linux-kernel - Re: [PATCH V3 2/2] rust: Add initial clk abstractions

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Message-ID: <20250306044028.5d2w4og2juclktqs@vireshk-i7>
Date: Thu, 6 Mar 2025 10:10:28 +0530
From: Viresh Kumar <viresh.kumar@...aro.org>
To: Stephen Boyd <sboyd@...nel.org>
Cc: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
	Michael Turquette <mturquette@...libre.com>,
	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 <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
	Russell King <linux@...linux.org.uk>, linux-clk@...r.kernel.org,
	linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Daniel Almeida <daniel.almeida@...labora.com>
Subject: Re: [PATCH V3 2/2] rust: Add initial clk abstractions

On 05-03-25, 14:31, Stephen Boyd wrote:
> Does this mean that a clk consumer has to keep the Result returned from
> enable() in scope until they want to disable the clk?

Yes and no.

> I don't see how
> that makes sense, because most of the time a consumer will enable a clk
> during probe and leave it enabled until system suspend or runtime PM
> suspend time. At that point, they would disable the clk explicitly with
> disable(), but now they would need to drop a reference to do that?

Broadly there are two type of clk users I believe:

1. clk is enabled / disabled from same routine:

   In this case the result can be kept in a local variable and the matching
   cleanup fn will be called at exit.

   fn transfer_data(...) -> Result {
        let _guard = clk.enable()?;

        ...
        transfer-data here
        ...
        // clk.disable() will be called automatically as soon as _guard goes out
        // of scope.
   }

2. clk is enabled / disabled from different routines:

   In this case the caller needs to call dismiss to avoid the automatic freeing
   of resource. Alternatively the returned value can be stored too somewhere,
   but I am not sure if it what users will end up doing.

   fn probe(...) -> Result {
        clk.enable()?.dismiss();

        ...
   }

   fn remove (...) {
        clk.disable();

        ...
   }

-- 
viresh