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

From: Michal Wilczynski <m.wilczynski@samsung.com>
To: "Uwe Kleine-König" <ukleinek@kernel.org>
Cc: "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>,
	"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>,
	"Benno Lossin" <lossin@kernel.org>,
	"Michael Turquette" <mturquette@baylibre.com>,
	"Drew Fustini" <fustini@kernel.org>,
	"Daniel Almeida" <daniel.almeida@collabora.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 v14 2/7] rust: pwm: Add Kconfig and basic data structures
Date: Wed, 24 Sep 2025 22:10:57 +0200	[thread overview]
Message-ID: <0bbdb7d1-5d07-4997-955e-497134a4aa30@samsung.com> (raw)
In-Reply-To: <upgthwp3cyohhe2gkzsramzshmvz3icjbhro6hgk2drbbqczi4@ygaanetydgjv>

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@samsung.com>

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