src/pcm/pcm_null.c

   1 /**
   2  * \file pcm/pcm_null.c
   3  * \ingroup PCM_Plugins
   4  * \brief PCM Null Plugin Interface
   5  * \author Abramo Bagnara <abramo@alsa-project.org>
   6  * \date 2000-2001
   7  */
   8 /*
   9  *  PCM - Null plugin
  10  *  Copyright (c) 2000 by Abramo Bagnara <abramo@alsa-project.org>
  11  *
  12  *
  13  *   This library is free software; you can redistribute it and/or modify
  14  *   it under the terms of the GNU Lesser General Public License as
  15  *   published by the Free Software Foundation; either version 2.1 of
  16  *   the License, or (at your option) any later version.
  17  *
  18  *   This program is distributed in the hope that it will be useful,
  19  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
  20  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21  *   GNU Lesser General Public License for more details.
  22  *
  23  *   You should have received a copy of the GNU Lesser General Public
  24  *   License along with this library; if not, write to the Free Software
  25  *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
  26  *
  27  */
  28
  29 #include <byteswap.h>
  30 #include <limits.h>
  31 #include <sys/shm.h>
  32 #include "pcm_local.h"
  33 #include "pcm_plugin.h"
  34
  35 #ifndef PIC
  36 /* entry for static linking */
  37 const char *_snd_module_pcm_null = "";
  38 #endif
  39
  40 #ifndef DOC_HIDDEN
  41 typedef struct {
  42         snd_timestamp_t trigger_tstamp;
  43         snd_pcm_state_t state;
  44         int shmid;
  45         snd_pcm_uframes_t appl_ptr;
  46         snd_pcm_uframes_t hw_ptr;
  47         int poll_fd;
  48 } snd_pcm_null_t;
  49 #endif
  50
  51 static int snd_pcm_null_close(snd_pcm_t *pcm)
  52 {
  53         snd_pcm_null_t *null = pcm->private_data;
  54         close(null->poll_fd);
  55         free(null);
  56         return 0;
  57 }
  58
  59 static int snd_pcm_null_nonblock(snd_pcm_t *pcm ATTRIBUTE_UNUSED, int nonblock ATTRIBUTE_UNUSED)
  60 {
  61         return 0;
  62 }
  63
  64 static int snd_pcm_null_async(snd_pcm_t *pcm ATTRIBUTE_UNUSED, int sig ATTRIBUTE_UNUSED, pid_t pid ATTRIBUTE_UNUSED)
  65 {
  66         return -ENOSYS;
  67 }
  68
  69 static int snd_pcm_null_info(snd_pcm_t *pcm ATTRIBUTE_UNUSED, snd_pcm_info_t * info)
  70 {
  71         memset(info, 0, sizeof(*info));
  72         info->stream = pcm->stream;
  73         info->card = -1;
  74         strncpy(info->id, pcm->name, sizeof(info->id));
  75         strncpy(info->name, pcm->name, sizeof(info->name));
  76         strncpy(info->subname, pcm->name, sizeof(info->subname));
  77         info->subdevices_count = 1;
  78         return 0;
  79 }
  80
  81 static int snd_pcm_null_channel_info(snd_pcm_t *pcm, snd_pcm_channel_info_t * info)
  82 {
  83         snd_pcm_null_t *null = pcm->private_data;
  84         return snd_pcm_channel_info_shm(pcm, info, null->shmid);
  85 }
  86
  87 static int snd_pcm_null_status(snd_pcm_t *pcm, snd_pcm_status_t * status)
  88 {
  89         snd_pcm_null_t *null = pcm->private_data;
  90         memset(status, 0, sizeof(*status));
  91         status->state = null->state;
  92         status->trigger_tstamp = null->trigger_tstamp;
  93         gettimeofday(&status->tstamp, 0);
  94         status->avail = pcm->buffer_size;
  95         status->avail_max = status->avail;
  96         return 0;
  97 }
  98
  99 static snd_pcm_state_t snd_pcm_null_state(snd_pcm_t *pcm)
 100 {
 101         snd_pcm_null_t *null = pcm->private_data;
 102         return null->state;
 103 }
 104
 105 static int snd_pcm_null_hwsync(snd_pcm_t *pcm ATTRIBUTE_UNUSED)
 106 {
 107         return 0;
 108 }
 109
 110 static int snd_pcm_null_delay(snd_pcm_t *pcm ATTRIBUTE_UNUSED, snd_pcm_sframes_t *delayp)
 111 {
 112         *delayp = 0;
 113         return 0;
 114 }
 115
 116 static int snd_pcm_null_prepare(snd_pcm_t *pcm)
 117 {
 118         snd_pcm_null_t *null = pcm->private_data;
 119         null->state = SND_PCM_STATE_PREPARED;
 120         *pcm->appl.ptr = 0;
 121         *pcm->hw.ptr = 0;
 122         return 0;
 123 }
 124
 125 static int snd_pcm_null_reset(snd_pcm_t *pcm)
 126 {
 127         *pcm->appl.ptr = 0;
 128         *pcm->hw.ptr = 0;
 129         return 0;
 130 }
 131
 132 static int snd_pcm_null_start(snd_pcm_t *pcm)
 133 {
 134         snd_pcm_null_t *null = pcm->private_data;
 135         assert(null->state == SND_PCM_STATE_PREPARED);
 136         null->state = SND_PCM_STATE_RUNNING;
 137         if (pcm->stream == SND_PCM_STREAM_CAPTURE)
 138                 *pcm->hw.ptr = *pcm->appl.ptr + pcm->buffer_size;
 139         else
 140                 *pcm->hw.ptr = *pcm->appl.ptr;
 141         return 0;
 142 }
 143
 144 static int snd_pcm_null_drop(snd_pcm_t *pcm)
 145 {
 146         snd_pcm_null_t *null = pcm->private_data;
 147         assert(null->state != SND_PCM_STATE_OPEN);
 148         null->state = SND_PCM_STATE_SETUP;
 149         return 0;
 150 }
 151
 152 static int snd_pcm_null_drain(snd_pcm_t *pcm)
 153 {
 154         snd_pcm_null_t *null = pcm->private_data;
 155         assert(null->state != SND_PCM_STATE_OPEN);
 156         null->state = SND_PCM_STATE_SETUP;
 157         return 0;
 158 }
 159
 160 static int snd_pcm_null_pause(snd_pcm_t *pcm, int enable)
 161 {
 162         snd_pcm_null_t *null = pcm->private_data;
 163         if (enable) {
 164                 if (null->state != SND_PCM_STATE_RUNNING)
 165                         return -EBADFD;
 166         } else if (null->state != SND_PCM_STATE_PAUSED)
 167                 return -EBADFD;
 168         null->state = SND_PCM_STATE_PAUSED;
 169         return 0;
 170 }
 171
 172 static snd_pcm_sframes_t snd_pcm_null_rewind(snd_pcm_t *pcm, snd_pcm_uframes_t frames)
 173 {
 174         snd_pcm_null_t *null = pcm->private_data;
 175         switch (null->state) {
 176         case SND_PCM_STATE_RUNNING:
 177                 snd_pcm_mmap_hw_backward(pcm, frames);
 178                 /* Fall through */
 179         case SND_PCM_STATE_PREPARED:
 180                 snd_pcm_mmap_appl_backward(pcm, frames);
 181                 return frames;
 182         default:
 183                 return -EBADFD;
 184         }
 185 }
 186
 187 static int snd_pcm_null_resume(snd_pcm_t *pcm ATTRIBUTE_UNUSED)
 188 {
 189         return 0;
 190 }
 191
 192 static snd_pcm_sframes_t snd_pcm_null_fwd(snd_pcm_t *pcm, snd_pcm_uframes_t size)
 193 {
 194         snd_pcm_null_t *null = pcm->private_data;
 195         switch (null->state) {
 196         case SND_PCM_STATE_RUNNING:
 197                 snd_pcm_mmap_hw_forward(pcm, size);
 198                 /* Fall through */
 199         case SND_PCM_STATE_PREPARED:
 200                 snd_pcm_mmap_appl_forward(pcm, size);
 201                 return size;
 202         default:
 203                 return -EBADFD;
 204         }
 205 }
 206
 207 static snd_pcm_sframes_t snd_pcm_null_xfer_areas(snd_pcm_t *pcm,
 208                                                  const snd_pcm_channel_area_t *areas ATTRIBUTE_UNUSED,
 209                                                  snd_pcm_uframes_t offset ATTRIBUTE_UNUSED,
 210                                                  snd_pcm_uframes_t size)
 211 {
 212         snd_pcm_mmap_appl_forward(pcm, size);
 213         snd_pcm_mmap_hw_forward(pcm, size);
 214         return size;
 215 }
 216
 217 static snd_pcm_sframes_t snd_pcm_null_writei(snd_pcm_t *pcm, const void *buffer ATTRIBUTE_UNUSED, snd_pcm_uframes_t size)
 218 {
 219         return snd_pcm_write_areas(pcm, NULL, 0, size, snd_pcm_null_xfer_areas);
 220 }
 221
 222 static snd_pcm_sframes_t snd_pcm_null_writen(snd_pcm_t *pcm, void **bufs ATTRIBUTE_UNUSED, snd_pcm_uframes_t size)
 223 {
 224         return snd_pcm_write_areas(pcm, NULL, 0, size, snd_pcm_null_xfer_areas);
 225 }
 226
 227 static snd_pcm_sframes_t snd_pcm_null_readi(snd_pcm_t *pcm, void *buffer ATTRIBUTE_UNUSED, snd_pcm_uframes_t size)
 228 {
 229         return snd_pcm_read_areas(pcm, NULL, 0, size, snd_pcm_null_xfer_areas);
 230 }
 231
 232 static snd_pcm_sframes_t snd_pcm_null_readn(snd_pcm_t *pcm, void **bufs ATTRIBUTE_UNUSED, snd_pcm_uframes_t size)
 233 {
 234         return snd_pcm_read_areas(pcm, NULL, 0, size, snd_pcm_null_xfer_areas);
 235 }
 236
 237 static snd_pcm_sframes_t snd_pcm_null_mmap_commit(snd_pcm_t *pcm,
 238                                                   snd_pcm_uframes_t offset ATTRIBUTE_UNUSED,
 239                                                   snd_pcm_uframes_t size)
 240 {
 241         snd_pcm_sframes_t res;
 242
 243         res = snd_pcm_null_fwd(pcm, size);
 244         if (res < 0)
 245                 return res;
 246         return res;
 247 }
 248
 249 static snd_pcm_sframes_t snd_pcm_null_avail_update(snd_pcm_t *pcm)
 250 {
 251         return pcm->buffer_size;
 252 }
 253
 254 static int snd_pcm_null_hw_refine(snd_pcm_t *pcm ATTRIBUTE_UNUSED, snd_pcm_hw_params_t *params)
 255 {
 256         int err = snd_pcm_hw_refine_soft(pcm, params);
 257         params->fifo_size = 0;
 258         return err;
 259 }
 260
 261 static int snd_pcm_null_hw_params(snd_pcm_t *pcm ATTRIBUTE_UNUSED, snd_pcm_hw_params_t * params ATTRIBUTE_UNUSED)
 262 {
 263         return 0;
 264 }
 265
 266 static int snd_pcm_null_hw_free(snd_pcm_t *pcm ATTRIBUTE_UNUSED)
 267 {
 268         return 0;
 269 }
 270
 271 static int snd_pcm_null_sw_params(snd_pcm_t *pcm ATTRIBUTE_UNUSED, snd_pcm_sw_params_t * params ATTRIBUTE_UNUSED)
 272 {
 273         return 0;
 274 }
 275
 276 static int snd_pcm_null_mmap(snd_pcm_t *pcm)
 277 {
 278         snd_pcm_null_t *null = pcm->private_data;
 279         if (!(pcm->info & SND_PCM_INFO_MMAP)) {
 280                 size_t size = snd_pcm_frames_to_bytes(pcm, pcm->buffer_size);
 281                 int id = shmget(IPC_PRIVATE, size, 0666);
 282                 if (id < 0) {
 283                         SYSERR("shmget failed");
 284                         return -errno;
 285                 }
 286                 null->shmid = id;
 287         }
 288         return 0;
 289 }
 290
 291 static int snd_pcm_null_munmap(snd_pcm_t *pcm)
 292 {
 293         snd_pcm_null_t *null = pcm->private_data;
 294         if (shmctl(null->shmid, IPC_RMID, 0) < 0) {
 295                 SYSERR("shmctl IPC_RMID failed");
 296                         return -errno;
 297         }
 298         return 0;
 299 }
 300
 301 static void snd_pcm_null_dump(snd_pcm_t *pcm, snd_output_t *out)
 302 {
 303         snd_output_printf(out, "Null PCM\n");
 304         if (pcm->setup) {
 305                 snd_output_printf(out, "Its setup is:\n");
 306                 snd_pcm_dump_setup(pcm, out);
 307         }
 308 }
 309
 310 static snd_pcm_ops_t snd_pcm_null_ops = {
 311         close: snd_pcm_null_close,
 312         info: snd_pcm_null_info,
 313         hw_refine: snd_pcm_null_hw_refine,
 314         hw_params: snd_pcm_null_hw_params,
 315         hw_free: snd_pcm_null_hw_free,
 316         sw_params: snd_pcm_null_sw_params,
 317         channel_info: snd_pcm_null_channel_info,
 318         dump: snd_pcm_null_dump,
 319         nonblock: snd_pcm_null_nonblock,
 320         async: snd_pcm_null_async,
 321         mmap: snd_pcm_null_mmap,
 322         munmap: snd_pcm_null_munmap,
 323 };
 324
 325 static snd_pcm_fast_ops_t snd_pcm_null_fast_ops = {
 326         status: snd_pcm_null_status,
 327         state: snd_pcm_null_state,
 328         hwsync: snd_pcm_null_hwsync,
 329         delay: snd_pcm_null_delay,
 330         prepare: snd_pcm_null_prepare,
 331         reset: snd_pcm_null_reset,
 332         start: snd_pcm_null_start,
 333         drop: snd_pcm_null_drop,
 334         drain: snd_pcm_null_drain,
 335         pause: snd_pcm_null_pause,
 336         rewind: snd_pcm_null_rewind,
 337         resume: snd_pcm_null_resume,
 338         writei: snd_pcm_null_writei,
 339         writen: snd_pcm_null_writen,
 340         readi: snd_pcm_null_readi,
 341         readn: snd_pcm_null_readn,
 342         avail_update: snd_pcm_null_avail_update,
 343         mmap_commit: snd_pcm_null_mmap_commit,
 344 };
 345
 346 /**
 347  * \brief Creates a new null PCM
 348  * \param pcmp Returns created PCM handle
 349  * \param name Name of PCM
 350  * \param stream Stream type
 351  * \param mode Stream mode
 352  * \retval zero on success otherwise a negative error code
 353  * \warning Using of this function might be dangerous in the sense
 354  *          of compatibility reasons. The prototype might be freely
 355  *          changed in future.
 356  */
 357 int snd_pcm_null_open(snd_pcm_t **pcmp, const char *name, snd_pcm_stream_t stream, int mode)
 358 {
 359         snd_pcm_t *pcm;
 360         snd_pcm_null_t *null;
 361         int fd;
 362         int err;
 363         assert(pcmp);
 364         if (stream == SND_PCM_STREAM_PLAYBACK) {
 365                 fd = open("/dev/null", O_WRONLY);
 366                 if (fd < 0) {
 367                         SYSERR("Cannot open /dev/null");
 368                         return -errno;
 369                 }
 370         } else {
 371                 fd = open("/dev/full", O_RDONLY);
 372                 if (fd < 0) {
 373                         SYSERR("Cannot open /dev/full");
 374                         return -errno;
 375                 }
 376         }
 377         null = calloc(1, sizeof(snd_pcm_null_t));
 378         if (!null) {
 379                 close(fd);
 380                 return -ENOMEM;
 381         }
 382         null->poll_fd = fd;
 383         null->state = SND_PCM_STATE_OPEN;
 384
 385         err = snd_pcm_new(&pcm, SND_PCM_TYPE_NULL, name, stream, mode);
 386         if (err < 0) {
 387                 close(fd);
 388                 free(null);
 389                 return err;
 390         }
 391         pcm->ops = &snd_pcm_null_ops;
 392         pcm->fast_ops = &snd_pcm_null_fast_ops;
 393         pcm->private_data = null;
 394         pcm->poll_fd = fd;
 395         snd_pcm_set_hw_ptr(pcm, &null->hw_ptr, -1, 0);
 396         snd_pcm_set_appl_ptr(pcm, &null->appl_ptr, -1, 0);
 397         *pcmp = pcm;
 398
 399         return 0;
 400 }
 401
 402 /*! \page pcm_plugins
 403
 404 \section pcm_plugins_null Plugin: Null
 405
 406 This plugin discards contents of a PCM stream or creates a stream with zero
 407 samples.
 408
 409 Note: This implementation uses devices /dev/null (playback, must be writable)
 410 and /dev/full (capture, must be readable).
 411
 412 \code
 413 pcm.name {
 414         type null               # Null PCM
 415 }
 416 \endcode
 417
 418 \subsection pcm_plugins_null_funcref Function reference
 419
 420 <UL>
 421   <LI>snd_pcm_null_open()
 422   <LI>_snd_pcm_null_open()
 423 </UL>
 424
 425 */
 426
 427 /**
 428  * \brief Creates a new Null PCM
 429  * \param pcmp Returns created PCM handle
 430  * \param name Name of PCM
 431  * \param root Root configuration node
 432  * \param conf Configuration node with Null PCM description
 433  * \param stream Stream type
 434  * \param mode Stream mode
 435  * \retval zero on success otherwise a negative error code
 436  * \warning Using of this function might be dangerous in the sense
 437  *          of compatibility reasons. The prototype might be freely
 438  *          changed in future.
 439  */
 440 int _snd_pcm_null_open(snd_pcm_t **pcmp, const char *name,
 441                        snd_config_t *root ATTRIBUTE_UNUSED, snd_config_t *conf,
 442                        snd_pcm_stream_t stream, int mode)
 443 {
 444         snd_config_iterator_t i, next;
 445         snd_config_for_each(i, next, conf) {
 446                 snd_config_t *n = snd_config_iterator_entry(i);
 447                 const char *id;
 448                 if (snd_config_get_id(n, &id) < 0)
 449                         continue;
 450                 if (snd_pcm_conf_generic_id(id))
 451                         continue;
 452                 SNDERR("Unknown field %s", id);
 453                 return -EINVAL;
 454         }
 455         return snd_pcm_null_open(pcmp, name, stream, mode);
 456 }
 457 #ifndef DOC_HIDDEN
 458 SND_DLSYM_BUILD_VERSION(_snd_pcm_null_open, SND_PCM_DLSYM_VERSION);
 459 #endif