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03ead842 | 1 | /* |
f30c2269 | 2 | * lib/reed_solomon/reed_solomon.c |
1da177e4 LT |
3 | * |
4 | * Overview: | |
5 | * Generic Reed Solomon encoder / decoder library | |
03ead842 | 6 | * |
1da177e4 LT |
7 | * Copyright (C) 2004 Thomas Gleixner (tglx@linutronix.de) |
8 | * | |
9 | * Reed Solomon code lifted from reed solomon library written by Phil Karn | |
10 | * Copyright 2002 Phil Karn, KA9Q | |
11 | * | |
03ead842 | 12 | * $Id: rslib.c,v 1.7 2005/11/07 11:14:59 gleixner Exp $ |
1da177e4 LT |
13 | * |
14 | * This program is free software; you can redistribute it and/or modify | |
15 | * it under the terms of the GNU General Public License version 2 as | |
16 | * published by the Free Software Foundation. | |
17 | * | |
18 | * Description: | |
03ead842 | 19 | * |
1da177e4 LT |
20 | * The generic Reed Solomon library provides runtime configurable |
21 | * encoding / decoding of RS codes. | |
22 | * Each user must call init_rs to get a pointer to a rs_control | |
23 | * structure for the given rs parameters. This structure is either | |
24 | * generated or a already available matching control structure is used. | |
25 | * If a structure is generated then the polynomial arrays for | |
26 | * fast encoding / decoding are built. This can take some time so | |
27 | * make sure not to call this function from a time critical path. | |
03ead842 | 28 | * Usually a module / driver should initialize the necessary |
1da177e4 LT |
29 | * rs_control structure on module / driver init and release it |
30 | * on exit. | |
03ead842 TG |
31 | * The encoding puts the calculated syndrome into a given syndrome |
32 | * buffer. | |
1da177e4 LT |
33 | * The decoding is a two step process. The first step calculates |
34 | * the syndrome over the received (data + syndrome) and calls the | |
35 | * second stage, which does the decoding / error correction itself. | |
36 | * Many hw encoders provide a syndrome calculation over the received | |
37 | * data + syndrome and can call the second stage directly. | |
38 | * | |
39 | */ | |
40 | ||
41 | #include <linux/errno.h> | |
42 | #include <linux/kernel.h> | |
43 | #include <linux/init.h> | |
44 | #include <linux/module.h> | |
45 | #include <linux/rslib.h> | |
46 | #include <linux/slab.h> | |
97d1f15b | 47 | #include <linux/mutex.h> |
1da177e4 LT |
48 | #include <asm/semaphore.h> |
49 | ||
50 | /* This list holds all currently allocated rs control structures */ | |
51 | static LIST_HEAD (rslist); | |
52 | /* Protection for the list */ | |
97d1f15b | 53 | static DEFINE_MUTEX(rslistlock); |
1da177e4 | 54 | |
03ead842 | 55 | /** |
1da177e4 | 56 | * rs_init - Initialize a Reed-Solomon codec |
1da177e4 LT |
57 | * @symsize: symbol size, bits (1-8) |
58 | * @gfpoly: Field generator polynomial coefficients | |
59 | * @fcr: first root of RS code generator polynomial, index form | |
60 | * @prim: primitive element to generate polynomial roots | |
61 | * @nroots: RS code generator polynomial degree (number of roots) | |
62 | * | |
63 | * Allocate a control structure and the polynom arrays for faster | |
9dc65576 | 64 | * en/decoding. Fill the arrays according to the given parameters. |
1da177e4 | 65 | */ |
03ead842 | 66 | static struct rs_control *rs_init(int symsize, int gfpoly, int fcr, |
1da177e4 LT |
67 | int prim, int nroots) |
68 | { | |
69 | struct rs_control *rs; | |
70 | int i, j, sr, root, iprim; | |
71 | ||
72 | /* Allocate the control structure */ | |
73 | rs = kmalloc(sizeof (struct rs_control), GFP_KERNEL); | |
74 | if (rs == NULL) | |
75 | return NULL; | |
76 | ||
77 | INIT_LIST_HEAD(&rs->list); | |
78 | ||
79 | rs->mm = symsize; | |
80 | rs->nn = (1 << symsize) - 1; | |
81 | rs->fcr = fcr; | |
82 | rs->prim = prim; | |
83 | rs->nroots = nroots; | |
84 | rs->gfpoly = gfpoly; | |
85 | ||
86 | /* Allocate the arrays */ | |
87 | rs->alpha_to = kmalloc(sizeof(uint16_t) * (rs->nn + 1), GFP_KERNEL); | |
88 | if (rs->alpha_to == NULL) | |
89 | goto errrs; | |
90 | ||
91 | rs->index_of = kmalloc(sizeof(uint16_t) * (rs->nn + 1), GFP_KERNEL); | |
92 | if (rs->index_of == NULL) | |
93 | goto erralp; | |
94 | ||
95 | rs->genpoly = kmalloc(sizeof(uint16_t) * (rs->nroots + 1), GFP_KERNEL); | |
96 | if(rs->genpoly == NULL) | |
97 | goto erridx; | |
98 | ||
99 | /* Generate Galois field lookup tables */ | |
100 | rs->index_of[0] = rs->nn; /* log(zero) = -inf */ | |
101 | rs->alpha_to[rs->nn] = 0; /* alpha**-inf = 0 */ | |
102 | sr = 1; | |
103 | for (i = 0; i < rs->nn; i++) { | |
104 | rs->index_of[sr] = i; | |
105 | rs->alpha_to[i] = sr; | |
106 | sr <<= 1; | |
107 | if (sr & (1 << symsize)) | |
108 | sr ^= gfpoly; | |
109 | sr &= rs->nn; | |
110 | } | |
111 | /* If it's not primitive, exit */ | |
112 | if(sr != 1) | |
113 | goto errpol; | |
114 | ||
115 | /* Find prim-th root of 1, used in decoding */ | |
116 | for(iprim = 1; (iprim % prim) != 0; iprim += rs->nn); | |
117 | /* prim-th root of 1, index form */ | |
118 | rs->iprim = iprim / prim; | |
119 | ||
120 | /* Form RS code generator polynomial from its roots */ | |
121 | rs->genpoly[0] = 1; | |
122 | for (i = 0, root = fcr * prim; i < nroots; i++, root += prim) { | |
123 | rs->genpoly[i + 1] = 1; | |
124 | /* Multiply rs->genpoly[] by @**(root + x) */ | |
125 | for (j = i; j > 0; j--) { | |
126 | if (rs->genpoly[j] != 0) { | |
03ead842 TG |
127 | rs->genpoly[j] = rs->genpoly[j -1] ^ |
128 | rs->alpha_to[rs_modnn(rs, | |
1da177e4 LT |
129 | rs->index_of[rs->genpoly[j]] + root)]; |
130 | } else | |
131 | rs->genpoly[j] = rs->genpoly[j - 1]; | |
132 | } | |
133 | /* rs->genpoly[0] can never be zero */ | |
03ead842 TG |
134 | rs->genpoly[0] = |
135 | rs->alpha_to[rs_modnn(rs, | |
1da177e4 LT |
136 | rs->index_of[rs->genpoly[0]] + root)]; |
137 | } | |
138 | /* convert rs->genpoly[] to index form for quicker encoding */ | |
139 | for (i = 0; i <= nroots; i++) | |
140 | rs->genpoly[i] = rs->index_of[rs->genpoly[i]]; | |
141 | return rs; | |
142 | ||
143 | /* Error exit */ | |
144 | errpol: | |
145 | kfree(rs->genpoly); | |
146 | erridx: | |
147 | kfree(rs->index_of); | |
148 | erralp: | |
149 | kfree(rs->alpha_to); | |
150 | errrs: | |
151 | kfree(rs); | |
152 | return NULL; | |
153 | } | |
154 | ||
155 | ||
03ead842 | 156 | /** |
9dc65576 | 157 | * free_rs - Free the rs control structure, if it is no longer used |
1da177e4 LT |
158 | * @rs: the control structure which is not longer used by the |
159 | * caller | |
160 | */ | |
161 | void free_rs(struct rs_control *rs) | |
162 | { | |
97d1f15b | 163 | mutex_lock(&rslistlock); |
1da177e4 LT |
164 | rs->users--; |
165 | if(!rs->users) { | |
166 | list_del(&rs->list); | |
167 | kfree(rs->alpha_to); | |
168 | kfree(rs->index_of); | |
169 | kfree(rs->genpoly); | |
170 | kfree(rs); | |
171 | } | |
97d1f15b | 172 | mutex_unlock(&rslistlock); |
1da177e4 LT |
173 | } |
174 | ||
03ead842 | 175 | /** |
1da177e4 | 176 | * init_rs - Find a matching or allocate a new rs control structure |
1da177e4 LT |
177 | * @symsize: the symbol size (number of bits) |
178 | * @gfpoly: the extended Galois field generator polynomial coefficients, | |
179 | * with the 0th coefficient in the low order bit. The polynomial | |
180 | * must be primitive; | |
03ead842 | 181 | * @fcr: the first consecutive root of the rs code generator polynomial |
1da177e4 LT |
182 | * in index form |
183 | * @prim: primitive element to generate polynomial roots | |
184 | * @nroots: RS code generator polynomial degree (number of roots) | |
185 | */ | |
03ead842 | 186 | struct rs_control *init_rs(int symsize, int gfpoly, int fcr, int prim, |
1da177e4 LT |
187 | int nroots) |
188 | { | |
189 | struct list_head *tmp; | |
190 | struct rs_control *rs; | |
191 | ||
192 | /* Sanity checks */ | |
193 | if (symsize < 1) | |
194 | return NULL; | |
195 | if (fcr < 0 || fcr >= (1<<symsize)) | |
196 | return NULL; | |
197 | if (prim <= 0 || prim >= (1<<symsize)) | |
198 | return NULL; | |
03ead842 | 199 | if (nroots < 0 || nroots >= (1<<symsize)) |
1da177e4 | 200 | return NULL; |
03ead842 | 201 | |
97d1f15b | 202 | mutex_lock(&rslistlock); |
1da177e4 LT |
203 | |
204 | /* Walk through the list and look for a matching entry */ | |
205 | list_for_each(tmp, &rslist) { | |
206 | rs = list_entry(tmp, struct rs_control, list); | |
207 | if (symsize != rs->mm) | |
208 | continue; | |
209 | if (gfpoly != rs->gfpoly) | |
210 | continue; | |
211 | if (fcr != rs->fcr) | |
03ead842 | 212 | continue; |
1da177e4 | 213 | if (prim != rs->prim) |
03ead842 | 214 | continue; |
1da177e4 LT |
215 | if (nroots != rs->nroots) |
216 | continue; | |
217 | /* We have a matching one already */ | |
218 | rs->users++; | |
219 | goto out; | |
220 | } | |
221 | ||
222 | /* Create a new one */ | |
223 | rs = rs_init(symsize, gfpoly, fcr, prim, nroots); | |
224 | if (rs) { | |
225 | rs->users = 1; | |
226 | list_add(&rs->list, &rslist); | |
227 | } | |
03ead842 | 228 | out: |
97d1f15b | 229 | mutex_unlock(&rslistlock); |
1da177e4 LT |
230 | return rs; |
231 | } | |
232 | ||
233 | #ifdef CONFIG_REED_SOLOMON_ENC8 | |
03ead842 | 234 | /** |
1da177e4 | 235 | * encode_rs8 - Calculate the parity for data values (8bit data width) |
1da177e4 LT |
236 | * @rs: the rs control structure |
237 | * @data: data field of a given type | |
03ead842 | 238 | * @len: data length |
1da177e4 LT |
239 | * @par: parity data, must be initialized by caller (usually all 0) |
240 | * @invmsk: invert data mask (will be xored on data) | |
241 | * | |
242 | * The parity uses a uint16_t data type to enable | |
243 | * symbol size > 8. The calling code must take care of encoding of the | |
244 | * syndrome result for storage itself. | |
245 | */ | |
03ead842 | 246 | int encode_rs8(struct rs_control *rs, uint8_t *data, int len, uint16_t *par, |
1da177e4 LT |
247 | uint16_t invmsk) |
248 | { | |
249 | #include "encode_rs.c" | |
250 | } | |
251 | EXPORT_SYMBOL_GPL(encode_rs8); | |
252 | #endif | |
253 | ||
254 | #ifdef CONFIG_REED_SOLOMON_DEC8 | |
03ead842 | 255 | /** |
1da177e4 | 256 | * decode_rs8 - Decode codeword (8bit data width) |
1da177e4 LT |
257 | * @rs: the rs control structure |
258 | * @data: data field of a given type | |
259 | * @par: received parity data field | |
260 | * @len: data length | |
261 | * @s: syndrome data field (if NULL, syndrome is calculated) | |
262 | * @no_eras: number of erasures | |
263 | * @eras_pos: position of erasures, can be NULL | |
264 | * @invmsk: invert data mask (will be xored on data, not on parity!) | |
265 | * @corr: buffer to store correction bitmask on eras_pos | |
266 | * | |
267 | * The syndrome and parity uses a uint16_t data type to enable | |
268 | * symbol size > 8. The calling code must take care of decoding of the | |
269 | * syndrome result and the received parity before calling this code. | |
270 | */ | |
271 | int decode_rs8(struct rs_control *rs, uint8_t *data, uint16_t *par, int len, | |
03ead842 | 272 | uint16_t *s, int no_eras, int *eras_pos, uint16_t invmsk, |
1da177e4 LT |
273 | uint16_t *corr) |
274 | { | |
275 | #include "decode_rs.c" | |
276 | } | |
277 | EXPORT_SYMBOL_GPL(decode_rs8); | |
278 | #endif | |
279 | ||
280 | #ifdef CONFIG_REED_SOLOMON_ENC16 | |
281 | /** | |
282 | * encode_rs16 - Calculate the parity for data values (16bit data width) | |
1da177e4 LT |
283 | * @rs: the rs control structure |
284 | * @data: data field of a given type | |
03ead842 | 285 | * @len: data length |
1da177e4 LT |
286 | * @par: parity data, must be initialized by caller (usually all 0) |
287 | * @invmsk: invert data mask (will be xored on data, not on parity!) | |
288 | * | |
289 | * Each field in the data array contains up to symbol size bits of valid data. | |
290 | */ | |
03ead842 | 291 | int encode_rs16(struct rs_control *rs, uint16_t *data, int len, uint16_t *par, |
1da177e4 LT |
292 | uint16_t invmsk) |
293 | { | |
294 | #include "encode_rs.c" | |
295 | } | |
296 | EXPORT_SYMBOL_GPL(encode_rs16); | |
297 | #endif | |
298 | ||
299 | #ifdef CONFIG_REED_SOLOMON_DEC16 | |
03ead842 | 300 | /** |
1da177e4 | 301 | * decode_rs16 - Decode codeword (16bit data width) |
1da177e4 LT |
302 | * @rs: the rs control structure |
303 | * @data: data field of a given type | |
304 | * @par: received parity data field | |
305 | * @len: data length | |
306 | * @s: syndrome data field (if NULL, syndrome is calculated) | |
307 | * @no_eras: number of erasures | |
308 | * @eras_pos: position of erasures, can be NULL | |
03ead842 | 309 | * @invmsk: invert data mask (will be xored on data, not on parity!) |
1da177e4 LT |
310 | * @corr: buffer to store correction bitmask on eras_pos |
311 | * | |
312 | * Each field in the data array contains up to symbol size bits of valid data. | |
313 | */ | |
314 | int decode_rs16(struct rs_control *rs, uint16_t *data, uint16_t *par, int len, | |
03ead842 | 315 | uint16_t *s, int no_eras, int *eras_pos, uint16_t invmsk, |
1da177e4 LT |
316 | uint16_t *corr) |
317 | { | |
318 | #include "decode_rs.c" | |
319 | } | |
320 | EXPORT_SYMBOL_GPL(decode_rs16); | |
321 | #endif | |
322 | ||
323 | EXPORT_SYMBOL_GPL(init_rs); | |
324 | EXPORT_SYMBOL_GPL(free_rs); | |
325 | ||
326 | MODULE_LICENSE("GPL"); | |
327 | MODULE_DESCRIPTION("Reed Solomon encoder/decoder"); | |
328 | MODULE_AUTHOR("Phil Karn, Thomas Gleixner"); | |
329 |