linux-kernel - [PATCH v2 2/4] rust: drm: gem: Add DriverObject type alias

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Message-ID: <20250516171030.776924-3-lyude@redhat.com>
Date: Fri, 16 May 2025 13:09:17 -0400
From: Lyude Paul <lyude@...hat.com>
To: dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	rust-for-linux@...r.kernel.org
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>,
	Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Boqun Feng <boqun.feng@...il.com>,
	Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>,
	Trevor Gross <tmgross@...ch.edu>,
	Danilo Krummrich <dakr@...nel.org>,
	Daniel Almeida <daniel.almeida@...labora.com>,
	Alyssa Rosenzweig <alyssa@...enzweig.io>,
	Asahi Lina <lina@...hilina.net>
Subject: [PATCH v2 2/4] rust: drm: gem: Add DriverObject type alias

Now that we've cleaned up the generics for gem objects a bit, we're still
left with a bit of generic soup around referring to the Object
implementation for a given driver. Let's clean this up a bit by re-using
the DriverObject identifier we just freed up and turning it into a type
alias for referring to a driver's gem object implementation.

Signed-off-by: Lyude Paul <lyude@...hat.com>
---
 rust/kernel/drm/gem/mod.rs | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs
index f0455cc2aff2d..c17b36948bae3 100644
--- a/rust/kernel/drm/gem/mod.rs
+++ b/rust/kernel/drm/gem/mod.rs
@@ -14,6 +14,9 @@
 };
 use core::{mem, ops::Deref, ptr::NonNull};
 
+/// A type alias for the Object type in use by a [`drm::Driver`].
+pub type DriverObject<T> = <<T as BaseDriverObject>::Driver as drm::Driver>::Object;
+
 /// GEM object functions, which must be implemented by drivers.
 pub trait BaseDriverObject: Sync + Send + Sized {
     /// Parent `Driver` for this object.
@@ -24,18 +27,14 @@ pub trait BaseDriverObject: Sync + Send + Sized {
 
     /// Open a new handle to an existing object, associated with a File.
     fn open(
-        _obj: &<Self::Driver as drm::Driver>::Object,
+        _obj: &DriverObject<Self>,
         _file: &drm::File<<Self::Driver as drm::Driver>::File>,
     ) -> Result {
         Ok(())
     }
 
     /// Close a handle to an existing object, associated with a File.
-    fn close(
-        _obj: &<Self::Driver as drm::Driver>::Object,
-        _file: &drm::File<<Self::Driver as drm::Driver>::File>,
-    ) {
-    }
+    fn close(_obj: &DriverObject<Self>, _file: &drm::File<<Self::Driver as drm::Driver>::File>) {}
 }
 
 /// Trait that represents a GEM object subtype
@@ -82,7 +81,7 @@ extern "C" fn open_callback<T: BaseDriverObject>(
     let file = unsafe { drm::File::<<T::Driver as drm::Driver>::File>::as_ref(raw_file) };
     // SAFETY: `open_callback` is specified in the AllocOps structure for `DriverObject<T>`,
     // ensuring that `raw_obj` is contained within a `DriverObject<T>`
-    let obj = unsafe { <<T::Driver as drm::Driver>::Object as IntoGEMObject>::as_ref(raw_obj) };
+    let obj = unsafe { DriverObject::<T>::as_ref(raw_obj) };
 
     match T::open(obj, file) {
         Err(e) => e.to_errno(),
@@ -99,7 +98,7 @@ extern "C" fn close_callback<T: BaseDriverObject>(
 
     // SAFETY: `close_callback` is specified in the AllocOps structure for `Object<T>`, ensuring
     // that `raw_obj` is indeed contained within a `Object<T>`.
-    let obj = unsafe { <<T::Driver as drm::Driver>::Object as IntoGEMObject>::as_ref(raw_obj) };
+    let obj = unsafe { DriverObject::<T>::as_ref(raw_obj) };
 
     T::close(obj, file);
 }
-- 
2.49.0