ioc_play_blocks
struct ioc_play_blocks tt_blocks;
int mcd_playblocks(struct mcd_softc *, struct ioc_play_blocks *);
mcd_playblocks(struct mcd_softc *sc, struct ioc_play_blocks *p)
struct ioc_play_blocks *args = addr;
#define CDIOCPLAYBLOCKS _IOW('c', 2, struct ioc_play_blocks)
struct ioc_play_blocks t;