[RFC v3 23/33] rust: drm/kms: Add RawPlaneState::crtc()

[Lyude Paul <lyude@redhat.com>]

Add a binding for checking drm_plane_state.crtc. Note that we don't have a
way of knowing what DriverCrtc implementation would be used here (and want
to make this function also available on OpaquePlaneState types), so we
return an OpaqueCrtc.

Signed-off-by: Lyude Paul <lyude@redhat.com>
---
 rust/kernel/drm/kms/plane.rs | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/drm/kms/plane.rs b/rust/kernel/drm/kms/plane.rs
index f3adc30c17489..a30f7f8caaafb 100644
--- a/rust/kernel/drm/kms/plane.rs
+++ b/rust/kernel/drm/kms/plane.rs
@@ -5,7 +5,8 @@
 //! C header: [`include/drm/drm_plane.h`](srctree/include/drm/drm_plane.h)
 
 use super::{
-    atomic::*, KmsDriver, ModeObject, ModeObjectVtable, StaticModeObject, UnregisteredKmsDevice,
+    atomic::*, crtc::*, KmsDriver, ModeObject, ModeObjectVtable, StaticModeObject,
+    UnregisteredKmsDevice,
 };
 use crate::{
     alloc::KBox,
@@ -608,6 +609,16 @@ fn plane(&self) -> &Self::Plane {
         // invariant throughout the lifetime of the Plane
         unsafe { Self::Plane::from_raw(self.as_raw().plane) }
     }
+
+    /// Return the current [`OpaqueCrtc`] assigned to this plane, if there is one.
+    fn crtc<'a, 'b: 'a, D>(&'a self) -> Option<&'b OpaqueCrtc<D>>
+    where
+        Self::Plane: ModeObject<Driver = D>,
+        D: KmsDriver,
+    {
+        // SAFETY: This cast is guaranteed safe by `OpaqueCrtc`s invariants.
+        NonNull::new(self.as_raw().crtc).map(|c| unsafe { OpaqueCrtc::from_raw(c.as_ptr()) })
+    }
 }
 impl<T: AsRawPlaneState + ?Sized> RawPlaneState for T {}
 
-- 
2.48.1