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sound_operations.c
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sound_operations.c
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/*
* simple Linux sound library
* Copyright (C) 2017, 2018 Ricardo Biehl Pasquali
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/*
* 19/07/2017
*
* Synchronize, start, stop.
*/
#ifdef BUILDING_FOR_GOOGLE_ANDROID
#include <bits/timespec.h>
#endif
/* ALSA header */
#include <sound/asound.h>
#include <sys/ioctl.h> /* ioctl() */
#include <time.h> /* struct timespec */
#include "sound_global.h"
#include "sound_operations.h" /* SND_SYNC_* */
/*
* synchronize hw_ptr, appl_ptr and avail_min
*
* If status and control are mmaped, ioctl() is called
* only when HWSYNC operation is requested.
*
* Flags (defined in sound_operations.h):
*
* SND_SYNC_GET: SNDRV_PCM_SYNC_PTR_APPL | SNDRV_PCM_SYNC_PTR_AVAIL_MIN
* SND_SYNC_SET: 0
* SND_SYNC_HW: SNDRV_PCM_SYNC_PTR_HWSYNC
*/
int
snd_sync(struct snd *snd, int flags)
{
if (snd->sync_ptr == NULL) {
/* status and control are mmaped */
if (flags & SND_SYNC_HW) {
if (ioctl(snd->fd, SNDRV_PCM_IOCTL_HWSYNC) < 0)
return -1;
}
} else {
snd->sync_ptr->flags = flags;
if (ioctl(snd->fd, SNDRV_PCM_IOCTL_SYNC_PTR, snd->sync_ptr) < 0)
return -1;
}
return 0;
}
/*
* Start and drop actions
* ======================
*/
int
snd_start(struct snd *pcm)
{
if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_PREPARE) == -1 ||
ioctl(pcm->fd, SNDRV_PCM_IOCTL_START) == -1)
return -1;
return 0;
}
/* DROP is internally the stop action */
int
snd_stop(struct snd *pcm)
{
if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_DROP) == -1)
return -1;
return 0;
}
/*
* About SNDRV_PCM_IOCTL_STATUS ioctl
* ==================================
*
* It's not interesting to store snd_pcm_status structure
* after STATUS ioctl because much of the information
* returned is the same as the SYNC_PTR or HWSYNC
* ioctl.
*
* It's being used only to get trigger timestamp.
*
* Trigger timestamp is set in START, STOP/DROP, PAUSE,
* SUSPEND and RESUME actions.
*/
int
snd_trigger_tstamp(struct snd *pcm, struct timespec *tstamp)
{
struct snd_pcm_status status;
if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_STATUS, &status) < 0)
return -1;
*tstamp = status.trigger_tstamp;
return 0;
}