linux-kernel - Re: [PATCH v14 2/7] rust: pwm: Add Kconfig and basic data structures

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Message-ID: <0bbdb7d1-5d07-4997-955e-497134a4aa30@samsung.com>
Date: Wed, 24 Sep 2025 22:10:57 +0200
From: Michal Wilczynski <m.wilczynski@...sung.com>
To: Uwe Kleine-König <ukleinek@...nel.org>
Cc: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>,
	Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>, Andreas
	Hindborg <a.hindborg@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, Trevor
	Gross <tmgross@...ch.edu>, Danilo Krummrich <dakr@...nel.org>, Guo Ren
	<guoren@...nel.org>, Fu Wei <wefu@...hat.com>, Rob Herring
	<robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
	<conor+dt@...nel.org>, Paul Walmsley <paul.walmsley@...ive.com>, Palmer
	Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, Alexandre
	Ghiti <alex@...ti.fr>, Marek Szyprowski <m.szyprowski@...sung.com>, Benno
	Lossin <lossin@...nel.org>, Michael Turquette <mturquette@...libre.com>,
	Drew Fustini <fustini@...nel.org>, Daniel Almeida
	<daniel.almeida@...labora.com>, linux-kernel@...r.kernel.org,
	linux-pwm@...r.kernel.org, rust-for-linux@...r.kernel.org,
	linux-riscv@...ts.infradead.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v14 2/7] rust: pwm: Add Kconfig and basic data
 structures



On 9/15/25 12:13, Uwe Kleine-König wrote:
> Hello Michal,
> 
> On Wed, Aug 20, 2025 at 10:35:37AM +0200, Michal Wilczynski wrote:
>> Introduce the foundational support for PWM abstractions in Rust.
>>
>> This commit adds the `RUST_PWM_ABSTRACTIONS` Kconfig option to enable
>> the feature, along with the necessary build-system support and C
>> helpers.
>>
>> It also introduces the first set of safe wrappers for the PWM
>> subsystem, covering the basic data carrying C structs and enums:
>> - `Polarity`: A safe wrapper for `enum pwm_polarity`.
>> - `Waveform`: A wrapper for `struct pwm_waveform`.
>> - `Args`: A wrapper for `struct pwm_args`.
>> - `State`: A wrapper for `struct pwm_state`.
> 
> Args, State and Polarity are only needed for the consumer side of the
> PWM API in Rust, right?
> 
> I don't particularily like like pwm_args and wonder if this really has
> to be exposed to Rust.

You're right that Args is primarily for the consumer side, and our
provider driver doesn't use it at all. I only included it for
completeness, so I'm happy to remove it from the abstractions.

I did use State on the provider side, however, to check if a channel is
enabled before writing new hardware values - I've seen your comment
about it that it's better to use the HW registers instead, I remember I
tried doing something like this back in May when started working on
this, but haven't succeeded - will refresh my memory and respond to the
driver comments.

> 
> I think for State (and thus Polarity) we have to have it for the
> forseeable future.
> 
> Best regards
> Uwe

Best regards,
-- 
Michal Wilczynski <m.wilczynski@...sung.com>