ioc_vol
struct ioc_vol tt_vol;
struct ioc_vol *arg = addr;
struct ioc_vol *arg = addr;
static int cd_getvol(struct cd_softc *, struct ioc_vol *, int);
static int cd_setvol(struct cd_softc *, const struct ioc_vol *, int);
cd_getvol(struct cd_softc *cd, struct ioc_vol *arg, int flags)
cd_setvol(struct cd_softc *cd, const struct ioc_vol *arg, int flags)
#define CDIOCGETVOL _IOR('c', 10, struct ioc_vol)
#define CDIOCSETVOL _IOW('c', 11, struct ioc_vol)
struct ioc_vol v;
struct ioc_vol v;