_LINUX_IOC_SIZEBITS   48 compat/linux/linux_ioctl.h #define	_LINUX_IOC_SIZEMASK	((1 << _LINUX_IOC_SIZEBITS) - 1)
_LINUX_IOC_SIZEBITS   53 compat/linux/linux_ioctl.h #define	_LINUX_IOC_DIRSHIFT	(_LINUX_IOC_SIZESHIFT + _LINUX_IOC_SIZEBITS)