drm/atomic: add plane iterator macros

Add helper macros to iterate the current, or incoming set of planes
attached to a crtc.  These helpers are only available for drivers
converted to use atomic-helpers.

Signed-off-by: Rob Clark <robdclark@gmail.com>
[danvet: Squash in fixup from Rob to move the planemask iterator to
drm_crtc.h and document it. That one is needed by the atomic ioctl so
can't be in a helper library.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/include/drm/drm_atomic_helper.h b/include/drm/drm_atomic_helper.h
index 70a8319..f956b41 100644
--- a/include/drm/drm_atomic_helper.h
+++ b/include/drm/drm_atomic_helper.h
@@ -98,5 +98,29 @@
 void drm_atomic_helper_connector_destroy_state(struct drm_connector *connector,
 					  struct drm_connector_state *state);
 
+/**
+ * drm_atomic_crtc_for_each_plane - iterate over planes currently attached to CRTC
+ * @plane: the loop cursor
+ * @crtc:  the crtc whose planes are iterated
+ *
+ * This iterates over the current state, useful (for example) when applying
+ * atomic state after it has been checked and swapped.  To iterate over the
+ * planes which *will* be attached (for ->atomic_check()) see
+ * drm_crtc_for_each_pending_plane()
+ */
+#define drm_atomic_crtc_for_each_plane(plane, crtc) \
+	drm_for_each_plane_mask(plane, (crtc)->dev, (crtc)->state->plane_mask)
+
+/**
+ * drm_crtc_atomic_state_for_each_plane - iterate over attached planes in new state
+ * @plane: the loop cursor
+ * @crtc_state: the incoming crtc-state
+ *
+ * Similar to drm_crtc_for_each_plane(), but iterates the planes that will be
+ * attached if the specified state is applied.  Useful during (for example)
+ * ->atomic_check() operations, to validate the incoming state
+ */
+#define drm_atomic_crtc_state_for_each_plane(plane, crtc_state) \
+	drm_for_each_plane_mask(plane, (crtc_state)->state->dev, (crtc_state)->plane_mask)
 
 #endif /* DRM_ATOMIC_HELPER_H_ */