1 files changed, 80 insertions, 24 deletions

diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs
index d49a9ba02635..75acda7ba500 100644
--- a/rust/kernel/drm/gem/mod.rs
+++ b/rust/kernel/drm/gem/mod.rs
@@ -5,15 +5,66 @@
 //! C header: [`include/drm/drm_gem.h`](srctree/include/drm/drm_gem.h)
 
 use crate::{
-    alloc::flags::*,
-    bindings, drm,
-    drm::driver::{AllocImpl, AllocOps},
-    error::{to_result, Result},
+    bindings,
+    drm::{
+        self,
+        driver::{
+            AllocImpl,
+            AllocOps, //
+        },
+    },
+    error::to_result,
     prelude::*,
-    sync::aref::{ARef, AlwaysRefCounted},
+    sync::aref::{
+        ARef,
+        AlwaysRefCounted, //
+    },
     types::Opaque,
 };
-use core::{ops::Deref, ptr::NonNull};
+use core::{
+    ops::Deref,
+    ptr::NonNull, //
+};
+
+#[cfg(CONFIG_RUST_DRM_GEM_SHMEM_HELPER)]
+pub mod shmem;
+
+/// A macro for implementing [`AlwaysRefCounted`] for any GEM object type.
+///
+/// Since all GEM objects use the same refcounting scheme.
+#[macro_export]
+macro_rules! impl_aref_for_gem_obj {
+    (
+        impl $( <$( $tparam_id:ident ),+> )? for $type:ty
+        $(
+            where
+                $( $bind_param:path : $bind_trait:path ),+
+        )?
+    ) => {
+        // SAFETY: All GEM objects are refcounted.
+        unsafe impl $( <$( $tparam_id ),+> )? $crate::sync::aref::AlwaysRefCounted for $type
+        where
+            Self: IntoGEMObject,
+            $( $( $bind_param : $bind_trait ),+ )?
+        {
+            fn inc_ref(&self) {
+                // SAFETY: The existence of a shared reference guarantees that the refcount is
+                // non-zero.
+                unsafe { bindings::drm_gem_object_get(self.as_raw()) };
+            }
+
+            unsafe fn dec_ref(obj: core::ptr::NonNull<Self>) {
+                // SAFETY: `obj` is a valid pointer to an `Object<T>`.
+                let obj = unsafe { obj.as_ref() }.as_raw();
+
+                // SAFETY: The safety requirements guarantee that the refcount is non-zero.
+                unsafe { bindings::drm_gem_object_put(obj) };
+            }
+        }
+    };
+}
+#[cfg_attr(not(CONFIG_RUST_DRM_GEM_SHMEM_HELPER), allow(unused))]
+pub(crate) use impl_aref_for_gem_obj;
 
 /// A type alias for retrieving a [`Driver`]s [`DriverFile`] implementation from its
 /// [`DriverObject`] implementation.
@@ -27,8 +78,15 @@ pub trait DriverObject: Sync + Send + Sized {
     /// Parent `Driver` for this object.
     type Driver: drm::Driver;
 
+    /// The data type to use for passing arguments to [`DriverObject::new`].
+    type Args;
+
     /// Create a new driver data object for a GEM object of a given size.
-    fn new(dev: &drm::Device<Self::Driver>, size: usize) -> impl PinInit<Self, Error>;
+    fn new(
+        dev: &drm::Device<Self::Driver>,
+        size: usize,
+        args: Self::Args,
+    ) -> impl PinInit<Self, Error>;
 
     /// Open a new handle to an existing object, associated with a File.
     fn open(_obj: &<Self::Driver as drm::Driver>::Object, _file: &DriverFile<Self>) -> Result {
@@ -162,6 +220,18 @@ pub trait BaseObject: IntoGEMObject {
 
 impl<T: IntoGEMObject> BaseObject for T {}
 
+/// Crate-private base operations shared by all GEM object classes.
+#[cfg_attr(not(CONFIG_RUST_DRM_GEM_SHMEM_HELPER), expect(unused))]
+pub(crate) trait BaseObjectPrivate: IntoGEMObject {
+    /// Return a pointer to this object's dma_resv.
+    fn raw_dma_resv(&self) -> *mut bindings::dma_resv {
+        // SAFETY: `self.as_raw()` always returns a valid pointer to the base DRM GEM object.
+        unsafe { (*self.as_raw()).resv }
+    }
+}
+
+impl<T: IntoGEMObject> BaseObjectPrivate for T {}
+
 /// A base GEM object.
 ///
 /// # Invariants
@@ -195,11 +265,11 @@ impl<T: DriverObject> Object<T> {
     };
 
     /// Create a new GEM object.
-    pub fn new(dev: &drm::Device<T::Driver>, size: usize) -> Result<ARef<Self>> {
+    pub fn new(dev: &drm::Device<T::Driver>, size: usize, args: T::Args) -> Result<ARef<Self>> {
         let obj: Pin<KBox<Self>> = KBox::pin_init(
             try_pin_init!(Self {
                 obj: Opaque::new(bindings::drm_gem_object::default()),
-                data <- T::new(dev, size),
+                data <- T::new(dev, size, args),
             }),
             GFP_KERNEL,
         )?;
@@ -252,21 +322,7 @@ impl<T: DriverObject> Object<T> {
     }
 }
 
-// SAFETY: Instances of `Object<T>` are always reference-counted.
-unsafe impl<T: DriverObject> crate::sync::aref::AlwaysRefCounted for Object<T> {
-    fn inc_ref(&self) {
-        // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
-        unsafe { bindings::drm_gem_object_get(self.as_raw()) };
-    }
-
-    unsafe fn dec_ref(obj: NonNull<Self>) {
-        // SAFETY: `obj` is a valid pointer to an `Object<T>`.
-        let obj = unsafe { obj.as_ref() };
-
-        // SAFETY: The safety requirements guarantee that the refcount is non-zero.
-        unsafe { bindings::drm_gem_object_put(obj.as_raw()) }
-    }
-}
+impl_aref_for_gem_obj!(impl<T> for Object<T> where T: DriverObject);
 
 impl<T: DriverObject> super::private::Sealed for Object<T> {}