[PATCH] rust: cpufreq: streamline find_supply_names

[PATCH] rust: cpufreq: streamline find_supply_names

[Thorsten Blum]

Remove local variables from find_supply_names() and use .and_then() with
the more concise kernel::kvec![] macro, instead of KVec::with_capacity()
followed by .push() and Some().

No functional changes intended.

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
 drivers/cpufreq/rcpufreq_dt.rs | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/drivers/cpufreq/rcpufreq_dt.rs b/drivers/cpufreq/rcpufreq_dt.rs
index 7e1fbf9a091f..224d063c7cec 100644
--- a/drivers/cpufreq/rcpufreq_dt.rs
+++ b/drivers/cpufreq/rcpufreq_dt.rs
@@ -28,15 +28,11 @@ 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>> {
     // Try "cpu0" for older DTs, fallback to "cpu".
-    let name = (cpu.as_u32() == 0)
+    (cpu.as_u32() == 0)
         .then(|| find_supply_name_exact(dev, "cpu0"))
         .flatten()
-        .or_else(|| find_supply_name_exact(dev, "cpu"))?;
-
-    let mut list = KVec::with_capacity(1, GFP_KERNEL).ok()?;
-    list.push(name, GFP_KERNEL).ok()?;
-
-    Some(list)
+        .or_else(|| find_supply_name_exact(dev, "cpu"))
+        .and_then(|name| kernel::kvec![name].ok())
 }
 
 /// Represents the cpufreq dt device.
-- 
2.51.0

Re: [PATCH] rust: cpufreq: streamline find_supply_names

[Viresh Kumar]

On 15-09-25, 15:59, Thorsten Blum wrote:
> Remove local variables from find_supply_names() and use .and_then() with
> the more concise kernel::kvec![] macro, instead of KVec::with_capacity()
> followed by .push() and Some().
> 
> No functional changes intended.
> 
> Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
> ---
>  drivers/cpufreq/rcpufreq_dt.rs | 10 +++-------
>  1 file changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/cpufreq/rcpufreq_dt.rs b/drivers/cpufreq/rcpufreq_dt.rs
> index 7e1fbf9a091f..224d063c7cec 100644
> --- a/drivers/cpufreq/rcpufreq_dt.rs
> +++ b/drivers/cpufreq/rcpufreq_dt.rs
> @@ -28,15 +28,11 @@ 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>> {
>      // Try "cpu0" for older DTs, fallback to "cpu".
> -    let name = (cpu.as_u32() == 0)
> +    (cpu.as_u32() == 0)
>          .then(|| find_supply_name_exact(dev, "cpu0"))
>          .flatten()
> -        .or_else(|| find_supply_name_exact(dev, "cpu"))?;
> -
> -    let mut list = KVec::with_capacity(1, GFP_KERNEL).ok()?;
> -    list.push(name, GFP_KERNEL).ok()?;
> -
> -    Some(list)
> +        .or_else(|| find_supply_name_exact(dev, "cpu"))
> +        .and_then(|name| kernel::kvec![name].ok())
>  }
>  
>  /// Represents the cpufreq dt device.

Applied. Thanks.

-- 
viresh

Re: [PATCH] rust: cpufreq: streamline find_supply_names

[Alice Ryhl]

On Mon, Sep 15, 2025 at 4:01 PM Thorsten Blum <thorsten.blum@linux.dev> wrote:
>
> Remove local variables from find_supply_names() and use .and_then() with
> the more concise kernel::kvec![] macro, instead of KVec::with_capacity()
> followed by .push() and Some().
>
> No functional changes intended.
>
> Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
> ---
>  drivers/cpufreq/rcpufreq_dt.rs | 10 +++-------
>  1 file changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/cpufreq/rcpufreq_dt.rs b/drivers/cpufreq/rcpufreq_dt.rs
> index 7e1fbf9a091f..224d063c7cec 100644
> --- a/drivers/cpufreq/rcpufreq_dt.rs
> +++ b/drivers/cpufreq/rcpufreq_dt.rs
> @@ -28,15 +28,11 @@ 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>> {
>      // Try "cpu0" for older DTs, fallback to "cpu".
> -    let name = (cpu.as_u32() == 0)
> +    (cpu.as_u32() == 0)
>          .then(|| find_supply_name_exact(dev, "cpu0"))
>          .flatten()
> -        .or_else(|| find_supply_name_exact(dev, "cpu"))?;
> -
> -    let mut list = KVec::with_capacity(1, GFP_KERNEL).ok()?;
> -    list.push(name, GFP_KERNEL).ok()?;
> -
> -    Some(list)
> +        .or_else(|| find_supply_name_exact(dev, "cpu"))
> +        .and_then(|name| kernel::kvec![name].ok())

This is a pre-existing issue, but ... this treats allocation failure
and non-existence the same way. That sounds wrong.

Alice

Re: [PATCH] rust: cpufreq: streamline find_supply_names

[Viresh Kumar]

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