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

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Message-ID: <Z6ShsuLykigNscz8@pollux>
Date: Thu, 6 Feb 2025 12:49:06 +0100
From: Danilo Krummrich <dakr@...nel.org>
To: Viresh Kumar <viresh.kumar@...aro.org>
Cc: "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>,
	Stephen Boyd <sboyd@...nel.org>, 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 02:58:27PM +0530, Viresh Kumar wrote:
> This adds very basic bindings for the clk framework, implements only
> clk_get() and clk_put(). These are the bare minimum bindings required
> for many users and are simple enough to add in the first attempt.
> 
> These will be used by Rust based cpufreq / OPP core to begin with.
> 
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
>  MAINTAINERS                     |  1 +
>  rust/bindings/bindings_helper.h |  1 +
>  rust/kernel/clk.rs              | 48 +++++++++++++++++++++++++++++++++
>  rust/kernel/lib.rs              |  2 ++
>  4 files changed, 52 insertions(+)
>  create mode 100644 rust/kernel/clk.rs
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index ff4511914e0a..604717065476 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -5780,6 +5780,7 @@ F:	include/dt-bindings/clock/
>  F:	include/linux/clk-pr*
>  F:	include/linux/clk/
>  F:	include/linux/of_clk.h
> +F:	rust/kernel/clk.rs
>  X:	drivers/clk/clkdev.c
>  
>  COMMON INTERNET FILE SYSTEM CLIENT (CIFS and SMB3)
> diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
> index 59b4bc49d039..4eadcf645df0 100644
> --- a/rust/bindings/bindings_helper.h
> +++ b/rust/bindings/bindings_helper.h
> @@ -10,6 +10,7 @@
>  #include <linux/blk-mq.h>
>  #include <linux/blk_types.h>
>  #include <linux/blkdev.h>
> +#include <linux/clk.h>
>  #include <linux/cpu.h>
>  #include <linux/cpumask.h>
>  #include <linux/cred.h>
> 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>.

> +
> +impl Clk {
> +    /// Creates `Clk` instance for a device and a connection id.
> +    pub fn new(dev: &Device, name: Option<&CStr>) -> Result<Self> {
> +        let con_id = if let Some(name) = name {
> +            name.as_ptr() as *const _
> +        } else {
> +            ptr::null()
> +        };
> +
> +        // SAFETY: It is safe to call `clk_get()`, on a device pointer earlier received from the C
> +        // code.
> +        Ok(Self(from_err_ptr(unsafe {
> +            bindings::clk_get(dev.as_raw(), con_id)
> +        })?))
> +    }
> +
> +    /// Obtain the raw `struct clk *`.
> +    pub fn as_raw(&self) -> *mut bindings::clk {
> +        self.0
> +    }
> +}
> +
> +impl Drop for Clk {
> +    fn drop(&mut self) {
> +        // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
> +        // relinquish it now.
> +        unsafe { bindings::clk_put(self.0) };
> +    }
> +}
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index ccbf7fa087a0..77d3b1f82154 100644
> --- a/rust/kernel/lib.rs
> +++ b/rust/kernel/lib.rs
> @@ -40,6 +40,8 @@
>  pub mod block;
>  #[doc(hidden)]
>  pub mod build_assert;
> +#[cfg(CONFIG_COMMON_CLK)]
> +pub mod clk;
>  pub mod cpu;
>  pub mod cpumask;
>  pub mod cred;
> -- 
> 2.31.1.272.g89b43f80a514
> 
>