DRM_MODE_TYPE_PREFERRED
newmode->type |= DRM_MODE_TYPE_PREFERRED;
cur_mode->type &= ~DRM_MODE_TYPE_PREFERRED;
preferred_mode->type |= DRM_MODE_TYPE_PREFERRED;
if (mode->type & DRM_MODE_TYPE_PREFERRED)
diff = ((b->type & DRM_MODE_TYPE_PREFERRED) != 0) -
((a->type & DRM_MODE_TYPE_PREFERRED) != 0);