IOC_TYPEMASK

ioctl_id

Constant IOC_TYPEMASK 

Source 
pub const IOC_TYPEMASK: IoctlId = _; // 255u64
Expand description

Bitmask for valid ioctl(2) type identifiers.

This is applied to the unshifted type identifier.

Reference: include/uapi/asm-generic/ioctl.h