drm: Don't implement empty prepare_fb()/cleanup_fb()

The plane .prepare_fb() and .cleanup_fb() helpers are optional, there's
no need to implement empty stubs, and no need to explicitly set the
function pointers to NULL either.

Signed-off-by: Laurent Pinchart <[e-mail]>
[danvet: Resolved conflicts with Chris' patch.]
Signed-off-by: Daniel Vetter <[e-mail]>

drivers/gpu/drm/arc/arcpgu_crtc.c

···
 }
 
 static const struct drm_plane_helper_funcs arc_pgu_plane_helper_funcs = {
-	.prepare_fb = NULL,
-	.cleanup_fb = NULL,
 	.atomic_update = arc_pgu_plane_atomic_update,
 };
 

drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_plane.c

···
 	return;
 }
 
-static void
-fsl_dcu_drm_plane_cleanup_fb(struct drm_plane *plane,
-			     struct drm_plane_state *new_state)
-{
-}
-
-static int
-fsl_dcu_drm_plane_prepare_fb(struct drm_plane *plane,
-			     struct drm_plane_state *new_state)
-{
-	return 0;
-}
-
 static const struct drm_plane_helper_funcs fsl_dcu_drm_plane_helper_funcs = {
 	.atomic_check = fsl_dcu_drm_plane_atomic_check,
 	.atomic_disable = fsl_dcu_drm_plane_atomic_disable,
 	.atomic_update = fsl_dcu_drm_plane_atomic_update,
-	.cleanup_fb = fsl_dcu_drm_plane_cleanup_fb,
-	.prepare_fb = fsl_dcu_drm_plane_prepare_fb,
 };
 
 static void fsl_dcu_drm_plane_destroy(struct drm_plane *plane)

drivers/gpu/drm/hisilicon/kirin/kirin_drm_ade.c

···
 	ade_compositor_routing_disable(base, ch);
 }
 
-static int ade_plane_prepare_fb(struct drm_plane *plane,
-				struct drm_plane_state *new_state)
-{
-	/* do nothing */
-	return 0;
-}
-
-static void ade_plane_cleanup_fb(struct drm_plane *plane,
-				 struct drm_plane_state *old_state)
-{
-	/* do nothing */
-}
-
 static int ade_plane_atomic_check(struct drm_plane *plane,
 				  struct drm_plane_state *state)
 {
···
 }
 
 static const struct drm_plane_helper_funcs ade_plane_helper_funcs = {
-	.prepare_fb = ade_plane_prepare_fb,
-	.cleanup_fb = ade_plane_cleanup_fb,
 	.atomic_check = ade_plane_atomic_check,
 	.atomic_update = ade_plane_atomic_update,
 	.atomic_disable = ade_plane_atomic_disable,

drivers/gpu/drm/tegra/dc.c

···
 	.atomic_destroy_state = tegra_plane_atomic_destroy_state,
 };
 
-static int tegra_plane_prepare_fb(struct drm_plane *plane,
-				  struct drm_plane_state *new_state)
-{
-	return 0;
-}
-
-static void tegra_plane_cleanup_fb(struct drm_plane *plane,
-				   struct drm_plane_state *old_fb)
-{
-}
-
 static int tegra_plane_state_add(struct tegra_plane *plane,
 				 struct drm_plane_state *state)
 {
···
 }
 
 static const struct drm_plane_helper_funcs tegra_primary_plane_helper_funcs = {
-	.prepare_fb = tegra_plane_prepare_fb,
-	.cleanup_fb = tegra_plane_cleanup_fb,
 	.atomic_check = tegra_plane_atomic_check,
 	.atomic_update = tegra_plane_atomic_update,
 	.atomic_disable = tegra_plane_atomic_disable,
···
 };
 
 static const struct drm_plane_helper_funcs tegra_cursor_plane_helper_funcs = {
-	.prepare_fb = tegra_plane_prepare_fb,
-	.cleanup_fb = tegra_plane_cleanup_fb,
 	.atomic_check = tegra_cursor_atomic_check,
 	.atomic_update = tegra_cursor_atomic_update,
 	.atomic_disable = tegra_cursor_atomic_disable,
···
 };
 
 static const struct drm_plane_helper_funcs tegra_overlay_plane_helper_funcs = {
-	.prepare_fb = tegra_plane_prepare_fb,
-	.cleanup_fb = tegra_plane_cleanup_fb,
 	.atomic_check = tegra_plane_atomic_check,
 	.atomic_update = tegra_plane_atomic_update,
 	.atomic_disable = tegra_plane_atomic_disable,

drivers/gpu/drm/vc4/vc4_plane.c

···
 }
 
 static const struct drm_plane_helper_funcs vc4_plane_helper_funcs = {
-	.prepare_fb = NULL,
-	.cleanup_fb = NULL,
 	.atomic_check = vc4_plane_atomic_check,
 	.atomic_update = vc4_plane_atomic_update,
 };