netdev - [net-next PATCH] rust: net: phy: Correct the safety comment for impl Sync

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Message-ID: <20231211194909.588574-1-boqun.feng@gmail.com>
Date: Mon, 11 Dec 2023 11:49:09 -0800
From: Boqun Feng <boqun.feng@...il.com>
To: netdev@...r.kernel.org
Cc: rust-for-linux@...r.kernel.org,
	andrew@...n.ch,
	tmgross@...ch.edu,
	miguel.ojeda.sandonis@...il.com,
	benno.lossin@...ton.me,
	wedsonaf@...il.com,
	aliceryhl@...gle.com,
	boqun.feng@...il.com
Subject: [net-next PATCH] rust: net: phy: Correct the safety comment for impl Sync

The current safety comment for impl Sync for DriverVTable has two
problem:

* the correctness is unclear, since all types impl Any[1], therefore all
  types have a `&self` method (Any::type_id).

* it doesn't explain why useless of immutable references can ensure the
  safety.

Fix this by rewritting the comment.

[1]: https://doc.rust-lang.org/std/any/trait.Any.html

Signed-off-by: Boqun Feng <boqun.feng@...il.com>
---
This is a follow-up for my ignored feedback:

	https://lore.kernel.org/rust-for-linux/ZV5FjEM1EWm6iTAm@boqun-archlinux/	

Honestly, I believe that people who are active in the review process all
get it right, but I want to make sure who read the code later can also
understand it and reuse the reasoning in their code. Hence this
improvement.

Tomo, feel free to fold it in your patch if you and others think the
wording is fine.

 rust/kernel/net/phy.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/rust/kernel/net/phy.rs b/rust/kernel/net/phy.rs
index d9cec139324a..e3377f8f36b7 100644
--- a/rust/kernel/net/phy.rs
+++ b/rust/kernel/net/phy.rs
@@ -489,8 +489,8 @@ impl<T: Driver> Adapter<T> {
 #[repr(transparent)]
 pub struct DriverVTable(Opaque<bindings::phy_driver>);

-// SAFETY: `DriverVTable` has no &self methods, so immutable references to it
-// are useless.
+// SAFETY: `DriverVTable` doesn't expose any &self method to access internal data, so it's safe to
+// share `&DriverVTable` across execution context boundries.
 unsafe impl Sync for DriverVTable {}

 /// Creates a [`DriverVTable`] instance from [`Driver`].
-- 
2.43.0