ALSA: usb-audio: Add mixer control for Digidesign Mbox 1 clock source

This patch provides the infrastructure for the Digidesign Mbox 1
to have a mixer control for selecting the clock source.
Valid options are Internal and S/PDIF external sync.
A non-documented command is sent to the device to enable this feature
found by reverse engineering and bus snooping.
Signed-off-by: Damien Zammit <damien@zamaudio.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/mixer_maps.c

@@ -179,6 +179,11 @@ static struct usbmix_name_map audigy2nx_map[] = {
 	{ 0 } /* terminator */
 };
 
+static struct usbmix_name_map mbox1_map[] = {
+	{ 1, "Clock" },
+	{ 0 } /* terminator */
+};
+
 static struct usbmix_selector_map c400_selectors[] = {
 	{
 		.id = 0x80,
@@ -415,6 +420,10 @@ static struct usbmix_ctl_map usbmix_ctl_maps[] = {
 		.id = USB_ID(0x0ccd, 0x0028),
 		.map = aureon_51_2_map,
 	},
+	{
+		.id = USB_ID(0x0dba, 0x1000),
+		.map = mbox1_map,
+	},
 	{
 		.id = USB_ID(0x13e5, 0x0001),
 		.map = scratch_live_map,

sound/usb/mixer_quirks.c

@@ -565,6 +565,131 @@ static int snd_xonar_u1_controls_create(struct usb_mixer_interface *mixer)
 	return 0;
 }
 
+/* Digidesign Mbox 1 clock source switch (internal/spdif) */
+
+static int snd_mbox1_switch_get(struct snd_kcontrol *kctl,
+				struct snd_ctl_elem_value *ucontrol)
+{
+	ucontrol->value.enumerated.item[0] = kctl->private_value;
+	return 0;
+}
+
+static int snd_mbox1_switch_put(struct snd_kcontrol *kctl,
+				struct snd_ctl_elem_value *ucontrol)
+{
+	struct snd_usb_audio *chip;
+	struct usb_mixer_interface *mixer;
+	int err;
+	bool cur_val, new_val;
+	unsigned char buff[3];
+
+	cur_val = kctl->private_value;
+	new_val = ucontrol->value.enumerated.item[0];
+
+	mixer = snd_kcontrol_chip(kctl);
+	if (snd_BUG_ON(!mixer))
+		return -EINVAL;
+
+	chip = mixer->chip;
+	if (snd_BUG_ON(!chip))
+		return -EINVAL;
+
+	if (cur_val == new_val)
+		return 0;
+
+	down_read(&chip->shutdown_rwsem);
+	if (chip->shutdown) {
+		err = -ENODEV;
+		goto err;
+	}
+
+	/* Prepare for magic command to toggle clock source */
+	err = snd_usb_ctl_msg(chip->dev,
+				usb_rcvctrlpipe(chip->dev, 0), 0x81,
+				USB_DIR_IN |
+				USB_TYPE_CLASS |
+				USB_RECIP_INTERFACE, 0x00, 0x500, buff, 1);
+	if (err < 0)
+		goto err;
+	err = snd_usb_ctl_msg(chip->dev,
+				usb_rcvctrlpipe(chip->dev, 0), 0x81,
+				USB_DIR_IN |
+				USB_TYPE_CLASS |
+				USB_RECIP_ENDPOINT, 0x100, 0x81, buff, 3);
+	if (err < 0)
+		goto err;
+
+	/* 2 possibilities:	Internal    -> send sample rate
+	 *			S/PDIF sync -> send zeroes
+	 * NB: Sample rate locked to 48kHz on purpose to
+	 *     prevent user from resetting the sample rate
+	 *     while S/PDIF sync is enabled and confusing
+	 *     this configuration.
+	 */
+	if (new_val == 0) {
+		buff[0] = 0x80;
+		buff[1] = 0xbb;
+		buff[2] = 0x00;
+	} else {
+		buff[0] = buff[1] = buff[2] = 0x00;
+	}
+
+	/* Send the magic command to toggle the clock source */
+	err = snd_usb_ctl_msg(chip->dev,
+				usb_sndctrlpipe(chip->dev, 0), 0x1,
+				USB_TYPE_CLASS |
+				USB_RECIP_ENDPOINT, 0x100, 0x81, buff, 3);
+	if (err < 0)
+		goto err;
+	err = snd_usb_ctl_msg(chip->dev,
+				usb_rcvctrlpipe(chip->dev, 0), 0x81,
+				USB_DIR_IN |
+				USB_TYPE_CLASS |
+				USB_RECIP_ENDPOINT, 0x100, 0x81, buff, 3);
+	if (err < 0)
+		goto err;
+	err = snd_usb_ctl_msg(chip->dev,
+				usb_rcvctrlpipe(chip->dev, 0), 0x81,
+				USB_DIR_IN |
+				USB_TYPE_CLASS |
+				USB_RECIP_ENDPOINT, 0x100, 0x2, buff, 3);
+	if (err < 0)
+		goto err;
+	kctl->private_value = new_val;
+
+err:
+	up_read(&chip->shutdown_rwsem);
+	return err < 0 ? err : 1;
+}
+
+static int snd_mbox1_switch_info(struct snd_kcontrol *kcontrol,
+				 struct snd_ctl_elem_info *uinfo)
+{
+	static const char *const texts[2] = {
+		"Internal",
+		"S/PDIF"
+	};
+
+	return snd_ctl_enum_info(uinfo, 1, ARRAY_SIZE(texts), texts);
+}
+
+static struct snd_kcontrol_new snd_mbox1_switch = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.name = "Clock Source",
+	.index = 0,
+	.access = SNDRV_CTL_ELEM_ACCESS_READWRITE,
+	.info = snd_mbox1_switch_info,
+	.get = snd_mbox1_switch_get,
+	.put = snd_mbox1_switch_put,
+	.private_value = 0
+};
+
+static int snd_mbox1_create_sync_switch(struct usb_mixer_interface *mixer)
+{
+	return snd_ctl_add(mixer->chip->card,
+			snd_ctl_new1(&snd_mbox1_switch, mixer));
+}
+
 /* Native Instruments device quirks */
 
 #define _MAKE_NI_CONTROL(bRequest,wIndex) ((bRequest) << 16 | (wIndex))
@@ -1632,6 +1757,10 @@ int snd_usb_mixer_apply_create_quirk(struct usb_mixer_interface *mixer)
 		err = snd_microii_controls_create(mixer);
 		break;
 
+	case USB_ID(0x0dba, 0x1000): /* Digidesign Mbox 1 */
+		err = snd_mbox1_create_sync_switch(mixer);
+		break;
+
 	case USB_ID(0x17cc, 0x1011): /* Traktor Audio 6 */
 		err = snd_nativeinstruments_create_mixer(mixer,
 				snd_nativeinstruments_ta6_mixers,