V4L/DVB (12376): em28xx: fix V4L2 API compliance: don't expose audio inputs for devices without it

V4L2 API (chapter 1.5) states that:

	Drivers must implement all input ioctls when the device has one
	or more inputs, all output ioctls when the device has one or more outputs.
	When the device has any audio inputs or outputs the driver must set the
	V4L2_CAP_AUDIO flag in the struct v4l2_capability returned by the
	VIDIOC_QUERYCAP ioctl.

So, devices without audio input should return -EINVAL.
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/em28xx/em28xx-video.c

@@ -1005,6 +1005,9 @@ static int vidioc_g_audio(struct file *file, void *priv, struct v4l2_audio *a)
 	struct em28xx_fh   *fh    = priv;
 	struct em28xx      *dev   = fh->dev;
 
+	if (!dev->audio_mode.has_audio)
+		return -EINVAL;
+
 	switch (a->index) {
 	case EM28XX_AMUX_VIDEO:
 		strcpy(a->name, "Television");
@@ -1046,6 +1049,9 @@ static int vidioc_s_audio(struct file *file, void *priv, struct v4l2_audio *a)
 	struct em28xx      *dev = fh->dev;
 
 
+	if (!dev->audio_mode.has_audio)
+		return -EINVAL;
+
 	if (a->index >= MAX_EM28XX_INPUT)
 		return -EINVAL;
 	if (0 == INPUT(a->index)->type)
@@ -1464,9 +1470,11 @@ static int vidioc_querycap(struct file *file, void  *priv,
 	cap->capabilities =
 			V4L2_CAP_SLICED_VBI_CAPTURE |
 			V4L2_CAP_VIDEO_CAPTURE |
-			V4L2_CAP_AUDIO |
 			V4L2_CAP_READWRITE | V4L2_CAP_STREAMING;
 
+	if (dev->audio_mode.has_audio)
+		cap->capabilities |= V4L2_CAP_AUDIO;
+
 	if (dev->tuner_type != TUNER_ABSENT)
 		cap->capabilities |= V4L2_CAP_TUNER;