linux-kernel - [PATCH 2/2] rust: drm: gem: Add ObjectFile type alias

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Message-ID: <20250515214425.671423-3-lyude@redhat.com>
Date: Thu, 15 May 2025 17:42:38 -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 2/2] rust: drm: gem: Add ObjectFile type alias

Just to reduce the clutter with the File<…> types in gem.rs.

Signed-off-by: Lyude Paul <lyude@...hat.com>
---
 rust/kernel/drm/gem/mod.rs | 34 ++++++++++++++--------------------
 1 file changed, 14 insertions(+), 20 deletions(-)

diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs
index ffd45419d563a..b1f2bd4aa8cf8 100644
--- a/rust/kernel/drm/gem/mod.rs
+++ b/rust/kernel/drm/gem/mod.rs
@@ -14,6 +14,13 @@
 };
 use core::{mem, ops::Deref, ptr::NonNull};
 
+/// A type alias for retrieving a [`Driver`]s [`DriverFile`] implementation from its
+/// [`DriverObject`] implementation.
+///
+/// [`Driver`]: drm::Driver
+/// [`DriverFile`]: drm::file::DriverFile
+pub type ObjectFile<T> = drm::File<<<T as DriverObject>::Driver as drm::Driver>::File>;
+
 /// GEM object functions, which must be implemented by drivers.
 pub trait DriverObject: Sync + Send + Sized {
     /// Parent `Driver` for this object.
@@ -23,18 +30,12 @@ pub trait DriverObject: Sync + Send + Sized {
     fn new(dev: &drm::Device<Self::Driver>, size: usize) -> impl PinInit<Self, Error>;
 
     /// Open a new handle to an existing object, associated with a File.
-    fn open(
-        _obj: &Object<Self>,
-        _file: &drm::File<<Self::Driver as drm::Driver>::File>,
-    ) -> Result {
+    fn open(_obj: &Object<Self>, _file: &ObjectFile<Self>) -> Result {
         Ok(())
     }
 
     /// Close a handle to an existing object, associated with a File.
-    fn close(
-        _obj: &Object<Self>,
-        _file: &drm::File<<Self::Driver as drm::Driver>::File>,
-    ) {
+    fn close(_obj: &Object<Self>, _file: &ObjectFile<Self>) {
     }
 }
 
@@ -79,9 +80,8 @@ extern "C" fn open_callback<T: DriverObject>(
     raw_file: *mut bindings::drm_file,
 ) -> core::ffi::c_int {
     // SAFETY: `open_callback` is only ever called with a valid pointer to a `struct drm_file`.
-    let file = unsafe {
-        drm::File::<<T::Driver as drm::Driver>::File>::as_ref(raw_file)
-    };
+    let file = unsafe { ObjectFile::<T>::as_ref(raw_file) };
+
     // SAFETY: `open_callback` is specified in the AllocOps structure for `Object<T>`, ensuring that
     // `raw_obj` is indeed contained within a `Object<T>`.
     let obj = unsafe { Object::<T>::as_ref(raw_obj) };
@@ -97,7 +97,7 @@ extern "C" fn close_callback<T: DriverObject>(
     raw_file: *mut bindings::drm_file,
 ) {
     // SAFETY: `open_callback` is only ever called with a valid pointer to a `struct drm_file`.
-    let file = unsafe { drm::File::<<T::Driver as drm::Driver>::File>::as_ref(raw_file) };
+    let file = unsafe { ObjectFile::<T>::as_ref(raw_file) };
 
     // SAFETY: `close_callback` is specified in the AllocOps structure for `Object<T>`, ensuring
     // that `raw_obj` is indeed contained within a `Object<T>`.
@@ -128,10 +128,7 @@ fn size(&self) -> usize {
 
     /// Creates a new handle for the object associated with a given `File`
     /// (or returns an existing one).
-    fn create_handle(
-        &self,
-        file: &drm::File<<Self::Driver as drm::Driver>::File>,
-    ) -> Result<u32>
+    fn create_handle(&self, file: &ObjectFile<Self>) -> Result<u32>
     where
         Self: DriverObject
     {
@@ -144,10 +141,7 @@ fn create_handle(
     }
 
     /// Looks up an object by its handle for a given `File`.
-    fn lookup_handle(
-        file: &drm::File<<Self::Driver as drm::Driver>::File>,
-        handle: u32,
-    ) -> Result<ARef<Self>>
+    fn lookup_handle(file: &ObjectFile<Self>, handle: u32) -> Result<ARef<Self>>
     where
         Self: DriverObject
     {
-- 
2.49.0