Function ctl_code 

pub const fn ctl_code(
    device_type: u32,
    function: u32,
    method: u32,
    access: u32,
) -> u32

Build a device control code, equivalent to the Win32 CTL_CODE macro:

((device_type) << 16) | ((access) << 14) | ((function) << 2) | (method)

function numbers below 0x800 are reserved by Microsoft; custom codes use 0x800..=0xFFF.