drm: add helper to sort panels to the head of the connector list

Userspace seems to like this, see

commit cb0953d734348e8862d6d7edc666cfb3bf6d8fae
Author: Adam Jackson <ajax@redhat.com>
Date:   Fri Jul 16 14:46:29 2010 -0400

    drm/i915: Initialize LVDS and eDP outputs before anything else

    This makes them sort to the front in X, which makes them likely to be
    the primary outputs if you haven't specified a preference in your DE,
    which is likely to be what you want.

    Signed-off-by: Adam Jackson <ajax@redhat.com>
    Signed-off-by: Eric Anholt <eric@anholt.net>

Sorting the connector list after the fact is much easier than trying
to be clever with the init sequence.

Acked-by: Dave Airlie <airlied@gmail.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_crtc_helper.c

@@ -39,6 +39,24 @@
 #include <drm/drm_fb_helper.h>
 #include <drm/drm_edid.h>
 
+void drm_helper_move_panel_connectors_to_head(struct drm_device *dev)
+{
+	struct drm_connector *connector, *tmp;
+	struct list_head panel_list;
+
+	INIT_LIST_HEAD(&panel_list);
+
+	list_for_each_entry_safe(connector, tmp,
+				 &dev->mode_config.connector_list, head) {
+		if (connector->connector_type == DRM_MODE_CONNECTOR_LVDS ||
+		    connector->connector_type == DRM_MODE_CONNECTOR_eDP)
+			list_move_tail(&connector->head, &panel_list);
+	}
+
+	list_splice(&panel_list, &dev->mode_config.connector_list);
+}
+EXPORT_SYMBOL(drm_helper_move_panel_connectors_to_head);
+
 static bool drm_kms_helper_poll = true;
 module_param_named(poll, drm_kms_helper_poll, bool, 0600);
 

include/drm/drm_crtc_helper.h

@@ -137,6 +137,8 @@ extern bool drm_helper_encoder_in_use(struct drm_encoder *encoder);
 
 extern void drm_helper_connector_dpms(struct drm_connector *connector, int mode);
 
+extern void drm_helper_move_panel_connectors_to_head(struct drm_device *);
+
 extern int drm_helper_mode_fill_fb_struct(struct drm_framebuffer *fb,
 					  struct drm_mode_fb_cmd2 *mode_cmd);