Re: [PATCH v2 2/2] rust: regulator: add devm_enable and devm_enable_optional

[Boqun Feng <boqun.feng@gmail.com>]

On Mon, Sep 08, 2025 at 08:10:28PM -0300, Daniel Almeida wrote:
> A lot of drivers only care about enabling the regulator for as long as
> the underlying Device is bound. This can be easily observed due to the
> extensive use of `devm_regulator_get_enable` and
> `devm_regulator_get_enable_optional` throughout the kernel.
> 
> Therefore, make this helper available in Rust. Also add an example
> noting how it should be the default API unless the driver needs more
> fine-grained control over the regulator.
> 
> Suggested-by: Danilo Krummrich <dakr@kernel.org>
> Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
> ---
>  rust/helpers/regulator.c | 10 +++++++++
>  rust/kernel/regulator.rs | 58 +++++++++++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 67 insertions(+), 1 deletion(-)
> 
> diff --git a/rust/helpers/regulator.c b/rust/helpers/regulator.c
> index cd8b7ba648ee33dd14326c9242fb6c96ab8e32a7..11bc332443bd064f4b5afd350ffc045badff9076 100644
> --- a/rust/helpers/regulator.c
> +++ b/rust/helpers/regulator.c
> @@ -40,4 +40,14 @@ int rust_helper_regulator_is_enabled(struct regulator *regulator)
>  	return regulator_is_enabled(regulator);
>  }
>  
> +int rust_helper_devm_regulator_get_enable(struct device *dev, const char *id)
> +{
> +	return devm_regulator_get_enable(dev, id);
> +}
> +
> +int rust_helper_devm_regulator_get_enable_optional(struct device *dev, const char *id)
> +{
> +	return devm_regulator_get_enable_optional(dev, id);
> +}
> +
>  #endif
> diff --git a/rust/kernel/regulator.rs b/rust/kernel/regulator.rs
> index 5ea2307f02df4a10c1c8c07b3b8c134d13519b69..d1c8c7308cdd9ae398883ddac52ff093b97764cd 100644
> --- a/rust/kernel/regulator.rs
> +++ b/rust/kernel/regulator.rs
> @@ -18,7 +18,7 @@
>  
>  use crate::{
>      bindings,
> -    device::Device,
> +    device::{Bound, Device},
>      error::{from_err_ptr, to_result, Result},
>      prelude::*,
>  };
> @@ -70,6 +70,39 @@ pub struct Error<State: RegulatorState> {
>      pub regulator: Regulator<State>,
>  }
>  
> +/// Enables a regulator whose lifetime is tied to the lifetime of `dev` through
> +/// [`devres`].

This description seems a bit wordy to me. How about "Obtains and
enables a [`devres`]-managed regulator for a device"? And if you want,
you could explain the `regulator_disable()` and `regulator_put()` in the
second paragraph.

The rest looks good to me. Feel free to add:

Reviewed-by: Boqun Feng <boqun.feng@gmail.com>

Regards,
Boqun

> +///
> +/// This calls `regulator_disable()` and `regulator_put()` automatically on
> +/// driver detach.
> +///
> +/// This API is identical to `devm_regulator_get_enable()`, and should be
> +/// preferred if the caller only cares about the regulator being on.
> +///
> +/// [`devres`]: https://docs.kernel.org/driver-api/driver-model/devres.html
> +pub fn devm_enable(dev: &Device<Bound>, name: &CStr) -> Result {
> +    // SAFETY: `dev` is a valid and bound device, while `name` is a valid C
> +    // string.
> +    to_result(unsafe { bindings::devm_regulator_get_enable(dev.as_raw(), name.as_ptr()) })
> +}
> +
> +/// Same as [`devm_enable`], but calls `devm_regulator_get_enable_optional`
> +/// instead.
> +///
> +/// This enables a regulator whose lifetime is tied to the lifetime of `dev`
> +/// through [`devres`], but does not print a message nor provides a dummy if the
> +/// regulator is not found.
> +///
> +/// This calls `regulator_disable()` and `regulator_put()` automatically on
> +/// driver detach.
> +///
> +/// [`devres`]: https://docs.kernel.org/driver-api/driver-model/devres.html
> +pub fn devm_enable_optional(dev: &Device<Bound>, name: &CStr) -> Result {
> +    // SAFETY: `dev` is a valid and bound device, while `name` is a valid C
> +    // string.
> +    to_result(unsafe { bindings::devm_regulator_get_enable_optional(dev.as_raw(), name.as_ptr()) })
> +}
> +
>  /// A `struct regulator` abstraction.
>  ///
>  /// # Examples
> @@ -146,6 +179,29 @@ pub struct Error<State: RegulatorState> {
>  /// }
>  /// ```
>  ///
> +/// If a driver only cares about the regulator being on for as long it is bound
> +/// to a device, then it should use [`devm_enable`] or [`devm_enable_optional`].
> +/// This should be the default use-case unless they need more fine-grained
> +/// control over the regulator's state.
> +///
> +/// [`devm_enable`]: crate::regulator::devm_enable
> +/// [`devm_optional`]: crate::regulator::devm_enable_optional
> +///
> +/// ```
> +/// # use kernel::prelude::*;
> +/// # use kernel::c_str;
> +/// # use kernel::device::{Bound, Device};
> +/// # use kernel::regulator;
> +/// fn enable(dev: &Device<Bound>) -> Result {
> +///     // Obtain a reference to a (fictitious) regulator and enable it. This
> +///     // call only returns whether the operation succeeded.
> +///     regulator::devm_enable(dev, c_str!("vcc"))?;
> +///
> +///     // The regulator will be disabled and put when `dev` is unbound.
> +///     Ok(())
> +/// }
> +/// ```
> +///
>  /// ## Disabling a regulator
>  ///
>  /// ```
> 
> -- 
> 2.51.0
>