Re: [PATCH V2 2/2] rust: Add basic bindings for clk APIs

[Daniel Almeida]

Hi Viresh, thank you for working on this.


> On 21 Feb 2025, at 03:33, Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote:
> 
> Add initial bindings for the clk APIs. These provide the minimal
> functionality needed for common use cases, making them straightforward
> to introduce in the first iteration.
> 
> These will be used by Rust based cpufreq / OPP layers to begin with.
> 
> Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
> ---
> MAINTAINERS        |   1 +
> rust/kernel/clk.rs | 104 +++++++++++++++++++++++++++++++++++++++++++++
> rust/kernel/lib.rs |   1 +
> 3 files changed, 106 insertions(+)
> create mode 100644 rust/kernel/clk.rs
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 726110d3c988..96e2574f41c0 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -5779,6 +5779,7 @@ F: include/linux/clk-pr*
> F: include/linux/clk/
> F: include/linux/of_clk.h
> F: rust/helpers/clk.c
> +F: rust/kernel/clk.rs
> X: drivers/clk/clkdev.c
> 
> COMMON INTERNET FILE SYSTEM CLIENT (CIFS and SMB3)
> diff --git a/rust/kernel/clk.rs b/rust/kernel/clk.rs
> new file mode 100644
> index 000000000000..c212cd3167e1
> --- /dev/null
> +++ b/rust/kernel/clk.rs
> @@ -0,0 +1,104 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! Clock abstractions.
> +//!
> +//! C header: [`include/linux/clk.h`](srctree/include/linux/clk.h)
> +
> +use crate::{
> +    bindings,
> +    device::Device,
> +    error::{from_err_ptr, to_result, Result},
> +    prelude::*,
> +};
> +
> +use core::ptr;
> +
> +/// A simple implementation of `struct clk` from the C code.
> +#[repr(transparent)]
> +pub struct Clk(*mut bindings::clk);

> +
> +impl Clk {
> +    /// Creates `Clk` instance for a device and a connection id.
> +    pub fn new(dev: &Device, name: Option<&CStr>) -> Result<Self> {
> +        let con_id = if let Some(name) = name {
> +            name.as_ptr() as *const _
> +        } else {
> +            ptr::null()
> +        };
> +
> +        // SAFETY: It is safe to call `clk_get()`, on a device pointer earlier received from the C
> +        // code.
> +        Ok(Self(from_err_ptr(unsafe {
> +            bindings::clk_get(dev.as_raw(), con_id)
> +        })?))
> +    }
> +
> +    /// Obtain the raw `struct clk *`.
> +    pub fn as_raw(&self) -> *mut bindings::clk {
> +        self.0
> +    }
> +
> +    /// Clock enable.
> +    pub fn enable(&self) -> Result<()> {
> +        // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
> +        // use it now.
> +        to_result(unsafe { bindings::clk_enable(self.0) })
> +    }
> +
> +    /// Clock disable.
> +    pub fn disable(&self) {
> +        // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
> +        // use it now.
> +        unsafe { bindings::clk_disable(self.0) };
> +    }
> +
> +    /// Clock prepare.
> +    pub fn prepare(&self) -> Result<()> {
> +        // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
> +        // use it now.
> +        to_result(unsafe { bindings::clk_prepare(self.0) })
> +    }
> +
> +    /// Clock unprepare.
> +    pub fn unprepare(&self) {
> +        // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
> +        // use it now.
> +        unsafe { bindings::clk_unprepare(self.0) };
> +    }
> +
> +    /// Clock prepare enable.
> +    pub fn prepare_enable(&self) -> Result<()> {
> +        // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
> +        // use it now.
> +        to_result(unsafe { bindings::clk_prepare_enable(self.0) })
> +    }
> +
> +    /// Clock disable unprepare.
> +    pub fn disable_unprepare(&self) {
> +        // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
> +        // use it now.
> +        unsafe { bindings::clk_disable_unprepare(self.0) };
> +    }
> +
> +    /// Clock get rate.
> +    pub fn rate(&self) -> usize {
> +        // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
> +        // use it now.
> +        unsafe { bindings::clk_get_rate(self.0) }
> +    }
> +
> +    /// Clock set rate.
> +    pub fn set_rate(&self, rate: usize) -> Result<()> {

It might be worth it to add a type here to make it clear what in what unit is `rate` expressed as.

Something like:

pub struct Hertz(pub u32);

pub fn set_rate(&self, rate: Hertz);

Assuming `rate` is in Hertz.


> +        // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
> +        // use it now.
> +        to_result(unsafe { bindings::clk_set_rate(self.0, rate) })
> +    }
> +}
> +
> +impl Drop for Clk {
> +    fn drop(&mut self) {
> +        // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
> +        // relinquish it now.
> +        unsafe { bindings::clk_put(self.0) };
> +    }
> +}
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index 496ed32b0911..324b86f127a0 100644
> --- a/rust/kernel/lib.rs
> +++ b/rust/kernel/lib.rs
> @@ -40,6 +40,7 @@
> pub mod block;
> #[doc(hidden)]
> pub mod build_assert;
> +pub mod clk;
> pub mod cred;
> pub mod device;
> pub mod device_id;
> -- 
> 2.31.1.272.g89b43f80a514
> 
> 


This is working fine on Tyr, so:

Tested-by: Daniel Almeida <daniel.almeida@xxxxxxxxxxxxx>

With the minor change above:

Reviewed-by: Daniel Almeida <daniel.almeida@xxxxxxxxxxxxx>