struct drm_connector_helper_funcs — helper operations for connectors
struct drm_connector_helper_funcs {
int (* get_modes) (struct drm_connector *connector);
enum drm_mode_status (* mode_valid) (struct drm_connector *connector,struct drm_display_mode *mode);
struct drm_encoder *(* best_encoder) (struct drm_connector *connector);
};