linux-kernel - Re: [PATCH v3] rust: regulator: add a bare minimum regulator abstraction

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Message-Id: <D9ZCE83VYX50.3415QQDCN4R0G@kernel.org>
Date: Sun, 18 May 2025 16:05:42 +0200
From: "Benno Lossin" <lossin@...nel.org>
To: "Alexandre Courbot" <acourbot@...dia.com>, "Daniel Almeida"
 <daniel.almeida@...labora.com>, "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>, "Benno Lossin" <benno.lossin@...ton.me>,
 "Andreas Hindborg" <a.hindborg@...nel.org>, "Alice Ryhl"
 <aliceryhl@...gle.com>, "Trevor Gross" <tmgross@...ch.edu>, "Danilo
 Krummrich" <dakr@...nel.org>, "Boris Brezillon"
 <boris.brezillon@...labora.com>, "Sebastian Reichel"
 <sebastian.reichel@...labora.com>, "Liam Girdwood" <lgirdwood@...il.com>,
 "Mark Brown" <broonie@...nel.org>
Cc: <linux-kernel@...r.kernel.org>, <rust-for-linux@...r.kernel.org>
Subject: Re: [PATCH v3] rust: regulator: add a bare minimum regulator
 abstraction

On Sun May 18, 2025 at 1:12 PM CEST, Alexandre Courbot wrote:
> On Sun May 18, 2025 at 6:57 PM JST, Benno Lossin wrote:
>> So just let users ensure that they always match each `enable` call with
>> a `disable` call in the `Dynamic` typestate?
>>
>> That is ok, if no memory issues can arise from forgetting to do so,
>> otherwise those functions need to be `unsafe`.
>
> There shouldn't be any, the only side effect would be that the regulator
> stays enabled when it shouldn't.
>
> It's also easy to implement more behaviors using more states. For
> instance, `Dynamic` just proxies the C API. But if we also think it its
> useful to have a regulator which use count is clamped to 0 and 1, you
> could have another state that includes a boolean (instead of being empty
> lke the others) to track whether the regulator is enabled or not, and an
> `enable` method that only calls the C `regulator_enable` if that boolean
> is not already true. That way you remove the need to mirror the calls to
> enable and disable, while only paying the memory overhead for doing so
> when you explicitly state you want this behavior.

Aren't we then duplicating the refcount from the C side?

---
Cheers,
Benno