[media] dtt200u: handle USB control message errors

If something bad happens while an USB control message is
transfered, return an error code.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/usb/dvb-usb/dtt200u.c

@@ -28,37 +28,42 @@ struct dtt200u_state {
 static int dtt200u_power_ctrl(struct dvb_usb_device *d, int onoff)
 {
 	struct dtt200u_state *st = d->priv;
+	int ret = 0;
 
 	mutex_lock(&st->data_mutex);
 
 	st->data[0] = SET_INIT;
 
 	if (onoff)
-		dvb_usb_generic_write(d, st->data, 2);
+		ret = dvb_usb_generic_write(d, st->data, 2);
 
 	mutex_unlock(&st->data_mutex);
-	return 0;
+	return ret;
 }
 
 static int dtt200u_streaming_ctrl(struct dvb_usb_adapter *adap, int onoff)
 {
 	struct dtt200u_state *st = adap->dev->priv;
+	int ret;
 
 	mutex_lock(&st->data_mutex);
 	st->data[0] = SET_STREAMING;
 	st->data[1] = onoff;
 
-	dvb_usb_generic_write(adap->dev, st->data, 2);
+	ret = dvb_usb_generic_write(adap->dev, st->data, 2);
+	if (ret < 0)
+		goto ret;
 
 	if (onoff)
-		return 0;
+		goto ret;
 
 	st->data[0] = RESET_PID_FILTER;
-	dvb_usb_generic_write(adap->dev, st->data, 1);
+	ret = dvb_usb_generic_write(adap->dev, st->data, 1);
 
+ret:
 	mutex_unlock(&st->data_mutex);
 
-	return 0;
+	return ret;
 }
 
 static int dtt200u_pid_filter(struct dvb_usb_adapter *adap, int index, u16 pid, int onoff)
@@ -84,11 +89,15 @@ static int dtt200u_rc_query(struct dvb_usb_device *d)
 {
 	struct dtt200u_state *st = d->priv;
 	u32 scancode;
+	int ret;
 
 	mutex_lock(&st->data_mutex);
 	st->data[0] = GET_RC_CODE;
 
-	dvb_usb_generic_rw(d, st->data, 1, st->data, 5, 0);
+	ret = dvb_usb_generic_rw(d, st->data, 1, st->data, 5, 0);
+	if (ret < 0)
+		goto ret;
+
 	if (st->data[0] == 1) {
 		enum rc_type proto = RC_TYPE_NEC;
 
@@ -116,8 +125,9 @@ static int dtt200u_rc_query(struct dvb_usb_device *d)
 	if (st->data[0] != 0)
 		deb_info("st->data: %*ph\n", 5, st->data);
 
+ret:
 	mutex_unlock(&st->data_mutex);
-	return 0;
+	return ret;
 }
 
 static int dtt200u_frontend_attach(struct dvb_usb_adapter *adap)