IOC_NRMASK

ioctl_id

Constant IOC_NRMASK 

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

Bitmask for valid ioctl(2) call identifiers.

This is applied to the unshifted call identifier.

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