[PATCH 3/3] drm/atomic: Refuse to steal encoders from connectors not part of the state.

[Maarten Lankhorst]

Because encoder <-> connector mapping is fixed when not moving to
another crtc we can just reject connectors trying to steal an encoder
from a connector not part of the state. This won't break MST on i915
because in that case connectors will be part of the state if you switch
them between crtc's. If they're not they stay on the same crtc, and
encoder stealing would have failed anyway.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
---
 drivers/gpu/drm/drm_atomic_helper.c | 43 +++++++++++++++++--------------------
 1 file changed, 20 insertions(+), 23 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index fa708559542c..b2028d592483 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -92,14 +92,21 @@ check_pending_encoder_assignment(struct drm_atomic_state *state,
 				 int conn_idx)
 {
 	struct drm_connector *connector;
-	struct drm_connector_state *conn_state;
-	int i;
 
-	for_each_connector_in_state(state, connector, conn_state, i) {
-		if (i >= conn_idx)
-			break;
+	drm_for_each_connector(connector, state->dev) {
+		struct drm_connector_state *conn_state =
+			drm_atomic_get_existing_connector_state(state,
+								connector);
 
-		if (conn_state->best_encoder == new_encoder)
+		if (!conn_state) {
+			if (connector->state->best_encoder == new_encoder)
+				return false;
+
+			continue;
+		}
+
+		if (drm_connector_index(connector) < conn_idx &&
+		    conn_state->best_encoder == new_encoder)
 			return false;
 	}
 
@@ -149,29 +156,19 @@ set_best_encoder(struct drm_atomic_state *state,
 
 static int
 steal_encoder(struct drm_atomic_state *state,
-	      struct drm_encoder *encoder)
+	      struct drm_encoder *encoder,
+	      int conn_idx)
 {
-	struct drm_mode_config *config = &state->dev->mode_config;
 	struct drm_crtc_state *crtc_state;
 	struct drm_connector *connector;
 	struct drm_connector_state *connector_state;
+	int i;
 
-	/*
-	 * We can only steal an encoder coming from a connector, which means we
-	 * must already hold the connection_mutex.
-	 */
-	WARN_ON(!drm_modeset_is_locked(&config->connection_mutex));
-
-	list_for_each_entry(connector, &config->connector_list, head) {
+	for_each_connector_in_state(state, connector, connector_state, i) {
 		struct drm_crtc *encoder_crtc;
 
-		if (connector->state->best_encoder != encoder)
-			continue;
-
-		connector_state = drm_atomic_get_connector_state(state,
-								 connector);
-		if (IS_ERR(connector_state))
-			return PTR_ERR(connector_state);
+		if (i >= conn_idx)
+			break;
 
 		if (connector_state->best_encoder != encoder ||
 		    WARN_ON(!connector_state->crtc))
@@ -279,7 +276,7 @@ update_connector_routing(struct drm_atomic_state *state,
 		return -EINVAL;
 	}
 
-	ret = steal_encoder(state, new_encoder);
+	ret = steal_encoder(state, new_encoder, conn_idx);
 	if (ret) {
 		DRM_DEBUG_ATOMIC("Encoder stealing failed for [CONNECTOR:%d:%s]\n",
 				 connector->base.id,
-- 
2.1.0