Functional C macros are not expanded.

So I'm generating bindings to <linux/uinput>. This works pretty well, but two c macros in particular do not produce any bindings in the output. Reduced input below:

Input C/C++ Header

#define UI_DEV_CREATE		_IO(UINPUT_IOCTL_BASE, 1)
#define UI_DEV_DESTROY		_IO(UINPUT_IOCTL_BASE, 2)

Bindgen Invocation

let bindings = bindgen::Builder::default()
        .no_unstable_rust()
        .header("wrapper/wrapper.h")
        .expect("Unable to generate bindings").

wrapper.h looks like this:

#include <linux/uinput.h>

Actual Results

No constant UI_DEV_CREATE or UI_DEV_DESTROY generated in output.

Expected Results

Constants UI_DEV_CREATE and UI_DEV_DESTROY generated in output.

I'm not really that familiar with the kernel macro _IO and not sure if this is technically even possible, but I figured to report just to get a more professional opinion. If it's not possible, workarounds welcome.

Start with the reduced macros in linux/uinput.h and the shown bindgen::Builder invocation, then trace bindgen's handling of functional C macros and ioctl-style expressions. Compare generated output with the expected UI_DEV_CREATE and UI_DEV_DESTROY constants; done means the constants are generated or the limitation and workaround are clearly documented.