[PATCH v3 04/13] rust: drm: restrict AlwaysRefCounted to Normal Device context

[Danilo Krummrich <dakr@kernel.org>]

Restrict the AlwaysRefCounted implementation for drm::Device to the
Normal context. Registered devices represent a non-owning view of a
device within a RegistrationGuard scope and must not be independently
reference-counted.

Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/kernel/drm/device.rs | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs
index d712387707d2..9825d52832af 100644
--- a/rust/kernel/drm/device.rs
+++ b/rust/kernel/drm/device.rs
@@ -85,6 +85,9 @@ pub trait DeviceContext: Sealed + Send + Sync {}
 ///
 /// A [`Device`] in this context may or may not be registered with userspace. This context is used
 /// for reference-counted device handles and during device setup via [`UnregisteredDevice`].
+///
+/// [`AlwaysRefCounted`] is only implemented for `Device<T, Normal>`, making this the required
+/// context for [`ARef`]-based device handles.
 pub struct Normal;
 
 impl Sealed for Normal {}
@@ -327,7 +330,7 @@ fn deref(&self) -> &Self::Target {
 
 // SAFETY: DRM device objects are always reference counted and the get/put functions
 // satisfy the requirements.
-unsafe impl<T: drm::Driver, C: DeviceContext> AlwaysRefCounted for Device<T, C> {
+unsafe impl<T: drm::Driver> AlwaysRefCounted for Device<T> {
     fn inc_ref(&self) {
         // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
         unsafe { bindings::drm_dev_get(self.as_raw()) };
@@ -357,12 +360,10 @@ unsafe impl<T: drm::Driver, C: DeviceContext> Send for Device<T, C> {}
 // by the synchronization in `struct drm_device`.
 unsafe impl<T: drm::Driver, C: DeviceContext> Sync for Device<T, C> {}
 
-impl<T, C, const ID: u64> WorkItem<ID> for Device<T, C>
+impl<T: drm::Driver, const ID: u64> WorkItem<ID> for Device<T>
 where
-    T: drm::Driver,
     T::Data: WorkItem<ID, Pointer = ARef<Self>>,
     T::Data: HasWork<Self, ID>,
-    C: DeviceContext,
 {
     type Pointer = ARef<Self>;
 
-- 
2.54.0