ALSA: usb-audio: scarlett2: Label 18i8 Gen 3 line outputs correctly

The 18i8 Gen 3 analogue 7/8 outputs are identified as line 3/4 on the
rear of the unit. Add support for remapping the channel numbers to
match the labelling.
Signed-off-by: Geoffrey D. Bennett <g@b4.vu>
Link: https://lore.kernel.org/r/461acb911509e60e9ab48109ece3bbadae7440c8.1624379707.git.g@b4.vuSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/mixer_scarlett_gen2.c

@@ -344,6 +344,12 @@ struct scarlett2_device_info {
 	 */
 	u8 direct_monitor;
 
+	/* remap analogue outputs; 18i8 Gen 3 has "line 3/4" connected
+	 * internally to the analogue 7/8 outputs
+	 */
+	u8 line_out_remap_enable;
+	u8 line_out_remap[SCARLETT2_ANALOGUE_MAX];
+
 	/* additional description for the line out volume controls */
 	const char * const line_out_descrs[SCARLETT2_ANALOGUE_MAX];
 
@@ -684,15 +690,18 @@ static const struct scarlett2_device_info s18i8_gen3_info = {
 	.phantom_count = 2,
 	.inputs_per_phantom = 2,
 
+	.line_out_remap_enable = 1,
+	.line_out_remap = { 0, 1, 6, 7, 2, 3, 4, 5 },
+
 	.line_out_descrs = {
 		"Monitor L",
 		"Monitor R",
+		"Alt Monitor L",
+		"Alt Monitor R",
 		"Headphones 1 L",
 		"Headphones 1 R",
 		"Headphones 2 L",
 		"Headphones 2 R",
-		"Alt Monitor L",
-		"Alt Monitor R",
 	},
 
 	.port_count = {
@@ -1716,13 +1725,22 @@ static int scarlett2_master_volume_ctl_get(struct snd_kcontrol *kctl,
 	return 0;
 }
 
+static int line_out_remap(struct scarlett2_data *private, int index)
+{
+	const struct scarlett2_device_info *info = private->info;
+
+	if (!info->line_out_remap_enable)
+		return index;
+	return info->line_out_remap[index];
+}
+
 static int scarlett2_volume_ctl_get(struct snd_kcontrol *kctl,
 				    struct snd_ctl_elem_value *ucontrol)
 {
 	struct usb_mixer_elem_info *elem = kctl->private_data;
 	struct usb_mixer_interface *mixer = elem->head.mixer;
 	struct scarlett2_data *private = mixer->private_data;
-	int index = elem->control;
+	int index = line_out_remap(private, elem->control);
 
 	mutex_lock(&private->data_mutex);
 	if (private->vol_updated)
@@ -1739,7 +1757,7 @@ static int scarlett2_volume_ctl_put(struct snd_kcontrol *kctl,
 	struct usb_mixer_elem_info *elem = kctl->private_data;
 	struct usb_mixer_interface *mixer = elem->head.mixer;
 	struct scarlett2_data *private = mixer->private_data;
-	int index = elem->control;
+	int index = line_out_remap(private, elem->control);
 	int oval, val, err = 0;
 
 	mutex_lock(&private->data_mutex);
@@ -1795,7 +1813,7 @@ static int scarlett2_mute_ctl_get(struct snd_kcontrol *kctl,
 {
 	struct usb_mixer_elem_info *elem = kctl->private_data;
 	struct scarlett2_data *private = elem->head.mixer->private_data;
-	int index = elem->control;
+	int index = line_out_remap(private, elem->control);
 
 	ucontrol->value.integer.value[0] = private->mute_switch[index];
 	return 0;
@@ -1807,7 +1825,7 @@ static int scarlett2_mute_ctl_put(struct snd_kcontrol *kctl,
 	struct usb_mixer_elem_info *elem = kctl->private_data;
 	struct usb_mixer_interface *mixer = elem->head.mixer;
 	struct scarlett2_data *private = mixer->private_data;
-	int index = elem->control;
+	int index = line_out_remap(private, elem->control);
 	int oval, val, err = 0;
 
 	mutex_lock(&private->data_mutex);
@@ -1854,9 +1872,9 @@ static int scarlett2_sw_hw_enum_ctl_get(struct snd_kcontrol *kctl,
 {
 	struct usb_mixer_elem_info *elem = kctl->private_data;
 	struct scarlett2_data *private = elem->head.mixer->private_data;
+	int index = line_out_remap(private, elem->control);
 
-	ucontrol->value.enumerated.item[0] =
-		private->vol_sw_hw_switch[elem->control];
+	ucontrol->value.enumerated.item[0] = private->vol_sw_hw_switch[index];
 	return 0;
 }
 
@@ -1892,8 +1910,8 @@ static int scarlett2_sw_hw_enum_ctl_put(struct snd_kcontrol *kctl,
 	struct usb_mixer_elem_info *elem = kctl->private_data;
 	struct usb_mixer_interface *mixer = elem->head.mixer;
 	struct scarlett2_data *private = mixer->private_data;
-
-	int index = elem->control;
+	int ctl_index = elem->control;
+	int index = line_out_remap(private, ctl_index);
 	int oval, val, err = 0;
 
 	mutex_lock(&private->data_mutex);
@@ -1909,7 +1927,7 @@ static int scarlett2_sw_hw_enum_ctl_put(struct snd_kcontrol *kctl,
 	/* Change access mode to RO (hardware controlled volume)
 	 * or RW (software controlled volume)
 	 */
-	scarlett2_vol_ctl_set_writable(mixer, index, !val);
+	scarlett2_vol_ctl_set_writable(mixer, ctl_index, !val);
 
 	/* Reset volume/mute to master volume/mute */
 	private->vol[index] = private->master_vol;
@@ -2441,13 +2459,16 @@ static int scarlett2_dim_mute_ctl_put(struct snd_kcontrol *kctl,
 		err = 1;
 
 	if (index == SCARLETT2_BUTTON_MUTE)
-		for (i = 0; i < num_line_out; i++)
-			if (private->vol_sw_hw_switch[i]) {
-				private->mute_switch[i] = val;
+		for (i = 0; i < num_line_out; i++) {
+			int line_index = line_out_remap(private, i);
+
+			if (private->vol_sw_hw_switch[line_index]) {
+				private->mute_switch[line_index] = val;
 				snd_ctl_notify(mixer->chip->card,
 					       SNDRV_CTL_EVENT_MASK_INFO,
 					       &private->mute_ctls[i]->id);
 			}
+		}
 
 unlock:
 	mutex_unlock(&private->data_mutex);
@@ -2486,6 +2507,7 @@ static int scarlett2_add_line_out_ctls(struct usb_mixer_interface *mixer)
 
 	/* Add volume controls */
 	for (i = 0; i < num_line_out; i++) {
+		int index = line_out_remap(private, i);
 
 		/* Fader */
 		if (info->line_out_descrs[i])
@@ -2516,7 +2538,7 @@ static int scarlett2_add_line_out_ctls(struct usb_mixer_interface *mixer)
 		/* Make the fader and mute controls read-only if the
 		 * SW/HW switch is set to HW
 		 */
-		if (private->vol_sw_hw_switch[i])
+		if (private->vol_sw_hw_switch[index])
 			scarlett2_vol_ctl_set_writable(mixer, i, 0);
 
 		/* SW/HW Switch */
@@ -2765,8 +2787,16 @@ static int scarlett2_mux_src_enum_ctl_get(struct snd_kcontrol *kctl,
 {
 	struct usb_mixer_elem_info *elem = kctl->private_data;
 	struct scarlett2_data *private = elem->head.mixer->private_data;
+	const struct scarlett2_device_info *info = private->info;
+	const int (*port_count)[SCARLETT2_PORT_DIRNS] = info->port_count;
+	int line_out_count =
+		port_count[SCARLETT2_PORT_TYPE_ANALOGUE][SCARLETT2_PORT_OUT];
+	int index = elem->control;
+
+	if (index < line_out_count)
+		index = line_out_remap(private, index);
 
-	ucontrol->value.enumerated.item[0] = private->mux[elem->control];
+	ucontrol->value.enumerated.item[0] = private->mux[index];
 	return 0;
 }
 
@@ -2776,9 +2806,16 @@ static int scarlett2_mux_src_enum_ctl_put(struct snd_kcontrol *kctl,
 	struct usb_mixer_elem_info *elem = kctl->private_data;
 	struct usb_mixer_interface *mixer = elem->head.mixer;
 	struct scarlett2_data *private = mixer->private_data;
+	const struct scarlett2_device_info *info = private->info;
+	const int (*port_count)[SCARLETT2_PORT_DIRNS] = info->port_count;
+	int line_out_count =
+		port_count[SCARLETT2_PORT_TYPE_ANALOGUE][SCARLETT2_PORT_OUT];
 	int index = elem->control;
 	int oval, val, err = 0;
 
+	if (index < line_out_count)
+		index = line_out_remap(private, index);
+
 	mutex_lock(&private->data_mutex);
 
 	oval = private->mux[index];
@@ -3179,6 +3216,7 @@ static void scarlett2_notify_sync(
 static void scarlett2_notify_monitor(
 	struct usb_mixer_interface *mixer)
 {
+	struct snd_card *card = mixer->chip->card;
 	struct scarlett2_data *private = mixer->private_data;
 	const struct scarlett2_device_info *info = private->info;
 	const int (*port_count)[SCARLETT2_PORT_DIRNS] = info->port_count;
@@ -3195,12 +3233,10 @@ static void scarlett2_notify_monitor(
 	snd_ctl_notify(mixer->chip->card, SNDRV_CTL_EVENT_MASK_VALUE,
 		       &private->master_vol_ctl->id);
 
-	for (i = 0; i < num_line_out; i++) {
-		if (!private->vol_sw_hw_switch[i])
-			continue;
-		snd_ctl_notify(mixer->chip->card, SNDRV_CTL_EVENT_MASK_VALUE,
+	for (i = 0; i < num_line_out; i++)
+		if (private->vol_sw_hw_switch[line_out_remap(private, i)])
+			snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE,
 				       &private->vol_ctls[i]->id);
-	}
 }
 
 /* Notify on dim/mute change */
@@ -3225,7 +3261,7 @@ static void scarlett2_notify_dim_mute(
 			       &private->dim_mute_ctls[i]->id);
 
 	for (i = 0; i < num_line_out; i++)
-		if (private->vol_sw_hw_switch[i])
+		if (private->vol_sw_hw_switch[line_out_remap(private, i)])
 			snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE,
 				       &private->mute_ctls[i]->id);
 }