drm/atomic: add connector mask to drm_crtc_state.

BugLink: http://bugs.launchpad.net/bugs/1540390

It can be useful to iterate over connectors without grabbing
connection_mutex. It can also be used to see how many connectors
are on a crtc without iterating over the list.
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1451908400-25147-4-git-send-email-maarten.lankhorst@linux.intel.comSigned-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
(cherry picked from commit 4cd9fa52)
Signed-off-by: Timo Aaltonen <timo.aaltonen@canonical.com>
Signed-off-by: Andy Whitcroft <apw@canonical.com>

drivers/gpu/drm/drm_atomic.c

@@ -1039,10 +1039,21 @@ drm_atomic_set_crtc_for_connector(struct drm_connector_state *conn_state,
 {
 	struct drm_crtc_state *crtc_state;
 
+	if (conn_state->crtc && conn_state->crtc != crtc) {
+		crtc_state = drm_atomic_get_existing_crtc_state(conn_state->state,
+								conn_state->crtc);
+
+		crtc_state->connector_mask &=
+			~(1 << drm_connector_index(conn_state->connector));
+	}
+
 	if (crtc) {
 		crtc_state = drm_atomic_get_crtc_state(conn_state->state, crtc);
 		if (IS_ERR(crtc_state))
 			return PTR_ERR(crtc_state);
+
+		crtc_state->connector_mask |=
+			1 << drm_connector_index(conn_state->connector);
 	}
 
 	conn_state->crtc = crtc;

include/drm/drm_crtc.h

@@ -260,6 +260,7 @@ struct drm_atomic_state;
  * @active_changed: crtc_state->active has been toggled.
  * @connectors_changed: connectors to this crtc have been updated
  * @plane_mask: bitmask of (1 << drm_plane_index(plane)) of attached planes
+ * @connector_mask: bitmask of (1 << drm_connector_index(connector)) of attached connectors
  * @last_vblank_count: for helpers and drivers to capture the vblank of the
  * 	update to ensure framebuffer cleanup isn't done too early
  * @adjusted_mode: for use by helpers and drivers to compute adjusted mode timings
@@ -293,6 +294,8 @@ struct drm_crtc_state {
 	 */
 	u32 plane_mask;
 
+	u32 connector_mask;
+
 	/* last_vblank_count: for vblank waits before cleanup */
 	u32 last_vblank_count;