linux-kernel - Re: [PATCH] rust: cpufreq: streamline find_supply

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Message-ID: <20250929110234.ukgwsnxyrvsimhst@vireshk-i7>
Date: Mon, 29 Sep 2025 16:32:34 +0530
From: Viresh Kumar <viresh.kumar@...aro.org>
To: Alice Ryhl <aliceryhl@...gle.com>
Cc: Thorsten Blum <thorsten.blum@...ux.dev>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>,
	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>,
	Danilo Krummrich <dakr@...nel.org>, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org
Subject: Re: [PATCH] rust: cpufreq: streamline find_supply_names

On 29-09-25, 11:38, Alice Ryhl wrote:
> This is a pre-existing issue, but ... this treats allocation failure
> and non-existence the same way. That sounds wrong.

What about this over the current patch:

diff --git a/drivers/cpufreq/rcpufreq_dt.rs b/drivers/cpufreq/rcpufreq_dt.rs
index 224d063c7cec..e509b46b64c7 100644
--- a/drivers/cpufreq/rcpufreq_dt.rs
+++ b/drivers/cpufreq/rcpufreq_dt.rs
@@ -26,13 +26,17 @@ fn find_supply_name_exact(dev: &Device, name: &str) -> Option<CString> {
 }

 /// Finds supply name for the CPU from DT.
-fn find_supply_names(dev: &Device, cpu: cpu::CpuId) -> Option<KVec<CString>> {
+fn find_supply_names(dev: &Device, cpu: cpu::CpuId) -> Result<Option<KVec<CString>>> {
     // Try "cpu0" for older DTs, fallback to "cpu".
-    (cpu.as_u32() == 0)
+    let name = (cpu.as_u32() == 0)
         .then(|| find_supply_name_exact(dev, "cpu0"))
         .flatten()
-        .or_else(|| find_supply_name_exact(dev, "cpu"))
-        .and_then(|name| kernel::kvec![name].ok())
+        .or_else(|| find_supply_name_exact(dev, "cpu"));
+
+    Ok(match name {
+        None => None,
+        Some(n) => Some(kernel::kvec![n]?),
+    })
 }

 /// Represents the cpufreq dt device.
@@ -68,7 +72,7 @@ fn init(policy: &mut cpufreq::Policy) -> Result<Self::PData> {

         mask.set(cpu);

-        let token = find_supply_names(dev, cpu)
+        let token = find_supply_names(dev, cpu)?
             .map(|names| {
                 opp::Config::<Self>::new()
                     .set_regulator_names(names)?

-- 
viresh