[media] tuner-core: map audmode to STEREO for radio devices

Fixes a v4l2-compliance error: setting audmode to a value other than mono
or stereo for a radio device should map to MODE_STEREO.
The spec specifies that for radio devices only mono and stereo audmodes are
valid. If the user specifies another audmode in v4l2_tuner, then that should
be mapped to valid audmode. That didn't happen here.
Note that tuner drivers might decide to limit the possible audmode even
further if it only supports mono. In that case the tuner driver can set
audmode to mono. However, that new value wasn't copied back to t->audmode,
and that has been fixed as well in this patch.

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

drivers/media/v4l2-core/tuner-core.c

@@ -1013,6 +1013,11 @@ static void set_radio_freq(struct i2c_client *c, unsigned int freq)
 	t->standby = false;
 
 	analog_ops->set_params(&t->fe, &params);
+	/*
+	 * The tuner driver might decide to change the audmode if it only
+	 * supports stereo, so update t->audmode.
+	 */
+	t->audmode = params.audmode;
 }
 
 /*
@@ -1235,8 +1240,18 @@ static int tuner_s_tuner(struct v4l2_subdev *sd, struct v4l2_tuner *vt)
 	if (set_mode(t, vt->type))
 		return 0;
 
-	if (t->mode == V4L2_TUNER_RADIO)
+	if (t->mode == V4L2_TUNER_RADIO) {
 		t->audmode = vt->audmode;
+		/*
+		 * For radio audmode can only be mono or stereo. Map any
+		 * other values to stereo. The actual tuner driver that is
+		 * called in set_radio_freq can decide to limit the audmode to
+		 * mono if only mono is supported.
+		 */
+		if (t->audmode != V4L2_TUNER_MODE_MONO &&
+		    t->audmode != V4L2_TUNER_MODE_STEREO)
+			t->audmode = V4L2_TUNER_MODE_STEREO;
+	}
 	set_freq(t, 0);
 
 	return 0;