linux-kernel - Re: [PATCH V8 06/14] rust: Add bare minimal bindings for clk framework

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Message-ID: <Z6VBo51g54xAmelQ@cassiopeiae>
Date: Fri, 7 Feb 2025 00:11:31 +0100
From: Danilo Krummrich <dakr@...nel.org>
To: Stephen Boyd <sboyd@...nel.org>
Cc: Viresh Kumar <viresh.kumar@...aro.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
	Danilo Krummrich <dakr@...hat.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>,
	Michael Turquette <mturquette@...libre.com>,
	linux-pm@...r.kernel.org,
	Vincent Guittot <vincent.guittot@...aro.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, linux-clk@...r.kernel.org
Subject: Re: [PATCH V8 06/14] rust: Add bare minimal bindings for clk
 framework

On Thu, Feb 06, 2025 at 12:05:59PM -0800, Stephen Boyd wrote:
> Quoting Danilo Krummrich (2025-02-06 03:52:41)
> > On Thu, Feb 06, 2025 at 12:49:14PM +0100, Danilo Krummrich wrote:
> > > On Thu, Feb 06, 2025 at 02:58:27PM +0530, Viresh Kumar wrote:
> > > > diff --git a/rust/kernel/clk.rs b/rust/kernel/clk.rs
> > > > new file mode 100644
> > > > index 000000000000..123cdb43b115
> > > > --- /dev/null
> > > > +++ b/rust/kernel/clk.rs
> > > > @@ -0,0 +1,48 @@
> > > > +// SPDX-License-Identifier: GPL-2.0
> > > > +
> > > > +//! Clock abstractions.
> > > > +//!
> > > > +//! C header: [`include/linux/clk.h`](srctree/include/linux/clk.h)
> > > > +
> > > > +use crate::{
> > > > +    bindings,
> > > > +    device::Device,
> > > > +    error::{from_err_ptr, Result},
> > > > +    prelude::*,
> > > > +};
> > > > +
> > > > +use core::ptr;
> > > > +
> > > > +/// A simple implementation of `struct clk` from the C code.
> > > > +#[repr(transparent)]
> > > > +pub struct Clk(*mut bindings::clk);
> > > 
> > > Guess this should be Opaque<bindings::clk>.
> > 
> > Sorry, I meant NonNull<bindings::clk>.
> 
> NULL is a valid clk. It's like "don't care" in the common clk framework

Thanks for clarifying!

> as most clk consumer operations bail out early in that case.

Most? Does that mean NULL isn't *always* valid?