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

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Message-Id: <D9VVPGM147GP.3V338KUZGRQ6D@kernel.org>
Date: Wed, 14 May 2025 14:23:04 +0200
From: "Benno Lossin" <lossin@...nel.org>
To: "Mark Brown" <broonie@...nel.org>
Cc: "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>,
 <linux-kernel@...r.kernel.org>, <rust-for-linux@...r.kernel.org>
Subject: Re: [PATCH v3] rust: regulator: add a bare minimum regulator
 abstraction

On Wed May 14, 2025 at 1:50 PM CEST, Mark Brown wrote:
> On Wed, May 14, 2025 at 12:31:38PM +0200, Benno Lossin wrote:
>> On Wed May 14, 2025 at 12:16 PM CEST, Mark Brown wrote:
>> > Practically speaking if the regulator disable fails the system is having
>> > an extremely bad time and the actual state of the regulator is not clear.
>> > Users might want to try some attempt at retrying, one of which could
>> > possibly succeed in future, but realistically if this happens there's
>> > something fairly catastrophic going on.  Some critical users might want
>> > to care and have a good idea what makes sense for them, but probably the
>> > majority of users of the API aren't going to have a good strategy here.
>
>> Makes sense. So does `regulator_disable` take ownership of the refcount?
>> If yes, then just put that in the comment above the `ManuallyDrop` & in
>> the `Drop` impl of `EnabledRegulator`.
>
> In the C API the disable operation just fails and it's treated as though
> you hadn't done anything from a refcounting point of view.

But if it succeeds it takes ownership? The function `regulator_disable`
is also used in the `Drop` impl of the `EnabledRegulator`, so it better
give up the refcount, otherwise we would leak it.

---
Cheers,
Benno