ioc_play_track
struct ioc_play_track tt_track;
int mcd_playtracks(struct mcd_softc *, struct ioc_play_track *);
mcd_playtracks(struct mcd_softc *sc, struct ioc_play_track *p)
struct ioc_play_track *args = addr;
#define CDIOCPLAYTRACKS _IOW('c', 1, struct ioc_play_track)
struct ioc_play_track t;