Re: [PATCH RFC 0/6] Rust Abstractions for PWM subsystem with TH1520 PWM driver

From: Drew Fustini <drew@pdp7.com>
To: Benno Lossin <lossin@kernel.org>,
	Michal Wilczynski <m.wilczynski@samsung.com>
Cc: "Uwe Kleine-König" <ukleinek@kernel.org>,
	"Miguel Ojeda" <ojeda@kernel.org>,
	"Alex Gaynor" <alex.gaynor@gmail.com>,
	"Boqun Feng" <boqun.feng@gmail.com>,
	"Gary Guo" <gary@garyguo.net>,
	"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
	"Benno Lossin" <benno.lossin@proton.me>,
	"Andreas Hindborg" <a.hindborg@kernel.org>,
	"Alice Ryhl" <aliceryhl@google.com>,
	"Trevor Gross" <tmgross@umich.edu>,
	"Danilo Krummrich" <dakr@kernel.org>,
	"Guo Ren" <guoren@kernel.org>, "Fu Wei" <wefu@redhat.com>,
	"Rob Herring" <robh@kernel.org>,
	"Krzysztof Kozlowski" <krzk+dt@kernel.org>,
	"Conor Dooley" <conor+dt@kernel.org>,
	"Paul Walmsley" <paul.walmsley@sifive.com>,
	"Palmer Dabbelt" <palmer@dabbelt.com>,
	"Albert Ou" <aou@eecs.berkeley.edu>,
	"Alexandre Ghiti" <alex@ghiti.fr>,
	"Marek Szyprowski" <m.szyprowski@samsung.com>,
	linux-kernel@vger.kernel.org, linux-pwm@vger.kernel.org,
	rust-for-linux@vger.kernel.org, linux-riscv@lists.infradead.org,
	devicetree@vger.kernel.org
Subject: Re: [PATCH RFC 0/6] Rust Abstractions for PWM subsystem with TH1520 PWM driver
Date: Sun, 8 Jun 2025 09:58:07 -0700	[thread overview]
Message-ID: <aEXBH5r05FkTxpV+@x1> (raw)
In-Reply-To: <DA5YY0YF28GO.3DONTQDLY6VBD@kernel.org>

On Mon, May 26, 2025 at 11:01:58AM +0200, Benno Lossin wrote:
> On Mon May 26, 2025 at 10:22 AM CEST, Michal Wilczynski wrote:
> > On 5/25/25 00:21, Drew Fustini wrote:
> >> Thanks for the patch series. It will be great to have PWM working
> >> upstream.
> >> 
> >> I've not built Linux with Rust before, so I'm going through the quick
> >> start [1]. I've also never built Linux with LLVM before but clang seems
> >> like the best compiler to use for Rust. Are you using LLVM?
> >
> > Hi Drew,
> > You're correct, Clang is the way to go for Rust in the kernel. I also
> > followed the official quick start guide. To answer your question
> > directly: yes, I'm using LLVM.
> 
> Just to let you know, there is an effort to get rustc to work with a gcc
> backend rustc_gcc_codegen [1]. And there also is the gccrs project [2]
> trying to create a gnu Rust compiler.
> 
> [1]: https://rust-for-linux.com/rustc_codegen_gcc
> [2]: https://rust-for-linux.com/gccrs
> 
> They have made a lot of progress over the last year, so we're hopeful
> that they become usable in the near future. But for the moment,
> Clang/LLVM is the way to go.
> 
> Hope this helps!
> 
> ---
> Cheers,
> Benno

Thanks for letting me know about gccrs.

I was able to build linux okay with clang:

make LLVM=1 ARCH=riscv -j16

It booted okay on the lpi4a:

Linux version 6.15.0-next-20250606 (pdp7@thelio) (Ubuntu clang version 18.1.3 (1ubuntu1), Ubuntu LLD 18.1.3) 

I installed rust with:

 rustup default beta
 rustup component add rust-src

 $ make LLVM=1 rustavailable
 ***
 *** Rust bindings generator 'bindgen' versions 0.66.0 and 0.66.1 may not
 *** work due to a bug (https://github.com/rust-lang/rust-bindgen/pull/2567),
 *** unless patched (like Debian's).
 ***   Your version:     0.66.1
 ***
 ***
 *** Please see Documentation/rust/quick-start.rst for details
 *** on how to set up the Rust support.
 ***
 Rust is available!

I'm not sure if that bindgen warning matters?

Thanks,
Drew