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 <[e-mail]>
[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 <[e-mail]>

Documentation/DocBook/drm.tmpl

···
 	<title>Atomic State Reset and Initialization</title>
 !Pdrivers/gpu/drm/drm_atomic_helper.c atomic state reset and initialization
       </sect3>
+!Iinclude/drm/drm_atomic_helper.h
 !Edrivers/gpu/drm/drm_atomic_helper.c
     </sect2>
     <sect2>

include/drm/drm_atomic_helper.h

···
 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_ */

include/drm/drm_crtc.h

···
 	uint32_t cursor_width, cursor_height;
 };
 
+/**
+ * drm_for_each_plane_mask - iterate over planes specified by bitmask
+ * @plane: the loop cursor
+ * @dev: the DRM device
+ * @plane_mask: bitmask of plane indices
+ *
+ * Iterate over all planes specified by bitmask.
+ */
+#define drm_for_each_plane_mask(plane, dev, plane_mask) \
+	list_for_each_entry((plane), &(dev)->mode_config.plane_list, head) \
+		if ((plane_mask) & (1 << drm_plane_index(plane)))
+
+
 #define obj_to_crtc(x) container_of(x, struct drm_crtc, base)
 #define obj_to_connector(x) container_of(x, struct drm_connector, base)
 #define obj_to_encoder(x) container_of(x, struct drm_encoder, base)