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

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Message-ID: <a1a6b2f8-af42-4942-ab62-678e37381d08@sirena.org.uk>
Date: Mon, 19 May 2025 10:56:50 +0100
From: Mark Brown <broonie@...nel.org>
To: Benno Lossin <lossin@...nel.org>
Cc: 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>, 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 04:04:24PM +0200, Benno Lossin wrote:

> I'm not sure if I understand correctly, so I'll just try to echo it and
> see if it's correct :)

> The `enable`/`disable` functions change a refcount on the underlying
> regulator that tracks if the regulator actually is enabled/disabled.
> Asking the hardware to enable or disable a regulator can fail, but if we
> already know that it is enabled, only the refcount is incremented.

Yes.

>     It's okay to leak this enabled-refcount, since when the regulators
> actual refcount (so the one adjusted by `_get` & `_put`) hits zero, we
> can also disable the regulator. So the enabled-refcount is essentially a
> weak refcount that only does something while the regulator exists.

No.  You should not leak any refcount, the per consumer refcount
duplicates what's being done for the regulator as a whole, one should
never be incremented or decremented without the other (but there may be
multiple consumers to choose from).

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