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

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Message-ID: <20250612050117.3oi6belkf5lrreoh@vireshk-i7>
Date: Thu, 12 Jun 2025 10:31:17 +0530
From: Viresh Kumar <viresh.kumar@...aro.org>
To: Boqun Feng <boqun.feng@...il.com>
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 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()) }
     }
 
     /// Set all CPUs in the cpumask.

-- 
viresh