Hi, --- On Tue, Nov 4, 2008 at 6:27 AM, Zhao, Joe <jozhao [ at ] ciena [ dot ] com> wrote: | Can we define the magic number with the value greater than 0xFF? Where | is this magic number used by linux kernel? \-- The size of _IOC_TYPEBITS is defined as 8. So, the maximum size is 0xFF. http://lxr.linux.no/linux+v2.6.27.4/include/asm-generic/ioctl.h#L23 Also read: http://lxr.linux.no/linux+v2.6.27.4/Documentation/ioctl-number.txt SK -- Shakthi Kannan http://www.shakthimaan.com