+ * Reed Solomon code lifted from reed solomon library written by Phil Karn
+ * Copyright 2002 Phil Karn, KA9Q
+ *
+ * $Id: rslib.c,v 1.5 2004/10/22 15:41:47 gleixner Exp $
+ *
+ * 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.
+ *
+ * Description:
+ *
+ * The generic Reed Solomon library provides runtime configurable
+ * encoding / decoding of RS codes.
+ * Each user must call init_rs to get a pointer to a rs_control
+ * structure for the given rs parameters. This structure is either
+ * generated or a already available matching control structure is used.
+ * If a structure is generated then the polynomial arrays for
+ * fast encoding / decoding are built. This can take some time so
+ * make sure not to call this function from a time critical path.
+ * Usually a module / driver should initialize the necessary
+ * rs_control structure on module / driver init and release it
+ * on exit.
+ * The encoding puts the calculated syndrome into a given syndrome
+ * buffer.
+ * The decoding is a two step process. The first step calculates
+ * the syndrome over the received (data + syndrome) and calls the
+ * second stage, which does the decoding / error correction itself.
+ * Many hw encoders provide a syndrome calculation over the received
+ * data + syndrome and can call the second stage directly.
+ *
+ */
+
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/rslib.h>
+#include <linux/slab.h>
+#include <asm/semaphore.h>
+
+/* This list holds all currently allocated rs control structures */
+static LIST_HEAD (rslist);
+/* Protection for the list */
+static DECLARE_MUTEX(rslistlock);
+
+/**
+ * rs_init - Initialize a Reed-Solomon codec
+ *
+ * @symsize: symbol size, bits (1-8)
+ * @gfpoly: Field generator polynomial coefficients
+ * @fcr: first root of RS code generator polynomial, index form
+ * @prim: primitive element to generate polynomial roots
+ * @nroots: RS code generator polynomial degree (number of roots)
+ *
+ * Allocate a control structure and the polynom arrays for faster
+ * en/decoding. Fill the arrays according to the given parameters
+ */
+static struct rs_control *rs_init(int symsize, int gfpoly, int fcr,
+ int prim, int nroots)
+{
+ struct rs_control *rs;
+ int i, j, sr, root, iprim;
+
+ /* Allocate the control structure */
+ rs = kmalloc(sizeof (struct rs_control), GFP_KERNEL);
+ if (rs == NULL)
+ return NULL;
+
+ INIT_LIST_HEAD(&rs->list);
+
+ rs->mm = symsize;
+ rs->nn = (1 << symsize) - 1;
+ rs->fcr = fcr;
+ rs->prim = prim;
+ rs->nroots = nroots;
+ rs->gfpoly = gfpoly;
+
+ /* Allocate the arrays */
+ rs->alpha_to = kmalloc(sizeof(uint16_t) * (rs->nn + 1), GFP_KERNEL);
+ if (rs->alpha_to == NULL)
+ goto errrs;
+
+ rs->index_of = kmalloc(sizeof(uint16_t) * (rs->nn + 1), GFP_KERNEL);
+ if (rs->index_of == NULL)
+ goto erralp;
+
+ rs->genpoly = kmalloc(sizeof(uint16_t) * (rs->nroots + 1), GFP_KERNEL);
+ if(rs->genpoly == NULL)
+ goto erridx;
+
+ /* Generate Galois field lookup tables */
+ rs->index_of[0] = rs->nn; /* log(zero) = -inf */
+ rs->alpha_to[rs->nn] = 0; /* alpha**-inf = 0 */
+ sr = 1;
+ for (i = 0; i < rs->nn; i++) {
+ rs->index_of[sr] = i;
+ rs->alpha_to[i] = sr;
+ sr <<= 1;
+ if (sr & (1 << symsize))
+ sr ^= gfpoly;
+ sr &= rs->nn;
+ }
+ /* If it's not primitive, exit */
+ if(sr != 1)
+ goto errpol;
+
+ /* Find prim-th root of 1, used in decoding */
+ for(iprim = 1; (iprim % prim) != 0; iprim += rs->nn);
+ /* prim-th root of 1, index form */
+ rs->iprim = iprim / prim;
+
+ /* Form RS code generator polynomial from its roots */
+ rs->genpoly[0] = 1;
+ for (i = 0, root = fcr * prim; i < nroots; i++, root += prim) {
+ rs->genpoly[i + 1] = 1;
+ /* Multiply rs->genpoly[] by @**(root + x) */
+ for (j = i; j > 0; j--) {
+ if (rs->genpoly[j] != 0) {
+ rs->genpoly[j] = rs->genpoly[j -1] ^
+ rs->alpha_to[rs_modnn(rs,
+ rs->index_of[rs->genpoly[j]] + root)];
+ } else
+ rs->genpoly[j] = rs->genpoly[j - 1];
+ }
+ /* rs->genpoly[0] can never be zero */
+ rs->genpoly[0] =
+ rs->alpha_to[rs_modnn(rs,
+ rs->index_of[rs->genpoly[0]] + root)];
+ }
+ /* convert rs->genpoly[] to index form for quicker encoding */
+ for (i = 0; i <= nroots; i++)
+ rs->genpoly[i] = rs->index_of[rs->genpoly[i]];
+ return rs;
+
+ /* Error exit */
+errpol:
+ kfree(rs->genpoly);
+erridx:
+ kfree(rs->index_of);
+erralp:
+ kfree(rs->alpha_to);
+errrs:
+ kfree(rs);
+ return NULL;
+}
+
+
+/**
+ * free_rs - Free the rs control structure, if its not longer used
+ *
+ * @rs: the control structure which is not longer used by the
+ * caller
+ */
+void free_rs(struct rs_control *rs)
+{
+ down(&rslistlock);
+ rs->users--;
+ if(!rs->users) {
+ list_del(&rs->list);
+ kfree(rs->alpha_to);
+ kfree(rs->index_of);
+ kfree(rs->genpoly);
+ kfree(rs);
+ }
+ up(&rslistlock);
+}
+
+/**
+ * init_rs - Find a matching or allocate a new rs control structure
+ *
+ * @symsize: the symbol size (number of bits)
+ * @gfpoly: the extended Galois field generator polynomial coefficients,
+ * with the 0th coefficient in the low order bit. The polynomial
+ * must be primitive;
+ * @fcr: the first consecutive root of the rs code generator polynomial
+ * in index form
+ * @prim: primitive element to generate polynomial roots
+ * @nroots: RS code generator polynomial degree (number of roots)
+ */
+struct rs_control *init_rs(int symsize, int gfpoly, int fcr, int prim,
+ int nroots)
+{
+ struct list_head *tmp;
+ struct rs_control *rs;
+
+ /* Sanity checks */
+ if (symsize < 1)
+ return NULL;
+ if (fcr < 0 || fcr >= (1<<symsize))
+ return NULL;
+ if (prim <= 0 || prim >= (1<<symsize))
+ return NULL;
+ if (nroots < 0 || nroots >= (1<<symsize) || nroots > 8)
+ return NULL;
+
+ down(&rslistlock);
+
+ /* Walk through the list and look for a matching entry */
+ list_for_each(tmp, &rslist) {
+ rs = list_entry(tmp, struct rs_control, list);
+ if (symsize != rs->mm)
+ continue;
+ if (gfpoly != rs->gfpoly)
+ continue;
+ if (fcr != rs->fcr)
+ continue;
+ if (prim != rs->prim)
+ continue;
+ if (nroots != rs->nroots)
+ continue;
+ /* We have a matching one already */
+ rs->users++;
+ goto out;
+ }
+
+ /* Create a new one */
+ rs = rs_init(symsize, gfpoly, fcr, prim, nroots);
+ if (rs) {
+ rs->users = 1;
+ list_add(&rs->list, &rslist);
+ }
+out:
+ up(&rslistlock);
+ return rs;
+}
+
+#ifdef CONFIG_REED_SOLOMON_ENC8
+/**
+ * encode_rs8 - Calculate the parity for data values (8bit data width)
+ *
+ * @rs: the rs control structure
+ * @data: data field of a given type
+ * @len: data length
+ * @par: parity data, must be initialized by caller (usually all 0)
+ * @invmsk: invert data mask (will be xored on data)
+ *
+ * The parity uses a uint16_t data type to enable
+ * symbol size > 8. The calling code must take care of encoding of the
+ * syndrome result for storage itself.
+ */
+int encode_rs8(struct rs_control *rs, uint8_t *data, int len, uint16_t *par,
+ uint16_t invmsk)
+{
+#include "encode_rs.c"
+}
+EXPORT_SYMBOL_GPL(encode_rs8);
+#endif
+
+#ifdef CONFIG_REED_SOLOMON_DEC8
+/**
+ * decode_rs8 - Decode codeword (8bit data width)
+ *
+ * @rs: the rs control structure
+ * @data: data field of a given type
+ * @par: received parity data field
+ * @len: data length
+ * @s: syndrome data field (if NULL, syndrome is calculated)
+ * @no_eras: number of erasures
+ * @eras_pos: position of erasures, can be NULL
+ * @invmsk: invert data mask (will be xored on data, not on parity!)
+ * @corr: buffer to store correction bitmask on eras_pos
+ *
+ * The syndrome and parity uses a uint16_t data type to enable
+ * symbol size > 8. The calling code must take care of decoding of the
+ * syndrome result and the received parity before calling this code.
+ */
+int decode_rs8(struct rs_control *rs, uint8_t *data, uint16_t *par, int len,
+ uint16_t *s, int no_eras, int *eras_pos, uint16_t invmsk,
+ uint16_t *corr)
+{
+#include "decode_rs.c"
+}
+EXPORT_SYMBOL_GPL(decode_rs8);
+#endif
+
+#ifdef CONFIG_REED_SOLOMON_ENC16
+/**
+ * encode_rs16 - Calculate the parity for data values (16bit data width)
+ *
+ * @rs: the rs control structure
+ * @data: data field of a given type
+ * @len: data length
+ * @par: parity data, must be initialized by caller (usually all 0)
+ * @invmsk: invert data mask (will be xored on data, not on parity!)
+ *
+ * Each field in the data array contains up to symbol size bits of valid data.
+ */
+int encode_rs16(struct rs_control *rs, uint16_t *data, int len, uint16_t *par,
+ uint16_t invmsk)
+{
+#include "encode_rs.c"
+}
+EXPORT_SYMBOL_GPL(encode_rs16);
+#endif
+
+#ifdef CONFIG_REED_SOLOMON_DEC16
+/**
+ * decode_rs16 - Decode codeword (16bit data width)
+ *
+ * @rs: the rs control structure
+ * @data: data field of a given type
+ * @par: received parity data field
+ * @len: data length
+ * @s: syndrome data field (if NULL, syndrome is calculated)
+ * @no_eras: number of erasures
+ * @eras_pos: position of erasures, can be NULL
+ * @invmsk: invert data mask (will be xored on data, not on parity!)
+ * @corr: buffer to store correction bitmask on eras_pos
+ *
+ * Each field in the data array contains up to symbol size bits of valid data.
+ */
+int decode_rs16(struct rs_control *rs, uint16_t *data, uint16_t *par, int len,
+ uint16_t *s, int no_eras, int *eras_pos, uint16_t invmsk,
+ uint16_t *corr)
+{
+#include "decode_rs.c"
+}
+EXPORT_SYMBOL_GPL(decode_rs16);
+#endif
+
+EXPORT_SYMBOL_GPL(init_rs);
+EXPORT_SYMBOL_GPL(free_rs);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Reed Solomon encoder/decoder");
+MODULE_AUTHOR("Phil Karn, Thomas Gleixner");
+