425 lines
12 KiB
C
425 lines
12 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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/*
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* Generic Reed Solomon encoder / decoder library
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*
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* Copyright (C) 2004 Thomas Gleixner (tglx@linutronix.de)
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*
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* Reed Solomon code lifted from reed solomon library written by Phil Karn
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* Copyright 2002 Phil Karn, KA9Q
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*
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* Description:
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*
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* The generic Reed Solomon library provides runtime configurable
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* encoding / decoding of RS codes.
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*
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* Each user must call init_rs to get a pointer to a rs_control structure
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* for the given rs parameters. The control struct is unique per instance.
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* It points to a codec which can be shared by multiple control structures.
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* If a codec is newly allocated then the polynomial arrays for fast
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* encoding / decoding are built. This can take some time so make sure not
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* to call this function from a time critical path. Usually a module /
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* driver should initialize the necessary rs_control structure on module /
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* driver init and release it on exit.
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*
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* The encoding puts the calculated syndrome into a given syndrome buffer.
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*
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* The decoding is a two step process. The first step calculates the
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* syndrome over the received (data + syndrome) and calls the second stage,
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* which does the decoding / error correction itself. Many hw encoders
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* provide a syndrome calculation over the received data + syndrome and can
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* call the second stage directly.
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*/
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#include <linux/errno.h>
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/rslib.h>
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#include <linux/slab.h>
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#include <linux/mutex.h>
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enum {
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RS_DECODE_LAMBDA,
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RS_DECODE_SYN,
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RS_DECODE_B,
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RS_DECODE_T,
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RS_DECODE_OMEGA,
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RS_DECODE_ROOT,
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RS_DECODE_REG,
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RS_DECODE_LOC,
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RS_DECODE_NUM_BUFFERS
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};
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/* This list holds all currently allocated rs codec structures */
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static LIST_HEAD(codec_list);
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/* Protection for the list */
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static DEFINE_MUTEX(rslistlock);
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/**
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* codec_init - Initialize a Reed-Solomon codec
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* @symsize: symbol size, bits (1-8)
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* @gfpoly: Field generator polynomial coefficients
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* @gffunc: Field generator function
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* @fcr: first root of RS code generator polynomial, index form
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* @prim: primitive element to generate polynomial roots
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* @nroots: RS code generator polynomial degree (number of roots)
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* @gfp: GFP_ flags for allocations
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*
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* Allocate a codec structure and the polynom arrays for faster
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* en/decoding. Fill the arrays according to the given parameters.
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*/
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static struct rs_codec *codec_init(int symsize, int gfpoly, int (*gffunc)(int),
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int fcr, int prim, int nroots, gfp_t gfp)
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{
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int i, j, sr, root, iprim;
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struct rs_codec *rs;
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rs = kzalloc(sizeof(*rs), gfp);
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if (!rs)
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return NULL;
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INIT_LIST_HEAD(&rs->list);
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rs->mm = symsize;
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rs->nn = (1 << symsize) - 1;
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rs->fcr = fcr;
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rs->prim = prim;
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rs->nroots = nroots;
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rs->gfpoly = gfpoly;
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rs->gffunc = gffunc;
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/* Allocate the arrays */
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rs->alpha_to = kmalloc_array(rs->nn + 1, sizeof(uint16_t), gfp);
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if (rs->alpha_to == NULL)
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goto err;
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rs->index_of = kmalloc_array(rs->nn + 1, sizeof(uint16_t), gfp);
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if (rs->index_of == NULL)
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goto err;
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rs->genpoly = kmalloc_array(rs->nroots + 1, sizeof(uint16_t), gfp);
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if(rs->genpoly == NULL)
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goto err;
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/* Generate Galois field lookup tables */
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rs->index_of[0] = rs->nn; /* log(zero) = -inf */
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rs->alpha_to[rs->nn] = 0; /* alpha**-inf = 0 */
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if (gfpoly) {
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sr = 1;
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for (i = 0; i < rs->nn; i++) {
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rs->index_of[sr] = i;
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rs->alpha_to[i] = sr;
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sr <<= 1;
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if (sr & (1 << symsize))
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sr ^= gfpoly;
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sr &= rs->nn;
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}
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} else {
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sr = gffunc(0);
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for (i = 0; i < rs->nn; i++) {
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rs->index_of[sr] = i;
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rs->alpha_to[i] = sr;
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sr = gffunc(sr);
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}
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}
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/* If it's not primitive, exit */
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if(sr != rs->alpha_to[0])
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goto err;
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/* Find prim-th root of 1, used in decoding */
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for(iprim = 1; (iprim % prim) != 0; iprim += rs->nn);
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/* prim-th root of 1, index form */
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rs->iprim = iprim / prim;
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/* Form RS code generator polynomial from its roots */
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rs->genpoly[0] = 1;
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for (i = 0, root = fcr * prim; i < nroots; i++, root += prim) {
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rs->genpoly[i + 1] = 1;
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/* Multiply rs->genpoly[] by @**(root + x) */
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for (j = i; j > 0; j--) {
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if (rs->genpoly[j] != 0) {
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rs->genpoly[j] = rs->genpoly[j -1] ^
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rs->alpha_to[rs_modnn(rs,
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rs->index_of[rs->genpoly[j]] + root)];
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} else
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rs->genpoly[j] = rs->genpoly[j - 1];
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}
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/* rs->genpoly[0] can never be zero */
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rs->genpoly[0] =
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rs->alpha_to[rs_modnn(rs,
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rs->index_of[rs->genpoly[0]] + root)];
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}
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/* convert rs->genpoly[] to index form for quicker encoding */
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for (i = 0; i <= nroots; i++)
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rs->genpoly[i] = rs->index_of[rs->genpoly[i]];
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rs->users = 1;
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list_add(&rs->list, &codec_list);
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return rs;
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err:
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kfree(rs->genpoly);
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kfree(rs->index_of);
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kfree(rs->alpha_to);
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kfree(rs);
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return NULL;
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}
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/**
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* free_rs - Free the rs control structure
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* @rs: The control structure which is not longer used by the
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* caller
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*
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* Free the control structure. If @rs is the last user of the associated
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* codec, free the codec as well.
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*/
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void free_rs(struct rs_control *rs)
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{
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struct rs_codec *cd;
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if (!rs)
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return;
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cd = rs->codec;
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mutex_lock(&rslistlock);
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cd->users--;
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if(!cd->users) {
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list_del(&cd->list);
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kfree(cd->alpha_to);
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kfree(cd->index_of);
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kfree(cd->genpoly);
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kfree(cd);
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}
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mutex_unlock(&rslistlock);
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kfree(rs);
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}
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EXPORT_SYMBOL_GPL(free_rs);
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/**
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* init_rs_internal - Allocate rs control, find a matching codec or allocate a new one
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* @symsize: the symbol size (number of bits)
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* @gfpoly: the extended Galois field generator polynomial coefficients,
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* with the 0th coefficient in the low order bit. The polynomial
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* must be primitive;
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* @gffunc: pointer to function to generate the next field element,
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* or the multiplicative identity element if given 0. Used
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* instead of gfpoly if gfpoly is 0
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* @fcr: the first consecutive root of the rs code generator polynomial
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* in index form
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* @prim: primitive element to generate polynomial roots
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* @nroots: RS code generator polynomial degree (number of roots)
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* @gfp: GFP_ flags for allocations
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*/
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static struct rs_control *init_rs_internal(int symsize, int gfpoly,
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int (*gffunc)(int), int fcr,
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int prim, int nroots, gfp_t gfp)
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{
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struct list_head *tmp;
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struct rs_control *rs;
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unsigned int bsize;
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/* Sanity checks */
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if (symsize < 1)
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return NULL;
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if (fcr < 0 || fcr >= (1<<symsize))
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return NULL;
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if (prim <= 0 || prim >= (1<<symsize))
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return NULL;
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if (nroots < 0 || nroots >= (1<<symsize))
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return NULL;
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/*
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* The decoder needs buffers in each control struct instance to
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* avoid variable size or large fixed size allocations on
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* stack. Size the buffers to arrays of [nroots + 1].
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*/
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bsize = sizeof(uint16_t) * RS_DECODE_NUM_BUFFERS * (nroots + 1);
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rs = kzalloc(sizeof(*rs) + bsize, gfp);
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if (!rs)
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return NULL;
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mutex_lock(&rslistlock);
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/* Walk through the list and look for a matching entry */
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list_for_each(tmp, &codec_list) {
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struct rs_codec *cd = list_entry(tmp, struct rs_codec, list);
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if (symsize != cd->mm)
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continue;
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if (gfpoly != cd->gfpoly)
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continue;
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if (gffunc != cd->gffunc)
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continue;
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if (fcr != cd->fcr)
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continue;
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if (prim != cd->prim)
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continue;
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if (nroots != cd->nroots)
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continue;
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/* We have a matching one already */
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cd->users++;
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rs->codec = cd;
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goto out;
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}
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/* Create a new one */
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rs->codec = codec_init(symsize, gfpoly, gffunc, fcr, prim, nroots, gfp);
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if (!rs->codec) {
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kfree(rs);
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rs = NULL;
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}
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out:
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mutex_unlock(&rslistlock);
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return rs;
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}
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/**
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* init_rs_gfp - Create a RS control struct and initialize it
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* @symsize: the symbol size (number of bits)
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* @gfpoly: the extended Galois field generator polynomial coefficients,
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* with the 0th coefficient in the low order bit. The polynomial
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* must be primitive;
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* @fcr: the first consecutive root of the rs code generator polynomial
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* in index form
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* @prim: primitive element to generate polynomial roots
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* @nroots: RS code generator polynomial degree (number of roots)
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* @gfp: Memory allocation flags.
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*/
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struct rs_control *init_rs_gfp(int symsize, int gfpoly, int fcr, int prim,
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int nroots, gfp_t gfp)
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{
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return init_rs_internal(symsize, gfpoly, NULL, fcr, prim, nroots, gfp);
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}
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EXPORT_SYMBOL_GPL(init_rs_gfp);
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/**
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* init_rs_non_canonical - Allocate rs control struct for fields with
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* non-canonical representation
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* @symsize: the symbol size (number of bits)
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* @gffunc: pointer to function to generate the next field element,
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* or the multiplicative identity element if given 0. Used
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* instead of gfpoly if gfpoly is 0
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* @fcr: the first consecutive root of the rs code generator polynomial
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* in index form
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* @prim: primitive element to generate polynomial roots
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* @nroots: RS code generator polynomial degree (number of roots)
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*/
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struct rs_control *init_rs_non_canonical(int symsize, int (*gffunc)(int),
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int fcr, int prim, int nroots)
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{
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return init_rs_internal(symsize, 0, gffunc, fcr, prim, nroots,
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GFP_KERNEL);
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}
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EXPORT_SYMBOL_GPL(init_rs_non_canonical);
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#ifdef CONFIG_REED_SOLOMON_ENC8
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/**
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* encode_rs8 - Calculate the parity for data values (8bit data width)
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* @rsc: the rs control structure
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* @data: data field of a given type
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* @len: data length
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* @par: parity data, must be initialized by caller (usually all 0)
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* @invmsk: invert data mask (will be xored on data)
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*
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* The parity uses a uint16_t data type to enable
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* symbol size > 8. The calling code must take care of encoding of the
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* syndrome result for storage itself.
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*/
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int encode_rs8(struct rs_control *rsc, uint8_t *data, int len, uint16_t *par,
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uint16_t invmsk)
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{
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#include "encode_rs.c"
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}
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EXPORT_SYMBOL_GPL(encode_rs8);
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#endif
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#ifdef CONFIG_REED_SOLOMON_DEC8
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/**
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* decode_rs8 - Decode codeword (8bit data width)
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* @rsc: the rs control structure
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* @data: data field of a given type
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* @par: received parity data field
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* @len: data length
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* @s: syndrome data field, must be in index form
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* (if NULL, syndrome is calculated)
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* @no_eras: number of erasures
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* @eras_pos: position of erasures, can be NULL
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* @invmsk: invert data mask (will be xored on data, not on parity!)
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* @corr: buffer to store correction bitmask on eras_pos
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*
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* The syndrome and parity uses a uint16_t data type to enable
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* symbol size > 8. The calling code must take care of decoding of the
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* syndrome result and the received parity before calling this code.
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*
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* Note: The rs_control struct @rsc contains buffers which are used for
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* decoding, so the caller has to ensure that decoder invocations are
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* serialized.
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*
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* Returns the number of corrected symbols or -EBADMSG for uncorrectable
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* errors. The count includes errors in the parity.
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*/
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int decode_rs8(struct rs_control *rsc, uint8_t *data, uint16_t *par, int len,
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uint16_t *s, int no_eras, int *eras_pos, uint16_t invmsk,
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|
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)
|
||
|
|
* @rsc: 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 *rsc, 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)
|
||
|
|
* @rsc: the rs control structure
|
||
|
|
* @data: data field of a given type
|
||
|
|
* @par: received parity data field
|
||
|
|
* @len: data length
|
||
|
|
* @s: syndrome data field, must be in index form
|
||
|
|
* (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.
|
||
|
|
*
|
||
|
|
* Note: The rc_control struct @rsc contains buffers which are used for
|
||
|
|
* decoding, so the caller has to ensure that decoder invocations are
|
||
|
|
* serialized.
|
||
|
|
*
|
||
|
|
* Returns the number of corrected symbols or -EBADMSG for uncorrectable
|
||
|
|
* errors. The count includes errors in the parity.
|
||
|
|
*/
|
||
|
|
int decode_rs16(struct rs_control *rsc, 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
|
||
|
|
|
||
|
|
MODULE_LICENSE("GPL");
|
||
|
|
MODULE_DESCRIPTION("Reed Solomon encoder/decoder");
|
||
|
|
MODULE_AUTHOR("Phil Karn, Thomas Gleixner");
|
||
|
|
|