MAX_IOCTL_REPLY
#define VINUM_SETSTATE _IOC(IOC_IN | IOC_OUT, L, 76, MAX_IOCTL_REPLY)
#define VINUM_LABEL _IOC(IOC_IN | IOC_OUT, L, 81, MAX_IOCTL_REPLY)
#define VINUM_SETSTATE_FORCE _IOC(IOC_IN | IOC_OUT, L, 85, MAX_IOCTL_REPLY)
char msg[MAX_IOCTL_REPLY];