[RFC v3 08/33] rust: drm/kms: Add UnregisteredConnector::attach_encoder()

[Lyude Paul]

This adds a simple binding for completing the last step of creating a DRM
connector - attaching its encoder. This function should only be called
before the connector is registered, and DRM should enforce this itself by
returning an error if a driver tries to add an encoder to an
already-registered DRM connector.

Note that unlike most of the methods we'll be adding to DRM mode objects,
this is directly implemented on the Connector<T> type since I don't really
think it would make sense for us to allow this operation on an
OpaqueConnector (a DRM connector without a known DriverConnector
implementation, something we'll be adding in the next few commits).

Signed-off-by: Lyude Paul <lyude@xxxxxxxxxx>

---

V3:
* Move to UnregisteredConnector interface
* Improve safety comments

Signed-off-by: Lyude Paul <lyude@xxxxxxxxxx>
---
 rust/kernel/drm/kms/connector.rs | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/drm/kms/connector.rs b/rust/kernel/drm/kms/connector.rs
index ed65c06ece627..6fe0a7517bd55 100644
--- a/rust/kernel/drm/kms/connector.rs
+++ b/rust/kernel/drm/kms/connector.rs
@@ -4,7 +4,7 @@
 //!
 //! C header: [`include/drm/drm_connector.h`](srctree/include/drm/drm_connector.h)
 
-use super::{KmsDriver, ModeObject, RcModeObject};
+use super::{encoder::*, KmsDriver, ModeObject, RcModeObject};
 use crate::{
     alloc::KBox,
     bindings,
@@ -362,6 +362,18 @@ pub fn new<'a>(
         // SAFETY: We just allocated the connector above, so this pointer must be valid
         Ok(unsafe { &*this })
     }
+
+    /// Attach an encoder to this [`Connector`].
+    #[must_use]
+    pub fn attach_encoder(&self, encoder: &impl AsRawEncoder) -> Result {
+        // SAFETY:
+        // - Both as_raw() calls are guaranteed to return a valid pointer
+        // - We're guaranteed this connector is not registered via our type invariants, thus this
+        //   function is safe to call
+        to_result(unsafe {
+            bindings::drm_connector_attach_encoder(self.as_raw(), encoder.as_raw())
+        })
+    }
 }
 
 unsafe extern "C" fn connector_destroy_callback<T: DriverConnector>(
-- 
2.48.1