drm/plane: remove drm_helper_get_plane_damage_clips

It's not used. Drivers should instead use the helpers anyway.

Currently both vbox and i915 hand-roll this and it's not the greatest.
vbox looks buggy, and i915 does a bit much that helpers would take
care of I think.

Also improve the kerneldocs while we're at it.
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Cc: José Roberto de Souza <jose.souza@intel.com>
Cc: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210723083457.696939-1-daniel.vetter@ffwll.ch

drivers/gpu/drm/drm_damage_helper.c

@@ -282,7 +282,7 @@ drm_atomic_helper_damage_iter_init(struct drm_atomic_helper_damage_iter *iter,
 	if (!state || !state->crtc || !state->fb || !state->visible)
 		return;
 
-	iter->clips = drm_helper_get_plane_damage_clips(state);
+	iter->clips = (struct drm_rect *)drm_plane_get_damage_clips(state);
 	iter->num_clips = drm_plane_get_damage_clips_count(state);
 
 	/* Round down for x1/y1 and round up for x2/y2 to catch all pixels */

include/drm/drm_damage_helper.h

@@ -82,21 +82,4 @@ bool drm_atomic_helper_damage_merged(const struct drm_plane_state *old_state,
 				     struct drm_plane_state *state,
 				     struct drm_rect *rect);
 
-/**
- * drm_helper_get_plane_damage_clips - Returns damage clips in &drm_rect.
- * @state: Plane state.
- *
- * Returns plane damage rectangles in internal &drm_rect. Currently &drm_rect
- * can be obtained by simply typecasting &drm_mode_rect. This is because both
- * are signed 32 and during drm_atomic_check_only() it is verified that damage
- * clips are inside fb.
- *
- * Return: Clips in plane fb_damage_clips blob property.
- */
-static inline struct drm_rect *
-drm_helper_get_plane_damage_clips(const struct drm_plane_state *state)
-{
-	return (struct drm_rect *)drm_plane_get_damage_clips(state);
-}
-
 #endif

include/drm/drm_plane.h

@@ -186,6 +186,9 @@ struct drm_plane_state {
 	 * since last plane update) as an array of &drm_mode_rect in framebuffer
 	 * coodinates of the attached framebuffer. Note that unlike plane src,
 	 * damage clips are not in 16.16 fixed point.
+	 *
+	 * See drm_plane_get_damage_clips() and
+	 * drm_plane_get_damage_clips_count() for accessing these.
 	 */
 	struct drm_property_blob *fb_damage_clips;
 
@@ -914,9 +917,10 @@ drm_plane_get_damage_clips_count(const struct drm_plane_state *state)
  * drm_plane_get_damage_clips - Returns damage clips.
  * @state: Plane state.
  *
- * Note that this function returns uapi type &drm_mode_rect. Drivers might
- * instead be interested in internal &drm_rect which can be obtained by calling
- * drm_helper_get_plane_damage_clips().
+ * Note that this function returns uapi type &drm_mode_rect. Drivers might want
+ * to use the helper functions drm_atomic_helper_damage_iter_init() and
+ * drm_atomic_helper_damage_iter_next() or drm_atomic_helper_damage_merged() if
+ * the driver can only handle a single damage region at most.
  *
  * Return: Damage clips in plane fb_damage_clips blob property.
  */

include/drm/drm_rect.h

@@ -39,6 +39,9 @@
  * @x2: horizontal ending coordinate (exclusive)
  * @y1: vertical starting coordinate (inclusive)
  * @y2: vertical ending coordinate (exclusive)
+ *
+ * Note that this must match the layout of struct drm_mode_rect or the damage
+ * helpers like drm_atomic_helper_damage_iter_init() break.
  */
 struct drm_rect {
 	int x1, y1, x2, y2;