typedef struct snd_mixer_callbacks { void *private_data; /* should be used with an application */ void (*rebuild) (void *private_data); void (*element) (void *private_data, int cmd, snd_mixer_eid_t * eid); void (*group) (void *private_data, int cmd, snd_mixer_gid_t * gid); void *reserved[28]; /* reserved for the future use - must be NULL!!! */ } snd_mixer_callbacks_t;REFERENCE