summaryrefslogtreecommitdiffstats
path: root/lib/reed_solomon/reed_solomon.c
diff options
context:
space:
mode:
Diffstat (limited to 'lib/reed_solomon/reed_solomon.c')
-rw-r--r--lib/reed_solomon/reed_solomon.c424
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");
+