ALSA: virtuoso: add HDMI enable switch for HDAV1.3

The GPIO bit that enables analog output on the Xonar HDAV1.3 also
disables the HDMI audio output, so we better add a switch for it.
Hopefully, this is sufficient to make the HDMI output work.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/pci/oxygen/xonar_pcm179x.c b/sound/pci/oxygen/xonar_pcm179x.c
index fe4b265..3850834 100644
--- a/sound/pci/oxygen/xonar_pcm179x.c
+++ b/sound/pci/oxygen/xonar_pcm179x.c
@@ -776,6 +776,15 @@
 	.put = os_128_put,
 };
 
+static const struct snd_kcontrol_new hdav_hdmi_control = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.name = "HDMI Playback Switch",
+	.info = snd_ctl_boolean_mono_info,
+	.get = xonar_gpio_bit_switch_get,
+	.put = xonar_gpio_bit_switch_put,
+	.private_value = GPIO_HDAV_OUTPUT_ENABLE | XONAR_GPIO_BIT_INVERT,
+};
+
 static int st_output_switch_info(struct snd_kcontrol *ctl,
 				 struct snd_ctl_elem_info *info)
 {
@@ -960,7 +969,15 @@
 
 static int xonar_hdav_mixer_init(struct oxygen *chip)
 {
-	return add_pcm1796_controls(chip);
+	int err;
+
+	err = snd_ctl_add(chip->card, snd_ctl_new1(&hdav_hdmi_control, chip));
+	if (err < 0)
+		return err;
+	err = add_pcm1796_controls(chip);
+	if (err < 0)
+		return err;
+	return 0;
 }
 
 static int xonar_st_mixer_init(struct oxygen *chip)