code.delx.au - pulseaudio/blob - src/modules/alsa-util.c

   1 /***
   2   This file is part of PulseAudio.
   3
   4   Copyright 2004-2006 Lennart Poettering
   5   Copyright 2006 Pierre Ossman <ossman@cendio.se> for Cendio AB
   6
   7   PulseAudio is free software; you can redistribute it and/or modify
   8   it under the terms of the GNU Lesser General Public License as published
   9   by the Free Software Foundation; either version 2 of the License,
  10   or (at your option) any later version.
  11
  12   PulseAudio is distributed in the hope that it will be useful, but
  13   WITHOUT ANY WARRANTY; without even the implied warranty of
  14   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  15   General Public License for more details.
  16
  17   You should have received a copy of the GNU Lesser General Public License
  18   along with PulseAudio; if not, write to the Free Software
  19   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
  20   USA.
  21 ***/
  22
  23 #ifdef HAVE_CONFIG_H
  24 #include <config.h>
  25 #endif
  26
  27 #include <sys/types.h>
  28 #include <limits.h>
  29 #include <asoundlib.h>
  30
  31 #include <pulse/sample.h>
  32 #include <pulse/xmalloc.h>
  33
  34 #include <pulsecore/log.h>
  35 #include <pulsecore/macro.h>
  36 #include <pulsecore/core-util.h>
  37 #include <pulsecore/atomic.h>
  38
  39 #include "alsa-util.h"
  40
  41 struct pa_alsa_fdlist {
  42     unsigned num_fds;
  43     struct pollfd *fds;
  44     /* This is a temporary buffer used to avoid lots of mallocs */
  45     struct pollfd *work_fds;
  46
  47     snd_mixer_t *mixer;
  48
  49     pa_mainloop_api *m;
  50     pa_defer_event *defer;
  51     pa_io_event **ios;
  52
  53     pa_bool_t polled;
  54
  55     void (*cb)(void *userdata);
  56     void *userdata;
  57 };
  58
  59 static void io_cb(pa_mainloop_api*a, pa_io_event* e, int fd, pa_io_event_flags_t events, void *userdata) {
  60
  61     struct pa_alsa_fdlist *fdl = userdata;
  62     int err;
  63     unsigned i;
  64     unsigned short revents;
  65
  66     pa_assert(a);
  67     pa_assert(fdl);
  68     pa_assert(fdl->mixer);
  69     pa_assert(fdl->fds);
  70     pa_assert(fdl->work_fds);
  71
  72     if (fdl->polled)
  73         return;
  74
  75     fdl->polled = TRUE;
  76
  77     memcpy(fdl->work_fds, fdl->fds, sizeof(struct pollfd) * fdl->num_fds);
  78
  79     for (i = 0; i < fdl->num_fds; i++) {
  80         if (e == fdl->ios[i]) {
  81             if (events & PA_IO_EVENT_INPUT)
  82                 fdl->work_fds[i].revents |= POLLIN;
  83             if (events & PA_IO_EVENT_OUTPUT)
  84                 fdl->work_fds[i].revents |= POLLOUT;
  85             if (events & PA_IO_EVENT_ERROR)
  86                 fdl->work_fds[i].revents |= POLLERR;
  87             if (events & PA_IO_EVENT_HANGUP)
  88                 fdl->work_fds[i].revents |= POLLHUP;
  89             break;
  90         }
  91     }
  92
  93     pa_assert(i != fdl->num_fds);
  94
  95     if ((err = snd_mixer_poll_descriptors_revents(fdl->mixer, fdl->work_fds, fdl->num_fds, &revents)) < 0) {
  96         pa_log_error("Unable to get poll revent: %s", snd_strerror(err));
  97         return;
  98     }
  99
 100     a->defer_enable(fdl->defer, 1);
 101
 102     if (revents)
 103         snd_mixer_handle_events(fdl->mixer);
 104 }
 105
 106 static void defer_cb(pa_mainloop_api*a, pa_defer_event* e, void *userdata) {
 107     struct pa_alsa_fdlist *fdl = userdata;
 108     unsigned num_fds, i;
 109     int err;
 110     struct pollfd *temp;
 111
 112     pa_assert(a);
 113     pa_assert(fdl);
 114     pa_assert(fdl->mixer);
 115
 116     a->defer_enable(fdl->defer, 0);
 117
 118     num_fds = (unsigned) snd_mixer_poll_descriptors_count(fdl->mixer);
 119
 120     if (num_fds != fdl->num_fds) {
 121         if (fdl->fds)
 122             pa_xfree(fdl->fds);
 123         if (fdl->work_fds)
 124             pa_xfree(fdl->work_fds);
 125         fdl->fds = pa_xnew0(struct pollfd, num_fds);
 126         fdl->work_fds = pa_xnew(struct pollfd, num_fds);
 127     }
 128
 129     memset(fdl->work_fds, 0, sizeof(struct pollfd) * num_fds);
 130
 131     if ((err = snd_mixer_poll_descriptors(fdl->mixer, fdl->work_fds, num_fds)) < 0) {
 132         pa_log_error("Unable to get poll descriptors: %s", snd_strerror(err));
 133         return;
 134     }
 135
 136     fdl->polled = FALSE;
 137
 138     if (memcmp(fdl->fds, fdl->work_fds, sizeof(struct pollfd) * num_fds) == 0)
 139         return;
 140
 141     if (fdl->ios) {
 142         for (i = 0; i < fdl->num_fds; i++)
 143             a->io_free(fdl->ios[i]);
 144
 145         if (num_fds != fdl->num_fds) {
 146             pa_xfree(fdl->ios);
 147             fdl->ios = NULL;
 148         }
 149     }
 150
 151     if (!fdl->ios)
 152         fdl->ios = pa_xnew(pa_io_event*, num_fds);
 153
 154     /* Swap pointers */
 155     temp = fdl->work_fds;
 156     fdl->work_fds = fdl->fds;
 157     fdl->fds = temp;
 158
 159     fdl->num_fds = num_fds;
 160
 161     for (i = 0;i < num_fds;i++)
 162         fdl->ios[i] = a->io_new(a, fdl->fds[i].fd,
 163             ((fdl->fds[i].events & POLLIN) ? PA_IO_EVENT_INPUT : 0) |
 164             ((fdl->fds[i].events & POLLOUT) ? PA_IO_EVENT_OUTPUT : 0),
 165             io_cb, fdl);
 166 }
 167
 168 struct pa_alsa_fdlist *pa_alsa_fdlist_new(void) {
 169     struct pa_alsa_fdlist *fdl;
 170
 171     fdl = pa_xnew0(struct pa_alsa_fdlist, 1);
 172
 173     fdl->num_fds = 0;
 174     fdl->fds = NULL;
 175     fdl->work_fds = NULL;
 176     fdl->mixer = NULL;
 177     fdl->m = NULL;
 178     fdl->defer = NULL;
 179     fdl->ios = NULL;
 180     fdl->polled = FALSE;
 181
 182     return fdl;
 183 }
 184
 185 void pa_alsa_fdlist_free(struct pa_alsa_fdlist *fdl) {
 186     pa_assert(fdl);
 187
 188     if (fdl->defer) {
 189         pa_assert(fdl->m);
 190         fdl->m->defer_free(fdl->defer);
 191     }
 192
 193     if (fdl->ios) {
 194         unsigned i;
 195         pa_assert(fdl->m);
 196         for (i = 0; i < fdl->num_fds; i++)
 197             fdl->m->io_free(fdl->ios[i]);
 198         pa_xfree(fdl->ios);
 199     }
 200
 201     if (fdl->fds)
 202         pa_xfree(fdl->fds);
 203     if (fdl->work_fds)
 204         pa_xfree(fdl->work_fds);
 205
 206     pa_xfree(fdl);
 207 }
 208
 209 int pa_alsa_fdlist_set_mixer(struct pa_alsa_fdlist *fdl, snd_mixer_t *mixer_handle, pa_mainloop_api* m) {
 210     pa_assert(fdl);
 211     pa_assert(mixer_handle);
 212     pa_assert(m);
 213     pa_assert(!fdl->m);
 214
 215     fdl->mixer = mixer_handle;
 216     fdl->m = m;
 217     fdl->defer = m->defer_new(m, defer_cb, fdl);
 218
 219     return 0;
 220 }
 221
 222 static int set_format(snd_pcm_t *pcm_handle, snd_pcm_hw_params_t *hwparams, pa_sample_format_t *f) {
 223
 224     static const snd_pcm_format_t format_trans[] = {
 225         [PA_SAMPLE_U8] = SND_PCM_FORMAT_U8,
 226         [PA_SAMPLE_ALAW] = SND_PCM_FORMAT_A_LAW,
 227         [PA_SAMPLE_ULAW] = SND_PCM_FORMAT_MU_LAW,
 228         [PA_SAMPLE_S16LE] = SND_PCM_FORMAT_S16_LE,
 229         [PA_SAMPLE_S16BE] = SND_PCM_FORMAT_S16_BE,
 230         [PA_SAMPLE_FLOAT32LE] = SND_PCM_FORMAT_FLOAT_LE,
 231         [PA_SAMPLE_FLOAT32BE] = SND_PCM_FORMAT_FLOAT_BE,
 232         [PA_SAMPLE_S32LE] = SND_PCM_FORMAT_S32_LE,
 233         [PA_SAMPLE_S32BE] = SND_PCM_FORMAT_S32_BE,
 234     };
 235
 236     static const pa_sample_format_t try_order[] = {
 237         PA_SAMPLE_FLOAT32NE,
 238         PA_SAMPLE_FLOAT32RE,
 239         PA_SAMPLE_S32NE,
 240         PA_SAMPLE_S32RE,
 241         PA_SAMPLE_S16NE,
 242         PA_SAMPLE_S16RE,
 243         PA_SAMPLE_ALAW,
 244         PA_SAMPLE_ULAW,
 245         PA_SAMPLE_U8,
 246         PA_SAMPLE_INVALID
 247     };
 248
 249     int i, ret;
 250
 251     pa_assert(pcm_handle);
 252     pa_assert(f);
 253
 254     if ((ret = snd_pcm_hw_params_set_format(pcm_handle, hwparams, format_trans[*f])) >= 0)
 255         return ret;
 256
 257     if (*f == PA_SAMPLE_FLOAT32BE)
 258         *f = PA_SAMPLE_FLOAT32LE;
 259     else if (*f == PA_SAMPLE_FLOAT32LE)
 260         *f = PA_SAMPLE_FLOAT32BE;
 261     else if (*f == PA_SAMPLE_S16BE)
 262         *f = PA_SAMPLE_S16LE;
 263     else if (*f == PA_SAMPLE_S16LE)
 264         *f = PA_SAMPLE_S16BE;
 265     else if (*f == PA_SAMPLE_S32BE)
 266         *f = PA_SAMPLE_S32LE;
 267     else if (*f == PA_SAMPLE_S32LE)
 268         *f = PA_SAMPLE_S32BE;
 269     else
 270         goto try_auto;
 271
 272     if ((ret = snd_pcm_hw_params_set_format(pcm_handle, hwparams, format_trans[*f])) >= 0)
 273         return ret;
 274
 275 try_auto:
 276
 277     for (i = 0; try_order[i] != PA_SAMPLE_INVALID; i++) {
 278         *f = try_order[i];
 279
 280         if ((ret = snd_pcm_hw_params_set_format(pcm_handle, hwparams, format_trans[*f])) >= 0)
 281             return ret;
 282     }
 283
 284     return -1;
 285 }
 286
 287 /* Set the hardware parameters of the given ALSA device. Returns the
 288  * selected fragment settings in *period and *period_size */
 289 int pa_alsa_set_hw_params(
 290         snd_pcm_t *pcm_handle,
 291         pa_sample_spec *ss,
 292         uint32_t *periods,
 293         snd_pcm_uframes_t *period_size,
 294         snd_pcm_uframes_t tsched_size,
 295         pa_bool_t *use_mmap,
 296         pa_bool_t *use_tsched,
 297         pa_bool_t require_exact_channel_number) {
 298
 299     int ret = -1;
 300     snd_pcm_uframes_t _period_size = *period_size;
 301     unsigned int _periods = *periods;
 302     snd_pcm_uframes_t buffer_size;
 303     unsigned int r = ss->rate;
 304     unsigned int c = ss->channels;
 305     pa_sample_format_t f = ss->format;
 306     snd_pcm_hw_params_t *hwparams;
 307     pa_bool_t _use_mmap = use_mmap && *use_mmap;
 308     pa_bool_t _use_tsched = use_tsched && *use_tsched;
 309     int dir;
 310
 311     pa_assert(pcm_handle);
 312     pa_assert(ss);
 313     pa_assert(periods);
 314     pa_assert(period_size);
 315
 316     snd_pcm_hw_params_alloca(&hwparams);
 317
 318     if ((ret = snd_pcm_hw_params_any(pcm_handle, hwparams)) < 0)
 319         goto finish;
 320
 321     if ((ret = snd_pcm_hw_params_set_rate_resample(pcm_handle, hwparams, 0)) < 0)
 322         goto finish;
 323
 324     if (_use_mmap) {
 325         if ((ret = snd_pcm_hw_params_set_access(pcm_handle, hwparams, SND_PCM_ACCESS_MMAP_INTERLEAVED)) < 0) {
 326
 327             /* mmap() didn't work, fall back to interleaved */
 328
 329             if ((ret = snd_pcm_hw_params_set_access(pcm_handle, hwparams, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0)
 330                 goto finish;
 331
 332             _use_mmap = FALSE;
 333         }
 334
 335     } else if ((ret = snd_pcm_hw_params_set_access(pcm_handle, hwparams, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0)
 336         goto finish;
 337
 338     if (!_use_mmap)
 339         _use_tsched = FALSE;
 340
 341     if ((ret = set_format(pcm_handle, hwparams, &f)) < 0)
 342         goto finish;
 343
 344     if ((ret = snd_pcm_hw_params_set_rate_near(pcm_handle, hwparams, &r, NULL)) < 0)
 345         goto finish;
 346
 347     /* Adjust the buffer sizes, if we didn't get the rate we were asking for */
 348     _period_size = (snd_pcm_uframes_t) (((uint64_t) _period_size * r) / ss->rate);
 349     tsched_size = (snd_pcm_uframes_t) (((uint64_t) tsched_size * r) / ss->rate);
 350
 351     if (require_exact_channel_number) {
 352         if ((ret = snd_pcm_hw_params_set_channels(pcm_handle, hwparams, c)) < 0)
 353             goto finish;
 354     } else {
 355         if ((ret = snd_pcm_hw_params_set_channels_near(pcm_handle, hwparams, &c)) < 0)
 356             goto finish;
 357     }
 358
 359     if (_use_tsched) {
 360         _period_size = tsched_size;
 361         _periods = 1;
 362
 363         pa_assert_se(snd_pcm_hw_params_get_buffer_size_max(hwparams, &buffer_size) == 0);
 364         pa_log_debug("Maximum hw buffer size is %u ms", (unsigned) buffer_size * 1000 / r);
 365     }
 366
 367     buffer_size = _periods * _period_size;
 368
 369     if ((ret = snd_pcm_hw_params_set_periods_integer(pcm_handle, hwparams)) < 0)
 370         goto finish;
 371
 372     if (_periods > 0) {
 373
 374         /* First we pass 0 as direction to get exactly what we asked
 375          * for. That this is necessary is presumably a bug in ALSA */
 376
 377         dir = 0;
 378         if ((ret = snd_pcm_hw_params_set_periods_near(pcm_handle, hwparams, &_periods, &dir)) < 0) {
 379             dir = 1;
 380             if ((ret = snd_pcm_hw_params_set_periods_near(pcm_handle, hwparams, &_periods, &dir)) < 0) {
 381                 dir = -1;
 382                 if ((ret = snd_pcm_hw_params_set_periods_near(pcm_handle, hwparams, &_periods, &dir)) < 0)
 383                     goto finish;
 384             }
 385         }
 386     }
 387
 388     if (_period_size > 0)
 389         if ((ret = snd_pcm_hw_params_set_buffer_size_near(pcm_handle, hwparams, &buffer_size)) < 0)
 390             goto finish;
 391
 392     if  ((ret = snd_pcm_hw_params(pcm_handle, hwparams)) < 0)
 393         goto finish;
 394
 395     if (ss->rate != r)
 396         pa_log_warn("Device %s doesn't support %u Hz, changed to %u Hz.", snd_pcm_name(pcm_handle), ss->rate, r);
 397
 398     if (ss->channels != c)
 399         pa_log_warn("Device %s doesn't support %u channels, changed to %u.", snd_pcm_name(pcm_handle), ss->channels, c);
 400
 401     if (ss->format != f)
 402         pa_log_warn("Device %s doesn't support sample format %s, changed to %s.", snd_pcm_name(pcm_handle), pa_sample_format_to_string(ss->format), pa_sample_format_to_string(f));
 403
 404     if ((ret = snd_pcm_prepare(pcm_handle)) < 0)
 405         goto finish;
 406
 407     if ((ret = snd_pcm_hw_params_get_period_size(hwparams, &_period_size, &dir)) < 0 ||
 408         (ret = snd_pcm_hw_params_get_periods(hwparams, &_periods, &dir)) < 0)
 409         goto finish;
 410
 411     /* If the sample rate deviates too much, we need to resample */
 412     if (r < ss->rate*.95 || r > ss->rate*1.05)
 413         ss->rate = r;
 414     ss->channels = (uint8_t) c;
 415     ss->format = f;
 416
 417     pa_assert(_periods > 0);
 418     pa_assert(_period_size > 0);
 419
 420     *periods = _periods;
 421     *period_size = _period_size;
 422
 423     if (use_mmap)
 424         *use_mmap = _use_mmap;
 425
 426     if (use_tsched)
 427         *use_tsched = _use_tsched;
 428
 429     ret = 0;
 430
 431     snd_pcm_nonblock(pcm_handle, 1);
 432
 433 finish:
 434
 435     return ret;
 436 }
 437
 438 int pa_alsa_set_sw_params(snd_pcm_t *pcm, snd_pcm_uframes_t avail_min) {
 439     snd_pcm_sw_params_t *swparams;
 440     int err;
 441
 442     pa_assert(pcm);
 443
 444     snd_pcm_sw_params_alloca(&swparams);
 445
 446     if ((err = snd_pcm_sw_params_current(pcm, swparams) < 0)) {
 447         pa_log_warn("Unable to determine current swparams: %s\n", snd_strerror(err));
 448         return err;
 449     }
 450
 451     if ((err = snd_pcm_sw_params_set_stop_threshold(pcm, swparams, (snd_pcm_uframes_t) -1)) < 0) {
 452         pa_log_warn("Unable to set stop threshold: %s\n", snd_strerror(err));
 453         return err;
 454     }
 455
 456     if ((err = snd_pcm_sw_params_set_start_threshold(pcm, swparams, (snd_pcm_uframes_t) -1)) < 0) {
 457         pa_log_warn("Unable to set start threshold: %s\n", snd_strerror(err));
 458         return err;
 459     }
 460
 461     if ((err = snd_pcm_sw_params_set_avail_min(pcm, swparams, avail_min)) < 0) {
 462         pa_log_error("snd_pcm_sw_params_set_avail_min() failed: %s", snd_strerror(err));
 463         return err;
 464     }
 465
 466     if ((err = snd_pcm_sw_params(pcm, swparams)) < 0) {
 467         pa_log_warn("Unable to set sw params: %s\n", snd_strerror(err));
 468         return err;
 469     }
 470
 471     return 0;
 472 }
 473
 474 struct device_info {
 475     pa_channel_map map;
 476     const char *name;
 477 };
 478
 479 static const struct device_info device_table[] = {
 480     {{ 2, { PA_CHANNEL_POSITION_LEFT, PA_CHANNEL_POSITION_RIGHT } }, "front" },
 481
 482     {{ 4, { PA_CHANNEL_POSITION_FRONT_LEFT, PA_CHANNEL_POSITION_FRONT_RIGHT,
 483             PA_CHANNEL_POSITION_REAR_LEFT, PA_CHANNEL_POSITION_REAR_RIGHT }}, "surround40" },
 484
 485     {{ 5, { PA_CHANNEL_POSITION_FRONT_LEFT, PA_CHANNEL_POSITION_FRONT_RIGHT,
 486             PA_CHANNEL_POSITION_REAR_LEFT, PA_CHANNEL_POSITION_REAR_RIGHT,
 487             PA_CHANNEL_POSITION_LFE }}, "surround41" },
 488
 489     {{ 5, { PA_CHANNEL_POSITION_FRONT_LEFT, PA_CHANNEL_POSITION_FRONT_RIGHT,
 490             PA_CHANNEL_POSITION_REAR_LEFT, PA_CHANNEL_POSITION_REAR_RIGHT,
 491             PA_CHANNEL_POSITION_CENTER }}, "surround50" },
 492
 493     {{ 6, { PA_CHANNEL_POSITION_FRONT_LEFT, PA_CHANNEL_POSITION_FRONT_RIGHT,
 494             PA_CHANNEL_POSITION_REAR_LEFT, PA_CHANNEL_POSITION_REAR_RIGHT,
 495             PA_CHANNEL_POSITION_CENTER, PA_CHANNEL_POSITION_LFE }}, "surround51" },
 496
 497     {{ 8, { PA_CHANNEL_POSITION_FRONT_LEFT, PA_CHANNEL_POSITION_FRONT_RIGHT,
 498             PA_CHANNEL_POSITION_REAR_LEFT, PA_CHANNEL_POSITION_REAR_RIGHT,
 499             PA_CHANNEL_POSITION_CENTER, PA_CHANNEL_POSITION_LFE,
 500             PA_CHANNEL_POSITION_SIDE_LEFT, PA_CHANNEL_POSITION_SIDE_RIGHT }} , "surround71" },
 501
 502     {{ 0, { 0 }}, NULL }
 503 };
 504
 505 static pa_bool_t channel_map_superset(const pa_channel_map *a, const pa_channel_map *b) {
 506     pa_bool_t in_a[PA_CHANNEL_POSITION_MAX];
 507     unsigned i;
 508
 509     pa_assert(a);
 510     pa_assert(b);
 511
 512     memset(in_a, 0, sizeof(in_a));
 513
 514     for (i = 0; i < a->channels; i++)
 515         in_a[a->map[i]] = TRUE;
 516
 517     for (i = 0; i < b->channels; i++)
 518         if (!in_a[b->map[i]])
 519             return FALSE;
 520
 521     return TRUE;
 522 }
 523
 524 snd_pcm_t *pa_alsa_open_by_device_id(
 525         const char *dev_id,
 526         char **dev,
 527         pa_sample_spec *ss,
 528         pa_channel_map* map,
 529         int mode,
 530         uint32_t *nfrags,
 531         snd_pcm_uframes_t *period_size,
 532         snd_pcm_uframes_t tsched_size,
 533         pa_bool_t *use_mmap,
 534         pa_bool_t *use_tsched) {
 535
 536     int i;
 537     int direction = 1;
 538     int err;
 539     char *d;
 540     snd_pcm_t *pcm_handle;
 541
 542     pa_assert(dev_id);
 543     pa_assert(dev);
 544     pa_assert(ss);
 545     pa_assert(map);
 546     pa_assert(nfrags);
 547     pa_assert(period_size);
 548
 549     /* First we try to find a device string with a superset of the
 550      * requested channel map and open it without the plug: prefix. We
 551      * iterate through our device table from top to bottom and take
 552      * the first that matches. If we didn't find a working device that
 553      * way, we iterate backwards, and check all devices that do not
 554      * provide a superset of the requested channel map.*/
 555
 556     for (i = 0;; i += direction) {
 557         pa_sample_spec try_ss;
 558
 559         if (i < 0) {
 560             pa_assert(direction == -1);
 561
 562             /* OK, so we iterated backwards, and now are at the
 563              * beginning of our list. */
 564
 565             break;
 566
 567         } else if (!device_table[i].name) {
 568             pa_assert(direction == 1);
 569
 570             /* OK, so we are at the end of our list. at iterated
 571              * forwards. */
 572
 573             i--;
 574             direction = -1;
 575         }
 576
 577         if ((direction > 0) == !channel_map_superset(&device_table[i].map, map))
 578             continue;
 579
 580         d = pa_sprintf_malloc("%s:%s", device_table[i].name, dev_id);
 581
 582         for (;;) {
 583             pa_log_debug("Trying %s...", d);
 584
 585             /* We don't pass SND_PCM_NONBLOCK here, since alsa-lib <=
 586              * 1.0.17a would then ignore the SND_PCM_NO_xxx
 587              * flags. Instead we enable nonblock mode afterwards via
 588              * snd_pcm_nonblock(). Also see
 589              * http://mailman.alsa-project.org/pipermail/alsa-devel/2008-August/010258.html */
 590
 591             if ((err = snd_pcm_open(&pcm_handle, d, mode,
 592                                     /* SND_PCM_NONBLOCK| */
 593                                     SND_PCM_NO_AUTO_RESAMPLE|
 594                                     SND_PCM_NO_AUTO_CHANNELS|
 595                                     SND_PCM_NO_AUTO_FORMAT)) < 0) {
 596                 pa_log_info("Couldn't open PCM device %s: %s", d, snd_strerror(err));
 597                 break;
 598             }
 599
 600             try_ss.channels = device_table[i].map.channels;
 601             try_ss.rate = ss->rate;
 602             try_ss.format = ss->format;
 603
 604             if ((err = pa_alsa_set_hw_params(pcm_handle, &try_ss, nfrags, period_size, tsched_size, use_mmap, use_tsched, TRUE)) < 0) {
 605
 606                 if (!pa_startswith(d, "plug:") && !pa_startswith(d, "plughw:")) {
 607                     char *t;
 608
 609                     t = pa_sprintf_malloc("plug:%s", d);
 610                     pa_xfree(d);
 611                     d = t;
 612
 613                     snd_pcm_close(pcm_handle);
 614                     continue;
 615                 }
 616
 617                 pa_log_info("PCM device %s refused our hw parameters: %s", d, snd_strerror(err));
 618                 snd_pcm_close(pcm_handle);
 619                 break;
 620             }
 621
 622             *ss = try_ss;
 623             *map = device_table[i].map;
 624             pa_assert(map->channels == ss->channels);
 625             *dev = d;
 626             return pcm_handle;
 627         }
 628
 629         pa_xfree(d);
 630     }
 631
 632     /* OK, we didn't find any good device, so let's try the raw plughw: stuff */
 633
 634     d = pa_sprintf_malloc("hw:%s", dev_id);
 635     pa_log_debug("Trying %s as last resort...", d);
 636     pcm_handle = pa_alsa_open_by_device_string(d, dev, ss, map, mode, nfrags, period_size, tsched_size, use_mmap, use_tsched);
 637     pa_xfree(d);
 638
 639     return pcm_handle;
 640 }
 641
 642 snd_pcm_t *pa_alsa_open_by_device_string(
 643         const char *device,
 644         char **dev,
 645         pa_sample_spec *ss,
 646         pa_channel_map* map,
 647         int mode,
 648         uint32_t *nfrags,
 649         snd_pcm_uframes_t *period_size,
 650         snd_pcm_uframes_t tsched_size,
 651         pa_bool_t *use_mmap,
 652         pa_bool_t *use_tsched) {
 653
 654     int err;
 655     char *d;
 656     snd_pcm_t *pcm_handle;
 657
 658     pa_assert(device);
 659     pa_assert(dev);
 660     pa_assert(ss);
 661     pa_assert(map);
 662     pa_assert(nfrags);
 663     pa_assert(period_size);
 664
 665     d = pa_xstrdup(device);
 666
 667     for (;;) {
 668         pa_log_debug("Trying %s...", d);
 669
 670         /* We don't pass SND_PCM_NONBLOCK here, since alsa-lib <=
 671          * 1.0.17a would then ignore the SND_PCM_NO_xxx flags. Instead
 672          * we enable nonblock mode afterwards via
 673          * snd_pcm_nonblock(). Also see
 674          * http://mailman.alsa-project.org/pipermail/alsa-devel/2008-August/010258.html */
 675
 676         if ((err = snd_pcm_open(&pcm_handle, d, mode,
 677                                 /*SND_PCM_NONBLOCK|*/
 678                                 SND_PCM_NO_AUTO_RESAMPLE|
 679                                 SND_PCM_NO_AUTO_CHANNELS|
 680                                 SND_PCM_NO_AUTO_FORMAT)) < 0) {
 681             pa_log("Error opening PCM device %s: %s", d, snd_strerror(err));
 682             pa_xfree(d);
 683             return NULL;
 684         }
 685
 686         if ((err = pa_alsa_set_hw_params(pcm_handle, ss, nfrags, period_size, tsched_size, use_mmap, use_tsched, FALSE)) < 0) {
 687
 688             /* Hmm, some hw is very exotic, so we retry with plug, if without it didn't work */
 689
 690             if (!pa_startswith(d, "plug:") && !pa_startswith(d, "plughw:")) {
 691                 char *t;
 692
 693                 t = pa_sprintf_malloc("plug:%s", d);
 694                 pa_xfree(d);
 695                 d = t;
 696
 697                 snd_pcm_close(pcm_handle);
 698                 continue;
 699             }
 700
 701             pa_log("Failed to set hardware parameters on %s: %s", d, snd_strerror(err));
 702             pa_xfree(d);
 703             snd_pcm_close(pcm_handle);
 704             return NULL;
 705         }
 706
 707         *dev = d;
 708
 709         if (ss->channels != map->channels)
 710             pa_channel_map_init_extend(map, ss->channels, PA_CHANNEL_MAP_ALSA);
 711
 712         return pcm_handle;
 713     }
 714 }
 715
 716 int pa_alsa_prepare_mixer(snd_mixer_t *mixer, const char *dev) {
 717     int err;
 718
 719     pa_assert(mixer);
 720     pa_assert(dev);
 721
 722     if ((err = snd_mixer_attach(mixer, dev)) < 0) {
 723         pa_log_info("Unable to attach to mixer %s: %s", dev, snd_strerror(err));
 724         return -1;
 725     }
 726
 727     if ((err = snd_mixer_selem_register(mixer, NULL, NULL)) < 0) {
 728         pa_log_warn("Unable to register mixer: %s", snd_strerror(err));
 729         return -1;
 730     }
 731
 732     if ((err = snd_mixer_load(mixer)) < 0) {
 733         pa_log_warn("Unable to load mixer: %s", snd_strerror(err));
 734         return -1;
 735     }
 736
 737     pa_log_info("Successfully attached to mixer '%s'", dev);
 738
 739     return 0;
 740 }
 741
 742 snd_mixer_elem_t *pa_alsa_find_elem(snd_mixer_t *mixer, const char *name, const char *fallback) {
 743     snd_mixer_elem_t *elem;
 744     snd_mixer_selem_id_t *sid = NULL;
 745
 746     snd_mixer_selem_id_alloca(&sid);
 747
 748     pa_assert(mixer);
 749     pa_assert(name);
 750
 751     snd_mixer_selem_id_set_name(sid, name);
 752
 753     if (!(elem = snd_mixer_find_selem(mixer, sid))) {
 754         pa_log_info("Cannot find mixer control \"%s\".", snd_mixer_selem_id_get_name(sid));
 755
 756         if (fallback) {
 757             snd_mixer_selem_id_set_name(sid, fallback);
 758
 759             if (!(elem = snd_mixer_find_selem(mixer, sid)))
 760                 pa_log_warn("Cannot find fallback mixer control \"%s\".", snd_mixer_selem_id_get_name(sid));
 761         }
 762     }
 763
 764     if (elem)
 765         pa_log_info("Using mixer control \"%s\".", snd_mixer_selem_id_get_name(sid));
 766
 767     return elem;
 768 }
 769
 770 static const snd_mixer_selem_channel_id_t alsa_channel_ids[PA_CHANNEL_POSITION_MAX] = {
 771     [PA_CHANNEL_POSITION_MONO] = SND_MIXER_SCHN_MONO, /* The ALSA name is just an alias! */
 772
 773     [PA_CHANNEL_POSITION_FRONT_CENTER] = SND_MIXER_SCHN_FRONT_CENTER,
 774     [PA_CHANNEL_POSITION_FRONT_LEFT] = SND_MIXER_SCHN_FRONT_LEFT,
 775     [PA_CHANNEL_POSITION_FRONT_RIGHT] = SND_MIXER_SCHN_FRONT_RIGHT,
 776
 777     [PA_CHANNEL_POSITION_REAR_CENTER] = SND_MIXER_SCHN_REAR_CENTER,
 778     [PA_CHANNEL_POSITION_REAR_LEFT] = SND_MIXER_SCHN_REAR_LEFT,
 779     [PA_CHANNEL_POSITION_REAR_RIGHT] = SND_MIXER_SCHN_REAR_RIGHT,
 780
 781     [PA_CHANNEL_POSITION_LFE] = SND_MIXER_SCHN_WOOFER,
 782
 783     [PA_CHANNEL_POSITION_FRONT_LEFT_OF_CENTER] = SND_MIXER_SCHN_UNKNOWN,
 784     [PA_CHANNEL_POSITION_FRONT_RIGHT_OF_CENTER] = SND_MIXER_SCHN_UNKNOWN,
 785
 786     [PA_CHANNEL_POSITION_SIDE_LEFT] = SND_MIXER_SCHN_SIDE_LEFT,
 787     [PA_CHANNEL_POSITION_SIDE_RIGHT] = SND_MIXER_SCHN_SIDE_RIGHT,
 788
 789     [PA_CHANNEL_POSITION_AUX0] = SND_MIXER_SCHN_UNKNOWN,
 790     [PA_CHANNEL_POSITION_AUX1] = SND_MIXER_SCHN_UNKNOWN,
 791     [PA_CHANNEL_POSITION_AUX2] = SND_MIXER_SCHN_UNKNOWN,
 792     [PA_CHANNEL_POSITION_AUX3] = SND_MIXER_SCHN_UNKNOWN,
 793     [PA_CHANNEL_POSITION_AUX4] = SND_MIXER_SCHN_UNKNOWN,
 794     [PA_CHANNEL_POSITION_AUX5] = SND_MIXER_SCHN_UNKNOWN,
 795     [PA_CHANNEL_POSITION_AUX6] = SND_MIXER_SCHN_UNKNOWN,
 796     [PA_CHANNEL_POSITION_AUX7] = SND_MIXER_SCHN_UNKNOWN,
 797     [PA_CHANNEL_POSITION_AUX8] = SND_MIXER_SCHN_UNKNOWN,
 798     [PA_CHANNEL_POSITION_AUX9] =  SND_MIXER_SCHN_UNKNOWN,
 799     [PA_CHANNEL_POSITION_AUX10] = SND_MIXER_SCHN_UNKNOWN,
 800     [PA_CHANNEL_POSITION_AUX11] = SND_MIXER_SCHN_UNKNOWN,
 801     [PA_CHANNEL_POSITION_AUX12] = SND_MIXER_SCHN_UNKNOWN,
 802     [PA_CHANNEL_POSITION_AUX13] = SND_MIXER_SCHN_UNKNOWN,
 803     [PA_CHANNEL_POSITION_AUX14] = SND_MIXER_SCHN_UNKNOWN,
 804     [PA_CHANNEL_POSITION_AUX15] = SND_MIXER_SCHN_UNKNOWN,
 805     [PA_CHANNEL_POSITION_AUX16] = SND_MIXER_SCHN_UNKNOWN,
 806     [PA_CHANNEL_POSITION_AUX17] = SND_MIXER_SCHN_UNKNOWN,
 807     [PA_CHANNEL_POSITION_AUX18] = SND_MIXER_SCHN_UNKNOWN,
 808     [PA_CHANNEL_POSITION_AUX19] = SND_MIXER_SCHN_UNKNOWN,
 809     [PA_CHANNEL_POSITION_AUX20] = SND_MIXER_SCHN_UNKNOWN,
 810     [PA_CHANNEL_POSITION_AUX21] = SND_MIXER_SCHN_UNKNOWN,
 811     [PA_CHANNEL_POSITION_AUX22] = SND_MIXER_SCHN_UNKNOWN,
 812     [PA_CHANNEL_POSITION_AUX23] = SND_MIXER_SCHN_UNKNOWN,
 813     [PA_CHANNEL_POSITION_AUX24] = SND_MIXER_SCHN_UNKNOWN,
 814     [PA_CHANNEL_POSITION_AUX25] = SND_MIXER_SCHN_UNKNOWN,
 815     [PA_CHANNEL_POSITION_AUX26] = SND_MIXER_SCHN_UNKNOWN,
 816     [PA_CHANNEL_POSITION_AUX27] = SND_MIXER_SCHN_UNKNOWN,
 817     [PA_CHANNEL_POSITION_AUX28] = SND_MIXER_SCHN_UNKNOWN,
 818     [PA_CHANNEL_POSITION_AUX29] = SND_MIXER_SCHN_UNKNOWN,
 819     [PA_CHANNEL_POSITION_AUX30] = SND_MIXER_SCHN_UNKNOWN,
 820     [PA_CHANNEL_POSITION_AUX31] = SND_MIXER_SCHN_UNKNOWN,
 821
 822     [PA_CHANNEL_POSITION_TOP_CENTER] = SND_MIXER_SCHN_UNKNOWN,
 823
 824     [PA_CHANNEL_POSITION_TOP_FRONT_CENTER] = SND_MIXER_SCHN_UNKNOWN,
 825     [PA_CHANNEL_POSITION_TOP_FRONT_LEFT] = SND_MIXER_SCHN_UNKNOWN,
 826     [PA_CHANNEL_POSITION_TOP_FRONT_RIGHT] = SND_MIXER_SCHN_UNKNOWN,
 827
 828     [PA_CHANNEL_POSITION_TOP_REAR_CENTER] = SND_MIXER_SCHN_UNKNOWN,
 829     [PA_CHANNEL_POSITION_TOP_REAR_LEFT] = SND_MIXER_SCHN_UNKNOWN,
 830     [PA_CHANNEL_POSITION_TOP_REAR_RIGHT] = SND_MIXER_SCHN_UNKNOWN
 831 };
 832
 833
 834 int pa_alsa_calc_mixer_map(snd_mixer_elem_t *elem, const pa_channel_map *channel_map, snd_mixer_selem_channel_id_t mixer_map[], pa_bool_t playback) {
 835     unsigned i;
 836     pa_bool_t alsa_channel_used[SND_MIXER_SCHN_LAST];
 837     pa_bool_t mono_used = FALSE;
 838
 839     pa_assert(elem);
 840     pa_assert(channel_map);
 841     pa_assert(mixer_map);
 842
 843     memset(&alsa_channel_used, 0, sizeof(alsa_channel_used));
 844
 845     if (channel_map->channels > 1 &&
 846         ((playback && snd_mixer_selem_has_playback_volume_joined(elem)) ||
 847          (!playback && snd_mixer_selem_has_capture_volume_joined(elem)))) {
 848         pa_log_info("ALSA device lacks independant volume controls for each channel.");
 849         return -1;
 850     }
 851
 852     for (i = 0; i < channel_map->channels; i++) {
 853         snd_mixer_selem_channel_id_t id;
 854         pa_bool_t is_mono;
 855
 856         is_mono = channel_map->map[i] == PA_CHANNEL_POSITION_MONO;
 857         id = alsa_channel_ids[channel_map->map[i]];
 858
 859         if (!is_mono && id == SND_MIXER_SCHN_UNKNOWN) {
 860             pa_log_info("Configured channel map contains channel '%s' that is unknown to the ALSA mixer.", pa_channel_position_to_string(channel_map->map[i]));
 861             return -1;
 862         }
 863
 864         if ((is_mono && mono_used) || (!is_mono && alsa_channel_used[id])) {
 865             pa_log_info("Channel map has duplicate channel '%s', falling back to software volume control.", pa_channel_position_to_string(channel_map->map[i]));
 866             return -1;
 867         }
 868
 869         if ((playback && (!snd_mixer_selem_has_playback_channel(elem, id) || (is_mono && !snd_mixer_selem_is_playback_mono(elem)))) ||
 870             (!playback && (!snd_mixer_selem_has_capture_channel(elem, id) || (is_mono && !snd_mixer_selem_is_capture_mono(elem))))) {
 871
 872             pa_log_info("ALSA device lacks separate volumes control for channel '%s'", pa_channel_position_to_string(channel_map->map[i]));
 873             return -1;
 874         }
 875
 876         if (is_mono) {
 877             mixer_map[i] = SND_MIXER_SCHN_MONO;
 878             mono_used = TRUE;
 879         } else {
 880             mixer_map[i] = id;
 881             alsa_channel_used[id] = TRUE;
 882         }
 883     }
 884
 885     pa_log_info("All %u channels can be mapped to mixer channels.", channel_map->channels);
 886
 887     return 0;
 888 }
 889
 890 void pa_alsa_dump(snd_pcm_t *pcm) {
 891     int err;
 892     snd_output_t *out;
 893
 894     pa_assert(pcm);
 895
 896     pa_assert_se(snd_output_buffer_open(&out) == 0);
 897
 898     if ((err = snd_pcm_dump(pcm, out)) < 0)
 899         pa_log_debug("snd_pcm_dump(): %s", snd_strerror(err));
 900     else {
 901         char *s = NULL;
 902         snd_output_buffer_string(out, &s);
 903         pa_log_debug("snd_pcm_dump():\n%s", pa_strnull(s));
 904     }
 905
 906     pa_assert_se(snd_output_close(out) == 0);
 907 }
 908
 909 void pa_alsa_dump_status(snd_pcm_t *pcm) {
 910     int err;
 911     snd_output_t *out;
 912     snd_pcm_status_t *status;
 913
 914     pa_assert(pcm);
 915
 916     snd_pcm_status_alloca(&status);
 917
 918     pa_assert_se(snd_output_buffer_open(&out) == 0);
 919
 920     pa_assert_se(snd_pcm_status(pcm, status) == 0);
 921
 922     if ((err = snd_pcm_status_dump(status, out)) < 0)
 923         pa_log_debug("snd_pcm_dump(): %s", snd_strerror(err));
 924     else {
 925         char *s = NULL;
 926         snd_output_buffer_string(out, &s);
 927         pa_log_debug("snd_pcm_dump():\n%s", pa_strnull(s));
 928     }
 929
 930     pa_assert_se(snd_output_close(out) == 0);
 931 }
 932
 933 static void alsa_error_handler(const char *file, int line, const char *function, int err, const char *fmt,...) {
 934     va_list ap;
 935     char *alsa_file;
 936
 937     alsa_file = pa_sprintf_malloc("(alsa-lib)%s", file);
 938
 939     va_start(ap, fmt);
 940
 941     pa_log_levelv_meta(PA_LOG_INFO, alsa_file, line, function, fmt, ap);
 942
 943     va_end(ap);
 944
 945     pa_xfree(alsa_file);
 946 }
 947
 948 static pa_atomic_t n_error_handler_installed = PA_ATOMIC_INIT(0);
 949
 950 void pa_alsa_redirect_errors_inc(void) {
 951     /* This is not really thread safe, but we do our best */
 952
 953     if (pa_atomic_inc(&n_error_handler_installed) == 0)
 954         snd_lib_error_set_handler(alsa_error_handler);
 955 }
 956
 957 void pa_alsa_redirect_errors_dec(void) {
 958     int r;
 959
 960     pa_assert_se((r = pa_atomic_dec(&n_error_handler_installed)) >= 1);
 961
 962     if (r == 1)
 963         snd_lib_error_set_handler(NULL);
 964 }
 965
 966 void pa_alsa_init_proplist(pa_proplist *p, snd_pcm_info_t *pcm_info) {
 967
 968     static const char * const alsa_class_table[SND_PCM_CLASS_LAST+1] = {
 969         [SND_PCM_CLASS_GENERIC] = "generic",
 970         [SND_PCM_CLASS_MULTI] = "multi",
 971         [SND_PCM_CLASS_MODEM] = "modem",
 972         [SND_PCM_CLASS_DIGITIZER] = "digitizer"
 973     };
 974     static const char * const class_table[SND_PCM_CLASS_LAST+1] = {
 975         [SND_PCM_CLASS_GENERIC] = "sound",
 976         [SND_PCM_CLASS_MULTI] = NULL,
 977         [SND_PCM_CLASS_MODEM] = "modem",
 978         [SND_PCM_CLASS_DIGITIZER] = NULL
 979     };
 980     static const char * const alsa_subclass_table[SND_PCM_SUBCLASS_LAST+1] = {
 981         [SND_PCM_SUBCLASS_GENERIC_MIX] = "generic-mix",
 982         [SND_PCM_SUBCLASS_MULTI_MIX] = "multi-mix"
 983     };
 984
 985     snd_pcm_class_t class;
 986     snd_pcm_subclass_t subclass;
 987     const char *n, *id, *sdn;
 988     char *cn = NULL, *lcn = NULL;
 989     int card;
 990
 991     pa_assert(p);
 992     pa_assert(pcm_info);
 993
 994     pa_proplist_sets(p, PA_PROP_DEVICE_API, "alsa");
 995
 996     class = snd_pcm_info_get_class(pcm_info);
 997     if (class <= SND_PCM_CLASS_LAST) {
 998         if (class_table[class])
 999             pa_proplist_sets(p, PA_PROP_DEVICE_CLASS, class_table[class]);
1000         if (alsa_class_table[class])
1001             pa_proplist_sets(p, "alsa.class", alsa_class_table[class]);
1002     }
1003     subclass = snd_pcm_info_get_subclass(pcm_info);
1004     if (subclass <= SND_PCM_SUBCLASS_LAST)
1005         if (alsa_subclass_table[subclass])
1006             pa_proplist_sets(p, "alsa.subclass", alsa_subclass_table[subclass]);
1007
1008     if ((n = snd_pcm_info_get_name(pcm_info)))
1009         pa_proplist_sets(p, "alsa.name", n);
1010
1011     if ((id = snd_pcm_info_get_id(pcm_info)))
1012         pa_proplist_sets(p, "alsa.id", id);
1013
1014     pa_proplist_setf(p, "alsa.subdevice", "%u", snd_pcm_info_get_subdevice(pcm_info));
1015     if ((sdn = snd_pcm_info_get_subdevice_name(pcm_info)))
1016         pa_proplist_sets(p, "alsa.subdevice_name", sdn);
1017
1018     pa_proplist_setf(p, "alsa.device", "%u", snd_pcm_info_get_device(pcm_info));
1019
1020     if ((card = snd_pcm_info_get_card(pcm_info)) >= 0) {
1021         pa_proplist_setf(p, "alsa.card", "%i", card);
1022
1023         if (snd_card_get_name(card, &cn) >= 0)
1024             pa_proplist_sets(p, "alsa.card_name", cn);
1025
1026         if (snd_card_get_longname(card, &lcn) >= 0)
1027             pa_proplist_sets(p, "alsa.long_card_name", lcn);
1028     }
1029
1030     if (cn && n)
1031         pa_proplist_setf(p, PA_PROP_DEVICE_DESCRIPTION, "%s - %s", cn, n);
1032     else if (cn)
1033         pa_proplist_sets(p, PA_PROP_DEVICE_DESCRIPTION, cn);
1034     else if (n)
1035         pa_proplist_sets(p, PA_PROP_DEVICE_DESCRIPTION, n);
1036
1037     free(lcn);
1038     free(cn);
1039 }
1040
1041 int pa_alsa_recover_from_poll(snd_pcm_t *pcm, int revents) {
1042     snd_pcm_state_t state;
1043     int err;
1044
1045     pa_assert(pcm);
1046
1047     if (revents & POLLERR)
1048         pa_log_warn("Got POLLERR from ALSA");
1049     if (revents & POLLNVAL)
1050         pa_log_warn("Got POLLNVAL from ALSA");
1051     if (revents & POLLHUP)
1052         pa_log_warn("Got POLLHUP from ALSA");
1053
1054     state = snd_pcm_state(pcm);
1055     pa_log_warn("PCM state is %s", snd_pcm_state_name(state));
1056
1057     /* Try to recover from this error */
1058
1059     switch (state) {
1060
1061         case SND_PCM_STATE_XRUN:
1062             if ((err = snd_pcm_recover(pcm, -EPIPE, 1)) != 0) {
1063                 pa_log_warn("Could not recover from POLLERR|POLLNVAL|POLLHUP and XRUN: %s", snd_strerror(err));
1064                 return -1;
1065             }
1066             break;
1067
1068         case SND_PCM_STATE_SUSPENDED:
1069             if ((err = snd_pcm_recover(pcm, -ESTRPIPE, 1)) != 0) {
1070                 pa_log_warn("Could not recover from POLLERR|POLLNVAL|POLLHUP and SUSPENDED: %s", snd_strerror(err));
1071                 return -1;
1072             }
1073             break;
1074
1075         default:
1076
1077             snd_pcm_drop(pcm);
1078
1079             if ((err = snd_pcm_prepare(pcm)) < 0) {
1080                 pa_log_warn("Could not recover from POLLERR|POLLNVAL|POLLHUP with snd_pcm_prepare(): %s", snd_strerror(err));
1081                 return -1;
1082             }
1083             break;
1084     }
1085
1086     return 0;
1087 }
1088
1089 pa_rtpoll_item* pa_alsa_build_pollfd(snd_pcm_t *pcm, pa_rtpoll *rtpoll) {
1090     int n, err;
1091     struct pollfd *pollfd;
1092     pa_rtpoll_item *item;
1093
1094     pa_assert(pcm);
1095
1096     if ((n = snd_pcm_poll_descriptors_count(pcm)) < 0) {
1097         pa_log("snd_pcm_poll_descriptors_count() failed: %s", snd_strerror(n));
1098         return NULL;
1099     }
1100
1101     item = pa_rtpoll_item_new(rtpoll, PA_RTPOLL_NEVER, (unsigned) n);
1102     pollfd = pa_rtpoll_item_get_pollfd(item, NULL);
1103
1104     if ((err = snd_pcm_poll_descriptors(pcm, pollfd, (unsigned) n)) < 0) {
1105         pa_log("snd_pcm_poll_descriptors() failed: %s", snd_strerror(err));
1106         pa_rtpoll_item_free(item);
1107         return NULL;
1108     }
1109
1110     return item;
1111 }
1112
1113 pa_cvolume *pa_alsa_volume_divide(pa_cvolume *r, const pa_cvolume *t) {
1114     unsigned i;
1115
1116     pa_assert(r);
1117     pa_assert(t);
1118     pa_assert(r->channels == t->channels);
1119
1120     for (i = 0; i < r->channels; i++) {
1121         double a, b, c;
1122
1123         a = pa_sw_volume_to_linear(r->values[i]); /* the hw volume */
1124         b = pa_sw_volume_to_linear(t->values[i]); /* the intended volume */
1125
1126         if (a <= 0)
1127             c = 0;
1128         else
1129             c = b / a;
1130
1131         r->values[i] = pa_sw_volume_from_linear(c);
1132     }
1133
1134     return r;
1135 }