[PATCH v4 12/16] rust: drm: return ParentDevice from Device AsRef

[Danilo Krummrich <dakr@kernel.org>]

Change AsRef for drm::Device to return &T::ParentDevice<device::Normal>
instead of &device::Device, and restrict it to the Normal context.
Device<T, Registered> still gets this through Deref coercion.

This provides access to the typed parent bus device rather than the raw
base device.

Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/kernel/drm/device.rs | 10 +++++++---
 rust/kernel/drm/driver.rs |  2 +-
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs
index c32cc0f0eba0..45bacd7b227f 100644
--- a/rust/kernel/drm/device.rs
+++ b/rust/kernel/drm/device.rs
@@ -450,11 +450,15 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
     }
 }
 
-impl<T: drm::Driver, C: DeviceContext> AsRef<device::Device> for Device<T, C> {
-    fn as_ref(&self) -> &device::Device {
+impl<T: drm::Driver> AsRef<T::ParentDevice<device::Normal>> for Device<T> {
+    fn as_ref(&self) -> &T::ParentDevice<device::Normal> {
         // SAFETY: `bindings::drm_device::dev` is valid as long as the DRM device itself is valid,
         // which is guaranteed by the type invariant.
-        unsafe { device::Device::from_raw((*self.as_raw()).dev) }
+        let dev = unsafe { device::Device::from_raw((*self.as_raw()).dev) };
+
+        // SAFETY: By the type invariant of `Device`, the parent device is embedded in
+        // `T::ParentDevice`.
+        unsafe { device::AsBusDevice::from_device(dev) }
     }
 }
 
diff --git a/rust/kernel/drm/driver.rs b/rust/kernel/drm/driver.rs
index 3cda8dceb498..ceb2829985c7 100644
--- a/rust/kernel/drm/driver.rs
+++ b/rust/kernel/drm/driver.rs
@@ -170,7 +170,7 @@ pub fn new_foreign_owned<'a>(
     where
         T: 'static,
     {
-        if drm.as_ref().as_raw() != dev.as_raw() {
+        if drm.as_ref().as_ref().as_raw() != dev.as_raw() {
             return Err(EINVAL);
         }
 
-- 
2.54.0