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

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Message-ID: <CAH5fLgiErvnziU-hSCV6djNq7Q56ZfX9gZudmX7+r06hWoX0Tw@mail.gmail.com>
Date: Wed, 19 Feb 2025 16:28:46 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Daniel Almeida <daniel.almeida@...labora.com>
Cc: lgirdwood@...il.com, broonie@...nel.org, sebastian.reichel@...labora.com, 
	sjoerd.simons@...labora.co.uk, ojeda@...nel.org, alex.gaynor@...il.com, 
	boqun.feng@...il.com, gary@...yguo.net, bjorn3_gh@...tonmail.com, 
	a.hindborg@...nel.org, benno.lossin@...ton.me, tmgross@...ch.edu, 
	dakr@...nel.org, rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rust: regulator: add a bare minimum regulator abstraction

On Wed, Feb 19, 2025 at 4:26 PM Daniel Almeida
<daniel.almeida@...labora.com> wrote:
>
> Add a bare minimum regulator abstraction to be used by Rust drivers.
> This abstraction adds a small subset of the regulator API, which is
> thought to be sufficient for the drivers we have now.
>
> Regulators provide the power needed by many hardware blocks and thus are
> likely to be needed by a lot of drivers.
>
> It was tested on rk3588, where it was used to power up the "mali"
> regulator in order to power up the GPU.
>
> Note that each instance of [`Regulator`] obtained from
> `Regulator::get()` can only be enabled once. This ensures that the calls
> to enable and disable are perfectly balanced before `regulator_put()` is
> called, as mandated by the C API.
>
> Signed-off-by: Daniel Almeida <daniel.almeida@...labora.com>
> ---
>  rust/bindings/bindings_helper.h |   1 +
>  rust/kernel/lib.rs              |   2 +
>  rust/kernel/regulator.rs        | 120 ++++++++++++++++++++++++++++++++
>  3 files changed, 123 insertions(+)
>  create mode 100644 rust/kernel/regulator.rs
>
> diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
> index 55354e4dec14..92504f19655e 100644
> --- a/rust/bindings/bindings_helper.h
> +++ b/rust/bindings/bindings_helper.h
> @@ -28,6 +28,7 @@
>  #include <linux/poll.h>
>  #include <linux/property.h>
>  #include <linux/refcount.h>
> +#include <linux/regulator/consumer.h>
>  #include <linux/sched.h>
>  #include <linux/security.h>
>  #include <linux/slab.h>
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index 496ed32b0911..0224f4c248c0 100644
> --- a/rust/kernel/lib.rs
> +++ b/rust/kernel/lib.rs
> @@ -68,6 +68,8 @@
>  pub mod prelude;
>  pub mod print;
>  pub mod rbtree;
> +#[cfg(CONFIG_REGULATOR)]
> +pub mod regulator;
>  pub mod revocable;
>  pub mod security;
>  pub mod seq_file;
> diff --git a/rust/kernel/regulator.rs b/rust/kernel/regulator.rs
> new file mode 100644
> index 000000000000..df6eb325d11a
> --- /dev/null
> +++ b/rust/kernel/regulator.rs
> @@ -0,0 +1,120 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! Regulator abstractions.
> +//!
> +//! C header: [`include/linux/regulator/consumer.h`](srctree/include/linux/regulator/consumer.h)
> +
> +use crate::{
> +    bindings,
> +    device::Device,
> +    error::{from_err_ptr, to_result, Result},
> +    prelude::*,
> +};
> +
> +use core::ptr::NonNull;
> +
> +/// A `struct regulator` abstraction.
> +///
> +/// Note that each instance of [`Regulator`] obtained from `Regulator::get()`
> +/// can only be enabled once. This ensures that the calls to enable and disable
> +/// are perfectly balanced before `regulator_put()` is called, as mandated by
> +/// the C API.
> +///
> +/// # Invariants
> +///
> +/// - [`Regulator`] is a non-null wrapper over a pointer to a `struct regulator`
> +///   obtained from `regulator_get()`.
> +/// - Each instance of [`Regulator`] obtained from `Regulator::get()` can only
> +///   be enabled once.
> +pub struct Regulator {
> +    inner: NonNull<bindings::regulator>,
> +    enabled: bool,
> +}

I wonder if enabled vs disabled should be two different types?

Alice