Re: [PATCH 06/11] rust: macros: convert `#[export]` to use `syn`

Tamir Duberstein
2026-01-04T22:56:43Z

On Thu, Dec 11, 2025 at 2:29 PM Gary Guo <gary@kernel.org> wrote:
>
> From: Gary Guo <gary@garyguo.net>
>
> This eliminates the custom `function_name` helper.
>
> Signed-off-by: Gary Guo <gary@garyguo.net>

Reviewed-by: Tamir Duberstein <tamird@gmail.com>

> ---
> rust/macros/export.rs | 24 +++++++++---------------
> rust/macros/helpers.rs | 18 ------------------
> rust/macros/lib.rs | 5 +++--
> 3 files changed, 12 insertions(+), 35 deletions(-)
>
> diff --git a/rust/macros/export.rs b/rust/macros/export.rs
> index 92d9b30971929..6d53521f62fc7 100644
> --- a/rust/macros/export.rs
> +++ b/rust/macros/export.rs
> @@ -3,19 +3,14 @@
> use proc_macro2::TokenStream;
> use quote::quote;
>
> -use crate::helpers::function_name;
> -
> /// Please see [`crate::export`] for documentation.
> -pub(crate) fn export(_attr: TokenStream, ts: TokenStream) -> TokenStream {
> - let Some(name) = function_name(ts.clone()) else {
> - return "::core::compile_error!(\"The #[export] attribute must be used on a function.\");"
> - .parse::<TokenStream>()
> - .unwrap();
> - };
> +pub(crate) fn export(f: syn::ItemFn) -> TokenStream {
> + let name = &f.sig.ident;
>
> - // This verifies that the function has the same signature as the declaration generated by
> - // bindgen. It makes use of the fact that all branches of an if/else must have the same type.
> - let signature_check = quote!(
> + quote! {
> + // This verifies that the function has the same signature as the declaration generated by
> + // bindgen. It makes use of the fact that all branches of an if/else must have the same
> + // type.
> const _: () = {
> if true {
> ::kernel::bindings::#name
> @@ -23,9 +18,8 @@ pub(crate) fn export(_attr: TokenStream, ts: TokenStream) -> TokenStream {
> #name
> };
> };
> - );
> -
> - let no_mangle = quote!(#[no_mangle]);
>
> - TokenStream::from_iter([signature_check, no_mangle, ts])
> + #[no_mangle]
> + #f
> + }
> }
> diff --git a/rust/macros/helpers.rs b/rust/macros/helpers.rs
> index f6bbdb02d9d7d..754c827cc21e1 100644
> --- a/rust/macros/helpers.rs
> +++ b/rust/macros/helpers.rs
> @@ -2,7 +2,6 @@
>
> use proc_macro2::{
> token_stream,
> - Ident,
> TokenStream,
> TokenTree, //
> };
> @@ -50,23 +49,6 @@ pub(crate) fn value(&self) -> String {
> }
> }
>
> -/// Given a function declaration, finds the name of the function.
> -pub(crate) fn function_name(input: TokenStream) -> Option<Ident> {
> - let mut input = input.into_iter();
> - while let Some(token) = input.next() {
> - match token {
> - TokenTree::Ident(i) if i.to_string() == "fn" => {
> - if let Some(TokenTree::Ident(i)) = input.next() {
> - return Some(i);
> - }
> - return None;
> - }
> - _ => continue,
> - }
> - }
> - None
> -}
> -
> pub(crate) fn file() -> String {
> #[cfg(not(CONFIG_RUSTC_HAS_SPAN_FILE))]
> {
> diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs
> index 4e440deaed853..870a42d41ac91 100644
> --- a/rust/macros/lib.rs
> +++ b/rust/macros/lib.rs
> @@ -206,8 +206,9 @@ pub fn vtable(attr: TokenStream, input: TokenStream) -> TokenStream {
> /// This macro is *not* the same as the C macros `EXPORT_SYMBOL_*`. All Rust symbols are currently
> /// automatically exported with `EXPORT_SYMBOL_GPL`.
> #[proc_macro_attribute]
> -pub fn export(attr: TokenStream, ts: TokenStream) -> TokenStream {
> - export::export(attr.into(), ts.into()).into()
> +pub fn export(attr: TokenStream, input: TokenStream) -> TokenStream {
> + parse_macro_input!(attr as syn::parse::Nothing);
> + export::export(parse_macro_input!(input)).into()
> }
>
> /// Like [`core::format_args!`], but automatically wraps arguments in [`kernel::fmt::Adapter`].
> --
> 2.51.2
>