linux-kernel - Re: [PATCH V4 8/8] cpufreq: Add Rust based cpufreq-dt driver

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Message-ID: <20240711130802.vk7af6zd4um3b2cm@vireshk-i7>
Date: Thu, 11 Jul 2024 18:38:02 +0530
From: Viresh Kumar <viresh.kumar@...aro.org>
To: Danilo Krummrich <dakr@...hat.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>,
	Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
	Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Wedson Almeida Filho <wedsonaf@...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@...sung.com>,
	Alice Ryhl <aliceryhl@...gle.com>, linux-pm@...r.kernel.org,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Stephen Boyd <sboyd@...nel.org>, Nishanth Menon <nm@...com>,
	rust-for-linux@...r.kernel.org,
	Manos Pitsidianakis <manos.pitsidianakis@...aro.org>,
	Erik Schilling <erik.schilling@...aro.org>,
	Alex Bennée <alex.bennee@...aro.org>,
	Joakim Bech <joakim.bech@...aro.org>, Rob Herring <robh@...nel.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V4 8/8] cpufreq: Add Rust based cpufreq-dt driver

On 11-07-24, 12:43, Danilo Krummrich wrote:
> Please just call this function `cpufreq::Registration::new`.
> 
> The existance of a `cpufreq::Registration` means that it's registered. Once it
> is dropped, it's unregistered. It's the whole point of a `Registration` type
> to bind the period of a driver being registered to the lifetime of a
> `Registration` instance.
> 
> Having `Registration::register` implies a bit, that we could ever have an
> unregistered `Registration`, which can never happen.
> 
> Besides that, it'd be nice to follow the same naming scheme everywhere.

Sure, ::new() looks fine.

> > +            c_str!("cpufreq-dt"),
> > +            (),
> > +            cpufreq::flags::NEED_INITIAL_FREQ_CHECK | cpufreq::flags::IS_COOLING_DEV,
> > +            true,
> > +        )?;
> > +
> > +        Devres::new_foreign_owned(dev.as_ref(), drv, GFP_KERNEL)?;
> 
> This should be called by `cpufreq::Registration` directly, otherwise it's every
> driver's responsibility to take care of the registration lifetime.

Some details were shared in another thread [1] earlier and I understand that
they are not very clear otherwise.

The problem is that it is not guaranteed that a struct device will be available
to the cpufreq core all the time, to which a platform driver (or other bus) can
be bound. And so this has to be taken care of by the individual drivers only.

-- 
viresh

[1] https://lore.kernel.org/all/20240620100556.xsehtd7ii25rtn7k@vireshk-i7/