[PATCH 4/4] WIP: rust/drm/kms: Add ShadowPlaneState<T>

[Lyude Paul <lyude@xxxxxxxxxx>]

Signed-off-by: Lyude Paul <lyude@xxxxxxxxxx>
---
 drivers/gpu/drm/rvkms/plane.rs           |  7 +++-
 rust/bindings/bindings_helper.h          |  2 +
 rust/kernel/drm/kms.rs                   |  1 +
 rust/kernel/drm/kms/gem_atomic_helper.rs | 48 ++++++++++++++++++++++++
 4 files changed, 56 insertions(+), 2 deletions(-)
 create mode 100644 rust/kernel/drm/kms/gem_atomic_helper.rs

diff --git a/drivers/gpu/drm/rvkms/plane.rs b/drivers/gpu/drm/rvkms/plane.rs
index d98a1f7bf79e2..5fb1b63842929 100644
--- a/drivers/gpu/drm/rvkms/plane.rs
+++ b/drivers/gpu/drm/rvkms/plane.rs
@@ -4,7 +4,10 @@
     prelude::*,
     drm::{
         device::Device,
-        kms::plane::{self, DriverPlaneState},
+        kms::{
+            plane::{self, DriverPlaneState},
+            gem_atomic_helper::ShadowPlaneState,
+        }
     },
 };
 
@@ -15,7 +18,7 @@ pub(crate) struct DriverPlane {
 }
 
 pub(crate) type Plane = plane::Plane<DriverPlane>;
-pub(crate) type PlaneState = plane::PlaneState<RvkmsPlaneState>;
+pub(crate) type PlaneState = ShadowPlaneState<RvkmsPlaneState>;
 
 impl plane::DriverPlane for DriverPlane {
     type Initializer = impl PinInit<Self, Error>;
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index 5856afbe6e8f6..73a5eb00e8625 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -12,6 +12,8 @@
 #include <drm/drm_edid.h>
 #include <drm/drm_file.h>
 #include <drm/drm_gem.h>
+#include <drm/drm_gem_atomic_helper.h>
+#include <drm/drm_gem_framebuffer_helper.h>
 #include <drm/drm_gem_framebuffer_helper.h>
 #include <drm/drm_gem_shmem_helper.h>
 #include <drm/drm_ioctl.h>
diff --git a/rust/kernel/drm/kms.rs b/rust/kernel/drm/kms.rs
index b55d14415367a..14f4c3842ada0 100644
--- a/rust/kernel/drm/kms.rs
+++ b/rust/kernel/drm/kms.rs
@@ -6,6 +6,7 @@
 pub mod crtc;
 pub mod encoder;
 pub mod plane;
+pub mod gem_atomic_helper;
 
 use crate::{
     drm::{drv, device::Device},
diff --git a/rust/kernel/drm/kms/gem_atomic_helper.rs b/rust/kernel/drm/kms/gem_atomic_helper.rs
new file mode 100644
index 0000000000000..85bc3df32d8b7
--- /dev/null
+++ b/rust/kernel/drm/kms/gem_atomic_helper.rs
@@ -0,0 +1,48 @@
+use crate::{
+    prelude::*,
+    private::Sealed,
+    bindings,
+    init::Zeroable,
+};
+use super::plane::{IntoPlaneState, DriverPlaneState};
+
+unsafe impl Zeroable for bindings::drm_shadow_plane_state {}
+
+#[derive(Default)]
+#[repr(C)]
+pub struct ShadowPlaneState<T: DriverPlaneState> {
+    shadow_state: bindings::drm_shadow_plane_state,
+    inner: T,
+}
+
+impl<T: DriverPlaneState> Sealed for ShadowPlaneState<T> {}
+
+static_assert!(crate::offset_of!(bindings::drm_shadow_plane_state, base) == 0);
+
+// SAFETY: Our data layout starts with drm_plane_state (contained at the start of
+// drm_shadow_plane_state)
+unsafe impl<T: DriverPlaneState> IntoPlaneState for ShadowPlaneState<T> {
+    fn __duplicate_state(&self, plane: *mut bindings::drm_plane) -> Result<Box<Self>> {
+        let mut new: Box<Self> = Box::try_init(try_init!(Self {
+            shadow_state: bindings::drm_shadow_plane_state { ..Default::default() },
+            inner: self.inner.clone()
+        }))?;
+
+        // SAFETY: FFI call with no special requirements
+        unsafe { bindings::__drm_gem_duplicate_shadow_plane_state(plane, &mut new.shadow_state) };
+
+        Ok(new)
+    }
+
+    fn __destroy_state(state: *mut bindings::drm_plane_state) {
+        // SAFETY: This would not be called without a plane state to destroy, and our data layout
+        // starts with `bindings::drm_plane_state`
+        unsafe { bindings::__drm_gem_destroy_shadow_plane_state(state.cast()) };
+    }
+
+    fn __reset_state(plane: *mut bindings::drm_plane, state: *mut bindings::drm_plane_state) {
+        // SAFETY: This would not be called without a plane state to reset, and our data layout
+        // starts with `bindings::drm_plane_state`
+        unsafe { bindings::__drm_gem_reset_shadow_plane(plane, state.cast()) }
+    }
+}
-- 
2.43.0