rust: auxiliary: implement Sync for Device<Bound>

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.

Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Uwe Kleine-König <ukleinek@kernel.org>
Tested-by: Dirk Behme <dirk.behme@de.bosch.com>
Link: https://patch.msgid.link/20260525202921.124698-9-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

diff --git a/rust/kernel/auxiliary.rs b/rust/kernel/auxiliary.rs
index 4e83f9e27d78fad706b1f9321c5ffff1599998b1..df2c97423dcc97be79aedd575ca3f0f9679da4eb 100644 (file)
--- 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]