ALSA: usb-audio: Input source control - digidesign mbox

This adds a second mixer control to Digidesign Mbox
to select between Analog/SPDIF capture.

Users will note that selecting the SPDIF input source
automatically switches the clock mode to sync to SPDIF,
which is a feature of the hardware.

(You can change the clock source back to internal if you want
to capture from spdif but not sync to its clock although this mode
is probably not recommended).

Unfortunately, starting the stream resets both modes
to Internally clocked and Analog input mode.
Signed-off-by: NDamien Zammit <damien@zamaudio.com>
Tested-by: NDamien Zammit <damien@zamaudio.com>
Link: https://lore.kernel.org/r/20210813113402.11849-1-damien@zamaudio.comSigned-off-by: NTakashi Iwai <tiwai@suse.de>

sound/usb/mixer_quirks.c

@@ -594,85 +594,208 @@ static int snd_xonar_u1_controls_create(struct usb_mixer_interface *mixer)
 					  &snd_xonar_u1_output_switch, NULL);
 }
 
+/* Digidesign Mbox 1 helper functions */
+
+static int snd_mbox1_is_spdif_synced(struct snd_usb_audio *chip)
+{
+	unsigned char buff[3];
+	int err;
+	int is_spdif_synced;
+
+	/* Read clock source */
+	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)
+		return err;
+
+	/* spdif sync: buff is all zeroes */
+	is_spdif_synced = !(buff[0] | buff[1] | buff[2]);
+	return is_spdif_synced;
+}
+
+static int snd_mbox1_set_clk_source(struct snd_usb_audio *chip, int rate_or_zero)
+{
+	/* 2 possibilities:	Internal    -> expects sample rate
+	 *			S/PDIF sync -> expects rate = 0
+	 */
+	unsigned char buff[3];
+
+	buff[0] = (rate_or_zero >>  0) & 0xff;
+	buff[1] = (rate_or_zero >>  8) & 0xff;
+	buff[2] = (rate_or_zero >> 16) & 0xff;
+
+	/* Set clock source */
+	return snd_usb_ctl_msg(chip->dev,
+			       usb_sndctrlpipe(chip->dev, 0), 0x1,
+			       USB_TYPE_CLASS |
+			       USB_RECIP_ENDPOINT, 0x100, 0x81, buff, 3);
+}
+
+static int snd_mbox1_is_spdif_input(struct snd_usb_audio *chip)
+{
+	/* Hardware gives 2 possibilities:	ANALOG Source  -> 0x01
+	 *					S/PDIF Source  -> 0x02
+	 */
+	int err;
+	unsigned char source[1];
+
+	/* Read input 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, source, 1);
+	if (err < 0)
+		return err;
+
+	return (source[0] == 2);
+}
+
+static int snd_mbox1_set_input_source(struct snd_usb_audio *chip, int is_spdif)
+{
+	/* NB: Setting the input source to S/PDIF resets the clock source to S/PDIF
+	 * Hardware expects 2 possibilities:	ANALOG Source  -> 0x01
+	 *					S/PDIF Source  -> 0x02
+	 */
+	unsigned char buff[1];
+
+	buff[0] = (is_spdif & 1) + 1;
+
+	/* Set input source */
+	return snd_usb_ctl_msg(chip->dev,
+			       usb_sndctrlpipe(chip->dev, 0), 0x1,
+			       USB_TYPE_CLASS |
+			       USB_RECIP_INTERFACE, 0x00, 0x500, buff, 1);
+}
+
 /* Digidesign Mbox 1 clock source switch (internal/spdif) */
 
-static int snd_mbox1_switch_get(struct snd_kcontrol *kctl,
-				struct snd_ctl_elem_value *ucontrol)
+static int snd_mbox1_clk_switch_get(struct snd_kcontrol *kctl,
+				    struct snd_ctl_elem_value *ucontrol)
 {
+	struct usb_mixer_elem_list *list = snd_kcontrol_chip(kctl);
+	struct snd_usb_audio *chip = list->mixer->chip;
+	int err;
+
+	err = snd_usb_lock_shutdown(chip);
+	if (err < 0)
+		goto err;
+
+	err = snd_mbox1_is_spdif_synced(chip);
+	if (err < 0)
+		goto err;
+
+	kctl->private_value = err;
+	err = 0;
 	ucontrol->value.enumerated.item[0] = kctl->private_value;
-	return 0;
+err:
+	snd_usb_unlock_shutdown(chip);
+	return err;
 }
 
-static int snd_mbox1_switch_update(struct usb_mixer_interface *mixer, int val)
+static int snd_mbox1_clk_switch_update(struct usb_mixer_interface *mixer, int is_spdif_sync)
 {
 	struct snd_usb_audio *chip = mixer->chip;
 	int err;
-	unsigned char buff[3];
 
 	err = snd_usb_lock_shutdown(chip);
 	if (err < 0)
 		return 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);
+	err = snd_mbox1_is_spdif_input(chip);
 	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);
+
+	err = snd_mbox1_is_spdif_synced(chip);
 	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 (val == 0) {
-		buff[0] = 0x80;
-		buff[1] = 0xbb;
-		buff[2] = 0x00;
-	} else {
-		buff[0] = buff[1] = buff[2] = 0x00;
-	}
+	/* FIXME: hardcoded sample rate */
+	err = snd_mbox1_set_clk_source(chip, is_spdif_sync ? 0 : 48000);
+	if (err < 0)
+		goto err;
 
-	/* 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);
+	err = snd_mbox1_is_spdif_synced(chip);
+err:
+	snd_usb_unlock_shutdown(chip);
+	return err;
+}
+
+static int snd_mbox1_clk_switch_put(struct snd_kcontrol *kctl,
+				    struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_list *list = snd_kcontrol_chip(kctl);
+	struct usb_mixer_interface *mixer = list->mixer;
+	int err;
+	bool cur_val, new_val;
+
+	cur_val = kctl->private_value;
+	new_val = ucontrol->value.enumerated.item[0];
+	if (cur_val == new_val)
+		return 0;
+
+	kctl->private_value = new_val;
+	err = snd_mbox1_clk_switch_update(mixer, new_val);
+	return err < 0 ? err : 1;
+}
+
+static int snd_mbox1_clk_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 int snd_mbox1_clk_switch_resume(struct usb_mixer_elem_list *list)
+{
+	return snd_mbox1_clk_switch_update(list->mixer, list->kctl->private_value);
+}
+
+/* Digidesign Mbox 1 input source switch (analog/spdif) */
+
+static int snd_mbox1_src_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_src_switch_update(struct usb_mixer_interface *mixer, int is_spdif_input)
+{
+	struct snd_usb_audio *chip = mixer->chip;
+	int err;
+
+	err = snd_usb_lock_shutdown(chip);
+	if (err < 0)
+		return err;
+
+	err = snd_mbox1_is_spdif_input(chip);
 	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);
+
+	err = snd_mbox1_set_input_source(chip, is_spdif_input);
 	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);
+
+	err = snd_mbox1_is_spdif_input(chip);
 	if (err < 0)
 		goto err;
 
+	err = snd_mbox1_is_spdif_synced(chip);
 err:
 	snd_usb_unlock_shutdown(chip);
 	return err;
 }
 
-static int snd_mbox1_switch_put(struct snd_kcontrol *kctl,
-				struct snd_ctl_elem_value *ucontrol)
+static int snd_mbox1_src_switch_put(struct snd_kcontrol *kctl,
+				    struct snd_ctl_elem_value *ucontrol)
 {
 	struct usb_mixer_elem_list *list = snd_kcontrol_chip(kctl);
 	struct usb_mixer_interface *mixer = list->mixer;
@@ -685,42 +808,60 @@ static int snd_mbox1_switch_put(struct snd_kcontrol *kctl,
 		return 0;
 
 	kctl->private_value = new_val;
-	err = snd_mbox1_switch_update(mixer, new_val);
+	err = snd_mbox1_src_switch_update(mixer, new_val);
 	return err < 0 ? err : 1;
 }
 
-static int snd_mbox1_switch_info(struct snd_kcontrol *kcontrol,
-				 struct snd_ctl_elem_info *uinfo)
+static int snd_mbox1_src_switch_info(struct snd_kcontrol *kcontrol,
+				     struct snd_ctl_elem_info *uinfo)
 {
 	static const char *const texts[2] = {
-		"Internal",
+		"Analog",
 		"S/PDIF"
 	};
 
 	return snd_ctl_enum_info(uinfo, 1, ARRAY_SIZE(texts), texts);
 }
 
-static int snd_mbox1_switch_resume(struct usb_mixer_elem_list *list)
+static int snd_mbox1_src_switch_resume(struct usb_mixer_elem_list *list)
 {
-	return snd_mbox1_switch_update(list->mixer, list->kctl->private_value);
+	return snd_mbox1_src_switch_update(list->mixer, list->kctl->private_value);
 }
 
-static const struct snd_kcontrol_new snd_mbox1_switch = {
+static const struct snd_kcontrol_new snd_mbox1_clk_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,
+	.info = snd_mbox1_clk_switch_info,
+	.get = snd_mbox1_clk_switch_get,
+	.put = snd_mbox1_clk_switch_put,
+	.private_value = 0
+};
+
+static const struct snd_kcontrol_new snd_mbox1_src_switch = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.name = "Input Source",
+	.index = 1,
+	.access = SNDRV_CTL_ELEM_ACCESS_READWRITE,
+	.info = snd_mbox1_src_switch_info,
+	.get = snd_mbox1_src_switch_get,
+	.put = snd_mbox1_src_switch_put,
 	.private_value = 0
 };
 
-static int snd_mbox1_create_sync_switch(struct usb_mixer_interface *mixer)
+static int snd_mbox1_controls_create(struct usb_mixer_interface *mixer)
 {
-	return add_single_ctl_with_resume(mixer, 0,
-					  snd_mbox1_switch_resume,
-					  &snd_mbox1_switch, NULL);
+	int err;
+	err = add_single_ctl_with_resume(mixer, 0,
+					 snd_mbox1_clk_switch_resume,
+					 &snd_mbox1_clk_switch, NULL);
+	if (err < 0)
+		return err;
+
+	return add_single_ctl_with_resume(mixer, 1,
+					  snd_mbox1_src_switch_resume,
+					  &snd_mbox1_src_switch, NULL);
 }
 
 /* Native Instruments device quirks */
@@ -3029,7 +3170,7 @@ int snd_usb_mixer_apply_create_quirk(struct usb_mixer_interface *mixer)
 		break;
 
 	case USB_ID(0x0dba, 0x1000): /* Digidesign Mbox 1 */
-		err = snd_mbox1_create_sync_switch(mixer);
+		err = snd_mbox1_controls_create(mixer);
 		break;
 
 	case USB_ID(0x17cc, 0x1011): /* Traktor Audio 6 */