drm/i915: use ACPI LID status for LVDS ->detect hook

We can't load or hotplug detect LVDS like we can other outputs, but if
there's a lid device present we can use it as a proxy.  This allows the
LFP state to be determined at ->detect time, making configurations
requiring manual intervention today "just work" assuming the lid device
status is correct.
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Eric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/intel_lvds.c

@@ -589,12 +589,18 @@ static void intel_lvds_mode_set(struct drm_encoder *encoder,
 /**
  * Detect the LVDS connection.
  *
- * This always returns CONNECTOR_STATUS_CONNECTED.  This connector should only have
- * been set up if the LVDS was actually connected anyway.
+ * Since LVDS doesn't have hotlug, we use the lid as a proxy.  Open means
+ * connected and closed means disconnected.  We also send hotplug events as
+ * needed, using lid status notification from the input layer.
  */
 static enum drm_connector_status intel_lvds_detect(struct drm_connector *connector)
 {
-	return connector_status_connected;
+	enum drm_connector_status status = connector_status_connected;
+
+	if (!acpi_lid_open())
+		status = connector_status_disconnected;
+
+	return status;
 }
 
 /**