sound/core/pcm_misc.c

   1 /*
   2  *  PCM Interface - misc routines
   3  *  Copyright (c) 1998 by Jaroslav Kysela <perex@perex.cz>
   4  *
   5  *
   6  *   This library is free software; you can redistribute it and/or modify
   7  *   it under the terms of the GNU Library General Public License as
   8  *   published by the Free Software Foundation; either version 2 of
   9  *   the License, or (at your option) any later version.
  10  *
  11  *   This program is distributed in the hope that it will be useful,
  12  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *   GNU Library General Public License for more details.
  15  *
  16  *   You should have received a copy of the GNU Library General Public
  17  *   License along with this library; if not, write to the Free Software
  18  *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
  19  *
  20  */
  21
  22 #include <linux/time.h>
  23 #include <linux/export.h>
  24 #include <sound/core.h>
  25 #include <sound/pcm.h>
  26
  27 #include "pcm_local.h"
  28
  29 #define SND_PCM_FORMAT_UNKNOWN (-1)
  30
  31 /* NOTE: "signed" prefix must be given below since the default char is
  32  *       unsigned on some architectures!
  33  */
  34 struct pcm_format_data {
  35         unsigned char width;    /* bit width */
  36         unsigned char phys;     /* physical bit width */
  37         signed char le; /* 0 = big-endian, 1 = little-endian, -1 = others */
  38         signed char signd;      /* 0 = unsigned, 1 = signed, -1 = others */
  39         unsigned char silence[8];       /* silence data to fill */
  40 };
  41
  42 /* we do lots of calculations on snd_pcm_format_t; shut up sparse */
  43 #define INT     __force int
  44
  45 static bool valid_format(snd_pcm_format_t format)
  46 {
  47         return (INT)format >= 0 && (INT)format <= (INT)SNDRV_PCM_FORMAT_LAST;
  48 }
  49
  50 static const struct pcm_format_data pcm_formats[(INT)SNDRV_PCM_FORMAT_LAST+1] = {
  51         [SNDRV_PCM_FORMAT_S8] = {
  52                 .width = 8, .phys = 8, .le = -1, .signd = 1,
  53                 .silence = {},
  54         },
  55         [SNDRV_PCM_FORMAT_U8] = {
  56                 .width = 8, .phys = 8, .le = -1, .signd = 0,
  57                 .silence = { 0x80 },
  58         },
  59         [SNDRV_PCM_FORMAT_S16_LE] = {
  60                 .width = 16, .phys = 16, .le = 1, .signd = 1,
  61                 .silence = {},
  62         },
  63         [SNDRV_PCM_FORMAT_S16_BE] = {
  64                 .width = 16, .phys = 16, .le = 0, .signd = 1,
  65                 .silence = {},
  66         },
  67         [SNDRV_PCM_FORMAT_U16_LE] = {
  68                 .width = 16, .phys = 16, .le = 1, .signd = 0,
  69                 .silence = { 0x00, 0x80 },
  70         },
  71         [SNDRV_PCM_FORMAT_U16_BE] = {
  72                 .width = 16, .phys = 16, .le = 0, .signd = 0,
  73                 .silence = { 0x80, 0x00 },
  74         },
  75         [SNDRV_PCM_FORMAT_S24_LE] = {
  76                 .width = 24, .phys = 32, .le = 1, .signd = 1,
  77                 .silence = {},
  78         },
  79         [SNDRV_PCM_FORMAT_S24_BE] = {
  80                 .width = 24, .phys = 32, .le = 0, .signd = 1,
  81                 .silence = {},
  82         },
  83         [SNDRV_PCM_FORMAT_U24_LE] = {
  84                 .width = 24, .phys = 32, .le = 1, .signd = 0,
  85                 .silence = { 0x00, 0x00, 0x80 },
  86         },
  87         [SNDRV_PCM_FORMAT_U24_BE] = {
  88                 .width = 24, .phys = 32, .le = 0, .signd = 0,
  89                 .silence = { 0x00, 0x80, 0x00, 0x00 },
  90         },
  91         [SNDRV_PCM_FORMAT_S32_LE] = {
  92                 .width = 32, .phys = 32, .le = 1, .signd = 1,
  93                 .silence = {},
  94         },
  95         [SNDRV_PCM_FORMAT_S32_BE] = {
  96                 .width = 32, .phys = 32, .le = 0, .signd = 1,
  97                 .silence = {},
  98         },
  99         [SNDRV_PCM_FORMAT_U32_LE] = {
 100                 .width = 32, .phys = 32, .le = 1, .signd = 0,
 101                 .silence = { 0x00, 0x00, 0x00, 0x80 },
 102         },
 103         [SNDRV_PCM_FORMAT_U32_BE] = {
 104                 .width = 32, .phys = 32, .le = 0, .signd = 0,
 105                 .silence = { 0x80, 0x00, 0x00, 0x00 },
 106         },
 107         [SNDRV_PCM_FORMAT_FLOAT_LE] = {
 108                 .width = 32, .phys = 32, .le = 1, .signd = -1,
 109                 .silence = {},
 110         },
 111         [SNDRV_PCM_FORMAT_FLOAT_BE] = {
 112                 .width = 32, .phys = 32, .le = 0, .signd = -1,
 113                 .silence = {},
 114         },
 115         [SNDRV_PCM_FORMAT_FLOAT64_LE] = {
 116                 .width = 64, .phys = 64, .le = 1, .signd = -1,
 117                 .silence = {},
 118         },
 119         [SNDRV_PCM_FORMAT_FLOAT64_BE] = {
 120                 .width = 64, .phys = 64, .le = 0, .signd = -1,
 121                 .silence = {},
 122         },
 123         [SNDRV_PCM_FORMAT_IEC958_SUBFRAME_LE] = {
 124                 .width = 32, .phys = 32, .le = 1, .signd = -1,
 125                 .silence = {},
 126         },
 127         [SNDRV_PCM_FORMAT_IEC958_SUBFRAME_BE] = {
 128                 .width = 32, .phys = 32, .le = 0, .signd = -1,
 129                 .silence = {},
 130         },
 131         [SNDRV_PCM_FORMAT_MU_LAW] = {
 132                 .width = 8, .phys = 8, .le = -1, .signd = -1,
 133                 .silence = { 0x7f },
 134         },
 135         [SNDRV_PCM_FORMAT_A_LAW] = {
 136                 .width = 8, .phys = 8, .le = -1, .signd = -1,
 137                 .silence = { 0x55 },
 138         },
 139         [SNDRV_PCM_FORMAT_IMA_ADPCM] = {
 140                 .width = 4, .phys = 4, .le = -1, .signd = -1,
 141                 .silence = {},
 142         },
 143         [SNDRV_PCM_FORMAT_G723_24] = {
 144                 .width = 3, .phys = 3, .le = -1, .signd = -1,
 145                 .silence = {},
 146         },
 147         [SNDRV_PCM_FORMAT_G723_40] = {
 148                 .width = 5, .phys = 5, .le = -1, .signd = -1,
 149                 .silence = {},
 150         },
 151         [SNDRV_PCM_FORMAT_DSD_U8] = {
 152                 .width = 8, .phys = 8, .le = 1, .signd = 0,
 153                 .silence = { 0x69 },
 154         },
 155         [SNDRV_PCM_FORMAT_DSD_U16_LE] = {
 156                 .width = 16, .phys = 16, .le = 1, .signd = 0,
 157                 .silence = { 0x69, 0x69 },
 158         },
 159         [SNDRV_PCM_FORMAT_DSD_U32_LE] = {
 160                 .width = 32, .phys = 32, .le = 1, .signd = 0,
 161                 .silence = { 0x69, 0x69, 0x69, 0x69 },
 162         },
 163         [SNDRV_PCM_FORMAT_DSD_U16_BE] = {
 164                 .width = 16, .phys = 16, .le = 0, .signd = 0,
 165                 .silence = { 0x69, 0x69 },
 166         },
 167         [SNDRV_PCM_FORMAT_DSD_U32_BE] = {
 168                 .width = 32, .phys = 32, .le = 0, .signd = 0,
 169                 .silence = { 0x69, 0x69, 0x69, 0x69 },
 170         },
 171         /* FIXME: the following two formats are not defined properly yet */
 172         [SNDRV_PCM_FORMAT_MPEG] = {
 173                 .le = -1, .signd = -1,
 174         },
 175         [SNDRV_PCM_FORMAT_GSM] = {
 176                 .le = -1, .signd = -1,
 177         },
 178         [SNDRV_PCM_FORMAT_S20_LE] = {
 179                 .width = 20, .phys = 32, .le = 1, .signd = 1,
 180                 .silence = {},
 181         },
 182         [SNDRV_PCM_FORMAT_S20_BE] = {
 183                 .width = 20, .phys = 32, .le = 0, .signd = 1,
 184                 .silence = {},
 185         },
 186         [SNDRV_PCM_FORMAT_U20_LE] = {
 187                 .width = 20, .phys = 32, .le = 1, .signd = 0,
 188                 .silence = { 0x00, 0x00, 0x08, 0x00 },
 189         },
 190         [SNDRV_PCM_FORMAT_U20_BE] = {
 191                 .width = 20, .phys = 32, .le = 0, .signd = 0,
 192                 .silence = { 0x00, 0x08, 0x00, 0x00 },
 193         },
 194         /* FIXME: the following format is not defined properly yet */
 195         [SNDRV_PCM_FORMAT_SPECIAL] = {
 196                 .le = -1, .signd = -1,
 197         },
 198         [SNDRV_PCM_FORMAT_S24_3LE] = {
 199                 .width = 24, .phys = 24, .le = 1, .signd = 1,
 200                 .silence = {},
 201         },
 202         [SNDRV_PCM_FORMAT_S24_3BE] = {
 203                 .width = 24, .phys = 24, .le = 0, .signd = 1,
 204                 .silence = {},
 205         },
 206         [SNDRV_PCM_FORMAT_U24_3LE] = {
 207                 .width = 24, .phys = 24, .le = 1, .signd = 0,
 208                 .silence = { 0x00, 0x00, 0x80 },
 209         },
 210         [SNDRV_PCM_FORMAT_U24_3BE] = {
 211                 .width = 24, .phys = 24, .le = 0, .signd = 0,
 212                 .silence = { 0x80, 0x00, 0x00 },
 213         },
 214         [SNDRV_PCM_FORMAT_S20_3LE] = {
 215                 .width = 20, .phys = 24, .le = 1, .signd = 1,
 216                 .silence = {},
 217         },
 218         [SNDRV_PCM_FORMAT_S20_3BE] = {
 219                 .width = 20, .phys = 24, .le = 0, .signd = 1,
 220                 .silence = {},
 221         },
 222         [SNDRV_PCM_FORMAT_U20_3LE] = {
 223                 .width = 20, .phys = 24, .le = 1, .signd = 0,
 224                 .silence = { 0x00, 0x00, 0x08 },
 225         },
 226         [SNDRV_PCM_FORMAT_U20_3BE] = {
 227                 .width = 20, .phys = 24, .le = 0, .signd = 0,
 228                 .silence = { 0x08, 0x00, 0x00 },
 229         },
 230         [SNDRV_PCM_FORMAT_S18_3LE] = {
 231                 .width = 18, .phys = 24, .le = 1, .signd = 1,
 232                 .silence = {},
 233         },
 234         [SNDRV_PCM_FORMAT_S18_3BE] = {
 235                 .width = 18, .phys = 24, .le = 0, .signd = 1,
 236                 .silence = {},
 237         },
 238         [SNDRV_PCM_FORMAT_U18_3LE] = {
 239                 .width = 18, .phys = 24, .le = 1, .signd = 0,
 240                 .silence = { 0x00, 0x00, 0x02 },
 241         },
 242         [SNDRV_PCM_FORMAT_U18_3BE] = {
 243                 .width = 18, .phys = 24, .le = 0, .signd = 0,
 244                 .silence = { 0x02, 0x00, 0x00 },
 245         },
 246         [SNDRV_PCM_FORMAT_G723_24_1B] = {
 247                 .width = 3, .phys = 8, .le = -1, .signd = -1,
 248                 .silence = {},
 249         },
 250         [SNDRV_PCM_FORMAT_G723_40_1B] = {
 251                 .width = 5, .phys = 8, .le = -1, .signd = -1,
 252                 .silence = {},
 253         },
 254 };
 255
 256
 257 /**
 258  * snd_pcm_format_signed - Check the PCM format is signed linear
 259  * @format: the format to check
 260  *
 261  * Return: 1 if the given PCM format is signed linear, 0 if unsigned
 262  * linear, and a negative error code for non-linear formats.
 263  */
 264 int snd_pcm_format_signed(snd_pcm_format_t format)
 265 {
 266         int val;
 267         if (!valid_format(format))
 268                 return -EINVAL;
 269         if ((val = pcm_formats[(INT)format].signd) < 0)
 270                 return -EINVAL;
 271         return val;
 272 }
 273 EXPORT_SYMBOL(snd_pcm_format_signed);
 274
 275 /**
 276  * snd_pcm_format_unsigned - Check the PCM format is unsigned linear
 277  * @format: the format to check
 278  *
 279  * Return: 1 if the given PCM format is unsigned linear, 0 if signed
 280  * linear, and a negative error code for non-linear formats.
 281  */
 282 int snd_pcm_format_unsigned(snd_pcm_format_t format)
 283 {
 284         int val;
 285
 286         val = snd_pcm_format_signed(format);
 287         if (val < 0)
 288                 return val;
 289         return !val;
 290 }
 291 EXPORT_SYMBOL(snd_pcm_format_unsigned);
 292
 293 /**
 294  * snd_pcm_format_linear - Check the PCM format is linear
 295  * @format: the format to check
 296  *
 297  * Return: 1 if the given PCM format is linear, 0 if not.
 298  */
 299 int snd_pcm_format_linear(snd_pcm_format_t format)
 300 {
 301         return snd_pcm_format_signed(format) >= 0;
 302 }
 303 EXPORT_SYMBOL(snd_pcm_format_linear);
 304
 305 /**
 306  * snd_pcm_format_little_endian - Check the PCM format is little-endian
 307  * @format: the format to check
 308  *
 309  * Return: 1 if the given PCM format is little-endian, 0 if
 310  * big-endian, or a negative error code if endian not specified.
 311  */
 312 int snd_pcm_format_little_endian(snd_pcm_format_t format)
 313 {
 314         int val;
 315         if (!valid_format(format))
 316                 return -EINVAL;
 317         if ((val = pcm_formats[(INT)format].le) < 0)
 318                 return -EINVAL;
 319         return val;
 320 }
 321 EXPORT_SYMBOL(snd_pcm_format_little_endian);
 322
 323 /**
 324  * snd_pcm_format_big_endian - Check the PCM format is big-endian
 325  * @format: the format to check
 326  *
 327  * Return: 1 if the given PCM format is big-endian, 0 if
 328  * little-endian, or a negative error code if endian not specified.
 329  */
 330 int snd_pcm_format_big_endian(snd_pcm_format_t format)
 331 {
 332         int val;
 333
 334         val = snd_pcm_format_little_endian(format);
 335         if (val < 0)
 336                 return val;
 337         return !val;
 338 }
 339 EXPORT_SYMBOL(snd_pcm_format_big_endian);
 340
 341 /**
 342  * snd_pcm_format_width - return the bit-width of the format
 343  * @format: the format to check
 344  *
 345  * Return: The bit-width of the format, or a negative error code
 346  * if unknown format.
 347  */
 348 int snd_pcm_format_width(snd_pcm_format_t format)
 349 {
 350         int val;
 351         if (!valid_format(format))
 352                 return -EINVAL;
 353         if ((val = pcm_formats[(INT)format].width) == 0)
 354                 return -EINVAL;
 355         return val;
 356 }
 357 EXPORT_SYMBOL(snd_pcm_format_width);
 358
 359 /**
 360  * snd_pcm_format_physical_width - return the physical bit-width of the format
 361  * @format: the format to check
 362  *
 363  * Return: The physical bit-width of the format, or a negative error code
 364  * if unknown format.
 365  */
 366 int snd_pcm_format_physical_width(snd_pcm_format_t format)
 367 {
 368         int val;
 369         if (!valid_format(format))
 370                 return -EINVAL;
 371         if ((val = pcm_formats[(INT)format].phys) == 0)
 372                 return -EINVAL;
 373         return val;
 374 }
 375 EXPORT_SYMBOL(snd_pcm_format_physical_width);
 376
 377 /**
 378  * snd_pcm_format_size - return the byte size of samples on the given format
 379  * @format: the format to check
 380  * @samples: sampling rate
 381  *
 382  * Return: The byte size of the given samples for the format, or a
 383  * negative error code if unknown format.
 384  */
 385 ssize_t snd_pcm_format_size(snd_pcm_format_t format, size_t samples)
 386 {
 387         int phys_width = snd_pcm_format_physical_width(format);
 388         if (phys_width < 0)
 389                 return -EINVAL;
 390         return samples * phys_width / 8;
 391 }
 392 EXPORT_SYMBOL(snd_pcm_format_size);
 393
 394 /**
 395  * snd_pcm_format_silence_64 - return the silent data in 8 bytes array
 396  * @format: the format to check
 397  *
 398  * Return: The format pattern to fill or %NULL if error.
 399  */
 400 const unsigned char *snd_pcm_format_silence_64(snd_pcm_format_t format)
 401 {
 402         if (!valid_format(format))
 403                 return NULL;
 404         if (! pcm_formats[(INT)format].phys)
 405                 return NULL;
 406         return pcm_formats[(INT)format].silence;
 407 }
 408 EXPORT_SYMBOL(snd_pcm_format_silence_64);
 409
 410 /**
 411  * snd_pcm_format_set_silence - set the silence data on the buffer
 412  * @format: the PCM format
 413  * @data: the buffer pointer
 414  * @samples: the number of samples to set silence
 415  *
 416  * Sets the silence data on the buffer for the given samples.
 417  *
 418  * Return: Zero if successful, or a negative error code on failure.
 419  */
 420 int snd_pcm_format_set_silence(snd_pcm_format_t format, void *data, unsigned int samples)
 421 {
 422         int width;
 423         unsigned char *dst;
 424         const unsigned char *pat;
 425
 426         if (!valid_format(format))
 427                 return -EINVAL;
 428         if (samples == 0)
 429                 return 0;
 430         width = pcm_formats[(INT)format].phys; /* physical width */
 431         pat = pcm_formats[(INT)format].silence;
 432         if (! width)
 433                 return -EINVAL;
 434         /* signed or 1 byte data */
 435         if (pcm_formats[(INT)format].signd == 1 || width <= 8) {
 436                 unsigned int bytes = samples * width / 8;
 437                 memset(data, *pat, bytes);
 438                 return 0;
 439         }
 440         /* non-zero samples, fill using a loop */
 441         width /= 8;
 442         dst = data;
 443 #if 0
 444         while (samples--) {
 445                 memcpy(dst, pat, width);
 446                 dst += width;
 447         }
 448 #else
 449         /* a bit optimization for constant width */
 450         switch (width) {
 451         case 2:
 452                 while (samples--) {
 453                         memcpy(dst, pat, 2);
 454                         dst += 2;
 455                 }
 456                 break;
 457         case 3:
 458                 while (samples--) {
 459                         memcpy(dst, pat, 3);
 460                         dst += 3;
 461                 }
 462                 break;
 463         case 4:
 464                 while (samples--) {
 465                         memcpy(dst, pat, 4);
 466                         dst += 4;
 467                 }
 468                 break;
 469         case 8:
 470                 while (samples--) {
 471                         memcpy(dst, pat, 8);
 472                         dst += 8;
 473                 }
 474                 break;
 475         }
 476 #endif
 477         return 0;
 478 }
 479 EXPORT_SYMBOL(snd_pcm_format_set_silence);
 480
 481 /**
 482  * snd_pcm_hw_limit_rates - determine rate_min/rate_max fields
 483  * @hw: the pcm hw instance
 484  *
 485  * Determines the rate_min and rate_max fields from the rates bits of
 486  * the given hw.
 487  *
 488  * Return: Zero if successful.
 489  */
 490 int snd_pcm_hw_limit_rates(struct snd_pcm_hardware *hw)
 491 {
 492         int i;
 493         for (i = 0; i < (int)snd_pcm_known_rates.count; i++) {
 494                 if (hw->rates & (1 << i)) {
 495                         hw->rate_min = snd_pcm_known_rates.list[i];
 496                         break;
 497                 }
 498         }
 499         for (i = (int)snd_pcm_known_rates.count - 1; i >= 0; i--) {
 500                 if (hw->rates & (1 << i)) {
 501                         hw->rate_max = snd_pcm_known_rates.list[i];
 502                         break;
 503                 }
 504         }
 505         return 0;
 506 }
 507 EXPORT_SYMBOL(snd_pcm_hw_limit_rates);
 508
 509 /**
 510  * snd_pcm_rate_to_rate_bit - converts sample rate to SNDRV_PCM_RATE_xxx bit
 511  * @rate: the sample rate to convert
 512  *
 513  * Return: The SNDRV_PCM_RATE_xxx flag that corresponds to the given rate, or
 514  * SNDRV_PCM_RATE_KNOT for an unknown rate.
 515  */
 516 unsigned int snd_pcm_rate_to_rate_bit(unsigned int rate)
 517 {
 518         unsigned int i;
 519
 520         for (i = 0; i < snd_pcm_known_rates.count; i++)
 521                 if (snd_pcm_known_rates.list[i] == rate)
 522                         return 1u << i;
 523         return SNDRV_PCM_RATE_KNOT;
 524 }
 525 EXPORT_SYMBOL(snd_pcm_rate_to_rate_bit);
 526
 527 /**
 528  * snd_pcm_rate_bit_to_rate - converts SNDRV_PCM_RATE_xxx bit to sample rate
 529  * @rate_bit: the rate bit to convert
 530  *
 531  * Return: The sample rate that corresponds to the given SNDRV_PCM_RATE_xxx flag
 532  * or 0 for an unknown rate bit.
 533  */
 534 unsigned int snd_pcm_rate_bit_to_rate(unsigned int rate_bit)
 535 {
 536         unsigned int i;
 537
 538         for (i = 0; i < snd_pcm_known_rates.count; i++)
 539                 if ((1u << i) == rate_bit)
 540                         return snd_pcm_known_rates.list[i];
 541         return 0;
 542 }
 543 EXPORT_SYMBOL(snd_pcm_rate_bit_to_rate);
 544
 545 static unsigned int snd_pcm_rate_mask_sanitize(unsigned int rates)
 546 {
 547         if (rates & SNDRV_PCM_RATE_CONTINUOUS)
 548                 return SNDRV_PCM_RATE_CONTINUOUS;
 549         else if (rates & SNDRV_PCM_RATE_KNOT)
 550                 return SNDRV_PCM_RATE_KNOT;
 551         return rates;
 552 }
 553
 554 /**
 555  * snd_pcm_rate_mask_intersect - computes the intersection between two rate masks
 556  * @rates_a: The first rate mask
 557  * @rates_b: The second rate mask
 558  *
 559  * This function computes the rates that are supported by both rate masks passed
 560  * to the function. It will take care of the special handling of
 561  * SNDRV_PCM_RATE_CONTINUOUS and SNDRV_PCM_RATE_KNOT.
 562  *
 563  * Return: A rate mask containing the rates that are supported by both rates_a
 564  * and rates_b.
 565  */
 566 unsigned int snd_pcm_rate_mask_intersect(unsigned int rates_a,
 567         unsigned int rates_b)
 568 {
 569         rates_a = snd_pcm_rate_mask_sanitize(rates_a);
 570         rates_b = snd_pcm_rate_mask_sanitize(rates_b);
 571
 572         if (rates_a & SNDRV_PCM_RATE_CONTINUOUS)
 573                 return rates_b;
 574         else if (rates_b & SNDRV_PCM_RATE_CONTINUOUS)
 575                 return rates_a;
 576         else if (rates_a & SNDRV_PCM_RATE_KNOT)
 577                 return rates_b;
 578         else if (rates_b & SNDRV_PCM_RATE_KNOT)
 579                 return rates_a;
 580         return rates_a & rates_b;
 581 }
 582 EXPORT_SYMBOL_GPL(snd_pcm_rate_mask_intersect);
 583
 584 /**
 585  * snd_pcm_rate_range_to_bits - converts rate range to SNDRV_PCM_RATE_xxx bit
 586  * @rate_min: the minimum sample rate
 587  * @rate_max: the maximum sample rate
 588  *
 589  * This function has an implicit assumption: the rates in the given range have
 590  * only the pre-defined rates like 44100 or 16000.
 591  *
 592  * Return: The SNDRV_PCM_RATE_xxx flag that corresponds to the given rate range,
 593  * or SNDRV_PCM_RATE_KNOT for an unknown range.
 594  */
 595 unsigned int snd_pcm_rate_range_to_bits(unsigned int rate_min,
 596         unsigned int rate_max)
 597 {
 598         unsigned int rates = 0;
 599         int i;
 600
 601         for (i = 0; i < snd_pcm_known_rates.count; i++) {
 602                 if (snd_pcm_known_rates.list[i] >= rate_min
 603                         && snd_pcm_known_rates.list[i] <= rate_max)
 604                         rates |= 1 << i;
 605         }
 606
 607         if (!rates)
 608                 rates = SNDRV_PCM_RATE_KNOT;
 609
 610         return rates;
 611 }
 612 EXPORT_SYMBOL_GPL(snd_pcm_rate_range_to_bits);