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

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Message-ID: <CAH5fLgg0_NBtfVMNBwXOe4BpyUKz_S=v0CiDxyKNYZcS9j7WHw@mail.gmail.com>
Date: Mon, 29 Sep 2025 11:38:37 +0200
From: Alice Ryhl <aliceryhl@...gle.com>
To: Thorsten Blum <thorsten.blum@...ux.dev>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Viresh Kumar <viresh.kumar@...aro.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 Mon, Sep 15, 2025 at 4:01 PM Thorsten Blum <thorsten.blum@...ux.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@...ux.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