ALSA: usb-audio: Scarlett Gen 2 mixer interface

Add mixer quirk for the Focusrite Scarlett 6i6, 18i8, and 18i20 Gen 2
audio interfaces. Although the interfaces are USB compliant,
additional input/output level controls and hardware routing/mixing
functionality are available using proprietary USB requests.
Signed-off-by: Geoffrey D. Bennett <g@b4.vu>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/Makefile

@@ -11,6 +11,7 @@ snd-usb-audio-objs := 	card.o \
 			mixer.o \
 			mixer_quirks.o \
 			mixer_scarlett.o \
+			mixer_scarlett_gen2.o \
 			mixer_us16x08.o \
 			pcm.o \
 			power.o \

sound/usb/mixer.c

@@ -3509,6 +3509,8 @@ void snd_usb_mixer_disconnect(struct usb_mixer_interface *mixer)
 		usb_kill_urb(mixer->urb);
 	if (mixer->rc_urb)
 		usb_kill_urb(mixer->rc_urb);
+	if (mixer->private_free)
+		mixer->private_free(mixer);
 	mixer->disconnected = true;
 }
 
@@ -3536,6 +3538,8 @@ static int snd_usb_mixer_activate(struct usb_mixer_interface *mixer)
 int snd_usb_mixer_suspend(struct usb_mixer_interface *mixer)
 {
 	snd_usb_mixer_inactivate(mixer);
+	if (mixer->private_suspend)
+		mixer->private_suspend(mixer);
 	return 0;
 }
 

sound/usb/mixer.h

@@ -28,6 +28,10 @@ struct usb_mixer_interface {
 	struct media_mixer_ctl *media_mixer_ctl;
 
 	bool disconnected;
+
+	void *private_data;
+	void (*private_free)(struct usb_mixer_interface *mixer);
+	void (*private_suspend)(struct usb_mixer_interface *mixer);
 };
 
 #define MAX_CHANNELS	16	/* max logical channels */

sound/usb/mixer_quirks.c

@@ -32,6 +32,7 @@
 #include "mixer.h"
 #include "mixer_quirks.h"
 #include "mixer_scarlett.h"
+#include "mixer_scarlett_gen2.h"
 #include "mixer_us16x08.h"
 #include "helper.h"
 
@@ -2258,6 +2259,12 @@ int snd_usb_mixer_apply_create_quirk(struct usb_mixer_interface *mixer)
 		err = snd_scarlett_controls_create(mixer);
 		break;
 
+	case USB_ID(0x1235, 0x8203): /* Focusrite Scarlett 6i6 2nd Gen */
+	case USB_ID(0x1235, 0x8204): /* Focusrite Scarlett 18i8 2nd Gen */
+	case USB_ID(0x1235, 0x8201): /* Focusrite Scarlett 18i20 2nd Gen */
+		err = snd_scarlett_gen2_controls_create(mixer);
+		break;
+
 	case USB_ID(0x041e, 0x323b): /* Creative Sound Blaster E1 */
 		err = snd_soundblaster_e1_switch_create(mixer);
 		break;

sound/usb/mixer_scarlett_gen2.h

+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __USB_MIXER_SCARLETT_GEN2_H
+#define __USB_MIXER_SCARLETT_GEN2_H
+
+int snd_scarlett_gen2_controls_create(struct usb_mixer_interface *mixer);
+
+#endif /* __USB_MIXER_SCARLETT_GEN2_H */