Re: [PATCH 13/17] docs: add Rust documentation

From: Nick Desaulniers <ndesaulniers@google.com>
To: ojeda@kernel.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	rust-for-linux@vger.kernel.org, linux-kbuild@vger.kernel.org,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	Alex Gaynor <alex.gaynor@gmail.com>,
	Geoffrey Thomas <geofft@ldpreload.com>,
	Finn Behrens <me@kloenk.de>,
	Adam Bratschi-Kaye <ark.email@gmail.com>,
	Wedson Almeida Filho <wedsonaf@google.com>,
	Boqun Feng <boqun.feng@gmail.com>,
	Sumera Priyadarsini <sylphrenadin@gmail.com>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Sven Van Asbroeck <thesven73@gmail.com>,
	Gary Guo <gary@garyguo.net>,
	Boris-Chengbiao Zhou <bobo1239@web.de>,
	Fox Chen <foxhlchen@gmail.com>,
	Ayaan Zaidi <zaidi.ayaan@gmail.com>,
	Douglas Su <d0u9.su@outlook.com>, Yuki Okushi <jtitor@2k36.org>
Subject: Re: [PATCH 13/17] docs: add Rust documentation
Date: Wed, 14 Jul 2021 11:37:54 -0700	[thread overview]
Message-ID: <CAKwvOdmei2Ckfk5xgkvo8wEXEFK=Yv5-yjKhHoi_bmVr4MiEnw@mail.gmail.com> (raw)
In-Reply-To: <20210704202756.29107-14-ojeda@kernel.org>

On Sun, Jul 4, 2021 at 1:29 PM <ojeda@kernel.org> wrote:
>
> From: Miguel Ojeda <ojeda@kernel.org>
>
> Most of the documentation for Rust is written within the source code
> itself, as it is idiomatic for Rust projects. This applies to both
> the shared infrastructure at `rust/` as well as any other Rust module
> (e.g. drivers) written across the kernel.
>
> These documents contain general information that does not fit
> particularly well in the source code, like the Quick Start guide.
>
... snip ...
> +rust-analyzer
> +*************
> +
> +The `rust-analyzer <https://rust-analyzer.github.io/>`_ language server can
> +be used with many editors to enable syntax highlighting, completion, go to
> +definition, and other features.
> +
> +``rust-analyzer`` will need to be
> +`configured <https://rust-analyzer.github.io/manual.html#non-cargo-based-projects>`_
> +to work with the kernel by adding a ``rust-project.json`` file in the root folder.
> +A ``rust-project.json`` can be generated by building the Make target ``rust-analyzer``,
> +which will create a ``rust-project.json`` in the root of the output directory.

Is rust-analyzer necessary to talk about? I think most kernel
developers aren't using LSP clients, so it doesn't seem necessary to
talk about for kernel development IMO.  If a developer would like to
use an LSP client, they should refer to the documentation of their LSP
client.

Should Documentation/process/changes.rst be updated to note which
versions of all of these tools are currently supported?

> +     - ``armv6`` and compatible only, ``RUST_OPT_LEVEL >= 2``

For the compat table, for 32b ARM, why is v6 supported but not v7? Why
only when optimizations are enabled?

> +Currently, the Rust compiler (``rustc``) uses LLVM for code generation,
> +which limits the supported architectures we can target. In addition, support
> +for building the kernel with LLVM/Clang varies (see :ref:`kbuild_llvm`),
> +which ``bindgen`` relies on through ``libclang``.

Doesn't this also depend on rustc having support for a given target
triple? Just because LLVM has a backend for a given architecture
doesn't mean rustc can target it, right?
-- 
Thanks,
~Nick Desaulniers