linux-kernel - [PATCH] rust: time: Seal the ClockSource trait

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Message-ID: <20250617232053.3927525-1-fujita.tomonori@gmail.com>
Date: Wed, 18 Jun 2025 08:20:53 +0900
From: FUJITA Tomonori <fujita.tomonori@...il.com>
To: a.hindborg@...nel.org,
	alex.gaynor@...il.com,
	ojeda@...nel.org
Cc: aliceryhl@...gle.com,
	anna-maria@...utronix.de,
	bjorn3_gh@...tonmail.com,
	boqun.feng@...il.com,
	dakr@...nel.org,
	frederic@...nel.org,
	gary@...yguo.net,
	jstultz@...gle.com,
	linux-kernel@...r.kernel.org,
	lossin@...nel.org,
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	rust-for-linux@...r.kernel.org,
	sboyd@...nel.org,
	tglx@...utronix.de,
	tmgross@...ch.edu
Subject: [PATCH] rust: time: Seal the ClockSource trait

Prevent downstream crates or drivers from implementing `ClockSource`
for arbitrary types, which could otherwise leads to unsupported
behavior.

Introduce a `private::Sealed` trait and implement it for all types
that implement `ClockSource`.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@...il.com>
---
 rust/kernel/time.rs | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/time.rs b/rust/kernel/time.rs
index eaa6d9ab5737..b1961652c884 100644
--- a/rust/kernel/time.rs
+++ b/rust/kernel/time.rs
@@ -51,6 +51,15 @@ pub fn msecs_to_jiffies(msecs: Msecs) -> Jiffies {
     unsafe { bindings::__msecs_to_jiffies(msecs) }
 }
 
+mod private {
+    pub trait Sealed {}
+
+    impl Sealed for super::Monotonic {}
+    impl Sealed for super::RealTime {}
+    impl Sealed for super::BootTime {}
+    impl Sealed for super::Tai {}
+}
+
 /// Trait for clock sources.
 ///
 /// Selection of the clock source depends on the use case. In some cases the usage of a
@@ -58,7 +67,7 @@ pub fn msecs_to_jiffies(msecs: Msecs) -> Jiffies {
 /// cases the user of the clock has to decide which clock is best suited for the
 /// purpose. In most scenarios clock [`Monotonic`] is the best choice as it
 /// provides a accurate monotonic notion of time (leap second smearing ignored).
-pub trait ClockSource {
+pub trait ClockSource: private::Sealed {
     /// The kernel clock ID associated with this clock source.
     ///
     /// This constant corresponds to the C side `clockid_t` value.

base-commit: 994393295c89711531583f6de8f296a30b0d944a
-- 
2.43.0