alsa-lib/include/mixer.h

/****************************************************************************
 *                                                                          *
 *                               mixer.h                                    *
 *                           Mixer Interface                                *
 *                                                                          *
 ****************************************************************************/

typedef struct snd_mixer_callbacks {
	void *private_data;	/* should be used by application */
	void (*channel_was_changed) (void *private_data, int channel);
	void (*switch_was_changed) (void *private_data, int switchn);
	void *reserved[14];	/* reserved for future use - must be NULL!!! */
} snd_mixer_callbacks_t;

#ifdef __cplusplus
extern "C" {
#endif

int snd_mixer_open(void **handle, int card, int device);
int snd_mixer_close(void *handle);
int snd_mixer_file_descriptor(void *handle);
int snd_mixer_channels(void *handle);
int snd_mixer_info(void *handle, snd_mixer_info_t * info);
int snd_mixer_exact_mode(void *handle, int enable);
int snd_mixer_channel(void *handle, const char *channel_id);
int snd_mixer_channel_info(void *handle, int channel, snd_mixer_channel_info_t * info);
int snd_mixer_channel_read(void *handle, int channel, snd_mixer_channel_t * data);
int snd_mixer_channel_write(void *handle, int channel, snd_mixer_channel_t * data);
int snd_mixer_switches(void *handle);
int snd_mixer_switch_read(void *handle, int switchn, snd_mixer_switch_t * data);
int snd_mixer_switch_write(void *handle, int switchn, snd_mixer_switch_t * data);
int snd_mixer_read(void *handle, snd_mixer_callbacks_t * callbacks);

#ifdef __cplusplus
}
#endif