static struct pwc_device *cd_to_pwc(struct class_device *cd)
{
	struct video_device *vdev = to_video_device(cd);
	return video_get_drvdata(vdev);
}
static struct pwc_device *cd_to_pwc(struct class_device *cd)
{
	struct video_device *vdev = to_video_device(cd);
	return video_get_drvdata(vdev);
}