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

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Message-Id: <B58EF4F3-6ADD-4311-BE9D-CCE82CBAEBF2@collabora.com>
Date: Wed, 14 May 2025 13:19:10 -0300
From: Daniel Almeida <daniel.almeida@...labora.com>
To: Benno Lossin <lossin@...nel.org>
Cc: Mark Brown <broonie@...nel.org>,
 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>,
 linux-kernel@...r.kernel.org,
 rust-for-linux@...r.kernel.org
Subject: Re: [PATCH v3] rust: regulator: add a bare minimum regulator
 abstraction



> On 14 May 2025, at 13:05, Benno Lossin <lossin@...nel.org> wrote:
> 
> On Wed May 14, 2025 at 5:50 PM CEST, Mark Brown wrote:
>> On Wed, May 14, 2025 at 05:38:40PM +0200, Benno Lossin wrote:
>>> On Wed May 14, 2025 at 4:40 PM CEST, Daniel Almeida wrote:
>>>> By the way, IIUC, regulator_disable() does not disable a regulator necessarily.
>>>> It just tells the system that you don't care about it being enabled anymore. It can
>>>> still remain on if there are other users.
>> 
>>> Hmm, so a `struct regulator` might already be enabled and calling
>>> `regulator_enable` doesn't do anything?
>> 
>> It takes a reference to the regulator.  This may or may not result in a
>> change in an underlying physical regulator.
> 
> Gotcha. So calling `regulator_enable` twice on the same regulator is
> fine?
> 
> If that is the case -- and after re-reading the functions exposed on
> both types `EnabledRegulator` and `Regulator` -- I am confused why we
> even need two different type states? Both expose the same functions
> (except `enable` and `disable`) and I don't otherwise see the purpose of
> having two types.
> 
> ---
> Cheers,
> Benno
> 


As Mark said:

> IIUC the point is to allow Rust's type system to keep track of the
> reference on the regulator, otherwise the user code has to keep track of
> the number of enables it's done like it currently does in C code.

So this all started because keeping track of the enables was rather clunky. See
v1 [0].

[0] https://lore.kernel.org/rust-for-linux/20250219162517.278362-1-daniel.almeida@collabora.com/