snd_ctl_elem_id 768 include/sound/asound.h struct snd_ctl_elem_id { snd_ctl_elem_id 856 include/sound/asound.h SNDRV_CTL_IOCTL_ELEM_LOCK = _IOW('U', 0x14, struct snd_ctl_elem_id), snd_ctl_elem_id 857 include/sound/asound.h SNDRV_CTL_IOCTL_ELEM_UNLOCK = _IOW('U', 0x15, struct snd_ctl_elem_id), snd_ctl_elem_id 861 include/sound/asound.h SNDRV_CTL_IOCTL_ELEM_REMOVE = _IOWR('U', 0x19, struct snd_ctl_elem_id),