linux-kernel - Re: [PATCH V3 2/3] rust: Use CpuId in place of raw CPU numbers

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Message-ID: <aExGUZ3H5mZ7Drqd@Mac.home>
Date: Fri, 13 Jun 2025 08:40:01 -0700
From: Boqun Feng <boqun.feng@...il.com>
To: Viresh Kumar <viresh.kumar@...aro.org>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...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>,
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
	Danilo Krummrich <dakr@...nel.org>,
	Yury Norov <yury.norov@...il.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	rust-for-linux@...r.kernel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 2/3] rust: Use CpuId in place of raw CPU numbers

On Thu, Jun 12, 2025 at 10:31:17AM +0530, Viresh Kumar wrote:
> On 11-06-25, 09:12, Boqun Feng wrote:
> > I generally found that `u32::from(cpu)` is more clear than `cpu.into()`,
> > but it's up to you. Same for the rest of `cpu.into()` cases.
> 
> Updated as:
> 
> diff --git a/rust/kernel/cpu.rs b/rust/kernel/cpu.rs
> index 7549594fad7f..abc780d7a8ec 100644
> --- a/rust/kernel/cpu.rs
> +++ b/rust/kernel/cpu.rs
> @@ -129,7 +129,7 @@ fn from(id: CpuId) -> Self {
>  /// any references to the CPU device within the notifier's callback.
>  pub unsafe fn from_cpu(cpu: CpuId) -> Result<&'static Device> {
>      // SAFETY: It is safe to call `get_cpu_device()` for any CPU.
> -    let ptr = unsafe { bindings::get_cpu_device(cpu.into()) };
> +    let ptr = unsafe { bindings::get_cpu_device(u32::from(cpu)) };
>      if ptr.is_null() {
>          return Err(ENODEV);
>      }
> diff --git a/rust/kernel/cpufreq.rs b/rust/kernel/cpufreq.rs
> index ea6106db5c29..11b03e9d7e89 100644
> --- a/rust/kernel/cpufreq.rs
> +++ b/rust/kernel/cpufreq.rs
> @@ -527,7 +527,7 @@ pub fn generic_suspend(&mut self) -> Result {
>      #[inline]
>      pub fn generic_get(&self) -> Result<u32> {
>          // SAFETY: By the type invariant, the pointer stored in `self` is valid.
> -        Ok(unsafe { bindings::cpufreq_generic_get(self.cpu().into()) })
> +        Ok(unsafe { bindings::cpufreq_generic_get(u32::from(self.cpu())) })
>      }
>  
>      /// Provides a wrapper to the register with energy model using the OPP core.
> @@ -682,7 +682,7 @@ fn clear_data<T: ForeignOwnable>(&mut self) -> Option<T> {
>  impl<'a> PolicyCpu<'a> {
>      fn from_cpu(cpu: CpuId) -> Result<Self> {
>          // SAFETY: It is safe to call `cpufreq_cpu_get` for any valid CPU.
> -        let ptr = from_err_ptr(unsafe { bindings::cpufreq_cpu_get(cpu.into()) })?;
> +        let ptr = from_err_ptr(unsafe { bindings::cpufreq_cpu_get(u32::from(cpu)) })?;
>  
>          Ok(Self(
>              // SAFETY: The `ptr` is guaranteed to be valid and remains valid for the lifetime of
> diff --git a/rust/kernel/cpumask.rs b/rust/kernel/cpumask.rs
> index 11ddd43edcb5..19c607709b5f 100644
> --- a/rust/kernel/cpumask.rs
> +++ b/rust/kernel/cpumask.rs
> @@ -94,7 +94,7 @@ pub fn as_raw(&self) -> *mut bindings::cpumask {
>      #[inline]
>      pub fn set(&mut self, cpu: CpuId) {
>          // SAFETY: By the type invariant, `self.as_raw` is a valid argument to `__cpumask_set_cpu`.
> -        unsafe { bindings::__cpumask_set_cpu(cpu.into(), self.as_raw()) };
> +        unsafe { bindings::__cpumask_set_cpu(u32::from(cpu), self.as_raw()) };
>      }
>  
>      /// Clear `cpu` in the cpumask.
> @@ -106,7 +106,7 @@ pub fn set(&mut self, cpu: CpuId) {
>      pub fn clear(&mut self, cpu: CpuId) {
>          // SAFETY: By the type invariant, `self.as_raw` is a valid argument to
>          // `__cpumask_clear_cpu`.
> -        unsafe { bindings::__cpumask_clear_cpu(cpu.into(), self.as_raw()) };
> +        unsafe { bindings::__cpumask_clear_cpu(i32::from(cpu), self.as_raw()) };
>      }
>  
>      /// Test `cpu` in the cpumask.
> @@ -115,7 +115,7 @@ pub fn clear(&mut self, cpu: CpuId) {
>      #[inline]
>      pub fn test(&self, cpu: CpuId) -> bool {
>          // SAFETY: By the type invariant, `self.as_raw` is a valid argument to `cpumask_test_cpu`.
> -        unsafe { bindings::cpumask_test_cpu(cpu.into(), self.as_raw()) }
> +        unsafe { bindings::cpumask_test_cpu(i32::from(cpu), self.as_raw()) }
>      }
>  

LGTM,thanks!

Regards,
Boqun

>      /// Set all CPUs in the cpumask.
> 
> -- 
> viresh