[alsa-devel] Simple Mixer help

[Bram Bos]

I want to get access to the ALSA Simple Mixer interface, but rather than
the 'default' sound device I want to target a specific USB sound device.

I'm at a loss how to refer to it...  I am using a modified version of the
code below but I have no idea what to replace the "card" and "selem_name"
strings with. The device name? The 'hwX.Y' string?

And do I need to change the index#?

Too many variables to solve this by trial and error.
Any hints appreciated!

void SetAlsaMasterVolume(long volume){
    long min, max;
    snd_mixer_t *handle;
    snd_mixer_selem_id_t *sid;
    const char *card = "default";
    const char *selem_name = "Master";

    snd_mixer_open(&handle, 0);
    snd_mixer_attach(handle, card);
    snd_mixer_selem_register(handle, NULL, NULL);
    snd_mixer_load(handle);

    snd_mixer_selem_id_alloca(&sid);
    snd_mixer_selem_id_set_index(sid, 0);
    snd_mixer_selem_id_set_name(sid, selem_name);
    snd_mixer_elem_t* elem = snd_mixer_find_selem(handle, sid);

    snd_mixer_selem_get_playback_volume_range(elem, &min, &max);
    snd_mixer_selem_set_playback_volume_all(elem, volume * max / 100);

    snd_mixer_close(handle);}