Add private controls to ctrl_handler

Hello,

I want to add some driver specific ctrls to my ctrl-handler which are not defined in the "/include/uapi/linux/v4l2-controls.h" (Linux version 3.10).
I read that I would need the "V4L2_CID_PRIVATE_BASE" to define the new IDs, but I don't get how I can add them to my ctrl-handler so that they are accessible by calling VIDIOC_S_CTRL.

Can someone give me a hint how I can add my own controls to my ctrl-handler?

what I tried:

#define V4L2_SENS_TEST1            (V4L2_CID_PRIVATE_BASE + 1)
#define V4L2_SENS_TEST2            (V4L2_CID_PRIVATE_BASE + 2)
#define V4L2_SENS_TEST3            (V4L2_CID_PRIVATE_BASE + 3)

static int ov3640_probe(struct i2c_client *client,
            const struct i2c_device_id *id)
{
                .
                .
                .
//I can add the standard controls as usual...

    v4l2_ctrl_handler_init(&ov3640->ctrl_handler, 19);

    v4l2_ctrl_new_std(&ov3640->ctrl_handler, &ov3640_ctrl_ops,
            V4L2_CID_BRIGHTNESS, -48, 48, 1, 0);
    v4l2_ctrl_new_std(&ov3640->ctrl_handler, &ov3640_ctrl_ops,
            V4L2_CID_CONTRAST, -12, 12, 1, 0);
    v4l2_ctrl_new_std(&ov3640->ctrl_handler, &ov3640_ctrl_ops,
            V4L2_CID_SATURATION, -32, 32, 1, 0);
                .
                .
                .
//so far so good...

    v4l2_ctrl_new_std(&ov3640->ctrl_handler, &ov3640_ctrl_ops,
            V4L2_SENS_TEST1, 0, 1, 1, 0);
    v4l2_ctrl_new_std(&ov3640->ctrl_handler, &ov3640_ctrl_ops,
            V4L2_SENS_TEST2, 0, 1, 1, 0);
    v4l2_ctrl_new_std(&ov3640->ctrl_handler, &ov3640_ctrl_ops,
            V4L2_SENS_TEST3, 0, 1, 1, 0);

//but I cannot add these three controls like this.

    if (ov3640->ctrl_handler.error) {
        dev_err(&client->dev, "control initialization error %d\n",
            ov3640->ctrl_handler.error);
        ret = ov3640->ctrl_handler.error;
        goto done;
    }

//the ctrl-handler will give me an ERROR back when adding these 3 controls

}

static int ov3640_ctrl(struct v4l2_ctrl *ctrl, int command)
{
    struct ov3640 *ov3640 = container_of(ctrl->handler, struct ov3640, ctrl_handler);
    int ret = 0;

    switch (ctrl->id) {
    case V4L2_CID_BRIGHTNESS:
        ret = ov3640_set_brightness(ov3640, ctrl->val, command);
        break;
    case V4L2_CID_CONTRAST:
        ret = ov3640_set_contrast(ov3640, ctrl->val, command);
        break;
    case V4L2_CID_SATURATION:
        ret = ov3640_set_saturation(ov3640, ctrl->val, command);
        break;
    case V4L2_SENS_TEST1://!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
    case V4L2_SENS_TEST2://!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
    case V4L2_SENS_TEST3://!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
        ret = ov3640_test(ov3640, ctrl->val, ctrl->id, command);
        break;
    }

    return ret;
}

static int ov3640_set_ctrl(struct v4l2_ctrl *ctrl)
{
    int ret;
    int command = SET_DATA;

    ret = ov3640_ctrl(ctrl, command);
    return ret;
}

static int ov3640_get_ctrl(struct v4l2_ctrl *ctrl)
{
    int ret;
    int command = GET_DATA;

    ret = ov3640_ctrl(ctrl, command);
    return ret;
}

static struct v4l2_ctrl_ops ov3640_ctrl_ops = {
    .s_ctrl = ov3640_set_ctrl,
    .g_volatile_ctrl = ov3640_get_ctrl,
};

Best Regards, Tom