linux-kernel - Re: [PATCH] rust: clk: implement Send and Sync

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Message-Id: <CB9F3786-48F0-46EE-BE61-8823E437C786@collabora.com>
Date: Thu, 4 Sep 2025 09:31:28 -0300
From: Daniel Almeida <daniel.almeida@...labora.com>
To: Alice Ryhl <aliceryhl@...gle.com>
Cc: Michael Turquette <mturquette@...libre.com>,
 Stephen Boyd <sboyd@...nel.org>,
 Viresh Kumar <viresh.kumar@...aro.org>,
 Miguel Ojeda <ojeda@...nel.org>,
 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>,
 Trevor Gross <tmgross@...ch.edu>,
 Danilo Krummrich <dakr@...nel.org>,
 linux-clk@...r.kernel.org,
 rust-for-linux@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rust: clk: implement Send and Sync

Hi Alice, good catch, this is indeed missing.

> On 4 Sep 2025, at 06:03, Alice Ryhl <aliceryhl@...gle.com> wrote:
> 
> These traits are required for drivers to embed the Clk type in their own
> data structures because driver data structures are usually required to
> be Send. See e.g. [1] for the kind of workaround that drivers currently
> need due to lacking this annotation.
> 
> Link: https://lore.kernel.org/rust-for-linux/20250812-tyr-v2-1-9e0f3dc9da95@collabora.com/ [1]
> Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>
> ---
> I'm not sure if there was already sent a patch for this. I recall
> being told that one had been sent, but I could not find it. Maybe I
> mixed it up with the regulator change, so now I'm sending a change for
> clk.
> ---
> rust/kernel/clk.rs | 7 +++++++
> 1 file changed, 7 insertions(+)
> 
> diff --git a/rust/kernel/clk.rs b/rust/kernel/clk.rs
> index 1e6c8c42fb3a321951e275101848b35e1ae5c2a8..0a290202da69669d670ddad2b6762a1d5f1d912e 100644
> --- a/rust/kernel/clk.rs
> +++ b/rust/kernel/clk.rs
> @@ -129,6 +129,13 @@ mod common_clk {
>     #[repr(transparent)]
>     pub struct Clk(*mut bindings::clk);
> 
> +    // SAFETY: It is safe to call `clk_put` on another thread than where `clk_get` was called.
> +    unsafe impl Send for Clk {}
> +
> +    // SAFETY: It is safe to call any combination of the `&self` methods in parallel, as the
> +    // methods are synchronized internally.
> +    unsafe impl Sync for Clk {}
> +
>     impl Clk {
>         /// Gets [`Clk`] corresponding to a [`Device`] and a connection id.
>         ///
> 
> ---
> base-commit: 1b237f190eb3d36f52dffe07a40b5eb210280e00
> change-id: 20250904-clk-send-sync-3cfa7f4e1ce2
> 
> Best regards,
> -- 
> Alice Ryhl <aliceryhl@...gle.com>
> 

Can you base your change on top of [0]? Otherwise it will become stale rather
quickly, as this introduces new types, i.e.: Clk<Unprepared>, Clk<Prepared>
etc.

I will push out a new version today.

[0]: https://lore.kernel.org/rust-for-linux/20250729-clk-type-state-v1-1-896b53816f7b@collabora.com/