drm/vkms: rename cursor to plane on ops of planes composition

Generalize variables and function names used for planes composition
(from cursor to plane), since we will reuse the operations for both
cursor and overlay types.

No functional change.

v4:
- use better names for functions of plane composition (Daniel)
Signed-off-by: Melissa Wen <melissa.srw@gmail.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/ef3249c9ac3a08b7079894f9f1ccf70960194ec7.1619250933.git.melissa.srw@gmail.com

drivers/gpu/drm/vkms/vkms_composer.c

@@ -125,24 +125,24 @@ static void blend(void *vaddr_dst, void *vaddr_src,
 	}
 }
 
-static void compose_cursor(struct vkms_composer *cursor_composer,
-			   struct vkms_composer *primary_composer,
+static void compose_plane(struct vkms_composer *primary_composer,
+			  struct vkms_composer *plane_composer,
 			  void *vaddr_out)
 {
-	struct drm_gem_object *cursor_obj;
-	struct drm_gem_shmem_object *cursor_shmem_obj;
+	struct drm_gem_object *plane_obj;
+	struct drm_gem_shmem_object *plane_shmem_obj;
 
-	cursor_obj = drm_gem_fb_get_obj(&cursor_composer->fb, 0);
-	cursor_shmem_obj = to_drm_gem_shmem_obj(cursor_obj);
+	plane_obj = drm_gem_fb_get_obj(&plane_composer->fb, 0);
+	plane_shmem_obj = to_drm_gem_shmem_obj(plane_obj);
 
-	if (WARN_ON(!cursor_shmem_obj->vaddr))
+	if (WARN_ON(!plane_shmem_obj->vaddr))
 		return;
 
-	blend(vaddr_out, cursor_shmem_obj->vaddr,
-	      primary_composer, cursor_composer);
+	blend(vaddr_out, plane_shmem_obj->vaddr,
+	      primary_composer, plane_composer);
 }
 
-static int compose_planes(void **vaddr_out,
+static int compose_active_planes(void **vaddr_out,
 				 struct vkms_composer *primary_composer,
 				 struct vkms_composer *cursor_composer)
 {
@@ -164,7 +164,7 @@ static int compose_planes(void **vaddr_out,
 	memcpy(*vaddr_out, shmem_obj->vaddr, shmem_obj->base.size);
 
 	if (cursor_composer)
-		compose_cursor(cursor_composer, primary_composer, *vaddr_out);
+		compose_plane(primary_composer, cursor_composer, *vaddr_out);
 
 	return 0;
 }
@@ -222,7 +222,8 @@ void vkms_composer_worker(struct work_struct *work)
 	if (wb_pending)
 		vaddr_out = crtc_state->active_writeback;
 
-	ret = compose_planes(&vaddr_out, primary_composer, cursor_composer);
+	ret = compose_active_planes(&vaddr_out, primary_composer,
+				    cursor_composer);
 	if (ret) {
 		if (ret == -EINVAL && !wb_pending)
 			kfree(vaddr_out);