linux-kernel - Re: [PATCH v3 2/3] rust: clk: add devres-managed clks

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Message-Id: <DFSN1M7NPLHX.20PQDYA5DU7RM@garyguo.net>
Date: Mon, 19 Jan 2026 14:33:37 +0000
From: "Gary Guo" <gary@...yguo.net>
To: "Daniel Almeida" <daniel.almeida@...labora.com>, "Rafael J. Wysocki"
 <rafael@...nel.org>, "Viresh Kumar" <viresh.kumar@...aro.org>, "Danilo
 Krummrich" <dakr@...nel.org>, "Alice Ryhl" <aliceryhl@...gle.com>, "Maarten
 Lankhorst" <maarten.lankhorst@...ux.intel.com>, "Maxime Ripard"
 <mripard@...nel.org>, "Thomas Zimmermann" <tzimmermann@...e.de>, "David
 Airlie" <airlied@...il.com>, "Simona Vetter" <simona@...ll.ch>, "Drew
 Fustini" <fustini@...nel.org>, "Guo Ren" <guoren@...nel.org>, "Fu Wei"
 <wefu@...hat.com>, Uwe Kleine-König <ukleinek@...nel.org>,
 "Michael Turquette" <mturquette@...libre.com>, "Stephen Boyd"
 <sboyd@...nel.org>, "Miguel Ojeda" <ojeda@...nel.org>, "Boqun Feng"
 <boqun.feng@...il.com>, "Gary Guo" <gary@...yguo.net>,
 Björn Roy Baron <bjorn3_gh@...tonmail.com>, "Benno Lossin"
 <lossin@...nel.org>, "Andreas Hindborg" <a.hindborg@...nel.org>, "Trevor
 Gross" <tmgross@...ch.edu>
Cc: <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
 <dri-devel@...ts.freedesktop.org>, <linux-riscv@...ts.infradead.org>,
 <linux-pwm@...r.kernel.org>, <linux-clk@...r.kernel.org>,
 <rust-for-linux@...r.kernel.org>
Subject: Re: [PATCH v3 2/3] rust: clk: add devres-managed clks

On Wed Jan 7, 2026 at 3:09 PM GMT, Daniel Almeida wrote:
> The clk API allows fine-grained control, but some drivers might be
> more interested in a "set and forget" API.
>
> Expand the current API to support this. The clock will automatically be
> disabled, unprepared and freed when the device is unbound from the bus
> without further intervention by the driver.
>
> Signed-off-by: Daniel Almeida <daniel.almeida@...labora.com>
> ---
>  rust/kernel/clk.rs | 43 +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 43 insertions(+)
>
> diff --git a/rust/kernel/clk.rs b/rust/kernel/clk.rs
> index 6323b40dc7ba..e840e7c20af7 100644
> --- a/rust/kernel/clk.rs
> +++ b/rust/kernel/clk.rs
> @@ -95,6 +95,49 @@ impl Sealed for super::Prepared {}
>          impl Sealed for super::Enabled {}
>      }
>  
> +    /// Obtains and enables a [`devres`]-managed [`Clk`] for a bound device.
> +    ///
> +    /// [`devres`]: crate::devres::Devres
> +    pub fn devm_enable(dev: &Device<Bound>, name: Option<&CStr>) -> Result {
> +        let name = name.map_or(ptr::null(), |n| n.as_char_ptr());
> +
> +        // SAFETY: It is safe to call [`devm_clk_get_enabled`] with a valid
> +        // device pointer.
> +        from_err_ptr(unsafe { bindings::devm_clk_get_enabled(dev.as_raw(), name) })?;
> +        Ok(())
> +    }

Would it make sense to have them as assoc functions instead of standalone?

Regardless, the code looks correct to me.

Reviewed-by: Gary Guo <gary@...yguo.net>

Best,
Gary

> +
> +    /// Obtains and enables a [`devres`]-managed [`Clk`] for a bound device.
> +    ///
> +    /// This does not print any error messages if the clock is not found.
> +    ///
> +    /// [`devres`]: crate::devres::Devres
> +    pub fn devm_enable_optional(dev: &Device<Bound>, name: Option<&CStr>) -> Result {
> +        let name = name.map_or(ptr::null(), |n| n.as_char_ptr());
> +
> +        // SAFETY: It is safe to call [`devm_clk_get_optional_enabled`] with a
> +        // valid device pointer.
> +        from_err_ptr(unsafe { bindings::devm_clk_get_optional_enabled(dev.as_raw(), name) })?;
> +        Ok(())
> +    }
> +
> +    /// Same as [`devm_enable_optional`], but also sets the rate.
> +    pub fn devm_enable_optional_with_rate(
> +        dev: &Device,
> +        name: Option<&CStr>,
> +        rate: Hertz,
> +    ) -> Result {
> +        let name = name.map_or(ptr::null(), |n| n.as_char_ptr());
> +
> +        // SAFETY: It is safe to call
> +        // [`devm_clk_get_optional_enabled_with_rate`] with a valid device
> +        // pointer.
> +        from_err_ptr(unsafe {
> +            bindings::devm_clk_get_optional_enabled_with_rate(dev.as_raw(), name, rate.as_hz())
> +        })?;
> +        Ok(())
> +    }
> +
>      /// A trait representing the different states that a [`Clk`] can be in.
>      pub trait ClkState: private::Sealed {
>          /// Whether the clock should be disabled when dropped.