zIOC
#define S_IOCGETMODE (zIOC|01) /* return struct scc_mode */
#define S_IOCSETMODE (zIOC|02) /* set SCC from struct scc_mode */
#define S_IOCGETSTATS (zIOC|03) /* return sync data stats */
#define S_IOCCLRSTATS (zIOC|04) /* clear sync stats */
#define S_IOCGETSPEED (zIOC|05) /* return int baudrate */
#define S_IOCGETMRU (zIOC|06) /* return int max receive unit */
#define S_IOCSETMRU (zIOC|07) /* set max receive unit */
#define S_IOCGETMTU (zIOC|010) /* return int max transmission unit */
#define S_IOCSETMTU (zIOC|011) /* set max transmission unit */
#define S_IOCGETMCTL (zIOC|012) /* return current CD/CTS state */
#define S_IOCSETDTR (zIOC|013) /* Drive DTR signal */