[WIP RFC v2 19/35] WIP: rust: drm/kms: Add OpaqueEncoder

[Lyude Paul]

Same thing as OpaquePlane, but for encoders now.

Signed-off-by: Lyude Paul <lyude at redhat.com>

---

TODO:
* Add upcast functions for this

Signed-off-by: Lyude Paul <lyude at redhat.com>
---
 rust/kernel/drm/kms/encoder.rs | 55 ++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/rust/kernel/drm/kms/encoder.rs b/rust/kernel/drm/kms/encoder.rs
index 3ae597093645e..71fae45d2d651 100644
--- a/rust/kernel/drm/kms/encoder.rs
+++ b/rust/kernel/drm/kms/encoder.rs
@@ -235,6 +235,61 @@ pub fn new<'a, 'b: 'a>(
     }
 }
 
+/// A [`struct drm_encoder`] without a known [`DriverEncoder`] implementation.
+///
+/// This is mainly for situations where our bindings can't infer the [`DriverEncoder`] implementation
+/// for a [`struct drm_encoder`] automatically. It is identical to [`Encoder`], except that it does not
+/// provide access to the driver's private data.
+///
+/// TODO: Add functions for upcasting.
+///
+/// # Invariants
+///
+/// Same as [`Encoder`].
+#[repr(transparent)]
+pub struct OpaqueEncoder<T: KmsDriver> {
+    encoder: Opaque<bindings::drm_encoder>,
+    _p: PhantomData<T>,
+}
+
+impl<T: KmsDriver> Sealed for OpaqueEncoder<T> {}
+
+// SAFETY: All of our encoder interfaces are thread-safe
+unsafe impl<T: KmsDriver> Send for OpaqueEncoder<T> {}
+
+// SAFETY: All of our encoder interfaces are thread-safe
+unsafe impl<T: KmsDriver> Sync for OpaqueEncoder<T> {}
+
+impl<T: KmsDriver> ModeObject for OpaqueEncoder<T> {
+    type Driver = T;
+
+    fn drm_dev(&self) -> &Device<Self::Driver> {
+        // SAFETY: DRM encoders exist for as long as the device does, so this pointer is always
+        // valid
+        unsafe { Device::borrow((*self.encoder.get()).dev) }
+    }
+
+    fn raw_mode_obj(&self) -> *mut bindings::drm_mode_object {
+        // SAFETY: We don't expose Encoder<T> to users before it's initialized, so `base` is always
+        // initialized
+        unsafe { addr_of_mut!((*self.encoder.get()).base) }
+    }
+}
+
+// SAFETY: Encoders do not have a refcount
+unsafe impl<T: KmsDriver> StaticModeObject for OpaqueEncoder<T> {}
+
+impl<T: KmsDriver> AsRawEncoder for OpaqueEncoder<T> {
+    fn as_raw(&self) -> *mut bindings::drm_encoder {
+        self.encoder.get()
+    }
+
+    unsafe fn from_raw<'a>(ptr: *mut bindings::drm_encoder) -> &'a Self {
+        // SAFETY: Our data layout is identical to `bindings::drm_encoder`
+        unsafe { &*ptr.cast() }
+    }
+}
+
 unsafe extern "C" fn encoder_destroy_callback<T: DriverEncoder>(
     encoder: *mut bindings::drm_encoder
 ) {
-- 
2.46.1