linux-kernel - [PATCH] rust: drm/gem: Remove Object.dev

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Message-ID: <20251016202044.2748678-1-lyude@redhat.com>
Date: Thu, 16 Oct 2025 16:18:58 -0400
From: Lyude Paul <lyude@...hat.com>
To: linux-kernel@...r.kernel.org,
	rust-for-linux@...r.kernel.org,
	dri-devel@...ts.freedesktop.org
Cc: Danilo Krummrich <dakr@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>,
	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 <lossin@...nel.org>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Trevor Gross <tmgross@...ch.edu>,
	Daniel Almeida <daniel.almeida@...labora.com>,
	Asahi Lina <lina+kernel@...hilina.net>,
	Shankari Anand <shankari.ak0208@...il.com>
Subject: [PATCH] rust: drm/gem: Remove Object.dev

I noticed by chance that there's actually already a pointer to this in
struct drm_gem_object. So, no use in carrying this around!

Signed-off-by: Lyude Paul <lyude@...hat.com>
---
 rust/kernel/drm/gem/mod.rs | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs
index 30c853988b942..28d929edae267 100644
--- a/rust/kernel/drm/gem/mod.rs
+++ b/rust/kernel/drm/gem/mod.rs
@@ -187,12 +187,10 @@ impl<T: IntoGEMObject> BaseObject for T {}
 /// Invariants
 ///
 /// - `self.obj` is a valid instance of a `struct drm_gem_object`.
-/// - `self.dev` is always a valid pointer to a `struct drm_device`.
 #[repr(C)]
 #[pin_data]
 pub struct Object<T: DriverObject + Send + Sync> {
     obj: Opaque<bindings::drm_gem_object>,
-    dev: NonNull<drm::Device<T::Driver>>,
     #[pin]
     data: T,
 }
@@ -222,9 +220,6 @@ pub fn new(dev: &drm::Device<T::Driver>, size: usize) -> Result<ARef<Self>> {
             try_pin_init!(Self {
                 obj: Opaque::new(bindings::drm_gem_object::default()),
                 data <- T::new(dev, size),
-                // INVARIANT: The drm subsystem guarantees that the `struct drm_device` will live
-                // as long as the GEM object lives.
-                dev: dev.into(),
             }),
             GFP_KERNEL,
         )?;
@@ -247,9 +242,9 @@ pub fn new(dev: &drm::Device<T::Driver>, size: usize) -> Result<ARef<Self>> {
 
     /// Returns the `Device` that owns this GEM object.
     pub fn dev(&self) -> &drm::Device<T::Driver> {
-        // SAFETY: The DRM subsystem guarantees that the `struct drm_device` will live as long as
-        // the GEM object lives, hence the pointer must be valid.
-        unsafe { self.dev.as_ref() }
+        // SAFETY: `struct drm_gem_object.dev` is initialized and valid for as long as the GEM
+        // object lives.
+        unsafe { drm::Device::from_raw((*self.as_raw()).dev) }
     }
 
     fn as_raw(&self) -> *mut bindings::drm_gem_object {

base-commit: 3a8660878839faadb4f1a6dd72c3179c1df56787
-- 
2.51.0