ioc_play_msf
struct ioc_play_msf *args
= (struct ioc_play_msf *) addr;
struct ioc_play_msf *args = (struct ioc_play_msf *)ap->a_data;
#define CDIOCPLAYMSF _IOW('c',25,struct ioc_play_msf)
struct ioc_play_msf a;