linux-kernel - Re: [PATCH v2 1/2] rust: clk: implement Send and Sync

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Message-ID: <aMG6JVMcMxVuX7De@tardis-2.local>
Date: Wed, 10 Sep 2025 10:49:25 -0700
From: Boqun Feng <boqun.feng@...il.com>
To: Daniel Almeida <daniel.almeida@...labora.com>
Cc: Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...nel.org>, Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...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>,
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
	Danilo Krummrich <dakr@...nel.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Viresh Kumar <viresh.kumar@...aro.org>, linux-clk@...r.kernel.org,
	rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org
Subject: Re: [PATCH v2 1/2] rust: clk: implement Send and Sync

On Wed, Sep 10, 2025 at 02:28:27PM -0300, Daniel Almeida wrote:
> From: Alice Ryhl <aliceryhl@...gle.com>
> 
> 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: Daniel Almeida <daniel.almeida@...labora.com>
> Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>
> Reviewed-by: Danilo Krummrich <dakr@...nel.org>
> Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
> Reviewed-by: Daniel Almeida <daniel.almeida@...labora.com>

This tag list looks a bit weird to me. Why is there a SoB from you
before Alice's SoB? At least for the usage I'm familiar with, outside
the case of Co-developed-bys, multiple SoBs is used for recording how
the patches are routed. For example, if I have a patch that has my SoB
and I send it to you, you queue in your tree and then send out to other
maintainers for merging, in general you would put your SoB after mine in
that case. But I don't think that's case here? Alice's patch has only
her SoB:

	https://lore.kernel.org/rust-for-linux/20250904-clk-send-sync-v1-1-48d023320eb8@google.com/

What's the intention of the SoB tag here?

Otherwise the patch looks good to me. If we get the tag list resolved,
feel free to add:

Reviewed-by: Boqun Feng <boqun.feng@...il.com>

Regards,
Boqun

> ---
>  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.
>          ///
> 
> -- 
> 2.51.0
>