drm/crtc: add interface to reinitialise the legacy mode group

This can be called to update things after dynamic connectors/encoders
are created/deleted.

Reviewed-by: Todd Previte <tprevite@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_crtc.c

@@ -1513,6 +1513,15 @@ int drm_mode_group_init_legacy_group(struct drm_device *dev,
 }
 EXPORT_SYMBOL(drm_mode_group_init_legacy_group);
 
+void drm_reinit_primary_mode_group(struct drm_device *dev)
+{
+	drm_modeset_lock_all(dev);
+	drm_mode_group_destroy(&dev->primary->mode_group);
+	drm_mode_group_init_legacy_group(dev, &dev->primary->mode_group);
+	drm_modeset_unlock_all(dev);
+}
+EXPORT_SYMBOL(drm_reinit_primary_mode_group);
+
 /**
  * drm_crtc_convert_to_umode - convert a drm_display_mode into a modeinfo
  * @out: drm_mode_modeinfo struct to return to the user

include/drm/drm_crtc.h

@@ -942,6 +942,7 @@ extern const char *drm_get_tv_select_name(int val);
 extern void drm_fb_release(struct drm_file *file_priv);
 extern int drm_mode_group_init_legacy_group(struct drm_device *dev, struct drm_mode_group *group);
 extern void drm_mode_group_destroy(struct drm_mode_group *group);
+extern void drm_reinit_primary_mode_group(struct drm_device *dev);
 extern bool drm_probe_ddc(struct i2c_adapter *adapter);
 extern struct edid *drm_get_edid(struct drm_connector *connector,
 				 struct i2c_adapter *adapter);