linux-kernel - Re: [PATCH RESEND v2] rust: regulator: add a bare minimum regulator abstraction

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Message-ID: <93581b77-7126-4d93-bc65-e1bc24f1ba77@sirena.org.uk>
Date: Thu, 27 Mar 2025 15:06:57 +0000
From: Mark Brown <broonie@...nel.org>
To: Sebastian Reichel <sebastian.reichel@...labora.com>
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>,
	lgirdwood@...il.com, linux-kernel@...r.kernel.org,
	rust-for-linux@...r.kernel.org
Subject: Re: [PATCH RESEND v2] rust: regulator: add a bare minimum regulator
 abstraction

On Thu, Mar 27, 2025 at 02:46:30PM +0100, Sebastian Reichel wrote:
> On Wed, Mar 26, 2025 at 03:39:33PM -0300, Daniel Almeida wrote:

> > +    pub fn get(dev: &Device, name: &CStr) -> Result<Self> {
> > +        // SAFETY: It is safe to call `regulator_get()`, on a device pointer
> > +        // received from the C code.
> > +        let inner = from_err_ptr(unsafe { bindings::regulator_get(dev.as_raw(), name.as_ptr()) })?;

> I think it's worth discussing using regulator_get() VS
> regulator_get_optional(). We somehow ended up with the C regulator
> API being more or less orthogonal to other in-kernel C APIs (clocks,
> gpio, reset, LED) with the _optional suffixed version returning
> -ENODEV for a missing regulator (and thus needing explicit handling)
> and the normal version creating a dummy regulator (and a warning).

regulator was first here...

> Considering the Rust API is new, it would be possible to let the
> Rust get() function call regulator_get_optional() instead and then
> introduce something like get_or_dummy() to call the normal
> regulator_get() C function.

> I see reasons in favor and against this. I just want to make sure it
> has been considered before the API is being used, which makes it a
> lot harder to change.

Unless rust somehow magically allows devices to work without power this
would just be broken.

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