Function wlc_sys_with_elogind::wlc_event_loop_add_fd

pub unsafe extern "C" fn wlc_event_loop_add_fd(
    fd: c_int, 
    mask: u32, 
    cb: Option<unsafe extern "C" fn(_: c_int, _: u32, _: *mut c_void) -> c_int>, 
    userdata: *mut c_void
) -> *mut wlc_event_source

Add fd to event loop. Return value of callback is unused, you should return 0.