[PATCH v3 07/27] rust: auxiliary: implement Sync for Device<Bound>

[Danilo Krummrich]

Implement Sync for Device<Bound> in addition to Device<Normal>.

Device<Bound> uses the same underlying struct auxiliary_device as
Device<Normal>; Bound is a zero-sized type-state marker that does not
affect thread safety.

This is needed for drivers to store &'bound auxiliary::Device<Bound> in
their private data while remaining Send.

Signed-off-by: Danilo Krummrich <dakr@xxxxxxxxxx>
---
 rust/kernel/auxiliary.rs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/rust/kernel/auxiliary.rs b/rust/kernel/auxiliary.rs
index 1b6ff3817a4d..c6d97c95c3e7 100644
--- a/rust/kernel/auxiliary.rs
+++ b/rust/kernel/auxiliary.rs
@@ -369,6 +369,10 @@ unsafe impl Send for Device {}
 // (i.e. `Device<Normal>) are thread safe.
 unsafe impl Sync for Device {}
 
+// SAFETY: Same as `Device<Normal>` -- the underlying `struct auxiliary_device` is the same;
+// `Bound` is a zero-sized type-state marker that does not affect thread safety.
+unsafe impl Sync for Device<device::Bound> {}
+
 /// Wrapper that stores a [`TypeId`] alongside the registration data for runtime type checking.
 #[repr(C)]
 #[pin_data]
-- 
2.54.0