Message-ID: <CAJ-ks9m8nfQoDp3ymF7Yhvp076t+55bZzJ7wCQqXhu6sjGBUNg@mail.gmail.com>
Date: Wed, 7 Jan 2026 11:40:17 -0500
From: Tamir Duberstein <tamird@...il.com>
To: Gary Guo <gary@...yguo.net>
Cc: Miguel Ojeda <ojeda@...nel.org>, Boqun Feng <boqun.feng@...il.com>, 
	Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
	Benno Lossin <lossin@...nel.org>, Andreas Hindborg <a.hindborg@...nel.org>, 
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>, 
	Danilo Krummrich <dakr@...nel.org>, Fiona Behrens <me@...enk.dev>, rust-for-linux@...r.kernel.org, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Christian Schrefl <chrisi.schrefl@...il.com>, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 01/11] rust: pin-init: internal: remove proc-macro[2]
 and quote workarounds

On Wed, Jan 7, 2026 at 11:29 AM Gary Guo <gary@...nel.org> wrote:
>
> From: Benno Lossin <lossin@...nel.org>
>
> The kernel only had the `proc-macro` library available, whereas the
> user-space version also used `proc-macro2` and `quote`. Now both are
> available to the kernel, making it possible to remove the workarounds.
>
> Clippy complains about unnecessary `.to_string()` as `proc-macro2`
> provides additional `PartialEq` impl, so they are removed.
>
> Signed-off-by: Benno Lossin <lossin@...nel.org>
> Co-developed-by: Gary Guo <gary@...yguo.net>
> Signed-off-by: Gary Guo <gary@...yguo.net>

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

> ---
>  rust/Makefile                             | 16 ++++++++++------
>  rust/pin-init/internal/src/helpers.rs     |  7 ++-----
>  rust/pin-init/internal/src/lib.rs         | 16 ----------------
>  rust/pin-init/internal/src/pin_data.rs    | 18 ++++++------------
>  rust/pin-init/internal/src/pinned_drop.rs | 10 ++++------
>  rust/pin-init/internal/src/zeroable.rs    |  6 ++----
>  scripts/generate_rust_analyzer.py         |  2 +-
>  7 files changed, 25 insertions(+), 50 deletions(-)
>
> diff --git a/rust/Makefile b/rust/Makefile
> index 5d357dce1704d..96f0ac53ec0e8 100644
> --- a/rust/Makefile
> +++ b/rust/Makefile
> @@ -212,9 +212,10 @@ rustdoc-ffi: $(src)/ffi.rs rustdoc-core FORCE
>
>  rustdoc-pin_init_internal: private rustdoc_host = yes
>  rustdoc-pin_init_internal: private rustc_target_flags = --cfg kernel \
> -    --extern proc_macro --crate-type proc-macro
> +    --extern proc_macro --extern proc_macro2 --extern quote --extern syn \
> +    --crate-type proc-macro
>  rustdoc-pin_init_internal: $(src)/pin-init/internal/src/lib.rs \
> -    rustdoc-clean FORCE
> +    rustdoc-clean rustdoc-proc_macro2 rustdoc-quote rustdoc-syn FORCE
>         +$(call if_changed,rustdoc)
>
>  rustdoc-pin_init: private rustdoc_host = yes
> @@ -273,9 +274,10 @@ rusttestlib-macros: $(src)/macros/lib.rs \
>         +$(call if_changed,rustc_test_library)
>
>  rusttestlib-pin_init_internal: private rustc_target_flags = --cfg kernel \
> -    --extern proc_macro
> +    --extern proc_macro --extern proc_macro2 --extern quote --extern syn
>  rusttestlib-pin_init_internal: private rustc_test_library_proc = yes
> -rusttestlib-pin_init_internal: $(src)/pin-init/internal/src/lib.rs FORCE
> +rusttestlib-pin_init_internal: $(src)/pin-init/internal/src/lib.rs \
> +    rusttestlib-proc_macro2 rusttestlib-quote rusttestlib-syn FORCE
>         +$(call if_changed,rustc_test_library)
>
>  rusttestlib-pin_init: private rustc_target_flags = --extern pin_init_internal \
> @@ -547,8 +549,10 @@ $(obj)/$(libmacros_name): $(src)/macros/lib.rs $(obj)/libproc_macro2.rlib \
>      $(obj)/libquote.rlib $(obj)/libsyn.rlib FORCE
>         +$(call if_changed_dep,rustc_procmacro)
>
> -$(obj)/$(libpin_init_internal_name): private rustc_target_flags = --cfg kernel
> -$(obj)/$(libpin_init_internal_name): $(src)/pin-init/internal/src/lib.rs FORCE
> +$(obj)/$(libpin_init_internal_name): private rustc_target_flags = --cfg kernel \
> +    --extern proc_macro2 --extern quote --extern syn
> +$(obj)/$(libpin_init_internal_name): $(src)/pin-init/internal/src/lib.rs \
> +       $(obj)/libproc_macro2.rlib $(obj)/libquote.rlib $(obj)/libsyn.rlib FORCE
>         +$(call if_changed_dep,rustc_procmacro)
>
>  quiet_cmd_rustc_library = $(if $(skip_clippy),RUSTC,$(RUSTC_OR_CLIPPY_QUIET)) L $@
> diff --git a/rust/pin-init/internal/src/helpers.rs b/rust/pin-init/internal/src/helpers.rs
> index 236f989a50f2f..90f85eaa41231 100644
> --- a/rust/pin-init/internal/src/helpers.rs
> +++ b/rust/pin-init/internal/src/helpers.rs
> @@ -1,9 +1,6 @@
>  // SPDX-License-Identifier: Apache-2.0 OR MIT
>
> -#[cfg(not(kernel))]
> -use proc_macro2 as proc_macro;
> -
> -use proc_macro::{TokenStream, TokenTree};
> +use proc_macro2::{TokenStream, TokenTree};
>
>  /// Parsed generics.
>  ///
> @@ -101,7 +98,7 @@ pub(crate) fn parse_generics(input: TokenStream) -> (Generics, Vec<TokenTree>) {
>                      1 => {
>                          // Here depending on the token, it might be a generic variable name.
>                          match tt.clone() {
> -                            TokenTree::Ident(i) if at_start && i.to_string() == "const" => {
> +                            TokenTree::Ident(i) if at_start && i == "const" => {
>                                  let Some(name) = toks.next() else {
>                                      // Parsing error.
>                                      break;
> diff --git a/rust/pin-init/internal/src/lib.rs b/rust/pin-init/internal/src/lib.rs
> index 297b0129a5bfd..4c4dc639ce823 100644
> --- a/rust/pin-init/internal/src/lib.rs
> +++ b/rust/pin-init/internal/src/lib.rs
> @@ -7,27 +7,11 @@
>  //! `pin-init` proc macros.
>
>  #![cfg_attr(not(RUSTC_LINT_REASONS_IS_STABLE), feature(lint_reasons))]
> -// Allow `.into()` to convert
> -// - `proc_macro2::TokenStream` into `proc_macro::TokenStream` in the user-space version.
> -// - `proc_macro::TokenStream` into `proc_macro::TokenStream` in the kernel version.
> -//   Clippy warns on this conversion, but it's required by the user-space version.
> -//
> -// Remove once we have `proc_macro2` in the kernel.
> -#![allow(clippy::useless_conversion)]
>  // Documentation is done in the pin-init crate instead.
>  #![allow(missing_docs)]
>
>  use proc_macro::TokenStream;
>
> -#[cfg(kernel)]
> -#[path = "../../../macros/quote.rs"]
> -#[macro_use]
> -#[cfg_attr(not(kernel), rustfmt::skip)]
> -mod quote;
> -#[cfg(not(kernel))]
> -#[macro_use]
> -extern crate quote;
> -
>  mod helpers;
>  mod pin_data;
>  mod pinned_drop;
> diff --git a/rust/pin-init/internal/src/pin_data.rs b/rust/pin-init/internal/src/pin_data.rs
> index 87d4a7eb1d35e..86a53b37cc660 100644
> --- a/rust/pin-init/internal/src/pin_data.rs
> +++ b/rust/pin-init/internal/src/pin_data.rs
> @@ -1,10 +1,8 @@
>  // SPDX-License-Identifier: Apache-2.0 OR MIT
>
> -#[cfg(not(kernel))]
> -use proc_macro2 as proc_macro;
> -
>  use crate::helpers::{parse_generics, Generics};
> -use proc_macro::{Group, Punct, Spacing, TokenStream, TokenTree};
> +use proc_macro2::{Group, Punct, Spacing, TokenStream, TokenTree};
> +use quote::quote;
>
>  pub(crate) fn pin_data(args: TokenStream, input: TokenStream) -> TokenStream {
>      // This proc-macro only does some pre-parsing and then delegates the actual parsing to
> @@ -28,7 +26,7 @@ pub(crate) fn pin_data(args: TokenStream, input: TokenStream) -> TokenStream {
>      // The name of the struct with ty_generics.
>      let struct_name = rest
>          .iter()
> -        .skip_while(|tt| !matches!(tt, TokenTree::Ident(i) if i.to_string() == "struct"))
> +        .skip_while(|tt| !matches!(tt, TokenTree::Ident(i) if i == "struct"))
>          .nth(1)
>          .and_then(|tt| match tt {
>              TokenTree::Ident(_) => {
> @@ -65,7 +63,7 @@ pub(crate) fn pin_data(args: TokenStream, input: TokenStream) -> TokenStream {
>          .into_iter()
>          .flat_map(|tt| {
>              // We ignore top level `struct` tokens, since they would emit a compile error.
> -            if matches!(&tt, TokenTree::Ident(i) if i.to_string() == "struct") {
> +            if matches!(&tt, TokenTree::Ident(i) if i == "struct") {
>                  vec![tt]
>              } else {
>                  replace_self_and_deny_type_defs(&struct_name, tt, &mut errs)
> @@ -98,11 +96,7 @@ fn replace_self_and_deny_type_defs(
>  ) -> Vec<TokenTree> {
>      match tt {
>          TokenTree::Ident(ref i)
> -            if i.to_string() == "enum"
> -                || i.to_string() == "trait"
> -                || i.to_string() == "struct"
> -                || i.to_string() == "union"
> -                || i.to_string() == "impl" =>
> +            if i == "enum" || i == "trait" || i == "struct" || i == "union" || i == "impl" =>
>          {
>              errs.extend(
>                  format!(
> @@ -119,7 +113,7 @@ fn replace_self_and_deny_type_defs(
>              );
>              vec![tt]
>          }
> -        TokenTree::Ident(i) if i.to_string() == "Self" => struct_name.clone(),
> +        TokenTree::Ident(i) if i == "Self" => struct_name.clone(),
>          TokenTree::Literal(_) | TokenTree::Punct(_) | TokenTree::Ident(_) => vec![tt],
>          TokenTree::Group(g) => vec![TokenTree::Group(Group::new(
>              g.delimiter(),
> diff --git a/rust/pin-init/internal/src/pinned_drop.rs b/rust/pin-init/internal/src/pinned_drop.rs
> index c4ca7a70b726a..cf8cd1c429849 100644
> --- a/rust/pin-init/internal/src/pinned_drop.rs
> +++ b/rust/pin-init/internal/src/pinned_drop.rs
> @@ -1,15 +1,13 @@
>  // SPDX-License-Identifier: Apache-2.0 OR MIT
>
> -#[cfg(not(kernel))]
> -use proc_macro2 as proc_macro;
> -
> -use proc_macro::{TokenStream, TokenTree};
> +use proc_macro2::{TokenStream, TokenTree};
> +use quote::quote;
>
>  pub(crate) fn pinned_drop(_args: TokenStream, input: TokenStream) -> TokenStream {
>      let mut toks = input.into_iter().collect::<Vec<_>>();
>      assert!(!toks.is_empty());
>      // Ensure that we have an `impl` item.
> -    assert!(matches!(&toks[0], TokenTree::Ident(i) if i.to_string() == "impl"));
> +    assert!(matches!(&toks[0], TokenTree::Ident(i) if i == "impl"));
>      // Ensure that we are implementing `PinnedDrop`.
>      let mut nesting: usize = 0;
>      let mut pinned_drop_idx = None;
> @@ -27,7 +25,7 @@ pub(crate) fn pinned_drop(_args: TokenStream, input: TokenStream) -> TokenStream
>          if i >= 1 && nesting == 0 {
>              // Found the end of the generics, this should be `PinnedDrop`.
>              assert!(
> -                matches!(tt, TokenTree::Ident(i) if i.to_string() == "PinnedDrop"),
> +                matches!(tt, TokenTree::Ident(i) if i == "PinnedDrop"),
>                  "expected 'PinnedDrop', found: '{tt:?}'"
>              );
>              pinned_drop_idx = Some(i);
> diff --git a/rust/pin-init/internal/src/zeroable.rs b/rust/pin-init/internal/src/zeroable.rs
> index e0ed3998445cf..d8a5ef3883f4b 100644
> --- a/rust/pin-init/internal/src/zeroable.rs
> +++ b/rust/pin-init/internal/src/zeroable.rs
> @@ -1,10 +1,8 @@
>  // SPDX-License-Identifier: GPL-2.0
>
> -#[cfg(not(kernel))]
> -use proc_macro2 as proc_macro;
> -
>  use crate::helpers::{parse_generics, Generics};
> -use proc_macro::{TokenStream, TokenTree};
> +use proc_macro2::{TokenStream, TokenTree};
> +use quote::quote;
>
>  pub(crate) fn parse_zeroable_derive_input(
>      input: TokenStream,
> diff --git a/scripts/generate_rust_analyzer.py b/scripts/generate_rust_analyzer.py
> index 147d0cc940681..d31d938886589 100755
> --- a/scripts/generate_rust_analyzer.py
> +++ b/scripts/generate_rust_analyzer.py
> @@ -123,7 +123,7 @@ def generate_crates(srctree, objtree, sysroot_src, external_src, cfgs, core_edit
>      append_crate(
>          "pin_init_internal",
>          srctree / "rust" / "pin-init" / "internal" / "src" / "lib.rs",
> -        [],
> +        ["std", "proc_macro", "proc_macro2", "quote", "syn"],
>          cfg=["kernel"],
>          is_proc_macro=True,
>      )
>
> base-commit: 9ace4753a5202b02191d54e9fdf7f9e3d02b85eb
> --
> 2.51.2
>

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