linux-kernel - Re: [PATCH] kbuild: rust: add rustc-min-version support function

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Message-ID: <20250213-masked-wombat-of-painting-8afb53@buildd>
Date: Thu, 13 Feb 2025 08:19:49 +0100
From: Nicolas Schier <n.schier@....de>
To: Miguel Ojeda <ojeda@...nel.org>
Cc: Masahiro Yamada <masahiroy@...nel.org>,
	Jonathan Corbet <corbet@....net>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>,
	Nathan Chancellor <nathan@...nel.org>, linux-kbuild@...r.kernel.org,
	linux-doc@...r.kernel.org,
	moderated for non-subscribers <linux-arm-kernel@...ts.infradead.org>,
	Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
	Danilo Krummrich <dakr@...nel.org>, rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org, patches@...ts.linux.dev
Subject: Re: [PATCH] kbuild: rust: add rustc-min-version support function

On Mon, Feb 10, 2025 at 05:42:45PM +0100, Miguel Ojeda wrote:
> Introduce `rustc-min-version` support function that mimics
> `{gcc,clang}-min-version` ones, following commit 88b61e3bff93
> ("Makefile.compiler: replace cc-ifversion with compiler-specific macros").
> 
> In addition, use it in the first use case we have in the kernel (which
> was done independently to minimize the changes needed for the fix).
> 
> Signed-off-by: Miguel Ojeda <ojeda@...nel.org>
> ---
> This is based on top of the fix so that the fix remains as simple as
> possible:
> 
>     https://lore.kernel.org/rust-for-linux/20250210163732.281786-1-ojeda@kernel.org/
> 
>  Documentation/kbuild/makefiles.rst | 14 ++++++++++++++
>  arch/arm64/Makefile                |  2 +-
>  scripts/Makefile.compiler          |  4 ++++
>  3 files changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst
> index d36519f194dc..2608aa32c762 100644
> --- a/Documentation/kbuild/makefiles.rst
> +++ b/Documentation/kbuild/makefiles.rst
> @@ -670,6 +670,20 @@ cc-cross-prefix
>              endif
>      endif
> 
> +$(RUSTC) support functions
> +--------------------------
> +
> +rustc-min-version
> +  rustc-min-version tests if the value of $(CONFIG_RUSTC_VERSION) is greater
> +  than or equal to the provided value and evaluates to y if so.
> +
> +  Example::
> +
> +    rustflags-$(call rustc-min-version, 108500) := -Cfoo
> +
> +  In this example, rustflags-y will be assigned the value -Cfoo if
> +  $(CONFIG_RUSTC_VERSION) is >= 1.85.0.
> +
>  $(LD) support functions
>  -----------------------
> 
> diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
> index 2b25d671365f..1d5dfcd1c13e 100644
> --- a/arch/arm64/Makefile
> +++ b/arch/arm64/Makefile
> @@ -48,7 +48,7 @@ KBUILD_CFLAGS	+= $(CC_FLAGS_NO_FPU) \
>  KBUILD_CFLAGS	+= $(call cc-disable-warning, psabi)
>  KBUILD_AFLAGS	+= $(compat_vdso)
> 
> -ifeq ($(call test-ge, $(CONFIG_RUSTC_VERSION), 108500),y)
> +ifeq ($(call rustc-min-version, 108500),y)
>  KBUILD_RUSTFLAGS += --target=aarch64-unknown-none-softfloat
>  else
>  KBUILD_RUSTFLAGS += --target=aarch64-unknown-none -Ctarget-feature="-neon"
> diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
> index 8c1029687e2e..8956587b8547 100644
> --- a/scripts/Makefile.compiler
> +++ b/scripts/Makefile.compiler
> @@ -67,6 +67,10 @@ gcc-min-version = $(call test-ge, $(CONFIG_GCC_VERSION), $1)
>  # Usage: cflags-$(call clang-min-version, 110000) += -foo
>  clang-min-version = $(call test-ge, $(CONFIG_CLANG_VERSION), $1)
> 
> +# rustc-min-version
> +# Usage: rustc-$(call rustc-min-version, 108500) += -Cfoo
> +rustc-min-version = $(call test-ge, $(CONFIG_RUSTC_VERSION), $1)
> +
>  # ld-option
>  # Usage: KBUILD_LDFLAGS += $(call ld-option, -X, -Y)
>  ld-option = $(call try-run, $(LD) $(KBUILD_LDFLAGS) $(1) -v,$(1),$(2),$(3))
> --
> 2.48.1

Reviewed-by: Nicolas Schier <n.schier@....de>