linux-kernel - Re: [PATCH] binder: use enum for binder ioctls

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Message-ID: <2023120936-decency-engraved-5346@gregkh>
Date:   Sat, 9 Dec 2023 10:05:32 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Alice Ryhl <aliceryhl@...gle.com>
Cc:     Arve Hjønnevåg <arve@...roid.com>,
        Todd Kjos <tkjos@...roid.com>,
        Martijn Coenen <maco@...roid.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Christian Brauner <christian@...uner.io>,
        Carlos Llamas <cmllamas@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Li Li <dualli@...gle.com>, linux-kernel@...r.kernel.org,
        kernel-team@...roid.com, rust-for-linux@...r.kernel.org
Subject: Re: [PATCH] binder: use enum for binder ioctls

On Fri, Dec 08, 2023 at 03:28:01PM +0000, Alice Ryhl wrote:
> All of the other constants in this file are defined using enums, so make
> the constants more consistent by defining the ioctls in an enum as well.
> 
> This is necessary for Rust Binder since the _IO macros are too
> complicated for bindgen to see that they expand to integer constants.
> Replacing the #defines with an enum forces bindgen to evaluate them
> properly, which allows us to access them from Rust.

Does this mean that we will have to wrap every ioctl definition in an
enum just to get access to it in rust code?

What makes these defines so magical that bindgen can't decode them?  Is
it just the complexity of the C preprocessor logic involved?  Any plans
for bindgen to resolve this?

Note, I'm not objecting to this patch (I'll queue it up next week when I
get the chance), just curious about the rust tooling side here.

thanks,

greg k-h