Re: [PATCH] rust: allow `unknown_lints` in the generated bindings

[Gary Guo]

On Fri Sep 11, 2026 at 8:52 PM BST, John Hubbard wrote:
> A build with bindgen 0.73.2 and the minimum supported rustc, 1.85.0,
> emits about 12000 `unknown_lints` warnings, all of them in bindgen's
> generated output. CONFIG_WERROR or W=e turns them into a failed build.
>
> Starting with 0.73.0, bindgen writes `#[allow(unnecessary_transmutes)]`
> onto every bitfield accessor and constructor it generates. It does so
> regardless of `--rust-target`, which rust/Makefile already sets to 1.85.
> That lint exists only since rustc 1.88.0.
>
> Commit 7129ea6e242b ("rust: clean Rust 1.88.0's `unnecessary_transmutes`
> lint") made the kernel's own attribute conditional, to keep
> `unknown_lints` enabled. That condition cannot be put on an attribute
> that bindgen writes.
>
> Allow `unknown_lints` in the bindings and uapi crates.

Already fixed: https://lore.kernel.org/rust-for-linux/CANiq72=fEYa1PygH-XJHONQKqf53dZFuGc-Z7wd4M7yeREq8Vw@xxxxxxxxxxxxxx/

Best,
Gary

>
> Cc: stable@xxxxxxxxxxxxxxx # Needed in 6.12.y and later (Rust is pinned in older LTSs).
> Assisted-by: LLM
> Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
> ---
>  rust/bindings/lib.rs | 2 ++
>  rust/uapi/lib.rs     | 2 ++
>  2 files changed, 4 insertions(+)
>
> diff --git a/rust/bindings/lib.rs b/rust/bindings/lib.rs
> index 812f8e5a08d5..a3af57d7d137 100644
> --- a/rust/bindings/lib.rs
> +++ b/rust/bindings/lib.rs
> @@ -26,6 +26,8 @@
>  #[allow(clippy::ptr_as_ptr)]
>  #[allow(clippy::ref_as_ptr)]
>  #[allow(clippy::undocumented_unsafe_blocks)]
> +// `bindgen` emits `#[allow(...)]` for lints newer than the minimum supported `rustc`.
> +#[allow(unknown_lints)]
>  #[cfg_attr(CONFIG_RUSTC_HAS_UNNECESSARY_TRANSMUTES, allow(unnecessary_transmutes))]
>  #[cfg_attr(
>      CONFIG_RUSTC_HAS_SUSPICIOUS_RUNTIME_SYMBOL_DEFINITIONS,
> diff --git a/rust/uapi/lib.rs b/rust/uapi/lib.rs
> index 797ead5b5626..361b490acc25 100644
> --- a/rust/uapi/lib.rs
> +++ b/rust/uapi/lib.rs
> @@ -23,6 +23,8 @@
>      unreachable_pub,
>      unsafe_op_in_unsafe_fn
>  )]
> +// `bindgen` emits `#[allow(...)]` for lints newer than the minimum supported `rustc`.
> +#![allow(unknown_lints)]
>  #![cfg_attr(CONFIG_RUSTC_HAS_UNNECESSARY_TRANSMUTES, allow(unnecessary_transmutes))]
>  #![cfg_attr(
>      CONFIG_RUSTC_HAS_SUSPICIOUS_RUNTIME_SYMBOL_DEFINITIONS,
>
> base-commit: 3026c6e4f223bdded6448fefe53ff85d9cbe51bd