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References: <20220212130410.6901-17-ojeda@kernel.org> <0396e38b-f681-a035-b6ea-21127fdf5615@physik.fu-berlin.de>
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From:   Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Date:   Sat, 12 Feb 2022 19:57:02 +0100
Message-ID: <CANiq72=U3A-5LfbOThPoex9PfFg+UsHuMY33nbtLH=aK=odh0Q@mail.gmail.com>
Subject: Re: [PATCH v4 16/20] Kbuild: add Rust support
To:     John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc:     Miguel Ojeda <ojeda@kernel.org>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Antonio Terceiro <antonio.terceiro@linaro.org>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Adam Bratschi-Kaye <ark.email@gmail.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Boris-Chengbiao Zhou <bobo1239@web.de>,
        Boqun Feng <boqun.feng@gmail.com>,
        Borislav Petkov <bp@alien8.de>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Douglas Su <d0u9.su@outlook.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Dariusz Sosnowski <dsosnowski@dsosnowski.pl>,
        Daniel Xu <dxu@dxuuu.xyz>, Gary Guo <gary@garyguo.net>,
        Greg KH <gregkh@linuxfoundation.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
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        linux-riscv <linux-riscv@lists.infradead.org>,
        Russell King - ARM Linux admin <linux@armlinux.org.uk>,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
        =?UTF-8?B?TWlndWVsIENhw7Fv?= <macanroj@gmail.com>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Finn Behrens <me@kloenk.de>,
        Michal Marek <michal.lkml@markovi.net>,
        Ingo Molnar <mingo@redhat.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
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        Paul Mackerras <paulus@samba.org>,
        rust-for-linux <rust-for-linux@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Sven Van Asbroeck <thesven73@gmail.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Wedson Almeida Filho <wedsonaf@google.com>,
        Will Deacon <will@kernel.org>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@kernel.org>
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Hi John Paul,

On Sat, Feb 12, 2022 at 7:27 PM John Paul Adrian Glaubitz
<glaubitz@physik.fu-berlin.de> wrote:
>
> Is there any particular reason why this list excludes MIPS*, i386, big-endian
> PowerPC and SPARC targets which are already supported by the Rust programming
> language?

The variations we have so far were intended to showcase the Rust
support in several major architectures, rather than cover everything.
But as long as LLVM (& the kernel, i.e. ClangBuiltLinux) supports the
target (and as long there are no compiler/toolchain issues), you
should be able to try it.

> Are the arch/$ARCH/rust/target.json files everything that's needed for supporting
> the other targets?

Mostly -- there is also `rust/kernel/c_types.rs` and you may need to
tweak `rust/compiler_builtins.rs`, but not much more.

Note that for the target spec files, the short-term plan is to
generate dynamically the target spec file according to what the
architecture requests, instead of using these static files. Longer
term, we need a Rust-stable way to setup custom targets from upstream
`rustc` (though it is not clear yet how it will look, e.g. it could be
via command-line flags).

Cheers,
Miguel