IOC_VOID
if (cmd & (IOC_IN | IOC_VOID))
if ((com & IOC_VOID) == 0 && size > sizeof(ubuf.stkbuf)) {
if (com & IOC_VOID) {
case IOC_VOID:
case IOC_VOID:
case IOC_VOID:
case IOC_VOID:
case IOC_VOID:
case IOC_VOID:
#define IOC_DIRMASK (IOC_VOID|IOC_OUT|IOC_IN)
#define _IO(g,n) _IOC(IOC_VOID, (g), (n), 0)
#define _IOWINT(g,n) _IOC(IOC_VOID, (g), (n), sizeof(int))