rust: drm: gem: Add GEM object abstraction

The DRM GEM subsystem is the DRM memory management subsystem used by
most modern drivers. Add a Rust abstraction to allow Rust DRM driver
implementations to use it.

Signed-off-by: Asahi Lina <lina@asahilina.net>

Author: hoshinolina

rust/bindings/bindings_helper.h

@@ -9,6 +9,7 @@
 #include <drm/drm_device.h>
 #include <drm/drm_drv.h>
 #include <drm/drm_file.h>
+#include <drm/drm_gem.h>
 #include <drm/drm_ioctl.h>
 #include <linux/delay.h>
 #include <linux/device.h>

rust/helpers.c

@@ -18,6 +18,7 @@
  * accidentally exposed.
  */
 
+#include <drm/drm_gem.h>
 #include <linux/bug.h>
 #include <linux/build_bug.h>
 #include <linux/device.h>
@@ -422,6 +423,28 @@ resource_size_t rust_helper_resource_size(const struct resource *res)
 }
 EXPORT_SYMBOL_GPL(rust_helper_resource_size);
 
+#ifdef CONFIG_DRM
+
+void rust_helper_drm_gem_object_get(struct drm_gem_object *obj)
+{
+	drm_gem_object_get(obj);
+}
+EXPORT_SYMBOL_GPL(rust_helper_drm_gem_object_get);
+
+void rust_helper_drm_gem_object_put(struct drm_gem_object *obj)
+{
+	drm_gem_object_put(obj);
+}
+EXPORT_SYMBOL_GPL(rust_helper_drm_gem_object_put);
+
+__u64 rust_helper_drm_vma_node_offset_addr(struct drm_vma_offset_node *node)
+{
+	return drm_vma_node_offset_addr(node);
+}
+EXPORT_SYMBOL_GPL(rust_helper_drm_vma_node_offset_addr);
+
+#endif
+
 /*
  * We use `bindgen`'s `--size_t-is-usize` option to bind the C `size_t` type
  * as the Rust `usize` type, so we can use it in contexts where Rust

rust/kernel/drm/drv.rs

@@ -120,7 +120,7 @@ pub struct AllocOps {
 }
 
 /// Trait for memory manager implementations. Implemented internally.
-pub trait AllocImpl: Sealed {
+pub trait AllocImpl: Sealed + drm::gem::IntoGEMObject {
     /// The C callback operations for this memory manager.
     const ALLOC_OPS: AllocOps;
 }
@@ -256,7 +256,7 @@ impl<T: Driver> Registration<T> {
             drm,
             registered: false,
             vtable,
-            fops: Default::default(), // TODO: GEM abstraction
+            fops: drm::gem::create_fops(),
             _pin: PhantomPinned,
             _p: PhantomData,
         })