[media] bt819: fix querystd

Return V4L2_STD_UNKNOWN if no signal is detected.
Otherwise AND the standard mask with the detected standards.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/i2c/bt819.c

@@ -215,15 +215,17 @@ static int bt819_status(struct v4l2_subdev *sd, u32 *pstatus, v4l2_std_id *pstd)
 	struct bt819 *decoder = to_bt819(sd);
 	int status = bt819_read(decoder, 0x00);
 	int res = V4L2_IN_ST_NO_SIGNAL;
-	v4l2_std_id std;
+	v4l2_std_id std = pstd ? *pstd : V4L2_STD_ALL;
 
 	if ((status & 0x80))
 		res = 0;
+	else
+		std = V4L2_STD_UNKNOWN;
 
 	if ((status & 0x10))
-		std = V4L2_STD_PAL;
+		std &= V4L2_STD_PAL;
 	else
-		std = V4L2_STD_NTSC;
+		std &= V4L2_STD_NTSC;
 	if (pstd)
 		*pstd = std;
 	if (pstatus)