osd-alsa.c

/*
 *	A Simple ALSA Volume Control via OSD
 *
 *	(c) 2012 Martin Mares <mj@ucw.cz>
 */

#undef DEBUG

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <getopt.h>
#include <alsa/asoundlib.h>

#include "util.h"
#include "osd.h"

static char *alsa_device = "default";
static char *mixer_control = "Master";
static int adjust_by;
static int want_mute = -1;

static snd_mixer_t *mixer;
static snd_mixer_elem_t *elem;

static void init_mixer(void)
{
  int err;

  if (err = snd_mixer_open(&mixer, 0))
    die("snd_mixer_open failed: error %d", err);

  if (err = snd_mixer_attach(mixer, alsa_device))
    die("snd_mixer_attach failed: error %d", err);

  if (err = snd_mixer_selem_register(mixer, NULL, NULL))
    die("snd_mixer_selem_register failed: error %d", err);

  if (err = snd_mixer_load(mixer))
    die("snd_mixer_load: error %d", err);

  for (elem = snd_mixer_first_elem(mixer); elem; elem = snd_mixer_elem_next(elem))
    {
      const char *name = snd_mixer_selem_get_name(elem);
      int index = snd_mixer_selem_get_index(elem);
      if (!strcmp(name, mixer_control) || index)
	{
	  if (snd_mixer_elem_get_type(elem) != SND_MIXER_ELEM_SIMPLE)
	    die("Unable to handle non-simple mixer controls");
	  if (!snd_mixer_selem_is_active(elem))
	    die("Selected mixer control is not active");
	  DBG("Found mixer control %s[%d]\n", name, index);
	  return;
	}
    }

  die("Unable to find mixer control %s", mixer_control);
}

static int get_mute(void)
{
  int mute_on = 0, mute_off = 0;

  if (snd_mixer_selem_has_playback_switch(elem))
    {
      for (snd_mixer_selem_channel_id_t ch=0; ch < SND_MIXER_SCHN_LAST; ch++)
	{
	  int val;
	  if (!snd_mixer_selem_get_playback_switch(elem, ch, &val))
	    {