SOUND_MIXER_IGAIN
#define SOUND_MASK_IGAIN (1 << SOUND_MIXER_IGAIN)
#define SOUND_MIXER_READ_IGAIN MIXER_READ(SOUND_MIXER_IGAIN)
#define SOUND_MIXER_WRITE_IGAIN MIXER_WRITE(SOUND_MIXER_IGAIN)
{ SOUND_MIXER_IGAIN, "Capture", 0 },