Commit | Line | Data |
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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 | |
d7e5a546 | 59 | * @gffunc: Field generator function |
1da177e4 LT |
60 | * @fcr: first root of RS code generator polynomial, index form |
61 | * @prim: primitive element to generate polynomial roots | |
62 | * @nroots: RS code generator polynomial degree (number of roots) | |
63 | * | |
64 | * Allocate a control structure and the polynom arrays for faster | |
9dc65576 | 65 | * en/decoding. Fill the arrays according to the given parameters. |
1da177e4 | 66 | */ |
d7e5a546 SB |
67 | static struct rs_control *rs_init(int symsize, int gfpoly, int (*gffunc)(int), |
68 | int fcr, int prim, int nroots) | |
1da177e4 LT |
69 | { |
70 | struct rs_control *rs; | |
71 | int i, j, sr, root, iprim; | |
72 | ||
73 | /* Allocate the control structure */ | |
74 | rs = kmalloc(sizeof (struct rs_control), GFP_KERNEL); | |
75 | if (rs == NULL) | |
76 | return NULL; | |
77 | ||
78 | INIT_LIST_HEAD(&rs->list); | |
79 | ||
80 | rs->mm = symsize; | |
81 | rs->nn = (1 << symsize) - 1; | |
82 | rs->fcr = fcr; | |
83 | rs->prim = prim; | |
84 | rs->nroots = nroots; | |
85 | rs->gfpoly = gfpoly; | |
d7e5a546 | 86 | rs->gffunc = gffunc; |
1da177e4 LT |
87 | |
88 | /* Allocate the arrays */ | |
89 | rs->alpha_to = kmalloc(sizeof(uint16_t) * (rs->nn + 1), GFP_KERNEL); | |
90 | if (rs->alpha_to == NULL) | |
91 | goto errrs; | |
92 | ||
93 | rs->index_of = kmalloc(sizeof(uint16_t) * (rs->nn + 1), GFP_KERNEL); | |
94 | if (rs->index_of == NULL) | |
95 | goto erralp; | |
96 | ||
97 | rs->genpoly = kmalloc(sizeof(uint16_t) * (rs->nroots + 1), GFP_KERNEL); | |
98 | if(rs->genpoly == NULL) | |
99 | goto erridx; | |
100 | ||
101 | /* Generate Galois field lookup tables */ | |
102 | rs->index_of[0] = rs->nn; /* log(zero) = -inf */ | |
103 | rs->alpha_to[rs->nn] = 0; /* alpha**-inf = 0 */ | |
d7e5a546 SB |
104 | if (gfpoly) { |
105 | sr = 1; | |
106 | for (i = 0; i < rs->nn; i++) { | |
107 | rs->index_of[sr] = i; | |
108 | rs->alpha_to[i] = sr; | |
109 | sr <<= 1; | |
110 | if (sr & (1 << symsize)) | |
111 | sr ^= gfpoly; | |
112 | sr &= rs->nn; | |
113 | } | |
114 | } else { | |
115 | sr = gffunc(0); | |
116 | for (i = 0; i < rs->nn; i++) { | |
117 | rs->index_of[sr] = i; | |
118 | rs->alpha_to[i] = sr; | |
119 | sr = gffunc(sr); | |
120 | } | |
1da177e4 LT |
121 | } |
122 | /* If it's not primitive, exit */ | |
d7e5a546 | 123 | if(sr != rs->alpha_to[0]) |
1da177e4 LT |
124 | goto errpol; |
125 | ||
126 | /* Find prim-th root of 1, used in decoding */ | |
127 | for(iprim = 1; (iprim % prim) != 0; iprim += rs->nn); | |
128 | /* prim-th root of 1, index form */ | |
129 | rs->iprim = iprim / prim; | |
130 | ||
131 | /* Form RS code generator polynomial from its roots */ | |
132 | rs->genpoly[0] = 1; | |
133 | for (i = 0, root = fcr * prim; i < nroots; i++, root += prim) { | |
134 | rs->genpoly[i + 1] = 1; | |
135 | /* Multiply rs->genpoly[] by @**(root + x) */ | |
136 | for (j = i; j > 0; j--) { | |
137 | if (rs->genpoly[j] != 0) { | |
03ead842 TG |
138 | rs->genpoly[j] = rs->genpoly[j -1] ^ |
139 | rs->alpha_to[rs_modnn(rs, | |
1da177e4 LT |
140 | rs->index_of[rs->genpoly[j]] + root)]; |
141 | } else | |
142 | rs->genpoly[j] = rs->genpoly[j - 1]; | |
143 | } | |
144 | /* rs->genpoly[0] can never be zero */ | |
03ead842 TG |
145 | rs->genpoly[0] = |
146 | rs->alpha_to[rs_modnn(rs, | |
1da177e4 LT |
147 | rs->index_of[rs->genpoly[0]] + root)]; |
148 | } | |
149 | /* convert rs->genpoly[] to index form for quicker encoding */ | |
150 | for (i = 0; i <= nroots; i++) | |
151 | rs->genpoly[i] = rs->index_of[rs->genpoly[i]]; | |
152 | return rs; | |
153 | ||
154 | /* Error exit */ | |
155 | errpol: | |
156 | kfree(rs->genpoly); | |
157 | erridx: | |
158 | kfree(rs->index_of); | |
159 | erralp: | |
160 | kfree(rs->alpha_to); | |
161 | errrs: | |
162 | kfree(rs); | |
163 | return NULL; | |
164 | } | |
165 | ||
166 | ||
03ead842 | 167 | /** |
9dc65576 | 168 | * free_rs - Free the rs control structure, if it is no longer used |
1da177e4 LT |
169 | * @rs: the control structure which is not longer used by the |
170 | * caller | |
171 | */ | |
172 | void free_rs(struct rs_control *rs) | |
173 | { | |
97d1f15b | 174 | mutex_lock(&rslistlock); |
1da177e4 LT |
175 | rs->users--; |
176 | if(!rs->users) { | |
177 | list_del(&rs->list); | |
178 | kfree(rs->alpha_to); | |
179 | kfree(rs->index_of); | |
180 | kfree(rs->genpoly); | |
181 | kfree(rs); | |
182 | } | |
97d1f15b | 183 | mutex_unlock(&rslistlock); |
1da177e4 LT |
184 | } |
185 | ||
03ead842 | 186 | /** |
d7e5a546 | 187 | * init_rs_internal - Find a matching or allocate a new rs control structure |
1da177e4 LT |
188 | * @symsize: the symbol size (number of bits) |
189 | * @gfpoly: the extended Galois field generator polynomial coefficients, | |
190 | * with the 0th coefficient in the low order bit. The polynomial | |
191 | * must be primitive; | |
d7e5a546 SB |
192 | * @gffunc: pointer to function to generate the next field element, |
193 | * or the multiplicative identity element if given 0. Used | |
194 | * instead of gfpoly if gfpoly is 0 | |
03ead842 | 195 | * @fcr: the first consecutive root of the rs code generator polynomial |
1da177e4 LT |
196 | * in index form |
197 | * @prim: primitive element to generate polynomial roots | |
198 | * @nroots: RS code generator polynomial degree (number of roots) | |
199 | */ | |
d7e5a546 SB |
200 | static struct rs_control *init_rs_internal(int symsize, int gfpoly, |
201 | int (*gffunc)(int), int fcr, | |
202 | int prim, int nroots) | |
1da177e4 LT |
203 | { |
204 | struct list_head *tmp; | |
205 | struct rs_control *rs; | |
206 | ||
207 | /* Sanity checks */ | |
208 | if (symsize < 1) | |
209 | return NULL; | |
210 | if (fcr < 0 || fcr >= (1<<symsize)) | |
211 | return NULL; | |
212 | if (prim <= 0 || prim >= (1<<symsize)) | |
213 | return NULL; | |
03ead842 | 214 | if (nroots < 0 || nroots >= (1<<symsize)) |
1da177e4 | 215 | return NULL; |
03ead842 | 216 | |
97d1f15b | 217 | mutex_lock(&rslistlock); |
1da177e4 LT |
218 | |
219 | /* Walk through the list and look for a matching entry */ | |
220 | list_for_each(tmp, &rslist) { | |
221 | rs = list_entry(tmp, struct rs_control, list); | |
222 | if (symsize != rs->mm) | |
223 | continue; | |
224 | if (gfpoly != rs->gfpoly) | |
225 | continue; | |
d7e5a546 SB |
226 | if (gffunc != rs->gffunc) |
227 | continue; | |
1da177e4 | 228 | if (fcr != rs->fcr) |
03ead842 | 229 | continue; |
1da177e4 | 230 | if (prim != rs->prim) |
03ead842 | 231 | continue; |
1da177e4 LT |
232 | if (nroots != rs->nroots) |
233 | continue; | |
234 | /* We have a matching one already */ | |
235 | rs->users++; | |
236 | goto out; | |
237 | } | |
238 | ||
239 | /* Create a new one */ | |
d7e5a546 | 240 | rs = rs_init(symsize, gfpoly, gffunc, fcr, prim, nroots); |
1da177e4 LT |
241 | if (rs) { |
242 | rs->users = 1; | |
243 | list_add(&rs->list, &rslist); | |
244 | } | |
03ead842 | 245 | out: |
97d1f15b | 246 | mutex_unlock(&rslistlock); |
1da177e4 LT |
247 | return rs; |
248 | } | |
249 | ||
d7e5a546 SB |
250 | /** |
251 | * init_rs - Find a matching or allocate a new rs control structure | |
252 | * @symsize: the symbol size (number of bits) | |
253 | * @gfpoly: the extended Galois field generator polynomial coefficients, | |
254 | * with the 0th coefficient in the low order bit. The polynomial | |
255 | * must be primitive; | |
256 | * @fcr: the first consecutive root of the rs code generator polynomial | |
257 | * in index form | |
258 | * @prim: primitive element to generate polynomial roots | |
259 | * @nroots: RS code generator polynomial degree (number of roots) | |
260 | */ | |
261 | struct rs_control *init_rs(int symsize, int gfpoly, int fcr, int prim, | |
262 | int nroots) | |
263 | { | |
264 | return init_rs_internal(symsize, gfpoly, NULL, fcr, prim, nroots); | |
265 | } | |
266 | ||
267 | /** | |
268 | * init_rs_non_canonical - Find a matching or allocate a new rs control | |
269 | * structure, for fields with non-canonical | |
270 | * representation | |
271 | * @symsize: the symbol size (number of bits) | |
272 | * @gffunc: pointer to function to generate the next field element, | |
273 | * or the multiplicative identity element if given 0. Used | |
274 | * instead of gfpoly if gfpoly is 0 | |
275 | * @fcr: the first consecutive root of the rs code generator polynomial | |
276 | * in index form | |
277 | * @prim: primitive element to generate polynomial roots | |
278 | * @nroots: RS code generator polynomial degree (number of roots) | |
279 | */ | |
280 | struct rs_control *init_rs_non_canonical(int symsize, int (*gffunc)(int), | |
281 | int fcr, int prim, int nroots) | |
282 | { | |
283 | return init_rs_internal(symsize, 0, gffunc, fcr, prim, nroots); | |
284 | } | |
285 | ||
1da177e4 | 286 | #ifdef CONFIG_REED_SOLOMON_ENC8 |
03ead842 | 287 | /** |
1da177e4 | 288 | * encode_rs8 - Calculate the parity for data values (8bit data width) |
1da177e4 LT |
289 | * @rs: the rs control structure |
290 | * @data: data field of a given type | |
03ead842 | 291 | * @len: data length |
1da177e4 LT |
292 | * @par: parity data, must be initialized by caller (usually all 0) |
293 | * @invmsk: invert data mask (will be xored on data) | |
294 | * | |
295 | * The parity uses a uint16_t data type to enable | |
296 | * symbol size > 8. The calling code must take care of encoding of the | |
297 | * syndrome result for storage itself. | |
298 | */ | |
03ead842 | 299 | int encode_rs8(struct rs_control *rs, uint8_t *data, int len, uint16_t *par, |
1da177e4 LT |
300 | uint16_t invmsk) |
301 | { | |
302 | #include "encode_rs.c" | |
303 | } | |
304 | EXPORT_SYMBOL_GPL(encode_rs8); | |
305 | #endif | |
306 | ||
307 | #ifdef CONFIG_REED_SOLOMON_DEC8 | |
03ead842 | 308 | /** |
1da177e4 | 309 | * decode_rs8 - Decode codeword (8bit data width) |
1da177e4 LT |
310 | * @rs: the rs control structure |
311 | * @data: data field of a given type | |
312 | * @par: received parity data field | |
313 | * @len: data length | |
314 | * @s: syndrome data field (if NULL, syndrome is calculated) | |
315 | * @no_eras: number of erasures | |
316 | * @eras_pos: position of erasures, can be NULL | |
317 | * @invmsk: invert data mask (will be xored on data, not on parity!) | |
318 | * @corr: buffer to store correction bitmask on eras_pos | |
319 | * | |
320 | * The syndrome and parity uses a uint16_t data type to enable | |
321 | * symbol size > 8. The calling code must take care of decoding of the | |
322 | * syndrome result and the received parity before calling this code. | |
323 | */ | |
324 | int decode_rs8(struct rs_control *rs, uint8_t *data, uint16_t *par, int len, | |
03ead842 | 325 | uint16_t *s, int no_eras, int *eras_pos, uint16_t invmsk, |
1da177e4 LT |
326 | uint16_t *corr) |
327 | { | |
328 | #include "decode_rs.c" | |
329 | } | |
330 | EXPORT_SYMBOL_GPL(decode_rs8); | |
331 | #endif | |
332 | ||
333 | #ifdef CONFIG_REED_SOLOMON_ENC16 | |
334 | /** | |
335 | * encode_rs16 - Calculate the parity for data values (16bit data width) | |
1da177e4 LT |
336 | * @rs: the rs control structure |
337 | * @data: data field of a given type | |
03ead842 | 338 | * @len: data length |
1da177e4 LT |
339 | * @par: parity data, must be initialized by caller (usually all 0) |
340 | * @invmsk: invert data mask (will be xored on data, not on parity!) | |
341 | * | |
342 | * Each field in the data array contains up to symbol size bits of valid data. | |
343 | */ | |
03ead842 | 344 | int encode_rs16(struct rs_control *rs, uint16_t *data, int len, uint16_t *par, |
1da177e4 LT |
345 | uint16_t invmsk) |
346 | { | |
347 | #include "encode_rs.c" | |
348 | } | |
349 | EXPORT_SYMBOL_GPL(encode_rs16); | |
350 | #endif | |
351 | ||
352 | #ifdef CONFIG_REED_SOLOMON_DEC16 | |
03ead842 | 353 | /** |
1da177e4 | 354 | * decode_rs16 - Decode codeword (16bit data width) |
1da177e4 LT |
355 | * @rs: the rs control structure |
356 | * @data: data field of a given type | |
357 | * @par: received parity data field | |
358 | * @len: data length | |
359 | * @s: syndrome data field (if NULL, syndrome is calculated) | |
360 | * @no_eras: number of erasures | |
361 | * @eras_pos: position of erasures, can be NULL | |
03ead842 | 362 | * @invmsk: invert data mask (will be xored on data, not on parity!) |
1da177e4 LT |
363 | * @corr: buffer to store correction bitmask on eras_pos |
364 | * | |
365 | * Each field in the data array contains up to symbol size bits of valid data. | |
366 | */ | |
367 | int decode_rs16(struct rs_control *rs, uint16_t *data, uint16_t *par, int len, | |
03ead842 | 368 | uint16_t *s, int no_eras, int *eras_pos, uint16_t invmsk, |
1da177e4 LT |
369 | uint16_t *corr) |
370 | { | |
371 | #include "decode_rs.c" | |
372 | } | |
373 | EXPORT_SYMBOL_GPL(decode_rs16); | |
374 | #endif | |
375 | ||
376 | EXPORT_SYMBOL_GPL(init_rs); | |
d7e5a546 | 377 | EXPORT_SYMBOL_GPL(init_rs_non_canonical); |
1da177e4 LT |
378 | EXPORT_SYMBOL_GPL(free_rs); |
379 | ||
380 | MODULE_LICENSE("GPL"); | |
381 | MODULE_DESCRIPTION("Reed Solomon encoder/decoder"); | |
382 | MODULE_AUTHOR("Phil Karn, Thomas Gleixner"); | |
383 |