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Diffstat (limited to '')
| -rw-r--r-- | lib/reed_solomon/reed_solomon.c | 424 |
1 files changed, 424 insertions, 0 deletions
diff --git a/lib/reed_solomon/reed_solomon.c b/lib/reed_solomon/reed_solomon.c new file mode 100644 index 0000000000..bbc01bad30 --- /dev/null +++ b/lib/reed_solomon/reed_solomon.c @@ -0,0 +1,424 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * 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 + * + * 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. The control struct is unique per instance. + * It points to a codec which can be shared by multiple control structures. + * If a codec is newly allocated 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 <linux/mutex.h> + +enum { + RS_DECODE_LAMBDA, + RS_DECODE_SYN, + RS_DECODE_B, + RS_DECODE_T, + RS_DECODE_OMEGA, + RS_DECODE_ROOT, + RS_DECODE_REG, + RS_DECODE_LOC, + RS_DECODE_NUM_BUFFERS +}; + +/* This list holds all currently allocated rs codec structures */ +static LIST_HEAD(codec_list); +/* Protection for the list */ +static DEFINE_MUTEX(rslistlock); + +/** + * codec_init - Initialize a Reed-Solomon codec + * @symsize: symbol size, bits (1-8) + * @gfpoly: Field generator polynomial coefficients + * @gffunc: Field generator function + * @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) + * @gfp: GFP_ flags for allocations + * + * Allocate a codec structure and the polynom arrays for faster + * en/decoding. Fill the arrays according to the given parameters. + */ +static struct rs_codec *codec_init(int symsize, int gfpoly, int (*gffunc)(int), + int fcr, int prim, int nroots, gfp_t gfp) +{ + int i, j, sr, root, iprim; + struct rs_codec *rs; + + rs = kzalloc(sizeof(*rs), gfp); + if (!rs) + 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; + rs->gffunc = gffunc; + + /* Allocate the arrays */ + rs->alpha_to = kmalloc_array(rs->nn + 1, sizeof(uint16_t), gfp); + if (rs->alpha_to == NULL) + goto err; + + rs->index_of = kmalloc_array(rs->nn + 1, sizeof(uint16_t), gfp); + if (rs->index_of == NULL) + goto err; + + rs->genpoly = kmalloc_array(rs->nroots + 1, sizeof(uint16_t), gfp); + if(rs->genpoly == NULL) + goto err; + + /* Generate Galois field lookup tables */ + rs->index_of[0] = rs->nn; /* log(zero) = -inf */ + rs->alpha_to[rs->nn] = 0; /* alpha**-inf = 0 */ + if (gfpoly) { + 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; + } + } else { + sr = gffunc(0); + for (i = 0; i < rs->nn; i++) { + rs->index_of[sr] = i; + rs->alpha_to[i] = sr; + sr = gffunc(sr); + } + } + /* If it's not primitive, exit */ + if(sr != rs->alpha_to[0]) + goto err; + + /* 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]]; + + rs->users = 1; + list_add(&rs->list, &codec_list); + return rs; + +err: + kfree(rs->genpoly); + kfree(rs->index_of); + kfree(rs->alpha_to); + kfree(rs); + return NULL; +} + + +/** + * free_rs - Free the rs control structure + * @rs: The control structure which is not longer used by the + * caller + * + * Free the control structure. If @rs is the last user of the associated + * codec, free the codec as well. + */ +void free_rs(struct rs_control *rs) +{ + struct rs_codec *cd; + + if (!rs) + return; + + cd = rs->codec; + mutex_lock(&rslistlock); + cd->users--; + if(!cd->users) { + list_del(&cd->list); + kfree(cd->alpha_to); + kfree(cd->index_of); + kfree(cd->genpoly); + kfree(cd); + } + mutex_unlock(&rslistlock); + kfree(rs); +} +EXPORT_SYMBOL_GPL(free_rs); + +/** + * init_rs_internal - Allocate rs control, find a matching codec or allocate a new one + * @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; + * @gffunc: pointer to function to generate the next field element, + * or the multiplicative identity element if given 0. Used + * instead of gfpoly if gfpoly is 0 + * @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) + * @gfp: GFP_ flags for allocations + */ +static struct rs_control *init_rs_internal(int symsize, int gfpoly, + int (*gffunc)(int), int fcr, + int prim, int nroots, gfp_t gfp) +{ + struct list_head *tmp; + struct rs_control *rs; + unsigned int bsize; + + /* 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)) + return NULL; + + /* + * The decoder needs buffers in each control struct instance to + * avoid variable size or large fixed size allocations on + * stack. Size the buffers to arrays of [nroots + 1]. + */ + bsize = sizeof(uint16_t) * RS_DECODE_NUM_BUFFERS * (nroots + 1); + rs = kzalloc(sizeof(*rs) + bsize, gfp); + if (!rs) + return NULL; + + mutex_lock(&rslistlock); + + /* Walk through the list and look for a matching entry */ + list_for_each(tmp, &codec_list) { + struct rs_codec *cd = list_entry(tmp, struct rs_codec, list); + + if (symsize != cd->mm) + continue; + if (gfpoly != cd->gfpoly) + continue; + if (gffunc != cd->gffunc) + continue; + if (fcr != cd->fcr) + continue; + if (prim != cd->prim) + continue; + if (nroots != cd->nroots) + continue; + /* We have a matching one already */ + cd->users++; + rs->codec = cd; + goto out; + } + + /* Create a new one */ + rs->codec = codec_init(symsize, gfpoly, gffunc, fcr, prim, nroots, gfp); + if (!rs->codec) { + kfree(rs); + rs = NULL; + } +out: + mutex_unlock(&rslistlock); + return rs; +} + +/** + * init_rs_gfp - Create a RS control struct and initialize it + * @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) + * @gfp: Memory allocation flags. + */ +struct rs_control *init_rs_gfp(int symsize, int gfpoly, int fcr, int prim, + int nroots, gfp_t gfp) +{ + return init_rs_internal(symsize, gfpoly, NULL, fcr, prim, nroots, gfp); +} +EXPORT_SYMBOL_GPL(init_rs_gfp); + +/** + * init_rs_non_canonical - Allocate rs control struct for fields with + * non-canonical representation + * @symsize: the symbol size (number of bits) + * @gffunc: pointer to function to generate the next field element, + * or the multiplicative identity element if given 0. Used + * instead of gfpoly if gfpoly is 0 + * @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_non_canonical(int symsize, int (*gffunc)(int), + int fcr, int prim, int nroots) +{ + return init_rs_internal(symsize, 0, gffunc, fcr, prim, nroots, + GFP_KERNEL); +} +EXPORT_SYMBOL_GPL(init_rs_non_canonical); + +#ifdef CONFIG_REED_SOLOMON_ENC8 +/** + * encode_rs8 - Calculate the parity for data values (8bit 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) + * + * 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 *rsc, 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) + * @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 + * + * 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. + * + * Note: The rs_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_rs8(struct rs_control *rsc, 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) + * @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"); + |