linux-kernel - Re: [PATCH] rust: clk: use the type-state pattern

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Message-Id: <9746F6D6-488C-4562-8FB1-BE268C69BA97@collabora.com>
Date: Wed, 30 Jul 2025 09:27:18 -0300
From: Daniel Almeida <daniel.almeida@...labora.com>
To: Viresh Kumar <viresh.kumar@...aro.org>
Cc: Michael Turquette <mturquette@...libre.com>,
 Stephen Boyd <sboyd@...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>,
 Alice Ryhl <aliceryhl@...gle.com>,
 Trevor Gross <tmgross@...ch.edu>,
 Danilo Krummrich <dakr@...nel.org>,
 "Rafael J. Wysocki" <rafael@...nel.org>,
 Alexandre Courbot <acourbot@...dia.com>,
 linux-clk@...r.kernel.org,
 rust-for-linux@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 linux-pm@...r.kernel.org
Subject: Re: [PATCH] rust: clk: use the type-state pattern

Hi Viresh,

> On 30 Jul 2025, at 03:23, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> 
> On 29-07-25, 18:38, Daniel Almeida wrote:
>> diff --git a/rust/kernel/clk.rs b/rust/kernel/clk.rs
>>     /// A reference-counted clock.
>>     ///
>>     /// Rust abstraction for the C [`struct clk`].
>>     ///
>> +    /// A [`Clk`] instance represents a clock that can be in one of several
>> +    /// states: [`Unprepared`], [`Prepared`], or [`Enabled`].
>> +    ///
>> +    /// No action needs to be taken when a [`Clk`] is dropped. The calls to
>> +    /// `clk_unprepare()` and `clk_disable()` will be placed as applicable.
>> +    ///
>> +    /// An optional [`Clk`] is treated just like a regular [`Clk`], but its
>> +    /// inner `struct clk` pointer is `NULL`. This interfaces correctly with the
>> +    /// C API and also exposes all the methods of a regular [`Clk`] to users.
>> +    ///
>>     /// # Invariants
>>     ///
>>     /// A [`Clk`] instance holds either a pointer to a valid [`struct clk`] created by the C
>> @@ -99,20 +160,39 @@ mod common_clk {
>>     /// Instances of this type are reference-counted. Calling [`Clk::get`] ensures that the
>>     /// allocation remains valid for the lifetime of the [`Clk`].
>>     ///
>> -    /// ## Examples
>> +    /// The [`Prepared`] state is associated with a single count of
>> +    /// `clk_prepare()`, and the [`Enabled`] state is associated with a single
>> +    /// count of `clk_enable()`, and the [`Enabled`] state is associated with a
>> +    /// single count of `clk_prepare` and `clk_enable()`.
> 
> You have mentioned the `Enabled` state twice. Also clk_prepare() ?

Ah, thanks for catching that.

What’s the issue with clk_prepare? You mean that the parenthesis are missing?

> 
> No objections from my side. Thanks.
> 
> -- 
> viresh

— Daniel