[PATCH v2 3/4] rust: workqueue: add delayed work support for ARef<T>

[Daniel Almeida <daniel.almeida@collabora.com>]

The preceding patches added support for ARef<T> work items. By the same
token, add support for delayed work items too.

The rationale is the same: it may be convenient or even necessary at times
to implement HasDelayedWork directly on ARef<T>. A follow up patch will
also implement support for drm::Device as the first user.

Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
---
 rust/kernel/workqueue.rs | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/rust/kernel/workqueue.rs b/rust/kernel/workqueue.rs
index 6ae7f3fb3496..4ee4ff567197 100644
--- a/rust/kernel/workqueue.rs
+++ b/rust/kernel/workqueue.rs
@@ -1007,6 +1007,17 @@ unsafe fn __enqueue<F>(self, queue_work_on: F) -> Self::EnqueueOutput
     }
 }
 
+// SAFETY: By the safety requirements of `HasDelayedWork`, the `work_struct` returned by methods in
+// `HasWork` provides a `work_struct` that is the `work` field of a `delayed_work`, and the rest of
+// the `delayed_work` has the same access rules as its `work` field.
+unsafe impl<T, const ID: u64> RawDelayedWorkItem<ID> for ARef<T>
+where
+    T: WorkItem<ID, Pointer = Self>,
+    T: HasDelayedWork<T, ID>,
+    T: AlwaysRefCounted,
+{
+}
+
 /// Returns the system work queue (`system_wq`).
 ///
 /// It is the one used by `schedule[_delayed]_work[_on]()`. Multi-CPU multi-threaded. There are

-- 
2.52.0