Merging upstream version 6.7.7.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 4638 insertions, 0 deletions

diff --git a/sound/usb/mixer_scarlett2.c b/sound/usb/mixer_scarlett2.c
new file mode 100644
index 0000000000..3b7fcd0907
--- /dev/null
+++ b/sound/usb/mixer_scarlett2.c
@@ -0,0 +1,4638 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *   Focusrite Scarlett 2 Protocol Driver for ALSA
+ *   (including Scarlett 2nd Gen, 3rd Gen, Clarett USB, and Clarett+
+ *   series products)
+ *
+ *   Supported models:
+ *   - 6i6/18i8/18i20 Gen 2
+ *   - Solo/2i2/4i4/8i6/18i8/18i20 Gen 3
+ *   - Clarett 2Pre/4Pre/8Pre USB
+ *   - Clarett+ 2Pre/4Pre/8Pre
+ *
+ *   Copyright (c) 2018-2023 by Geoffrey D. Bennett <g at b4.vu>
+ *   Copyright (c) 2020-2021 by Vladimir Sadovnikov <sadko4u@gmail.com>
+ *   Copyright (c) 2022 by Christian Colglazier <christian@cacolglazier.com>
+ *
+ *   Based on the Scarlett (Gen 1) Driver for ALSA:
+ *
+ *   Copyright (c) 2013 by Tobias Hoffmann
+ *   Copyright (c) 2013 by Robin Gareus <robin at gareus.org>
+ *   Copyright (c) 2002 by Takashi Iwai <tiwai at suse.de>
+ *   Copyright (c) 2014 by Chris J Arges <chris.j.arges at canonical.com>
+ *
+ *   Many codes borrowed from audio.c by
+ *     Alan Cox (alan at lxorguk.ukuu.org.uk)
+ *     Thomas Sailer (sailer at ife.ee.ethz.ch)
+ *
+ *   Code cleanup:
+ *   David Henningsson <david.henningsson at canonical.com>
+ */
+
+/* The protocol was reverse engineered by looking at the communication
+ * between Focusrite Control 2.3.4 and the Focusrite(R) Scarlett 18i20
+ * (firmware 1083) using usbmon in July-August 2018.
+ *
+ * Scarlett 18i8 support added in April 2019.
+ *
+ * Scarlett 6i6 support added in June 2019 (thanks to Martin Wittmann
+ * for providing usbmon output and testing).
+ *
+ * Scarlett 4i4/8i6 Gen 3 support added in May 2020 (thanks to Laurent
+ * Debricon for donating a 4i4 and to Fredrik Unger for providing 8i6
+ * usbmon output and testing).
+ *
+ * Scarlett 18i8/18i20 Gen 3 support added in June 2020 (thanks to
+ * Darren Jaeckel, Alex Sedlack, and Clovis Lunel for providing usbmon
+ * output, protocol traces and testing).
+ *
+ * Support for loading mixer volume and mux configuration from the
+ * interface during driver initialisation added in May 2021 (thanks to
+ * Vladimir Sadovnikov for figuring out how).
+ *
+ * Support for Solo/2i2 Gen 3 added in May 2021 (thanks to Alexander
+ * Vorona for 2i2 protocol traces).
+ *
+ * Support for phantom power, direct monitoring, speaker switching,
+ * and talkback added in May-June 2021.
+ *
+ * Support for Clarett+ 8Pre added in Aug 2022 by Christian
+ * Colglazier.
+ *
+ * Support for Clarett 8Pre USB added in Sep 2023 (thanks to Philippe
+ * Perrot for confirmation).
+ *
+ * Support for Clarett+ 4Pre and 2Pre added in Sep 2023 (thanks to
+ * Gregory Rozzo for donating a 4Pre, and David Sherwood and Patrice
+ * Peterson for usbmon output).
+ *
+ * Support for Clarett 2Pre and 4Pre USB added in Oct 2023.
+ *
+ * This ALSA mixer gives access to (model-dependent):
+ *  - input, output, mixer-matrix muxes
+ *  - mixer-matrix gain stages
+ *  - gain/volume/mute controls
+ *  - level meters
+ *  - line/inst level, pad, and air controls
+ *  - phantom power, direct monitor, speaker switching, and talkback
+ *    controls
+ *  - disable/enable MSD mode
+ *  - disable/enable standalone mode
+ *
+ * <ditaa>
+ *    /--------------\    18chn            20chn     /--------------\
+ *    | Hardware  in +--+------\    /-------------+--+ ALSA PCM out |
+ *    \--------------/  |      |    |             |  \--------------/
+ *                      |      |    |    /-----\  |
+ *                      |      |    |    |     |  |
+ *                      |      v    v    v     |  |
+ *                      |   +---------------+  |  |
+ *                      |    \ Matrix  Mux /   |  |
+ *                      |     +-----+-----+    |  |
+ *                      |           |          |  |
+ *                      |           |18chn     |  |
+ *                      |           |          |  |
+ *                      |           |     10chn|  |
+ *                      |           v          |  |
+ *                      |     +------------+   |  |
+ *                      |     | Mixer      |   |  |
+ *                      |     |     Matrix |   |  |
+ *                      |     |            |   |  |
+ *                      |     | 18x10 Gain |   |  |
+ *                      |     |   stages   |   |  |
+ *                      |     +-----+------+   |  |
+ *                      |           |          |  |
+ *                      |18chn      |10chn     |  |20chn
+ *                      |           |          |  |
+ *                      |           +----------/  |
+ *                      |           |             |
+ *                      v           v             v
+ *                      ===========================
+ *               +---------------+       +--—------------+
+ *                \ Output  Mux /         \ Capture Mux /
+ *                 +---+---+---+           +-----+-----+
+ *                     |   |                     |
+ *                10chn|   |                     |18chn
+ *                     |   |                     |
+ *  /--------------\   |   |                     |   /--------------\
+ *  | S/PDIF, ADAT |<--/   |10chn                \-->| ALSA PCM in  |
+ *  | Hardware out |       |                         \--------------/
+ *  \--------------/       |
+ *                         v
+ *                  +-------------+    Software gain per channel.
+ *                  | Master Gain |<-- 18i20 only: Switch per channel
+ *                  +------+------+    to select HW or SW gain control.
+ *                         |
+ *                         |10chn
+ *  /--------------\       |
+ *  | Analogue     |<------/
+ *  | Hardware out |
+ *  \--------------/
+ * </ditaa>
+ *
+ * Gen 3 devices have a Mass Storage Device (MSD) mode where a small
+ * disk with registration and driver download information is presented
+ * to the host. To access the full functionality of the device without
+ * proprietary software, MSD mode can be disabled by:
+ * - holding down the 48V button for five seconds while powering on
+ *   the device, or
+ * - using this driver and alsamixer to change the "MSD Mode" setting
+ *   to Off and power-cycling the device
+ */
+
+#include <linux/slab.h>
+#include <linux/usb.h>
+#include <linux/moduleparam.h>
+
+#include <sound/control.h>
+#include <sound/tlv.h>
+
+#include "usbaudio.h"
+#include "mixer.h"
+#include "helper.h"
+
+#include "mixer_scarlett2.h"
+
+/* device_setup value to allow turning MSD mode back on */
+#define SCARLETT2_MSD_ENABLE 0x02
+
+/* device_setup value to disable this mixer driver */
+#define SCARLETT2_DISABLE 0x04
+
+/* some gui mixers can't handle negative ctl values */
+#define SCARLETT2_VOLUME_BIAS 127
+
+/* mixer range from -80dB to +6dB in 0.5dB steps */
+#define SCARLETT2_MIXER_MIN_DB -80
+#define SCARLETT2_MIXER_BIAS (-SCARLETT2_MIXER_MIN_DB * 2)
+#define SCARLETT2_MIXER_MAX_DB 6
+#define SCARLETT2_MIXER_MAX_VALUE \
+	((SCARLETT2_MIXER_MAX_DB - SCARLETT2_MIXER_MIN_DB) * 2)
+#define SCARLETT2_MIXER_VALUE_COUNT (SCARLETT2_MIXER_MAX_VALUE + 1)
+
+/* map from (dB + 80) * 2 to mixer value
+ * for dB in 0 .. 172: int(8192 * pow(10, ((dB - 160) / 2 / 20)))
+ */
+static const u16 scarlett2_mixer_values[SCARLETT2_MIXER_VALUE_COUNT] = {
+	0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2,
+	2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 6, 6, 6, 7, 7, 8, 8,
+	9, 9, 10, 10, 11, 12, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,
+	23, 24, 25, 27, 29, 30, 32, 34, 36, 38, 41, 43, 46, 48, 51,
+	54, 57, 61, 65, 68, 73, 77, 81, 86, 91, 97, 103, 109, 115,
+	122, 129, 137, 145, 154, 163, 173, 183, 194, 205, 217, 230,
+	244, 259, 274, 290, 307, 326, 345, 365, 387, 410, 434, 460,
+	487, 516, 547, 579, 614, 650, 689, 730, 773, 819, 867, 919,
+	973, 1031, 1092, 1157, 1225, 1298, 1375, 1456, 1543, 1634,
+	1731, 1833, 1942, 2057, 2179, 2308, 2445, 2590, 2744, 2906,
+	3078, 3261, 3454, 3659, 3876, 4105, 4349, 4606, 4879, 5168,
+	5475, 5799, 6143, 6507, 6892, 7301, 7733, 8192, 8677, 9191,
+	9736, 10313, 10924, 11571, 12257, 12983, 13752, 14567, 15430,
+	16345
+};
+
+/* Maximum number of analogue outputs */
+#define SCARLETT2_ANALOGUE_MAX 10
+
+/* Maximum number of level and pad switches */
+#define SCARLETT2_LEVEL_SWITCH_MAX 2
+#define SCARLETT2_PAD_SWITCH_MAX 8
+#define SCARLETT2_AIR_SWITCH_MAX 8
+#define SCARLETT2_PHANTOM_SWITCH_MAX 2
+
+/* Maximum number of inputs to the mixer */
+#define SCARLETT2_INPUT_MIX_MAX 25
+
+/* Maximum number of outputs from the mixer */
+#define SCARLETT2_OUTPUT_MIX_MAX 12
+
+/* Maximum size of the data in the USB mux assignment message:
+ * 20 inputs, 20 outputs, 25 matrix inputs, 12 spare
+ */
+#define SCARLETT2_MUX_MAX 77
+
+/* Maximum number of sources (sum of input port counts) */
+#define SCARLETT2_MAX_SRCS 52
+
+/* Maximum number of meters (sum of output port counts) */
+#define SCARLETT2_MAX_METERS 65
+
+/* There are different sets of configuration parameters across the
+ * devices, dependent on series and model.
+ */
+enum {
+	SCARLETT2_CONFIG_SET_GEN_2   = 0,
+	SCARLETT2_CONFIG_SET_GEN_3A  = 1,
+	SCARLETT2_CONFIG_SET_GEN_3B  = 2,
+	SCARLETT2_CONFIG_SET_CLARETT = 3,
+	SCARLETT2_CONFIG_SET_COUNT   = 4
+};
+
+/* Hardware port types:
+ * - None (no input to mux)
+ * - Analogue I/O
+ * - S/PDIF I/O
+ * - ADAT I/O
+ * - Mixer I/O
+ * - PCM I/O
+ */
+enum {
+	SCARLETT2_PORT_TYPE_NONE     = 0,
+	SCARLETT2_PORT_TYPE_ANALOGUE = 1,
+	SCARLETT2_PORT_TYPE_SPDIF    = 2,
+	SCARLETT2_PORT_TYPE_ADAT     = 3,
+	SCARLETT2_PORT_TYPE_MIX      = 4,
+	SCARLETT2_PORT_TYPE_PCM      = 5,
+	SCARLETT2_PORT_TYPE_COUNT    = 6,
+};
+
+/* I/O count of each port type kept in struct scarlett2_ports */
+enum {
+	SCARLETT2_PORT_IN    = 0,
+	SCARLETT2_PORT_OUT   = 1,
+	SCARLETT2_PORT_DIRNS = 2,
+};
+
+/* Dim/Mute buttons on the 18i20 */
+enum {
+	SCARLETT2_BUTTON_MUTE    = 0,
+	SCARLETT2_BUTTON_DIM     = 1,
+	SCARLETT2_DIM_MUTE_COUNT = 2,
+};
+
+static const char *const scarlett2_dim_mute_names[SCARLETT2_DIM_MUTE_COUNT] = {
+	"Mute Playback Switch", "Dim Playback Switch"
+};
+
+/* Description of each hardware port type:
+ * - id: hardware ID of this port type
+ * - src_descr: printf format string for mux input selections
+ * - src_num_offset: added to channel number for the fprintf
+ * - dst_descr: printf format string for mixer controls
+ */
+struct scarlett2_port {
+	u16 id;
+	const char * const src_descr;
+	int src_num_offset;
+	const char * const dst_descr;
+};
+
+static const struct scarlett2_port scarlett2_ports[SCARLETT2_PORT_TYPE_COUNT] = {
+	[SCARLETT2_PORT_TYPE_NONE] = {
+		.id = 0x000,
+		.src_descr = "Off"
+	},
+	[SCARLETT2_PORT_TYPE_ANALOGUE] = {
+		.id = 0x080,
+		.src_descr = "Analogue %d",
+		.src_num_offset = 1,
+		.dst_descr = "Analogue Output %02d Playback"
+	},
+	[SCARLETT2_PORT_TYPE_SPDIF] = {
+		.id = 0x180,
+		.src_descr = "S/PDIF %d",
+		.src_num_offset = 1,
+		.dst_descr = "S/PDIF Output %d Playback"
+	},
+	[SCARLETT2_PORT_TYPE_ADAT] = {
+		.id = 0x200,
+		.src_descr = "ADAT %d",
+		.src_num_offset = 1,
+		.dst_descr = "ADAT Output %d Playback"
+	},
+	[SCARLETT2_PORT_TYPE_MIX] = {
+		.id = 0x300,
+		.src_descr = "Mix %c",
+		.src_num_offset = 'A',
+		.dst_descr = "Mixer Input %02d Capture"
+	},
+	[SCARLETT2_PORT_TYPE_PCM] = {
+		.id = 0x600,
+		.src_descr = "PCM %d",
+		.src_num_offset = 1,
+		.dst_descr = "PCM %02d Capture"
+	},
+};
+
+/* Number of mux tables: one for each band of sample rates
+ * (44.1/48kHz, 88.2/96kHz, and 176.4/176kHz)
+ */
+#define SCARLETT2_MUX_TABLES 3
+
+/* Maximum number of entries in a mux table */
+#define SCARLETT2_MAX_MUX_ENTRIES 10
+
+/* One entry within mux_assignment defines the port type and range of
+ * ports to add to the set_mux message. The end of the list is marked
+ * with count == 0.
+ */
+struct scarlett2_mux_entry {
+	u8 port_type;
+	u8 start;
+	u8 count;
+};
+
+/* Maximum number of entries in a mux table */
+#define SCARLETT2_MAX_METER_ENTRIES 9
+
+/* One entry within meter_assignment defines the range of mux outputs
+ * that consecutive meter entries are mapped to. The end of the list
+ * is marked with count == 0.
+ */
+struct scarlett2_meter_entry {
+	u8 start;
+	u8 count;
+};
+
+struct scarlett2_device_info {
+	/* Gen 3 devices have an internal MSD mode switch that needs
+	 * to be disabled in order to access the full functionality of
+	 * the device.
+	 */
+	u8 has_msd_mode;
+
+	/* which set of configuration parameters the device uses */
+	u8 config_set;
+
+	/* line out hw volume is sw controlled */
+	u8 line_out_hw_vol;
+
+	/* support for main/alt speaker switching */
+	u8 has_speaker_switching;
+
+	/* support for talkback microphone */
+	u8 has_talkback;
+
+	/* the number of analogue inputs with a software switchable
+	 * level control that can be set to line or instrument
+	 */
+	u8 level_input_count;
+
+	/* the first input with a level control (0-based) */
+	u8 level_input_first;
+
+	/* the number of analogue inputs with a software switchable
+	 * 10dB pad control
+	 */
+	u8 pad_input_count;
+
+	/* the number of analogue inputs with a software switchable
+	 * "air" control
+	 */
+	u8 air_input_count;
+
+	/* the number of phantom (48V) software switchable controls */
+	u8 phantom_count;
+
+	/* the number of inputs each phantom switch controls */
+	u8 inputs_per_phantom;
+
+	/* the number of direct monitor options
+	 * (0 = none, 1 = mono only, 2 = mono/stereo)
+	 */
+	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];
+	u8 line_out_unmap[SCARLETT2_ANALOGUE_MAX];
+
+	/* additional description for the line out volume controls */
+	const char * const line_out_descrs[SCARLETT2_ANALOGUE_MAX];
+
+	/* number of sources/destinations of each port type */
+	const int port_count[SCARLETT2_PORT_TYPE_COUNT][SCARLETT2_PORT_DIRNS];
+
+	/* layout/order of the entries in the set_mux message */
+	struct scarlett2_mux_entry mux_assignment[SCARLETT2_MUX_TABLES]
+						 [SCARLETT2_MAX_MUX_ENTRIES];
+
+	/* map from meter level order returned by
+	 * SCARLETT2_USB_GET_METER to index into mux[] entries (same
+	 * as the order returned by scarlett2_meter_ctl_get())
+	 */
+	struct scarlett2_meter_entry meter_map[SCARLETT2_MAX_METER_ENTRIES];
+};
+
+struct scarlett2_data {
+	struct usb_mixer_interface *mixer;
+	struct mutex usb_mutex; /* prevent sending concurrent USB requests */
+	struct mutex data_mutex; /* lock access to this data */
+	struct delayed_work work;
+	const struct scarlett2_device_info *info;
+	const char *series_name;
+	__u8 bInterfaceNumber;
+	__u8 bEndpointAddress;
+	__u16 wMaxPacketSize;
+	__u8 bInterval;
+	int num_mux_srcs;
+	int num_mux_dsts;
+	u32 firmware_version;
+	u16 scarlett2_seq;
+	u8 sync_updated;
+	u8 vol_updated;
+	u8 input_other_updated;
+	u8 monitor_other_updated;
+	u8 mux_updated;
+	u8 speaker_switching_switched;
+	u8 sync;
+	u8 master_vol;
+	u8 vol[SCARLETT2_ANALOGUE_MAX];
+	u8 vol_sw_hw_switch[SCARLETT2_ANALOGUE_MAX];
+	u8 mute_switch[SCARLETT2_ANALOGUE_MAX];
+	u8 level_switch[SCARLETT2_LEVEL_SWITCH_MAX];
+	u8 pad_switch[SCARLETT2_PAD_SWITCH_MAX];
+	u8 dim_mute[SCARLETT2_DIM_MUTE_COUNT];
+	u8 air_switch[SCARLETT2_AIR_SWITCH_MAX];
+	u8 phantom_switch[SCARLETT2_PHANTOM_SWITCH_MAX];
+	u8 phantom_persistence;
+	u8 direct_monitor_switch;
+	u8 speaker_switching_switch;
+	u8 talkback_switch;
+	u8 talkback_map[SCARLETT2_OUTPUT_MIX_MAX];
+	u8 msd_switch;
+	u8 standalone_switch;
+	u8 meter_level_map[SCARLETT2_MAX_METERS];
+	struct snd_kcontrol *sync_ctl;
+	struct snd_kcontrol *master_vol_ctl;
+	struct snd_kcontrol *vol_ctls[SCARLETT2_ANALOGUE_MAX];
+	struct snd_kcontrol *sw_hw_ctls[SCARLETT2_ANALOGUE_MAX];
+	struct snd_kcontrol *mute_ctls[SCARLETT2_ANALOGUE_MAX];
+	struct snd_kcontrol *dim_mute_ctls[SCARLETT2_DIM_MUTE_COUNT];
+	struct snd_kcontrol *level_ctls[SCARLETT2_LEVEL_SWITCH_MAX];
+	struct snd_kcontrol *pad_ctls[SCARLETT2_PAD_SWITCH_MAX];
+	struct snd_kcontrol *air_ctls[SCARLETT2_AIR_SWITCH_MAX];
+	struct snd_kcontrol *phantom_ctls[SCARLETT2_PHANTOM_SWITCH_MAX];
+	struct snd_kcontrol *mux_ctls[SCARLETT2_MUX_MAX];
+	struct snd_kcontrol *direct_monitor_ctl;
+	struct snd_kcontrol *speaker_switching_ctl;
+	struct snd_kcontrol *talkback_ctl;
+	u8 mux[SCARLETT2_MUX_MAX];
+	u8 mix[SCARLETT2_INPUT_MIX_MAX * SCARLETT2_OUTPUT_MIX_MAX];
+};
+
+/*** Model-specific data ***/
+
+static const struct scarlett2_device_info s6i6_gen2_info = {
+	.config_set = SCARLETT2_CONFIG_SET_GEN_2,
+	.level_input_count = 2,
+	.pad_input_count = 2,
+
+	.line_out_descrs = {
+		"Headphones 1 L",
+		"Headphones 1 R",
+		"Headphones 2 L",
+		"Headphones 2 R",
+	},
+
+	.port_count = {
+		[SCARLETT2_PORT_TYPE_NONE]     = {  1,  0 },
+		[SCARLETT2_PORT_TYPE_ANALOGUE] = {  4,  4 },
+		[SCARLETT2_PORT_TYPE_SPDIF]    = {  2,  2 },
+		[SCARLETT2_PORT_TYPE_MIX]      = { 10, 18 },
+		[SCARLETT2_PORT_TYPE_PCM]      = {  6,  6 },
+	},
+
+	.mux_assignment = { {
+		{ SCARLETT2_PORT_TYPE_PCM,      0,  6 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE, 0,  4 },
+		{ SCARLETT2_PORT_TYPE_SPDIF,    0,  2 },
+		{ SCARLETT2_PORT_TYPE_MIX,      0, 18 },
+		{ SCARLETT2_PORT_TYPE_NONE,     0,  8 },
+		{ 0,                            0,  0 },
+	}, {
+		{ SCARLETT2_PORT_TYPE_PCM,      0,  6 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE, 0,  4 },
+		{ SCARLETT2_PORT_TYPE_SPDIF,    0,  2 },
+		{ SCARLETT2_PORT_TYPE_MIX,      0, 18 },
+		{ SCARLETT2_PORT_TYPE_NONE,     0,  8 },
+		{ 0,                            0,  0 },
+	}, {
+		{ SCARLETT2_PORT_TYPE_PCM,      0,  6 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE, 0,  4 },
+		{ SCARLETT2_PORT_TYPE_SPDIF,    0,  2 },
+		{ SCARLETT2_PORT_TYPE_MIX,      0, 18 },
+		{ SCARLETT2_PORT_TYPE_NONE,     0,  8 },
+		{ 0,                            0,  0 },
+	} },
+
+	.meter_map = {
+		{ 24,  6 },
+		{  0, 24 },
+		{  0,  0 },
+	}
+};
+
+static const struct scarlett2_device_info s18i8_gen2_info = {
+	.config_set = SCARLETT2_CONFIG_SET_GEN_2,
+	.level_input_count = 2,
+	.pad_input_count = 4,
+
+	.line_out_descrs = {
+		"Monitor L",
+		"Monitor R",
+		"Headphones 1 L",
+		"Headphones 1 R",
+		"Headphones 2 L",
+		"Headphones 2 R",
+	},
+
+	.port_count = {
+		[SCARLETT2_PORT_TYPE_NONE]     = {  1,  0 },
+		[SCARLETT2_PORT_TYPE_ANALOGUE] = {  8,  6 },
+		[SCARLETT2_PORT_TYPE_SPDIF]    = {  2,  2 },
+		[SCARLETT2_PORT_TYPE_ADAT]     = {  8,  0 },
+		[SCARLETT2_PORT_TYPE_MIX]      = { 10, 18 },
+		[SCARLETT2_PORT_TYPE_PCM]      = {  8, 18 },
+	},
+
+	.mux_assignment = { {
+		{ SCARLETT2_PORT_TYPE_PCM,      0, 18 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE, 0,  6 },
+		{ SCARLETT2_PORT_TYPE_SPDIF,    0,  2 },
+		{ SCARLETT2_PORT_TYPE_MIX,      0, 18 },
+		{ SCARLETT2_PORT_TYPE_NONE,     0,  8 },
+		{ 0,                            0,  0 },
+	}, {
+		{ SCARLETT2_PORT_TYPE_PCM,      0, 14 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE, 0,  6 },
+		{ SCARLETT2_PORT_TYPE_SPDIF,    0,  2 },
+		{ SCARLETT2_PORT_TYPE_MIX,      0, 18 },
+		{ SCARLETT2_PORT_TYPE_NONE,     0,  8 },
+		{ 0,                            0,  0 },
+	}, {
+		{ SCARLETT2_PORT_TYPE_PCM,      0, 10 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE, 0,  6 },
+		{ SCARLETT2_PORT_TYPE_SPDIF,    0,  2 },
+		{ SCARLETT2_PORT_TYPE_MIX,      0, 18 },
+		{ SCARLETT2_PORT_TYPE_NONE,     0,  4 },
+		{ 0,                            0,  0 },
+	} },
+
+	.meter_map = {
+		{ 26, 18 },
+		{  0, 26 },
+		{  0,  0 },
+	}
+};
+
+static const struct scarlett2_device_info s18i20_gen2_info = {
+	.config_set = SCARLETT2_CONFIG_SET_GEN_2,
+	.line_out_hw_vol = 1,
+
+	.line_out_descrs = {
+		"Monitor L",
+		"Monitor R",
+		NULL,
+		NULL,
+		NULL,
+		NULL,
+		"Headphones 1 L",
+		"Headphones 1 R",
+		"Headphones 2 L",
+		"Headphones 2 R",
+	},
+
+	.port_count = {
+		[SCARLETT2_PORT_TYPE_NONE]     = {  1,  0 },
+		[SCARLETT2_PORT_TYPE_ANALOGUE] = {  8, 10 },
+		[SCARLETT2_PORT_TYPE_SPDIF]    = {  2,  2 },
+		[SCARLETT2_PORT_TYPE_ADAT]     = {  8,  8 },
+		[SCARLETT2_PORT_TYPE_MIX]      = { 10, 18 },
+		[SCARLETT2_PORT_TYPE_PCM]      = { 20, 18 },
+	},
+
+	.mux_assignment = { {
+		{ SCARLETT2_PORT_TYPE_PCM,      0, 18 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE, 0, 10 },
+		{ SCARLETT2_PORT_TYPE_SPDIF,    0,  2 },
+		{ SCARLETT2_PORT_TYPE_ADAT,     0,  8 },
+		{ SCARLETT2_PORT_TYPE_MIX,      0, 18 },
+		{ SCARLETT2_PORT_TYPE_NONE,     0,  8 },
+		{ 0,                            0,  0 },
+	}, {
+		{ SCARLETT2_PORT_TYPE_PCM,      0, 14 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE, 0, 10 },
+		{ SCARLETT2_PORT_TYPE_SPDIF,    0,  2 },
+		{ SCARLETT2_PORT_TYPE_ADAT,     0,  4 },
+		{ SCARLETT2_PORT_TYPE_MIX,      0, 18 },
+		{ SCARLETT2_PORT_TYPE_NONE,     0,  8 },
+		{ 0,                            0,  0 },
+	}, {
+		{ SCARLETT2_PORT_TYPE_PCM,      0, 10 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE, 0, 10 },
+		{ SCARLETT2_PORT_TYPE_SPDIF,    0,  2 },
+		{ SCARLETT2_PORT_TYPE_MIX,      0, 18 },
+		{ SCARLETT2_PORT_TYPE_NONE,     0,  6 },
+		{ 0,                            0,  0 },
+	} },
+
+	.meter_map = {
+		{ 38, 18 },
+		{  0, 38 },
+		{  0,  0 },
+	}
+};
+
+static const struct scarlett2_device_info solo_gen3_info = {
+	.has_msd_mode = 1,
+	.config_set = SCARLETT2_CONFIG_SET_GEN_3A,
+	.level_input_count = 1,
+	.level_input_first = 1,
+	.air_input_count = 1,
+	.phantom_count = 1,
+	.inputs_per_phantom = 1,
+	.direct_monitor = 1,
+};
+
+static const struct scarlett2_device_info s2i2_gen3_info = {
+	.has_msd_mode = 1,
+	.config_set = SCARLETT2_CONFIG_SET_GEN_3A,
+	.level_input_count = 2,
+	.air_input_count = 2,
+	.phantom_count = 1,
+	.inputs_per_phantom = 2,
+	.direct_monitor = 2,
+};
+
+static const struct scarlett2_device_info s4i4_gen3_info = {
+	.has_msd_mode = 1,
+	.config_set = SCARLETT2_CONFIG_SET_GEN_3B,
+	.level_input_count = 2,
+	.pad_input_count = 2,
+	.air_input_count = 2,
+	.phantom_count = 1,
+	.inputs_per_phantom = 2,
+
+	.line_out_descrs = {
+		"Monitor L",
+		"Monitor R",
+		"Headphones L",
+		"Headphones R",
+	},
+
+	.port_count = {
+		[SCARLETT2_PORT_TYPE_NONE]     = { 1, 0 },
+		[SCARLETT2_PORT_TYPE_ANALOGUE] = { 4, 4 },
+		[SCARLETT2_PORT_TYPE_MIX]      = { 6, 8 },
+		[SCARLETT2_PORT_TYPE_PCM]      = { 4, 6 },
+	},
+
+	.mux_assignment = { {
+		{ SCARLETT2_PORT_TYPE_PCM,      0,  6 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE, 0,  4 },
+		{ SCARLETT2_PORT_TYPE_MIX,      0,  8 },
+		{ SCARLETT2_PORT_TYPE_NONE,     0, 16 },
+		{ 0,                            0,  0 },
+	}, {
+		{ SCARLETT2_PORT_TYPE_PCM,      0,  6 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE, 0,  4 },
+		{ SCARLETT2_PORT_TYPE_MIX,      0,  8 },
+		{ SCARLETT2_PORT_TYPE_NONE,     0, 16 },
+		{ 0,                            0,  0 },
+	}, {
+		{ SCARLETT2_PORT_TYPE_PCM,      0,  6 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE, 0,  4 },
+		{ SCARLETT2_PORT_TYPE_MIX,      0,  8 },
+		{ SCARLETT2_PORT_TYPE_NONE,     0, 16 },
+		{ 0,                            0,  0 },
+	} },
+
+	.meter_map = {
+		{ 12,  6 },
+		{  0, 12 },
+		{  0,  0 },
+	}
+};
+
+static const struct scarlett2_device_info s8i6_gen3_info = {
+	.has_msd_mode = 1,
+	.config_set = SCARLETT2_CONFIG_SET_GEN_3B,
+	.level_input_count = 2,
+	.pad_input_count = 2,
+	.air_input_count = 2,
+	.phantom_count = 1,
+	.inputs_per_phantom = 2,
+
+	.line_out_descrs = {
+		"Headphones 1 L",
+		"Headphones 1 R",
+		"Headphones 2 L",
+		"Headphones 2 R",
+	},
+
+	.port_count = {
+		[SCARLETT2_PORT_TYPE_NONE]     = { 1,  0 },
+		[SCARLETT2_PORT_TYPE_ANALOGUE] = { 6,  4 },
+		[SCARLETT2_PORT_TYPE_SPDIF]    = { 2,  2 },
+		[SCARLETT2_PORT_TYPE_MIX]      = { 8,  8 },
+		[SCARLETT2_PORT_TYPE_PCM]      = { 6, 10 },
+	},
+
+	.mux_assignment = { {
+		{ SCARLETT2_PORT_TYPE_PCM,      0,  8 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE, 0,  4 },
+		{ SCARLETT2_PORT_TYPE_SPDIF,    0,  2 },
+		{ SCARLETT2_PORT_TYPE_PCM,      8,  2 },
+		{ SCARLETT2_PORT_TYPE_MIX,      0,  8 },
+		{ SCARLETT2_PORT_TYPE_NONE,     0, 18 },
+		{ 0,                            0,  0 },
+	}, {
+		{ SCARLETT2_PORT_TYPE_PCM,      0,  8 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE, 0,  4 },
+		{ SCARLETT2_PORT_TYPE_SPDIF,    0,  2 },
+		{ SCARLETT2_PORT_TYPE_PCM,      8,  2 },
+		{ SCARLETT2_PORT_TYPE_MIX,      0,  8 },
+		{ SCARLETT2_PORT_TYPE_NONE,     0, 18 },
+		{ 0,                            0,  0 },
+	}, {
+		{ SCARLETT2_PORT_TYPE_PCM,      0,  8 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE, 0,  4 },
+		{ SCARLETT2_PORT_TYPE_SPDIF,    0,  2 },
+		{ SCARLETT2_PORT_TYPE_PCM,      8,  2 },
+		{ SCARLETT2_PORT_TYPE_MIX,      0,  8 },
+		{ SCARLETT2_PORT_TYPE_NONE,     0, 18 },
+		{ 0,                            0,  0 },
+	} },
+
+	.meter_map = {
+		{ 14, 8 },
+		{  0, 6 },
+		{ 22, 2 },
+		{  6, 8 },
+		{  0, 0 },
+	}
+};
+
+static const struct scarlett2_device_info s18i8_gen3_info = {
+	.has_msd_mode = 1,
+	.config_set = SCARLETT2_CONFIG_SET_GEN_3B,
+	.line_out_hw_vol = 1,
+	.has_speaker_switching = 1,
+	.level_input_count = 2,
+	.pad_input_count = 4,
+	.air_input_count = 4,
+	.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_unmap = { 0, 1, 4, 5, 6, 7, 2, 3 },
+
+	.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",
+	},
+
+	.port_count = {
+		[SCARLETT2_PORT_TYPE_NONE]     = {  1,  0 },
+		[SCARLETT2_PORT_TYPE_ANALOGUE] = {  8,  8 },
+		[SCARLETT2_PORT_TYPE_SPDIF]    = {  2,  2 },
+		[SCARLETT2_PORT_TYPE_ADAT]     = {  8,  0 },
+		[SCARLETT2_PORT_TYPE_MIX]      = { 10, 20 },
+		[SCARLETT2_PORT_TYPE_PCM]      = {  8, 20 },
+	},
+
+	.mux_assignment = { {
+		{ SCARLETT2_PORT_TYPE_PCM,       0, 10 },
+		{ SCARLETT2_PORT_TYPE_PCM,      12,  8 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE,  0,  2 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE,  6,  2 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE,  2,  4 },
+		{ SCARLETT2_PORT_TYPE_SPDIF,     0,  2 },
+		{ SCARLETT2_PORT_TYPE_PCM,      10,  2 },
+		{ SCARLETT2_PORT_TYPE_MIX,       0, 20 },
+		{ SCARLETT2_PORT_TYPE_NONE,      0, 10 },
+		{ 0,                             0,  0 },
+	}, {
+		{ SCARLETT2_PORT_TYPE_PCM,       0, 10 },
+		{ SCARLETT2_PORT_TYPE_PCM,      12,  4 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE,  0,  2 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE,  6,  2 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE,  2,  4 },
+		{ SCARLETT2_PORT_TYPE_SPDIF,     0,  2 },
+		{ SCARLETT2_PORT_TYPE_PCM,      10,  2 },
+		{ SCARLETT2_PORT_TYPE_MIX,       0, 20 },
+		{ SCARLETT2_PORT_TYPE_NONE,      0, 10 },
+		{ 0,                             0,  0 },
+	}, {
+		{ SCARLETT2_PORT_TYPE_PCM,       0, 10 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE,  0,  2 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE,  6,  2 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE,  2,  4 },
+		{ SCARLETT2_PORT_TYPE_SPDIF,     0,  2 },
+		{ SCARLETT2_PORT_TYPE_MIX,       0, 20 },
+		{ SCARLETT2_PORT_TYPE_NONE,      0, 10 },
+		{ 0,                             0,  0 },
+	} },
+
+	.meter_map = {
+		{ 30, 10 },
+		{ 42,  8 },
+		{  0,  2 },
+		{  6,  2 },
+		{  2,  4 },
+		{  8,  2 },
+		{ 40,  2 },
+		{ 10, 20 },
+		{  0,  0 }
+	}
+};
+
+static const struct scarlett2_device_info s18i20_gen3_info = {
+	.has_msd_mode = 1,
+	.config_set = SCARLETT2_CONFIG_SET_GEN_3B,
+	.line_out_hw_vol = 1,
+	.has_speaker_switching = 1,
+	.has_talkback = 1,
+	.level_input_count = 2,
+	.pad_input_count = 8,
+	.air_input_count = 8,
+	.phantom_count = 2,
+	.inputs_per_phantom = 4,
+
+	.line_out_descrs = {
+		"Monitor 1 L",
+		"Monitor 1 R",
+		"Monitor 2 L",
+		"Monitor 2 R",
+		NULL,
+		NULL,
+		"Headphones 1 L",
+		"Headphones 1 R",
+		"Headphones 2 L",
+		"Headphones 2 R",
+	},
+
+	.port_count = {
+		[SCARLETT2_PORT_TYPE_NONE]     = {  1,  0 },
+		[SCARLETT2_PORT_TYPE_ANALOGUE] = {  9, 10 },
+		[SCARLETT2_PORT_TYPE_SPDIF]    = {  2,  2 },
+		[SCARLETT2_PORT_TYPE_ADAT]     = {  8,  8 },
+		[SCARLETT2_PORT_TYPE_MIX]      = { 12, 25 },
+		[SCARLETT2_PORT_TYPE_PCM]      = { 20, 20 },
+	},
+
+	.mux_assignment = { {
+		{ SCARLETT2_PORT_TYPE_PCM,       0,  8 },
+		{ SCARLETT2_PORT_TYPE_PCM,      10, 10 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE,  0, 10 },
+		{ SCARLETT2_PORT_TYPE_SPDIF,     0,  2 },
+		{ SCARLETT2_PORT_TYPE_ADAT,      0,  8 },
+		{ SCARLETT2_PORT_TYPE_PCM,       8,  2 },
+		{ SCARLETT2_PORT_TYPE_MIX,       0, 25 },
+		{ SCARLETT2_PORT_TYPE_NONE,      0, 12 },
+		{ 0,                             0,  0 },
+	}, {
+		{ SCARLETT2_PORT_TYPE_PCM,       0,  8 },
+		{ SCARLETT2_PORT_TYPE_PCM,      10,  8 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE,  0, 10 },
+		{ SCARLETT2_PORT_TYPE_SPDIF,     0,  2 },
+		{ SCARLETT2_PORT_TYPE_ADAT,      0,  8 },
+		{ SCARLETT2_PORT_TYPE_PCM,       8,  2 },
+		{ SCARLETT2_PORT_TYPE_MIX,       0, 25 },
+		{ SCARLETT2_PORT_TYPE_NONE,      0, 10 },
+		{ 0,                             0,  0 },
+	}, {
+		{ SCARLETT2_PORT_TYPE_PCM,       0, 10 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE,  0, 10 },
+		{ SCARLETT2_PORT_TYPE_SPDIF,     0,  2 },
+		{ SCARLETT2_PORT_TYPE_NONE,      0, 24 },
+		{ 0,                             0,  0 },
+	} },
+
+	.meter_map = {
+		{ 45,  8 },
+		{ 55, 10 },
+		{  0, 20 },
+		{ 53,  2 },
+		{ 20, 25 },
+		{  0,  0 },
+	}
+};
+
+static const struct scarlett2_device_info clarett_2pre_info = {
+	.config_set = SCARLETT2_CONFIG_SET_CLARETT,
+	.line_out_hw_vol = 1,
+	.level_input_count = 2,
+	.air_input_count = 2,
+
+	.line_out_descrs = {
+		"Monitor L",
+		"Monitor R",
+		"Headphones L",
+		"Headphones R",
+	},
+
+	.port_count = {
+		[SCARLETT2_PORT_TYPE_NONE]     = {  1,  0 },
+		[SCARLETT2_PORT_TYPE_ANALOGUE] = {  2,  4 },
+		[SCARLETT2_PORT_TYPE_SPDIF]    = {  2,  0 },
+		[SCARLETT2_PORT_TYPE_ADAT]     = {  8,  0 },
+		[SCARLETT2_PORT_TYPE_MIX]      = { 10, 18 },
+		[SCARLETT2_PORT_TYPE_PCM]      = {  4, 12 },
+	},
+
+	.mux_assignment = { {
+		{ SCARLETT2_PORT_TYPE_PCM,      0, 12 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE, 0,  4 },
+		{ SCARLETT2_PORT_TYPE_MIX,      0, 18 },
+		{ SCARLETT2_PORT_TYPE_NONE,     0,  8 },
+		{ 0,                            0,  0 },
+	}, {
+		{ SCARLETT2_PORT_TYPE_PCM,      0,  8 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE, 0,  4 },
+		{ SCARLETT2_PORT_TYPE_MIX,      0, 18 },
+		{ SCARLETT2_PORT_TYPE_NONE,     0,  8 },
+		{ 0,                            0,  0 },
+	}, {
+		{ SCARLETT2_PORT_TYPE_PCM,      0,  2 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE, 0,  4 },
+		{ SCARLETT2_PORT_TYPE_NONE,     0, 26 },
+		{ 0,                            0,  0 },
+	} },
+
+	.meter_map = {
+		{ 22, 12 },
+		{  0, 22 },
+		{  0,  0 }
+	}
+};
+
+static const struct scarlett2_device_info clarett_4pre_info = {
+	.config_set = SCARLETT2_CONFIG_SET_CLARETT,
+	.line_out_hw_vol = 1,
+	.level_input_count = 2,
+	.air_input_count = 4,
+
+	.line_out_descrs = {
+		"Monitor L",
+		"Monitor R",
+		"Headphones 1 L",
+		"Headphones 1 R",
+		"Headphones 2 L",
+		"Headphones 2 R",
+	},
+
+	.port_count = {
+		[SCARLETT2_PORT_TYPE_NONE]     = {  1,  0 },
+		[SCARLETT2_PORT_TYPE_ANALOGUE] = {  8,  6 },
+		[SCARLETT2_PORT_TYPE_SPDIF]    = {  2,  2 },
+		[SCARLETT2_PORT_TYPE_ADAT]     = {  8,  0 },
+		[SCARLETT2_PORT_TYPE_MIX]      = { 10, 18 },
+		[SCARLETT2_PORT_TYPE_PCM]      = {  8, 18 },
+	},
+
+	.mux_assignment = { {
+		{ SCARLETT2_PORT_TYPE_PCM,      0, 18 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE, 0,  6 },
+		{ SCARLETT2_PORT_TYPE_SPDIF,    0,  2 },
+		{ SCARLETT2_PORT_TYPE_MIX,      0, 18 },
+		{ SCARLETT2_PORT_TYPE_NONE,     0,  8 },
+		{ 0,                            0,  0 },
+	}, {
+		{ SCARLETT2_PORT_TYPE_PCM,      0, 14 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE, 0,  6 },
+		{ SCARLETT2_PORT_TYPE_SPDIF,    0,  2 },
+		{ SCARLETT2_PORT_TYPE_MIX,      0, 18 },
+		{ SCARLETT2_PORT_TYPE_NONE,     0,  8 },
+		{ 0,                            0,  0 },
+	}, {
+		{ SCARLETT2_PORT_TYPE_PCM,      0, 12 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE, 0,  6 },
+		{ SCARLETT2_PORT_TYPE_SPDIF,    0,  2 },
+		{ SCARLETT2_PORT_TYPE_NONE,     0, 24 },
+		{ 0,                            0,  0 },
+	} },
+
+	.meter_map = {
+		{ 26, 18 },
+		{  0, 26 },
+		{  0,  0 }
+	}
+};
+
+static const struct scarlett2_device_info clarett_8pre_info = {
+	.config_set = SCARLETT2_CONFIG_SET_CLARETT,
+	.line_out_hw_vol = 1,
+	.level_input_count = 2,
+	.air_input_count = 8,
+
+	.line_out_descrs = {
+		"Monitor L",
+		"Monitor R",
+		NULL,
+		NULL,
+		NULL,
+		NULL,
+		"Headphones 1 L",
+		"Headphones 1 R",
+		"Headphones 2 L",
+		"Headphones 2 R",
+	},
+
+	.port_count = {
+		[SCARLETT2_PORT_TYPE_NONE]     = {  1,  0 },
+		[SCARLETT2_PORT_TYPE_ANALOGUE] = {  8, 10 },
+		[SCARLETT2_PORT_TYPE_SPDIF]    = {  2,  2 },
+		[SCARLETT2_PORT_TYPE_ADAT]     = {  8,  8 },
+		[SCARLETT2_PORT_TYPE_MIX]      = { 10, 18 },
+		[SCARLETT2_PORT_TYPE_PCM]      = { 20, 18 },
+	},
+
+	.mux_assignment = { {
+		{ SCARLETT2_PORT_TYPE_PCM,      0, 18 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE, 0, 10 },
+		{ SCARLETT2_PORT_TYPE_SPDIF,    0,  2 },
+		{ SCARLETT2_PORT_TYPE_ADAT,     0,  8 },
+		{ SCARLETT2_PORT_TYPE_MIX,      0, 18 },
+		{ SCARLETT2_PORT_TYPE_NONE,     0,  8 },
+		{ 0,                            0,  0 },
+	}, {
+		{ SCARLETT2_PORT_TYPE_PCM,      0, 14 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE, 0, 10 },
+		{ SCARLETT2_PORT_TYPE_SPDIF,    0,  2 },
+		{ SCARLETT2_PORT_TYPE_ADAT,     0,  4 },
+		{ SCARLETT2_PORT_TYPE_MIX,      0, 18 },
+		{ SCARLETT2_PORT_TYPE_NONE,     0,  8 },
+		{ 0,                            0,  0 },
+	}, {
+		{ SCARLETT2_PORT_TYPE_PCM,      0, 12 },
+		{ SCARLETT2_PORT_TYPE_ANALOGUE, 0, 10 },
+		{ SCARLETT2_PORT_TYPE_SPDIF,    0,  2 },
+		{ SCARLETT2_PORT_TYPE_NONE,     0, 22 },
+		{ 0,                            0,  0 },
+	} },
+
+	.meter_map = {
+		{ 38, 18 },
+		{  0, 38 },
+		{  0,  0 }
+	}
+};
+
+struct scarlett2_device_entry {
+	const u32 usb_id; /* USB device identifier */
+	const struct scarlett2_device_info *info;
+	const char *series_name;
+};
+
+static const struct scarlett2_device_entry scarlett2_devices[] = {
+	/* Supported Gen 2 devices */
+	{ USB_ID(0x1235, 0x8203), &s6i6_gen2_info, "Scarlett Gen 2" },
+	{ USB_ID(0x1235, 0x8204), &s18i8_gen2_info, "Scarlett Gen 2" },
+	{ USB_ID(0x1235, 0x8201), &s18i20_gen2_info, "Scarlett Gen 2" },
+
+	/* Supported Gen 3 devices */
+	{ USB_ID(0x1235, 0x8211), &solo_gen3_info, "Scarlett Gen 3" },
+	{ USB_ID(0x1235, 0x8210), &s2i2_gen3_info, "Scarlett Gen 3" },
+	{ USB_ID(0x1235, 0x8212), &s4i4_gen3_info, "Scarlett Gen 3" },
+	{ USB_ID(0x1235, 0x8213), &s8i6_gen3_info, "Scarlett Gen 3" },
+	{ USB_ID(0x1235, 0x8214), &s18i8_gen3_info, "Scarlett Gen 3" },
+	{ USB_ID(0x1235, 0x8215), &s18i20_gen3_info, "Scarlett Gen 3" },
+
+	/* Supported Clarett USB/Clarett+ devices */
+	{ USB_ID(0x1235, 0x8206), &clarett_2pre_info, "Clarett USB" },
+	{ USB_ID(0x1235, 0x8207), &clarett_4pre_info, "Clarett USB" },
+	{ USB_ID(0x1235, 0x8208), &clarett_8pre_info, "Clarett USB" },
+	{ USB_ID(0x1235, 0x820a), &clarett_2pre_info, "Clarett+" },
+	{ USB_ID(0x1235, 0x820b), &clarett_4pre_info, "Clarett+" },
+	{ USB_ID(0x1235, 0x820c), &clarett_8pre_info, "Clarett+" },
+
+	/* End of list */
+	{ 0, NULL },
+};
+
+/* get the starting port index number for a given port type/direction */
+static int scarlett2_get_port_start_num(
+	const int port_count[][SCARLETT2_PORT_DIRNS],
+	int direction, int port_type)
+{
+	int i, num = 0;
+
+	for (i = 0; i < port_type; i++)
+		num += port_count[i][direction];
+
+	return num;
+}
+
+/*** USB Interactions ***/
+
+/* Notifications from the interface */
+#define SCARLETT2_USB_NOTIFY_SYNC          0x00000008
+#define SCARLETT2_USB_NOTIFY_DIM_MUTE      0x00200000
+#define SCARLETT2_USB_NOTIFY_MONITOR       0x00400000
+#define SCARLETT2_USB_NOTIFY_INPUT_OTHER   0x00800000
+#define SCARLETT2_USB_NOTIFY_MONITOR_OTHER 0x01000000
+
+/* Commands for sending/receiving requests/responses */
+#define SCARLETT2_USB_CMD_INIT 0
+#define SCARLETT2_USB_CMD_REQ  2
+#define SCARLETT2_USB_CMD_RESP 3
+
+#define SCARLETT2_USB_INIT_1    0x00000000
+#define SCARLETT2_USB_INIT_2    0x00000002
+#define SCARLETT2_USB_GET_METER 0x00001001
+#define SCARLETT2_USB_GET_MIX   0x00002001
+#define SCARLETT2_USB_SET_MIX   0x00002002
+#define SCARLETT2_USB_GET_MUX   0x00003001
+#define SCARLETT2_USB_SET_MUX   0x00003002
+#define SCARLETT2_USB_GET_SYNC  0x00006004
+#define SCARLETT2_USB_GET_DATA  0x00800000
+#define SCARLETT2_USB_SET_DATA  0x00800001
+#define SCARLETT2_USB_DATA_CMD  0x00800002
+
+#define SCARLETT2_USB_CONFIG_SAVE 6
+
+#define SCARLETT2_USB_VOLUME_STATUS_OFFSET 0x31
+#define SCARLETT2_USB_METER_LEVELS_GET_MAGIC 1
+
+/* volume status is read together (matches scarlett2_config_items[1]) */
+struct scarlett2_usb_volume_status {
+	/* dim/mute buttons */
+	u8 dim_mute[SCARLETT2_DIM_MUTE_COUNT];
+
+	u8 pad1;
+
+	/* software volume setting */
+	s16 sw_vol[SCARLETT2_ANALOGUE_MAX];
+
+	/* actual volume of output inc. dim (-18dB) */
+	s16 hw_vol[SCARLETT2_ANALOGUE_MAX];
+
+	/* internal mute buttons */
+	u8 mute_switch[SCARLETT2_ANALOGUE_MAX];
+
+	/* sw (0) or hw (1) controlled */
+	u8 sw_hw_switch[SCARLETT2_ANALOGUE_MAX];
+
+	u8 pad3[6];
+
+	/* front panel volume knob */
+	s16 master_vol;
+} __packed;
+
+/* Configuration parameters that can be read and written */
+enum {
+	SCARLETT2_CONFIG_DIM_MUTE = 0,
+	SCARLETT2_CONFIG_LINE_OUT_VOLUME = 1,
+	SCARLETT2_CONFIG_MUTE_SWITCH = 2,
+	SCARLETT2_CONFIG_SW_HW_SWITCH = 3,
+	SCARLETT2_CONFIG_LEVEL_SWITCH = 4,
+	SCARLETT2_CONFIG_PAD_SWITCH = 5,
+	SCARLETT2_CONFIG_MSD_SWITCH = 6,
+	SCARLETT2_CONFIG_AIR_SWITCH = 7,
+	SCARLETT2_CONFIG_STANDALONE_SWITCH = 8,
+	SCARLETT2_CONFIG_PHANTOM_SWITCH = 9,
+	SCARLETT2_CONFIG_PHANTOM_PERSISTENCE = 10,
+	SCARLETT2_CONFIG_DIRECT_MONITOR = 11,
+	SCARLETT2_CONFIG_MONITOR_OTHER_SWITCH = 12,
+	SCARLETT2_CONFIG_MONITOR_OTHER_ENABLE = 13,
+	SCARLETT2_CONFIG_TALKBACK_MAP = 14,
+	SCARLETT2_CONFIG_COUNT = 15
+};
+
+/* Location, size, and activation command number for the configuration
+ * parameters. Size is in bits and may be 1, 8, or 16.
+ */
+struct scarlett2_config {
+	u8 offset;
+	u8 size;
+	u8 activate;
+};
+
+static const struct scarlett2_config
+	scarlett2_config_items[SCARLETT2_CONFIG_SET_COUNT]
+			      [SCARLETT2_CONFIG_COUNT] =
+
+/* Gen 2 devices: 6i6, 18i8, 18i20 */
+{ {
+	[SCARLETT2_CONFIG_DIM_MUTE] = {
+		.offset = 0x31, .size = 8, .activate = 2 },
+
+	[SCARLETT2_CONFIG_LINE_OUT_VOLUME] = {
+		.offset = 0x34, .size = 16, .activate = 1 },
+
+	[SCARLETT2_CONFIG_MUTE_SWITCH] = {
+		.offset = 0x5c, .size = 8, .activate = 1 },
+
+	[SCARLETT2_CONFIG_SW_HW_SWITCH] = {
+		.offset = 0x66, .size = 8, .activate = 3 },
+
+	[SCARLETT2_CONFIG_LEVEL_SWITCH] = {
+		.offset = 0x7c, .size = 8, .activate = 7 },
+
+	[SCARLETT2_CONFIG_PAD_SWITCH] = {
+		.offset = 0x84, .size = 8, .activate = 8 },
+
+	[SCARLETT2_CONFIG_STANDALONE_SWITCH] = {
+		.offset = 0x8d, .size = 8, .activate = 6 },
+
+/* Gen 3 devices without a mixer (Solo and 2i2) */
+}, {
+	[SCARLETT2_CONFIG_MSD_SWITCH] = {
+		.offset = 0x04, .size = 8, .activate = 6 },
+
+	[SCARLETT2_CONFIG_PHANTOM_PERSISTENCE] = {
+		.offset = 0x05, .size = 8, .activate = 6 },
+
+	[SCARLETT2_CONFIG_PHANTOM_SWITCH] = {
+		.offset = 0x06, .size = 8, .activate = 3 },
+
+	[SCARLETT2_CONFIG_DIRECT_MONITOR] = {
+		.offset = 0x07, .size = 8, .activate = 4 },
+
+	[SCARLETT2_CONFIG_LEVEL_SWITCH] = {
+		.offset = 0x08, .size = 1, .activate = 7 },
+
+	[SCARLETT2_CONFIG_AIR_SWITCH] = {
+		.offset = 0x09, .size = 1, .activate = 8 },
+
+/* Gen 3 devices: 4i4, 8i6, 18i8, 18i20 */
+}, {
+	[SCARLETT2_CONFIG_DIM_MUTE] = {
+		.offset = 0x31, .size = 8, .activate = 2 },
+
+	[SCARLETT2_CONFIG_LINE_OUT_VOLUME] = {
+		.offset = 0x34, .size = 16, .activate = 1 },
+
+	[SCARLETT2_CONFIG_MUTE_SWITCH] = {
+		.offset = 0x5c, .size = 8, .activate = 1 },
+
+	[SCARLETT2_CONFIG_SW_HW_SWITCH] = {
+		.offset = 0x66, .size = 8, .activate = 3 },
+
+	[SCARLETT2_CONFIG_LEVEL_SWITCH] = {
+		.offset = 0x7c, .size = 8, .activate = 7 },
+
+	[SCARLETT2_CONFIG_PAD_SWITCH] = {
+		.offset = 0x84, .size = 8, .activate = 8 },
+
+	[SCARLETT2_CONFIG_AIR_SWITCH] = {
+		.offset = 0x8c, .size = 8, .activate = 8 },
+
+	[SCARLETT2_CONFIG_STANDALONE_SWITCH] = {
+		.offset = 0x95, .size = 8, .activate = 6 },
+
+	[SCARLETT2_CONFIG_PHANTOM_SWITCH] = {
+		.offset = 0x9c, .size = 1, .activate = 8 },
+
+	[SCARLETT2_CONFIG_MSD_SWITCH] = {
+		.offset = 0x9d, .size = 8, .activate = 6 },
+
+	[SCARLETT2_CONFIG_PHANTOM_PERSISTENCE] = {
+		.offset = 0x9e, .size = 8, .activate = 6 },
+
+	[SCARLETT2_CONFIG_MONITOR_OTHER_SWITCH] = {
+		.offset = 0x9f, .size = 1, .activate = 10 },
+
+	[SCARLETT2_CONFIG_MONITOR_OTHER_ENABLE] = {
+		.offset = 0xa0, .size = 1, .activate = 10 },
+
+	[SCARLETT2_CONFIG_TALKBACK_MAP] = {
+		.offset = 0xb0, .size = 16, .activate = 10 },
+
+/* Clarett USB and Clarett+ devices: 2Pre, 4Pre, 8Pre */
+}, {
+	[SCARLETT2_CONFIG_DIM_MUTE] = {
+		.offset = 0x31, .size = 8, .activate = 2 },
+
+	[SCARLETT2_CONFIG_LINE_OUT_VOLUME] = {
+		.offset = 0x34, .size = 16, .activate = 1 },
+
+	[SCARLETT2_CONFIG_MUTE_SWITCH] = {
+		.offset = 0x5c, .size = 8, .activate = 1 },
+
+	[SCARLETT2_CONFIG_SW_HW_SWITCH] = {
+		.offset = 0x66, .size = 8, .activate = 3 },
+
+	[SCARLETT2_CONFIG_LEVEL_SWITCH] = {
+		.offset = 0x7c, .size = 8, .activate = 7 },
+
+	[SCARLETT2_CONFIG_AIR_SWITCH] = {
+		.offset = 0x95, .size = 8, .activate = 8 },
+
+	[SCARLETT2_CONFIG_STANDALONE_SWITCH] = {
+		.offset = 0x8d, .size = 8, .activate = 6 },
+} };
+
+/* proprietary request/response format */
+struct scarlett2_usb_packet {
+	__le32 cmd;
+	__le16 size;
+	__le16 seq;
+	__le32 error;
+	__le32 pad;
+	u8 data[];
+};
+
+static void scarlett2_fill_request_header(struct scarlett2_data *private,
+					  struct scarlett2_usb_packet *req,
+					  u32 cmd, u16 req_size)
+{
+	/* sequence must go up by 1 for each request */
+	u16 seq = private->scarlett2_seq++;
+
+	req->cmd = cpu_to_le32(cmd);
+	req->size = cpu_to_le16(req_size);
+	req->seq = cpu_to_le16(seq);
+	req->error = 0;
+	req->pad = 0;
+}
+
+static int scarlett2_usb_tx(struct usb_device *dev, int interface,
+			    void *buf, u16 size)
+{
+	return snd_usb_ctl_msg(dev, usb_sndctrlpipe(dev, 0),
+			SCARLETT2_USB_CMD_REQ,
+			USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_OUT,
+			0, interface, buf, size);
+}
+
+static int scarlett2_usb_rx(struct usb_device *dev, int interface,
+			    u32 usb_req, void *buf, u16 size)
+{
+	return snd_usb_ctl_msg(dev, usb_rcvctrlpipe(dev, 0),
+			usb_req,
+			USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_IN,
+			0, interface, buf, size);
+}
+
+/* Send a proprietary format request to the Scarlett interface */
+static int scarlett2_usb(
+	struct usb_mixer_interface *mixer, u32 cmd,
+	void *req_data, u16 req_size, void *resp_data, u16 resp_size)
+{
+	struct scarlett2_data *private = mixer->private_data;
+	struct usb_device *dev = mixer->chip->dev;
+	struct scarlett2_usb_packet *req, *resp = NULL;
+	size_t req_buf_size = struct_size(req, data, req_size);
+	size_t resp_buf_size = struct_size(resp, data, resp_size);
+	int err;
+
+	req = kmalloc(req_buf_size, GFP_KERNEL);
+	if (!req) {
+		err = -ENOMEM;
+		goto error;
+	}
+
+	resp = kmalloc(resp_buf_size, GFP_KERNEL);
+	if (!resp) {
+		err = -ENOMEM;
+		goto error;
+	}
+
+	mutex_lock(&private->usb_mutex);
+
+	/* build request message and send it */
+
+	scarlett2_fill_request_header(private, req, cmd, req_size);
+
+	if (req_size)
+		memcpy(req->data, req_data, req_size);
+
+	err = scarlett2_usb_tx(dev, private->bInterfaceNumber,
+			       req, req_buf_size);
+
+	if (err != req_buf_size) {
+		usb_audio_err(
+			mixer->chip,
+			"%s USB request result cmd %x was %d\n",
+			private->series_name, cmd, err);
+		err = -EINVAL;
+		goto unlock;
+	}
+
+	/* send a second message to get the response */
+
+	err = scarlett2_usb_rx(dev, private->bInterfaceNumber,
+			       SCARLETT2_USB_CMD_RESP,
+			       resp, resp_buf_size);
+
+	/* validate the response */
+
+	if (err != resp_buf_size) {
+		usb_audio_err(
+			mixer->chip,
+			"%s USB response result cmd %x was %d expected %zu\n",
+			private->series_name, cmd, err, resp_buf_size);
+		err = -EINVAL;
+		goto unlock;
+	}
+
+	/* cmd/seq/size should match except when initialising
+	 * seq sent = 1, response = 0
+	 */
+	if (resp->cmd != req->cmd ||
+	    (resp->seq != req->seq &&
+		(le16_to_cpu(req->seq) != 1 || resp->seq != 0)) ||
+	    resp_size != le16_to_cpu(resp->size) ||
+	    resp->error ||
+	    resp->pad) {
+		usb_audio_err(
+			mixer->chip,
+			"%s USB invalid response; "
+			   "cmd tx/rx %d/%d seq %d/%d size %d/%d "
+			   "error %d pad %d\n",
+			private->series_name,
+			le32_to_cpu(req->cmd), le32_to_cpu(resp->cmd),
+			le16_to_cpu(req->seq), le16_to_cpu(resp->seq),
+			resp_size, le16_to_cpu(resp->size),
+			le32_to_cpu(resp->error),
+			le32_to_cpu(resp->pad));
+		err = -EINVAL;
+		goto unlock;
+	}
+
+	if (resp_data && resp_size > 0)
+		memcpy(resp_data, resp->data, resp_size);
+
+unlock:
+	mutex_unlock(&private->usb_mutex);
+error:
+	kfree(req);
+	kfree(resp);
+	return err;
+}
+
+/* Send a USB message to get data; result placed in *buf */
+static int scarlett2_usb_get(
+	struct usb_mixer_interface *mixer,
+	int offset, void *buf, int size)
+{
+	struct {
+		__le32 offset;
+		__le32 size;
+	} __packed req;
+
+	req.offset = cpu_to_le32(offset);
+	req.size = cpu_to_le32(size);
+	return scarlett2_usb(mixer, SCARLETT2_USB_GET_DATA,
+			     &req, sizeof(req), buf, size);
+}
+
+/* Send a USB message to get configuration parameters; result placed in *buf */
+static int scarlett2_usb_get_config(
+	struct usb_mixer_interface *mixer,
+	int config_item_num, int count, void *buf)
+{
+	struct scarlett2_data *private = mixer->private_data;
+	const struct scarlett2_device_info *info = private->info;
+	const struct scarlett2_config *config_item =
+		&scarlett2_config_items[info->config_set][config_item_num];
+	int size, err, i;
+	u8 *buf_8;
+	u8 value;
+
+	/* For byte-sized parameters, retrieve directly into buf */
+	if (config_item->size >= 8) {
+		size = config_item->size / 8 * count;
+		err = scarlett2_usb_get(mixer, config_item->offset, buf, size);
+		if (err < 0)
+			return err;
+		if (size == 2) {
+			u16 *buf_16 = buf;
+
+			for (i = 0; i < count; i++, buf_16++)
+				*buf_16 = le16_to_cpu(*(__le16 *)buf_16);
+		}
+		return 0;
+	}
+
+	/* For bit-sized parameters, retrieve into value */
+	err = scarlett2_usb_get(mixer, config_item->offset, &value, 1);
+	if (err < 0)
+		return err;
+
+	/* then unpack from value into buf[] */
+	buf_8 = buf;
+	for (i = 0; i < 8 && i < count; i++, value >>= 1)
+		*buf_8++ = value & 1;
+
+	return 0;
+}
+
+/* Send SCARLETT2_USB_DATA_CMD SCARLETT2_USB_CONFIG_SAVE */
+static void scarlett2_config_save(struct usb_mixer_interface *mixer)
+{
+	__le32 req = cpu_to_le32(SCARLETT2_USB_CONFIG_SAVE);
+
+	int err = scarlett2_usb(mixer, SCARLETT2_USB_DATA_CMD,
+				&req, sizeof(u32),
+				NULL, 0);
+	if (err < 0)
+		usb_audio_err(mixer->chip, "config save failed: %d\n", err);
+}
+
+/* Delayed work to save config */
+static void scarlett2_config_save_work(struct work_struct *work)
+{
+	struct scarlett2_data *private =
+		container_of(work, struct scarlett2_data, work.work);
+
+	scarlett2_config_save(private->mixer);
+}
+
+/* Send a USB message to set a SCARLETT2_CONFIG_* parameter */
+static int scarlett2_usb_set_config(
+	struct usb_mixer_interface *mixer,
+	int config_item_num, int index, int value)
+{
+	struct scarlett2_data *private = mixer->private_data;
+	const struct scarlett2_device_info *info = private->info;
+	const struct scarlett2_config *config_item =
+	       &scarlett2_config_items[info->config_set][config_item_num];
+	struct {
+		__le32 offset;
+		__le32 bytes;
+		__le32 value;
+	} __packed req;
+	__le32 req2;
+	int offset, size;
+	int err;
+
+	/* Cancel any pending NVRAM save */
+	cancel_delayed_work_sync(&private->work);
+
+	/* Convert config_item->size in bits to size in bytes and
+	 * calculate offset
+	 */
+	if (config_item->size >= 8) {
+		size = config_item->size / 8;
+		offset = config_item->offset + index * size;
+
+	/* If updating a bit, retrieve the old value, set/clear the
+	 * bit as needed, and update value
+	 */
+	} else {
+		u8 tmp;
+
+		size = 1;
+		offset = config_item->offset;
+
+		err = scarlett2_usb_get(mixer, offset, &tmp, 1);
+		if (err < 0)
+			return err;
+
+		if (value)
+			tmp |= (1 << index);
+		else
+			tmp &= ~(1 << index);
+
+		value = tmp;
+	}
+
+	/* Send the configuration parameter data */
+	req.offset = cpu_to_le32(offset);
+	req.bytes = cpu_to_le32(size);
+	req.value = cpu_to_le32(value);
+	err = scarlett2_usb(mixer, SCARLETT2_USB_SET_DATA,
+			    &req, sizeof(u32) * 2 + size,
+			    NULL, 0);
+	if (err < 0)
+		return err;
+
+	/* Activate the change */
+	req2 = cpu_to_le32(config_item->activate);
+	err = scarlett2_usb(mixer, SCARLETT2_USB_DATA_CMD,
+			    &req2, sizeof(req2), NULL, 0);
+	if (err < 0)
+		return err;
+
+	/* Schedule the change to be written to NVRAM */
+	if (config_item->activate != SCARLETT2_USB_CONFIG_SAVE)
+		schedule_delayed_work(&private->work, msecs_to_jiffies(2000));
+
+	return 0;
+}
+
+/* Send a USB message to get sync status; result placed in *sync */
+static int scarlett2_usb_get_sync_status(
+	struct usb_mixer_interface *mixer,
+	u8 *sync)
+{
+	__le32 data;
+	int err;
+
+	err = scarlett2_usb(mixer, SCARLETT2_USB_GET_SYNC,
+			    NULL, 0, &data, sizeof(data));
+	if (err < 0)
+		return err;
+
+	*sync = !!data;
+	return 0;
+}
+
+/* Send a USB message to get volume status; result placed in *buf */
+static int scarlett2_usb_get_volume_status(
+	struct usb_mixer_interface *mixer,
+	struct scarlett2_usb_volume_status *buf)
+{
+	return scarlett2_usb_get(mixer, SCARLETT2_USB_VOLUME_STATUS_OFFSET,
+				 buf, sizeof(*buf));
+}
+
+/* Send a USB message to get the volumes for all inputs of one mix
+ * and put the values into private->mix[]
+ */
+static int scarlett2_usb_get_mix(struct usb_mixer_interface *mixer,
+				 int mix_num)
+{
+	struct scarlett2_data *private = mixer->private_data;
+	const struct scarlett2_device_info *info = private->info;
+
+	int num_mixer_in =
+		info->port_count[SCARLETT2_PORT_TYPE_MIX][SCARLETT2_PORT_OUT];
+	int err, i, j, k;
+
+	struct {
+		__le16 mix_num;
+		__le16 count;
+	} __packed req;
+
+	__le16 data[SCARLETT2_INPUT_MIX_MAX];
+
+	req.mix_num = cpu_to_le16(mix_num);
+	req.count = cpu_to_le16(num_mixer_in);
+
+	err = scarlett2_usb(mixer, SCARLETT2_USB_GET_MIX,
+			    &req, sizeof(req),
+			    data, num_mixer_in * sizeof(u16));
+	if (err < 0)
+		return err;
+
+	for (i = 0, j = mix_num * num_mixer_in; i < num_mixer_in; i++, j++) {
+		u16 mixer_value = le16_to_cpu(data[i]);
+
+		for (k = 0; k < SCARLETT2_MIXER_VALUE_COUNT; k++)
+			if (scarlett2_mixer_values[k] >= mixer_value)
+				break;
+		if (k == SCARLETT2_MIXER_VALUE_COUNT)
+			k = SCARLETT2_MIXER_MAX_VALUE;
+		private->mix[j] = k;
+	}
+
+	return 0;
+}
+
+/* Send a USB message to set the volumes for all inputs of one mix
+ * (values obtained from private->mix[])
+ */
+static int scarlett2_usb_set_mix(struct usb_mixer_interface *mixer,
+				 int mix_num)
+{
+	struct scarlett2_data *private = mixer->private_data;
+	const struct scarlett2_device_info *info = private->info;
+
+	struct {
+		__le16 mix_num;
+		__le16 data[SCARLETT2_INPUT_MIX_MAX];
+	} __packed req;
+
+	int i, j;
+	int num_mixer_in =
+		info->port_count[SCARLETT2_PORT_TYPE_MIX][SCARLETT2_PORT_OUT];
+
+	req.mix_num = cpu_to_le16(mix_num);
+
+	for (i = 0, j = mix_num * num_mixer_in; i < num_mixer_in; i++, j++)
+		req.data[i] = cpu_to_le16(
+			scarlett2_mixer_values[private->mix[j]]
+		);
+
+	return scarlett2_usb(mixer, SCARLETT2_USB_SET_MIX,
+			     &req, (num_mixer_in + 1) * sizeof(u16),
+			     NULL, 0);
+}
+
+/* Convert a port number index (per info->port_count) to a hardware ID */
+static u32 scarlett2_mux_src_num_to_id(
+	const int port_count[][SCARLETT2_PORT_DIRNS], int num)
+{
+	int port_type;
+
+	for (port_type = 0;
+	     port_type < SCARLETT2_PORT_TYPE_COUNT;
+	     port_type++) {
+		if (num < port_count[port_type][SCARLETT2_PORT_IN])
+			return scarlett2_ports[port_type].id | num;
+		num -= port_count[port_type][SCARLETT2_PORT_IN];
+	}
+
+	/* Oops */
+	return 0;
+}
+
+/* Convert a hardware ID to a port number index */
+static u32 scarlett2_mux_id_to_num(
+	const int port_count[][SCARLETT2_PORT_DIRNS], int direction, u32 id)
+{
+	int port_type;
+	int port_num = 0;
+
+	for (port_type = 0;
+	     port_type < SCARLETT2_PORT_TYPE_COUNT;
+	     port_type++) {
+		int base = scarlett2_ports[port_type].id;
+		int count = port_count[port_type][direction];
+
+		if (id >= base && id < base + count)
+			return port_num + id - base;
+		port_num += count;
+	}
+
+	/* Oops */
+	return -1;
+}
+
+/* Convert one mux entry from the interface and load into private->mux[] */
+static void scarlett2_usb_populate_mux(struct scarlett2_data *private,
+				       u32 mux_entry)
+{
+	const struct scarlett2_device_info *info = private->info;
+	const int (*port_count)[SCARLETT2_PORT_DIRNS] = info->port_count;
+
+	int dst_idx, src_idx;
+
+	dst_idx = scarlett2_mux_id_to_num(port_count, SCARLETT2_PORT_OUT,
+					  mux_entry & 0xFFF);
+	if (dst_idx < 0)
+		return;
+
+	if (dst_idx >= private->num_mux_dsts) {
+		usb_audio_err(private->mixer->chip,
+			"BUG: scarlett2_mux_id_to_num(%06x, OUT): %d >= %d",
+			mux_entry, dst_idx, private->num_mux_dsts);
+		return;
+	}
+
+	src_idx = scarlett2_mux_id_to_num(port_count, SCARLETT2_PORT_IN,
+					  mux_entry >> 12);
+	if (src_idx < 0)
+		return;
+
+	if (src_idx >= private->num_mux_srcs) {
+		usb_audio_err(private->mixer->chip,
+			"BUG: scarlett2_mux_id_to_num(%06x, IN): %d >= %d",
+			mux_entry, src_idx, private->num_mux_srcs);
+		return;
+	}
+
+	private->mux[dst_idx] = src_idx;
+}
+
+/* Update the meter level map
+ *
+ * The meter level data from the interface (SCARLETT2_USB_GET_METER
+ * request) is returned in mux_assignment order, but to avoid exposing
+ * that to userspace, scarlett2_meter_ctl_get() rearranges the data
+ * into scarlett2_ports order using the meter_level_map[] array which
+ * is set up by this function.
+ *
+ * In addition, the meter level data values returned from the
+ * interface are invalid for destinations where:
+ *
+ * - the source is "Off"; therefore we set those values to zero (map
+ *   value of 255)
+ *
+ * - the source is assigned to a previous (with respect to the
+ *   mux_assignment order) destination; therefore we set those values
+ *   to the value previously reported for that source
+ */
+static void scarlett2_update_meter_level_map(struct scarlett2_data *private)
+{
+	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];
+	const struct scarlett2_meter_entry *entry;
+
+	/* sources already assigned to a destination
+	 * value is 255 for None, otherwise the value of i
+	 * (index into array returned by
+	 * scarlett2_usb_get_meter_levels())
+	 */
+	u8 seen_src[SCARLETT2_MAX_SRCS] = { 1 };
+	u8 seen_src_value[SCARLETT2_MAX_SRCS] = { 255 };
+
+	/* index in meter_map[] order */
+	int i = 0;
+
+	/* go through the meter_map[] entries */
+	for (entry = info->meter_map;
+	     entry->count;
+	     entry++) {
+
+		/* fill in each meter_level_map[] entry */
+		int j, mux_idx;
+
+		for (j = 0, mux_idx = entry->start;
+		     j < entry->count;
+		     i++, j++, mux_idx++) {
+
+			/* convert mux_idx using line_out_unmap[] */
+			int map_mux_idx = (
+			    info->line_out_remap_enable &&
+			    mux_idx < line_out_count
+			) ? info->line_out_unmap[mux_idx]
+			  : mux_idx;
+
+			/* check which source is connected, and if
+			 * that source is already connected elsewhere,
+			 * use that existing connection's destination
+			 * for this meter entry instead
+			 */
+			int mux_src = private->mux[mux_idx];
+
+			if (!seen_src[mux_src]) {
+				seen_src[mux_src] = 1;
+				seen_src_value[mux_src] = i;
+			}
+			private->meter_level_map[map_mux_idx] =
+				seen_src_value[mux_src];
+		}
+	}
+}
+
+/* Send USB message to get mux inputs and then populate private->mux[] */
+static int scarlett2_usb_get_mux(struct usb_mixer_interface *mixer)
+{
+	struct scarlett2_data *private = mixer->private_data;
+	int count = private->num_mux_dsts;
+	int err, i;
+
+	struct {
+		__le16 num;
+		__le16 count;
+	} __packed req;
+
+	__le32 data[SCARLETT2_MUX_MAX];
+
+	private->mux_updated = 0;
+
+	req.num = 0;
+	req.count = cpu_to_le16(count);
+
+	err = scarlett2_usb(mixer, SCARLETT2_USB_GET_MUX,
+			    &req, sizeof(req),
+			    data, count * sizeof(u32));
+	if (err < 0)
+		return err;
+
+	for (i = 0; i < count; i++)
+		scarlett2_usb_populate_mux(private, le32_to_cpu(data[i]));
+
+	scarlett2_update_meter_level_map(private);
+
+	return 0;
+}
+
+/* Send USB messages to set mux inputs */
+static int scarlett2_usb_set_mux(struct usb_mixer_interface *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 table;
+
+	struct {
+		__le16 pad;
+		__le16 num;
+		__le32 data[SCARLETT2_MUX_MAX];
+	} __packed req;
+
+	req.pad = 0;
+
+	/* set mux settings for each rate */
+	for (table = 0; table < SCARLETT2_MUX_TABLES; table++) {
+		const struct scarlett2_mux_entry *entry;
+
+		/* i counts over the output array */
+		int i = 0, err;
+
+		req.num = cpu_to_le16(table);
+
+		/* loop through each entry */
+		for (entry = info->mux_assignment[table];
+		     entry->count;
+		     entry++) {
+			int j;
+			int port_type = entry->port_type;
+			int port_idx = entry->start;
+			int mux_idx = scarlett2_get_port_start_num(port_count,
+				SCARLETT2_PORT_OUT, port_type) + port_idx;
+			int dst_id = scarlett2_ports[port_type].id + port_idx;
+
+			/* Empty slots */
+			if (!dst_id) {
+				for (j = 0; j < entry->count; j++)
+					req.data[i++] = 0;
+				continue;
+			}
+
+			/* Non-empty mux slots use the lower 12 bits
+			 * for the destination and next 12 bits for
+			 * the source
+			 */
+			for (j = 0; j < entry->count; j++) {
+				int src_id = scarlett2_mux_src_num_to_id(
+					port_count, private->mux[mux_idx++]);
+				req.data[i++] = cpu_to_le32(dst_id |
+							    src_id << 12);
+				dst_id++;
+			}
+		}
+
+		err = scarlett2_usb(mixer, SCARLETT2_USB_SET_MUX,
+				    &req, (i + 1) * sizeof(u32),
+				    NULL, 0);
+		if (err < 0)
+			return err;
+	}
+
+	scarlett2_update_meter_level_map(private);
+
+	return 0;
+}
+
+/* Send USB message to get meter levels */
+static int scarlett2_usb_get_meter_levels(struct usb_mixer_interface *mixer,
+					  u16 num_meters, u16 *levels)
+{
+	struct {
+		__le16 pad;
+		__le16 num_meters;
+		__le32 magic;
+	} __packed req;
+	__le32 resp[SCARLETT2_MAX_METERS];
+	int i, err;
+
+	req.pad = 0;
+	req.num_meters = cpu_to_le16(num_meters);
+	req.magic = cpu_to_le32(SCARLETT2_USB_METER_LEVELS_GET_MAGIC);
+	err = scarlett2_usb(mixer, SCARLETT2_USB_GET_METER,
+			    &req, sizeof(req), resp, num_meters * sizeof(u32));
+	if (err < 0)
+		return err;
+
+	/* copy, convert to u16 */
+	for (i = 0; i < num_meters; i++)
+		levels[i] = le32_to_cpu(resp[i]);
+
+	return 0;
+}
+
+/*** Control Functions ***/
+
+/* helper function to create a new control */
+static int scarlett2_add_new_ctl(struct usb_mixer_interface *mixer,
+				 const struct snd_kcontrol_new *ncontrol,
+				 int index, int channels, const char *name,
+				 struct snd_kcontrol **kctl_return)
+{
+	struct snd_kcontrol *kctl;
+	struct usb_mixer_elem_info *elem;
+	int err;
+
+	elem = kzalloc(sizeof(*elem), GFP_KERNEL);
+	if (!elem)
+		return -ENOMEM;
+
+	/* We set USB_MIXER_BESPOKEN type, so that the core USB mixer code
+	 * ignores them for resume and other operations.
+	 * Also, the head.id field is set to 0, as we don't use this field.
+	 */
+	elem->head.mixer = mixer;
+	elem->control = index;
+	elem->head.id = 0;
+	elem->channels = channels;
+	elem->val_type = USB_MIXER_BESPOKEN;
+
+	kctl = snd_ctl_new1(ncontrol, elem);
+	if (!kctl) {
+		kfree(elem);
+		return -ENOMEM;
+	}
+	kctl->private_free = snd_usb_mixer_elem_free;
+
+	strscpy(kctl->id.name, name, sizeof(kctl->id.name));
+
+	err = snd_usb_mixer_add_control(&elem->head, kctl);
+	if (err < 0)
+		return err;
+
+	if (kctl_return)
+		*kctl_return = kctl;
+
+	return 0;
+}
+
+/*** Firmware Version Control ***/
+
+static int scarlett2_firmware_version_ctl_get(
+	struct snd_kcontrol *kctl,
+	struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_info *elem = kctl->private_data;
+	struct scarlett2_data *private = elem->head.mixer->private_data;
+
+	ucontrol->value.integer.value[0] = private->firmware_version;
+
+	return 0;
+}
+
+static int scarlett2_firmware_version_ctl_info(
+	struct snd_kcontrol *kctl,
+	struct snd_ctl_elem_info *uinfo)
+{
+	uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
+	uinfo->count = 1;
+
+	return 0;
+}
+
+static const struct snd_kcontrol_new scarlett2_firmware_version_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_CARD,
+	.access = SNDRV_CTL_ELEM_ACCESS_READ,
+	.name = "",
+	.info = scarlett2_firmware_version_ctl_info,
+	.get  = scarlett2_firmware_version_ctl_get
+};
+
+static int scarlett2_add_firmware_version_ctl(
+	struct usb_mixer_interface *mixer)
+{
+	return scarlett2_add_new_ctl(mixer, &scarlett2_firmware_version_ctl,
+				     0, 0, "Firmware Version", NULL);
+}
+/*** Sync Control ***/
+
+/* Update sync control after receiving notification that the status
+ * has changed
+ */
+static int scarlett2_update_sync(struct usb_mixer_interface *mixer)
+{
+	struct scarlett2_data *private = mixer->private_data;
+
+	private->sync_updated = 0;
+	return scarlett2_usb_get_sync_status(mixer, &private->sync);
+}
+
+static int scarlett2_sync_ctl_info(struct snd_kcontrol *kctl,
+				   struct snd_ctl_elem_info *uinfo)
+{
+	static const char *texts[2] = {
+		"Unlocked", "Locked"
+	};
+	return snd_ctl_enum_info(uinfo, 1, 2, texts);
+}
+
+static int scarlett2_sync_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 err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	if (private->sync_updated) {
+		err = scarlett2_update_sync(mixer);
+		if (err < 0)
+			goto unlock;
+	}
+	ucontrol->value.enumerated.item[0] = private->sync;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static const struct snd_kcontrol_new scarlett2_sync_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.access = SNDRV_CTL_ELEM_ACCESS_READ,
+	.name = "",
+	.info = scarlett2_sync_ctl_info,
+	.get  = scarlett2_sync_ctl_get
+};
+
+static int scarlett2_add_sync_ctl(struct usb_mixer_interface *mixer)
+{
+	struct scarlett2_data *private = mixer->private_data;
+
+	/* devices without a mixer also don't support reporting sync status */
+	if (private->info->config_set == SCARLETT2_CONFIG_SET_GEN_3A)
+		return 0;
+
+	return scarlett2_add_new_ctl(mixer, &scarlett2_sync_ctl,
+				     0, 1, "Sync Status", &private->sync_ctl);
+}
+
+/*** Analogue Line Out Volume Controls ***/
+
+/* Update hardware volume controls after receiving notification that
+ * they have changed
+ */
+static int scarlett2_update_volumes(struct usb_mixer_interface *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;
+	struct scarlett2_usb_volume_status volume_status;
+	int num_line_out =
+		port_count[SCARLETT2_PORT_TYPE_ANALOGUE][SCARLETT2_PORT_OUT];
+	int err, i;
+	int mute;
+
+	private->vol_updated = 0;
+
+	err = scarlett2_usb_get_volume_status(mixer, &volume_status);
+	if (err < 0)
+		return err;
+
+	private->master_vol = clamp(
+		volume_status.master_vol + SCARLETT2_VOLUME_BIAS,
+		0, SCARLETT2_VOLUME_BIAS);
+
+	if (info->line_out_hw_vol)
+		for (i = 0; i < SCARLETT2_DIM_MUTE_COUNT; i++)
+			private->dim_mute[i] = !!volume_status.dim_mute[i];
+
+	mute = private->dim_mute[SCARLETT2_BUTTON_MUTE];
+
+	for (i = 0; i < num_line_out; i++)
+		if (private->vol_sw_hw_switch[i]) {
+			private->vol[i] = private->master_vol;
+			private->mute_switch[i] = mute;
+		}
+
+	return 0;
+}
+
+static int scarlett2_volume_ctl_info(struct snd_kcontrol *kctl,
+				     struct snd_ctl_elem_info *uinfo)
+{
+	struct usb_mixer_elem_info *elem = kctl->private_data;
+
+	uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
+	uinfo->count = elem->channels;
+	uinfo->value.integer.min = 0;
+	uinfo->value.integer.max = SCARLETT2_VOLUME_BIAS;
+	uinfo->value.integer.step = 1;
+	return 0;
+}
+
+static int scarlett2_master_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 err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	if (private->vol_updated) {
+		err = scarlett2_update_volumes(mixer);
+		if (err < 0)
+			goto unlock;
+	}
+	ucontrol->value.integer.value[0] = private->master_vol;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static int line_out_remap(struct scarlett2_data *private, int index)
+{
+	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];
+
+	if (!info->line_out_remap_enable)
+		return index;
+
+	if (index >= line_out_count)
+		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 = line_out_remap(private, elem->control);
+	int err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	if (private->vol_updated) {
+		err = scarlett2_update_volumes(mixer);
+		if (err < 0)
+			goto unlock;
+	}
+	ucontrol->value.integer.value[0] = private->vol[index];
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static int scarlett2_volume_ctl_put(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 = line_out_remap(private, elem->control);
+	int oval, val, err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	oval = private->vol[index];
+	val = ucontrol->value.integer.value[0];
+
+	if (oval == val)
+		goto unlock;
+
+	private->vol[index] = val;
+	err = scarlett2_usb_set_config(mixer, SCARLETT2_CONFIG_LINE_OUT_VOLUME,
+				       index, val - SCARLETT2_VOLUME_BIAS);
+	if (err == 0)
+		err = 1;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static const DECLARE_TLV_DB_MINMAX(
+	db_scale_scarlett2_gain, -SCARLETT2_VOLUME_BIAS * 100, 0
+);
+
+static const struct snd_kcontrol_new scarlett2_master_volume_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.access = SNDRV_CTL_ELEM_ACCESS_READ |
+		  SNDRV_CTL_ELEM_ACCESS_TLV_READ,
+	.name = "",
+	.info = scarlett2_volume_ctl_info,
+	.get  = scarlett2_master_volume_ctl_get,
+	.private_value = 0, /* max value */
+	.tlv = { .p = db_scale_scarlett2_gain }
+};
+
+static const struct snd_kcontrol_new scarlett2_line_out_volume_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.access = SNDRV_CTL_ELEM_ACCESS_READWRITE |
+		  SNDRV_CTL_ELEM_ACCESS_TLV_READ,
+	.name = "",
+	.info = scarlett2_volume_ctl_info,
+	.get  = scarlett2_volume_ctl_get,
+	.put  = scarlett2_volume_ctl_put,
+	.private_value = 0, /* max value */
+	.tlv = { .p = db_scale_scarlett2_gain }
+};
+
+/*** Mute Switch Controls ***/
+
+static int scarlett2_mute_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 = line_out_remap(private, elem->control);
+	int err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	if (private->vol_updated) {
+		err = scarlett2_update_volumes(mixer);
+		if (err < 0)
+			goto unlock;
+	}
+	ucontrol->value.integer.value[0] = private->mute_switch[index];
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static int scarlett2_mute_ctl_put(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 = line_out_remap(private, elem->control);
+	int oval, val, err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	oval = private->mute_switch[index];
+	val = !!ucontrol->value.integer.value[0];
+
+	if (oval == val)
+		goto unlock;
+
+	private->mute_switch[index] = val;
+
+	/* Send mute change to the device */
+	err = scarlett2_usb_set_config(mixer, SCARLETT2_CONFIG_MUTE_SWITCH,
+				       index, val);
+	if (err == 0)
+		err = 1;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static const struct snd_kcontrol_new scarlett2_mute_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.name = "",
+	.info = snd_ctl_boolean_mono_info,
+	.get  = scarlett2_mute_ctl_get,
+	.put  = scarlett2_mute_ctl_put,
+};
+
+/*** HW/SW Volume Switch Controls ***/
+
+static void scarlett2_sw_hw_ctl_ro(struct scarlett2_data *private, int index)
+{
+	private->sw_hw_ctls[index]->vd[0].access &=
+		~SNDRV_CTL_ELEM_ACCESS_WRITE;
+}
+
+static void scarlett2_sw_hw_ctl_rw(struct scarlett2_data *private, int index)
+{
+	private->sw_hw_ctls[index]->vd[0].access |=
+		SNDRV_CTL_ELEM_ACCESS_WRITE;
+}
+
+static int scarlett2_sw_hw_enum_ctl_info(struct snd_kcontrol *kctl,
+					 struct snd_ctl_elem_info *uinfo)
+{
+	static const char *const values[2] = {
+		"SW", "HW"
+	};
+
+	return snd_ctl_enum_info(uinfo, 1, 2, values);
+}
+
+static int scarlett2_sw_hw_enum_ctl_get(struct snd_kcontrol *kctl,
+					struct snd_ctl_elem_value *ucontrol)
+{
+	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[index];
+	return 0;
+}
+
+static void scarlett2_vol_ctl_set_writable(struct usb_mixer_interface *mixer,
+					   int index, int value)
+{
+	struct scarlett2_data *private = mixer->private_data;
+	struct snd_card *card = mixer->chip->card;
+
+	/* Set/Clear write bits */
+	if (value) {
+		private->vol_ctls[index]->vd[0].access |=
+			SNDRV_CTL_ELEM_ACCESS_WRITE;
+		private->mute_ctls[index]->vd[0].access |=
+			SNDRV_CTL_ELEM_ACCESS_WRITE;
+	} else {
+		private->vol_ctls[index]->vd[0].access &=
+			~SNDRV_CTL_ELEM_ACCESS_WRITE;
+		private->mute_ctls[index]->vd[0].access &=
+			~SNDRV_CTL_ELEM_ACCESS_WRITE;
+	}
+
+	/* Notify of write bit and possible value change */
+	snd_ctl_notify(card,
+		       SNDRV_CTL_EVENT_MASK_VALUE | SNDRV_CTL_EVENT_MASK_INFO,
+		       &private->vol_ctls[index]->id);
+	snd_ctl_notify(card,
+		       SNDRV_CTL_EVENT_MASK_VALUE | SNDRV_CTL_EVENT_MASK_INFO,
+		       &private->mute_ctls[index]->id);
+}
+
+static int scarlett2_sw_hw_change(struct usb_mixer_interface *mixer,
+				  int ctl_index, int val)
+{
+	struct scarlett2_data *private = mixer->private_data;
+	int index = line_out_remap(private, ctl_index);
+	int err;
+
+	private->vol_sw_hw_switch[index] = val;
+
+	/* Change access mode to RO (hardware controlled volume)
+	 * or RW (software controlled volume)
+	 */
+	scarlett2_vol_ctl_set_writable(mixer, ctl_index, !val);
+
+	/* Reset volume/mute to master volume/mute */
+	private->vol[index] = private->master_vol;
+	private->mute_switch[index] = private->dim_mute[SCARLETT2_BUTTON_MUTE];
+
+	/* Set SW volume to current HW volume */
+	err = scarlett2_usb_set_config(
+		mixer, SCARLETT2_CONFIG_LINE_OUT_VOLUME,
+		index, private->master_vol - SCARLETT2_VOLUME_BIAS);
+	if (err < 0)
+		return err;
+
+	/* Set SW mute to current HW mute */
+	err = scarlett2_usb_set_config(
+		mixer, SCARLETT2_CONFIG_MUTE_SWITCH,
+		index, private->dim_mute[SCARLETT2_BUTTON_MUTE]);
+	if (err < 0)
+		return err;
+
+	/* Send SW/HW switch change to the device */
+	return scarlett2_usb_set_config(mixer, SCARLETT2_CONFIG_SW_HW_SWITCH,
+					index, val);
+}
+
+static int scarlett2_sw_hw_enum_ctl_put(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 ctl_index = elem->control;
+	int index = line_out_remap(private, ctl_index);
+	int oval, val, err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	oval = private->vol_sw_hw_switch[index];
+	val = !!ucontrol->value.enumerated.item[0];
+
+	if (oval == val)
+		goto unlock;
+
+	err = scarlett2_sw_hw_change(mixer, ctl_index, val);
+	if (err == 0)
+		err = 1;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static const struct snd_kcontrol_new scarlett2_sw_hw_enum_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.name = "",
+	.info = scarlett2_sw_hw_enum_ctl_info,
+	.get  = scarlett2_sw_hw_enum_ctl_get,
+	.put  = scarlett2_sw_hw_enum_ctl_put,
+};
+
+/*** Line Level/Instrument Level Switch Controls ***/
+
+static int scarlett2_update_input_other(struct usb_mixer_interface *mixer)
+{
+	struct scarlett2_data *private = mixer->private_data;
+	const struct scarlett2_device_info *info = private->info;
+
+	private->input_other_updated = 0;
+
+	if (info->level_input_count) {
+		int err = scarlett2_usb_get_config(
+			mixer, SCARLETT2_CONFIG_LEVEL_SWITCH,
+			info->level_input_count + info->level_input_first,
+			private->level_switch);
+		if (err < 0)
+			return err;
+	}
+
+	if (info->pad_input_count) {
+		int err = scarlett2_usb_get_config(
+			mixer, SCARLETT2_CONFIG_PAD_SWITCH,
+			info->pad_input_count, private->pad_switch);
+		if (err < 0)
+			return err;
+	}
+
+	if (info->air_input_count) {
+		int err = scarlett2_usb_get_config(
+			mixer, SCARLETT2_CONFIG_AIR_SWITCH,
+			info->air_input_count, private->air_switch);
+		if (err < 0)
+			return err;
+	}
+
+	if (info->phantom_count) {
+		int err = scarlett2_usb_get_config(
+			mixer, SCARLETT2_CONFIG_PHANTOM_SWITCH,
+			info->phantom_count, private->phantom_switch);
+		if (err < 0)
+			return err;
+
+		err = scarlett2_usb_get_config(
+			mixer, SCARLETT2_CONFIG_PHANTOM_PERSISTENCE,
+			1, &private->phantom_persistence);
+		if (err < 0)
+			return err;
+	}
+
+	return 0;
+}
+
+static int scarlett2_level_enum_ctl_info(struct snd_kcontrol *kctl,
+					 struct snd_ctl_elem_info *uinfo)
+{
+	static const char *const values[2] = {
+		"Line", "Inst"
+	};
+
+	return snd_ctl_enum_info(uinfo, 1, 2, values);
+}
+
+static int scarlett2_level_enum_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;
+	const struct scarlett2_device_info *info = private->info;
+
+	int index = elem->control + info->level_input_first;
+	int err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	if (private->input_other_updated) {
+		err = scarlett2_update_input_other(mixer);
+		if (err < 0)
+			goto unlock;
+	}
+	ucontrol->value.enumerated.item[0] = private->level_switch[index];
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static int scarlett2_level_enum_ctl_put(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;
+	const struct scarlett2_device_info *info = private->info;
+
+	int index = elem->control + info->level_input_first;
+	int oval, val, err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	oval = private->level_switch[index];
+	val = !!ucontrol->value.enumerated.item[0];
+
+	if (oval == val)
+		goto unlock;
+
+	private->level_switch[index] = val;
+
+	/* Send switch change to the device */
+	err = scarlett2_usb_set_config(mixer, SCARLETT2_CONFIG_LEVEL_SWITCH,
+				       index, val);
+	if (err == 0)
+		err = 1;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static const struct snd_kcontrol_new scarlett2_level_enum_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.name = "",
+	.info = scarlett2_level_enum_ctl_info,
+	.get  = scarlett2_level_enum_ctl_get,
+	.put  = scarlett2_level_enum_ctl_put,
+};
+
+/*** Pad Switch Controls ***/
+
+static int scarlett2_pad_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 err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	if (private->input_other_updated) {
+		err = scarlett2_update_input_other(mixer);
+		if (err < 0)
+			goto unlock;
+	}
+	ucontrol->value.integer.value[0] =
+		private->pad_switch[elem->control];
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static int scarlett2_pad_ctl_put(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 oval, val, err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	oval = private->pad_switch[index];
+	val = !!ucontrol->value.integer.value[0];
+
+	if (oval == val)
+		goto unlock;
+
+	private->pad_switch[index] = val;
+
+	/* Send switch change to the device */
+	err = scarlett2_usb_set_config(mixer, SCARLETT2_CONFIG_PAD_SWITCH,
+				       index, val);
+	if (err == 0)
+		err = 1;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static const struct snd_kcontrol_new scarlett2_pad_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.name = "",
+	.info = snd_ctl_boolean_mono_info,
+	.get  = scarlett2_pad_ctl_get,
+	.put  = scarlett2_pad_ctl_put,
+};
+
+/*** Air Switch Controls ***/
+
+static int scarlett2_air_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 err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	if (private->input_other_updated) {
+		err = scarlett2_update_input_other(mixer);
+		if (err < 0)
+			goto unlock;
+	}
+	ucontrol->value.integer.value[0] = private->air_switch[elem->control];
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static int scarlett2_air_ctl_put(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 oval, val, err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	oval = private->air_switch[index];
+	val = !!ucontrol->value.integer.value[0];
+
+	if (oval == val)
+		goto unlock;
+
+	private->air_switch[index] = val;
+
+	/* Send switch change to the device */
+	err = scarlett2_usb_set_config(mixer, SCARLETT2_CONFIG_AIR_SWITCH,
+				       index, val);
+	if (err == 0)
+		err = 1;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static const struct snd_kcontrol_new scarlett2_air_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.name = "",
+	.info = snd_ctl_boolean_mono_info,
+	.get  = scarlett2_air_ctl_get,
+	.put  = scarlett2_air_ctl_put,
+};
+
+/*** Phantom Switch Controls ***/
+
+static int scarlett2_phantom_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 err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	if (private->input_other_updated) {
+		err = scarlett2_update_input_other(mixer);
+		if (err < 0)
+			goto unlock;
+	}
+	ucontrol->value.integer.value[0] =
+		private->phantom_switch[elem->control];
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static int scarlett2_phantom_ctl_put(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 oval, val, err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	oval = private->phantom_switch[index];
+	val = !!ucontrol->value.integer.value[0];
+
+	if (oval == val)
+		goto unlock;
+
+	private->phantom_switch[index] = val;
+
+	/* Send switch change to the device */
+	err = scarlett2_usb_set_config(mixer, SCARLETT2_CONFIG_PHANTOM_SWITCH,
+				       index, val);
+	if (err == 0)
+		err = 1;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static const struct snd_kcontrol_new scarlett2_phantom_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.name = "",
+	.info = snd_ctl_boolean_mono_info,
+	.get  = scarlett2_phantom_ctl_get,
+	.put  = scarlett2_phantom_ctl_put,
+};
+
+/*** Phantom Persistence Control ***/
+
+static int scarlett2_phantom_persistence_ctl_get(
+	struct snd_kcontrol *kctl, struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_info *elem = kctl->private_data;
+	struct scarlett2_data *private = elem->head.mixer->private_data;
+
+	ucontrol->value.integer.value[0] = private->phantom_persistence;
+	return 0;
+}
+
+static int scarlett2_phantom_persistence_ctl_put(
+	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 oval, val, err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	oval = private->phantom_persistence;
+	val = !!ucontrol->value.integer.value[0];
+
+	if (oval == val)
+		goto unlock;
+
+	private->phantom_persistence = val;
+
+	/* Send switch change to the device */
+	err = scarlett2_usb_set_config(
+		mixer, SCARLETT2_CONFIG_PHANTOM_PERSISTENCE, index, val);
+	if (err == 0)
+		err = 1;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static const struct snd_kcontrol_new scarlett2_phantom_persistence_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.name = "",
+	.info = snd_ctl_boolean_mono_info,
+	.get  = scarlett2_phantom_persistence_ctl_get,
+	.put  = scarlett2_phantom_persistence_ctl_put,
+};
+
+/*** Direct Monitor Control ***/
+
+static int scarlett2_update_monitor_other(struct usb_mixer_interface *mixer)
+{
+	struct scarlett2_data *private = mixer->private_data;
+	const struct scarlett2_device_info *info = private->info;
+	int err;
+
+	/* monitor_other_enable[0] enables speaker switching
+	 * monitor_other_enable[1] enables talkback
+	 */
+	u8 monitor_other_enable[2];
+
+	/* monitor_other_switch[0] activates the alternate speakers
+	 * monitor_other_switch[1] activates talkback
+	 */
+	u8 monitor_other_switch[2];
+
+	private->monitor_other_updated = 0;
+
+	if (info->direct_monitor)
+		return scarlett2_usb_get_config(
+			mixer, SCARLETT2_CONFIG_DIRECT_MONITOR,
+			1, &private->direct_monitor_switch);
+
+	/* if it doesn't do speaker switching then it also doesn't do
+	 * talkback
+	 */
+	if (!info->has_speaker_switching)
+		return 0;
+
+	err = scarlett2_usb_get_config(
+		mixer, SCARLETT2_CONFIG_MONITOR_OTHER_ENABLE,
+		2, monitor_other_enable);
+	if (err < 0)
+		return err;
+
+	err = scarlett2_usb_get_config(
+		mixer, SCARLETT2_CONFIG_MONITOR_OTHER_SWITCH,
+		2, monitor_other_switch);
+	if (err < 0)
+		return err;
+
+	if (!monitor_other_enable[0])
+		private->speaker_switching_switch = 0;
+	else
+		private->speaker_switching_switch = monitor_other_switch[0] + 1;
+
+	if (info->has_talkback) {
+		const int (*port_count)[SCARLETT2_PORT_DIRNS] =
+			info->port_count;
+		int num_mixes =
+			port_count[SCARLETT2_PORT_TYPE_MIX][SCARLETT2_PORT_IN];
+		u16 bitmap;
+		int i;
+
+		if (!monitor_other_enable[1])
+			private->talkback_switch = 0;
+		else
+			private->talkback_switch = monitor_other_switch[1] + 1;
+
+		err = scarlett2_usb_get_config(mixer,
+					       SCARLETT2_CONFIG_TALKBACK_MAP,
+					       1, &bitmap);
+		if (err < 0)
+			return err;
+		for (i = 0; i < num_mixes; i++, bitmap >>= 1)
+			private->talkback_map[i] = bitmap & 1;
+	}
+
+	return 0;
+}
+
+static int scarlett2_direct_monitor_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 = elem->head.mixer->private_data;
+	int err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	if (private->monitor_other_updated) {
+		err = scarlett2_update_monitor_other(mixer);
+		if (err < 0)
+			goto unlock;
+	}
+	ucontrol->value.enumerated.item[0] = private->direct_monitor_switch;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static int scarlett2_direct_monitor_ctl_put(
+	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 oval, val, err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	oval = private->direct_monitor_switch;
+	val = min(ucontrol->value.enumerated.item[0], 2U);
+
+	if (oval == val)
+		goto unlock;
+
+	private->direct_monitor_switch = val;
+
+	/* Send switch change to the device */
+	err = scarlett2_usb_set_config(
+		mixer, SCARLETT2_CONFIG_DIRECT_MONITOR, index, val);
+	if (err == 0)
+		err = 1;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static int scarlett2_direct_monitor_stereo_enum_ctl_info(
+	struct snd_kcontrol *kctl, struct snd_ctl_elem_info *uinfo)
+{
+	static const char *const values[3] = {
+		"Off", "Mono", "Stereo"
+	};
+
+	return snd_ctl_enum_info(uinfo, 1, 3, values);
+}
+
+/* Direct Monitor for Solo is mono-only and only needs a boolean control
+ * Direct Monitor for 2i2 is selectable between Off/Mono/Stereo
+ */
+static const struct snd_kcontrol_new scarlett2_direct_monitor_ctl[2] = {
+	{
+		.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+		.name = "",
+		.info = snd_ctl_boolean_mono_info,
+		.get  = scarlett2_direct_monitor_ctl_get,
+		.put  = scarlett2_direct_monitor_ctl_put,
+	},
+	{
+		.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+		.name = "",
+		.info = scarlett2_direct_monitor_stereo_enum_ctl_info,
+		.get  = scarlett2_direct_monitor_ctl_get,
+		.put  = scarlett2_direct_monitor_ctl_put,
+	}
+};
+
+static int scarlett2_add_direct_monitor_ctl(struct usb_mixer_interface *mixer)
+{
+	struct scarlett2_data *private = mixer->private_data;
+	const struct scarlett2_device_info *info = private->info;
+	const char *s;
+
+	if (!info->direct_monitor)
+		return 0;
+
+	s = info->direct_monitor == 1
+	      ? "Direct Monitor Playback Switch"
+	      : "Direct Monitor Playback Enum";
+
+	return scarlett2_add_new_ctl(
+		mixer, &scarlett2_direct_monitor_ctl[info->direct_monitor - 1],
+		0, 1, s, &private->direct_monitor_ctl);
+}
+
+/*** Speaker Switching Control ***/
+
+static int scarlett2_speaker_switch_enum_ctl_info(
+	struct snd_kcontrol *kctl, struct snd_ctl_elem_info *uinfo)
+{
+	static const char *const values[3] = {
+		"Off", "Main", "Alt"
+	};
+
+	return snd_ctl_enum_info(uinfo, 1, 3, values);
+}
+
+static int scarlett2_speaker_switch_enum_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 err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	if (private->monitor_other_updated) {
+		err = scarlett2_update_monitor_other(mixer);
+		if (err < 0)
+			goto unlock;
+	}
+	ucontrol->value.enumerated.item[0] = private->speaker_switching_switch;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+/* when speaker switching gets enabled, switch the main/alt speakers
+ * to HW volume and disable those controls
+ */
+static int scarlett2_speaker_switch_enable(struct usb_mixer_interface *mixer)
+{
+	struct snd_card *card = mixer->chip->card;
+	struct scarlett2_data *private = mixer->private_data;
+	int i, err;
+
+	for (i = 0; i < 4; i++) {
+		int index = line_out_remap(private, i);
+
+		/* switch the main/alt speakers to HW volume */
+		if (!private->vol_sw_hw_switch[index]) {
+			err = scarlett2_sw_hw_change(private->mixer, i, 1);
+			if (err < 0)
+				return err;
+		}
+
+		/* disable the line out SW/HW switch */
+		scarlett2_sw_hw_ctl_ro(private, i);
+		snd_ctl_notify(card,
+			       SNDRV_CTL_EVENT_MASK_VALUE |
+				 SNDRV_CTL_EVENT_MASK_INFO,
+			       &private->sw_hw_ctls[i]->id);
+	}
+
+	/* when the next monitor-other notify comes in, update the mux
+	 * configuration
+	 */
+	private->speaker_switching_switched = 1;
+
+	return 0;
+}
+
+/* when speaker switching gets disabled, reenable the hw/sw controls
+ * and invalidate the routing
+ */
+static void scarlett2_speaker_switch_disable(struct usb_mixer_interface *mixer)
+{
+	struct snd_card *card = mixer->chip->card;
+	struct scarlett2_data *private = mixer->private_data;
+	int i;
+
+	/* enable the line out SW/HW switch */
+	for (i = 0; i < 4; i++) {
+		scarlett2_sw_hw_ctl_rw(private, i);
+		snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_INFO,
+			       &private->sw_hw_ctls[i]->id);
+	}
+
+	/* when the next monitor-other notify comes in, update the mux
+	 * configuration
+	 */
+	private->speaker_switching_switched = 1;
+}
+
+static int scarlett2_speaker_switch_enum_ctl_put(
+	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 oval, val, err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	oval = private->speaker_switching_switch;
+	val = min(ucontrol->value.enumerated.item[0], 2U);
+
+	if (oval == val)
+		goto unlock;
+
+	private->speaker_switching_switch = val;
+
+	/* enable/disable speaker switching */
+	err = scarlett2_usb_set_config(
+		mixer, SCARLETT2_CONFIG_MONITOR_OTHER_ENABLE,
+		0, !!val);
+	if (err < 0)
+		goto unlock;
+
+	/* if speaker switching is enabled, select main or alt */
+	err = scarlett2_usb_set_config(
+		mixer, SCARLETT2_CONFIG_MONITOR_OTHER_SWITCH,
+		0, val == 2);
+	if (err < 0)
+		goto unlock;
+
+	/* update controls if speaker switching gets enabled or disabled */
+	if (!oval && val)
+		err = scarlett2_speaker_switch_enable(mixer);
+	else if (oval && !val)
+		scarlett2_speaker_switch_disable(mixer);
+
+	if (err == 0)
+		err = 1;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static const struct snd_kcontrol_new scarlett2_speaker_switch_enum_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.name = "",
+	.info = scarlett2_speaker_switch_enum_ctl_info,
+	.get  = scarlett2_speaker_switch_enum_ctl_get,
+	.put  = scarlett2_speaker_switch_enum_ctl_put,
+};
+
+static int scarlett2_add_speaker_switch_ctl(
+	struct usb_mixer_interface *mixer)
+{
+	struct scarlett2_data *private = mixer->private_data;
+	const struct scarlett2_device_info *info = private->info;
+
+	if (!info->has_speaker_switching)
+		return 0;
+
+	return scarlett2_add_new_ctl(
+		mixer, &scarlett2_speaker_switch_enum_ctl,
+		0, 1, "Speaker Switching Playback Enum",
+		&private->speaker_switching_ctl);
+}
+
+/*** Talkback and Talkback Map Controls ***/
+
+static int scarlett2_talkback_enum_ctl_info(
+	struct snd_kcontrol *kctl, struct snd_ctl_elem_info *uinfo)
+{
+	static const char *const values[3] = {
+		"Disabled", "Off", "On"
+	};
+
+	return snd_ctl_enum_info(uinfo, 1, 3, values);
+}
+
+static int scarlett2_talkback_enum_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 err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	if (private->monitor_other_updated) {
+		err = scarlett2_update_monitor_other(mixer);
+		if (err < 0)
+			goto unlock;
+	}
+	ucontrol->value.enumerated.item[0] = private->talkback_switch;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static int scarlett2_talkback_enum_ctl_put(
+	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 oval, val, err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	oval = private->talkback_switch;
+	val = min(ucontrol->value.enumerated.item[0], 2U);
+
+	if (oval == val)
+		goto unlock;
+
+	private->talkback_switch = val;
+
+	/* enable/disable talkback */
+	err = scarlett2_usb_set_config(
+		mixer, SCARLETT2_CONFIG_MONITOR_OTHER_ENABLE,
+		1, !!val);
+	if (err < 0)
+		goto unlock;
+
+	/* if talkback is enabled, select main or alt */
+	err = scarlett2_usb_set_config(
+		mixer, SCARLETT2_CONFIG_MONITOR_OTHER_SWITCH,
+		1, val == 2);
+	if (err == 0)
+		err = 1;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static const struct snd_kcontrol_new scarlett2_talkback_enum_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.name = "",
+	.info = scarlett2_talkback_enum_ctl_info,
+	.get  = scarlett2_talkback_enum_ctl_get,
+	.put  = scarlett2_talkback_enum_ctl_put,
+};
+
+static int scarlett2_talkback_map_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;
+
+	ucontrol->value.integer.value[0] = private->talkback_map[index];
+
+	return 0;
+}
+
+static int scarlett2_talkback_map_ctl_put(
+	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;
+	const int (*port_count)[SCARLETT2_PORT_DIRNS] =
+		private->info->port_count;
+	int num_mixes = port_count[SCARLETT2_PORT_TYPE_MIX][SCARLETT2_PORT_IN];
+
+	int index = elem->control;
+	int oval, val, err = 0, i;
+	u16 bitmap = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	oval = private->talkback_map[index];
+	val = !!ucontrol->value.integer.value[0];
+
+	if (oval == val)
+		goto unlock;
+
+	private->talkback_map[index] = val;
+
+	for (i = 0; i < num_mixes; i++)
+		bitmap |= private->talkback_map[i] << i;
+
+	/* Send updated bitmap to the device */
+	err = scarlett2_usb_set_config(mixer, SCARLETT2_CONFIG_TALKBACK_MAP,
+				       0, bitmap);
+	if (err == 0)
+		err = 1;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static const struct snd_kcontrol_new scarlett2_talkback_map_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.name = "",
+	.info = snd_ctl_boolean_mono_info,
+	.get  = scarlett2_talkback_map_ctl_get,
+	.put  = scarlett2_talkback_map_ctl_put,
+};
+
+static int scarlett2_add_talkback_ctls(
+	struct usb_mixer_interface *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 num_mixes = port_count[SCARLETT2_PORT_TYPE_MIX][SCARLETT2_PORT_IN];
+	int err, i;
+	char s[SNDRV_CTL_ELEM_ID_NAME_MAXLEN];
+
+	if (!info->has_talkback)
+		return 0;
+
+	err = scarlett2_add_new_ctl(
+		mixer, &scarlett2_talkback_enum_ctl,
+		0, 1, "Talkback Playback Enum",
+		&private->talkback_ctl);
+	if (err < 0)
+		return err;
+
+	for (i = 0; i < num_mixes; i++) {
+		snprintf(s, sizeof(s),
+			 "Talkback Mix %c Playback Switch", i + 'A');
+		err = scarlett2_add_new_ctl(mixer, &scarlett2_talkback_map_ctl,
+					    i, 1, s, NULL);
+		if (err < 0)
+			return err;
+	}
+
+	return 0;
+}
+
+/*** Dim/Mute Controls ***/
+
+static int scarlett2_dim_mute_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 err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	if (private->vol_updated) {
+		err = scarlett2_update_volumes(mixer);
+		if (err < 0)
+			goto unlock;
+	}
+	ucontrol->value.integer.value[0] = private->dim_mute[elem->control];
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static int scarlett2_dim_mute_ctl_put(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;
+	const struct scarlett2_device_info *info = private->info;
+	const int (*port_count)[SCARLETT2_PORT_DIRNS] = info->port_count;
+	int num_line_out =
+		port_count[SCARLETT2_PORT_TYPE_ANALOGUE][SCARLETT2_PORT_OUT];
+
+	int index = elem->control;
+	int oval, val, err = 0, i;
+
+	mutex_lock(&private->data_mutex);
+
+	oval = private->dim_mute[index];
+	val = !!ucontrol->value.integer.value[0];
+
+	if (oval == val)
+		goto unlock;
+
+	private->dim_mute[index] = val;
+
+	/* Send switch change to the device */
+	err = scarlett2_usb_set_config(mixer, SCARLETT2_CONFIG_DIM_MUTE,
+				       index, val);
+	if (err == 0)
+		err = 1;
+
+	if (index == SCARLETT2_BUTTON_MUTE)
+		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_VALUE,
+					       &private->mute_ctls[i]->id);
+			}
+		}
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static const struct snd_kcontrol_new scarlett2_dim_mute_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.name = "",
+	.info = snd_ctl_boolean_mono_info,
+	.get  = scarlett2_dim_mute_ctl_get,
+	.put  = scarlett2_dim_mute_ctl_put
+};
+
+/*** Create the analogue output controls ***/
+
+static int scarlett2_add_line_out_ctls(struct usb_mixer_interface *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 num_line_out =
+		port_count[SCARLETT2_PORT_TYPE_ANALOGUE][SCARLETT2_PORT_OUT];
+	int err, i;
+	char s[SNDRV_CTL_ELEM_ID_NAME_MAXLEN];
+
+	/* Add R/O HW volume control */
+	if (info->line_out_hw_vol) {
+		snprintf(s, sizeof(s), "Master HW Playback Volume");
+		err = scarlett2_add_new_ctl(mixer,
+					    &scarlett2_master_volume_ctl,
+					    0, 1, s, &private->master_vol_ctl);
+		if (err < 0)
+			return err;
+	}
+
+	/* 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])
+			snprintf(s, sizeof(s),
+				 "Line %02d (%s) Playback Volume",
+				 i + 1, info->line_out_descrs[i]);
+		else
+			snprintf(s, sizeof(s),
+				 "Line %02d Playback Volume",
+				 i + 1);
+		err = scarlett2_add_new_ctl(mixer,
+					    &scarlett2_line_out_volume_ctl,
+					    i, 1, s, &private->vol_ctls[i]);
+		if (err < 0)
+			return err;
+
+		/* Mute Switch */
+		snprintf(s, sizeof(s),
+			 "Line %02d Mute Playback Switch",
+			 i + 1);
+		err = scarlett2_add_new_ctl(mixer,
+					    &scarlett2_mute_ctl,
+					    i, 1, s,
+					    &private->mute_ctls[i]);
+		if (err < 0)
+			return err;
+
+		/* Make the fader and mute controls read-only if the
+		 * SW/HW switch is set to HW
+		 */
+		if (private->vol_sw_hw_switch[index])
+			scarlett2_vol_ctl_set_writable(mixer, i, 0);
+
+		/* SW/HW Switch */
+		if (info->line_out_hw_vol) {
+			snprintf(s, sizeof(s),
+				 "Line Out %02d Volume Control Playback Enum",
+				 i + 1);
+			err = scarlett2_add_new_ctl(mixer,
+						    &scarlett2_sw_hw_enum_ctl,
+						    i, 1, s,
+						    &private->sw_hw_ctls[i]);
+			if (err < 0)
+				return err;
+
+			/* Make the switch read-only if the line is
+			 * involved in speaker switching
+			 */
+			if (private->speaker_switching_switch && i < 4)
+				scarlett2_sw_hw_ctl_ro(private, i);
+		}
+	}
+
+	/* Add dim/mute controls */
+	if (info->line_out_hw_vol)
+		for (i = 0; i < SCARLETT2_DIM_MUTE_COUNT; i++) {
+			err = scarlett2_add_new_ctl(
+				mixer, &scarlett2_dim_mute_ctl,
+				i, 1, scarlett2_dim_mute_names[i],
+				&private->dim_mute_ctls[i]);
+			if (err < 0)
+				return err;
+		}
+
+	return 0;
+}
+
+/*** Create the analogue input controls ***/
+
+static int scarlett2_add_line_in_ctls(struct usb_mixer_interface *mixer)
+{
+	struct scarlett2_data *private = mixer->private_data;
+	const struct scarlett2_device_info *info = private->info;
+	int err, i;
+	char s[SNDRV_CTL_ELEM_ID_NAME_MAXLEN];
+	const char *fmt = "Line In %d %s Capture %s";
+	const char *fmt2 = "Line In %d-%d %s Capture %s";
+
+	/* Add input level (line/inst) controls */
+	for (i = 0; i < info->level_input_count; i++) {
+		snprintf(s, sizeof(s), fmt, i + 1 + info->level_input_first,
+			 "Level", "Enum");
+		err = scarlett2_add_new_ctl(mixer, &scarlett2_level_enum_ctl,
+					    i, 1, s, &private->level_ctls[i]);
+		if (err < 0)
+			return err;
+	}
+
+	/* Add input pad controls */
+	for (i = 0; i < info->pad_input_count; i++) {
+		snprintf(s, sizeof(s), fmt, i + 1, "Pad", "Switch");
+		err = scarlett2_add_new_ctl(mixer, &scarlett2_pad_ctl,
+					    i, 1, s, &private->pad_ctls[i]);
+		if (err < 0)
+			return err;
+	}
+
+	/* Add input air controls */
+	for (i = 0; i < info->air_input_count; i++) {
+		snprintf(s, sizeof(s), fmt, i + 1, "Air", "Switch");
+		err = scarlett2_add_new_ctl(mixer, &scarlett2_air_ctl,
+					    i, 1, s, &private->air_ctls[i]);
+		if (err < 0)
+			return err;
+	}
+
+	/* Add input phantom controls */
+	if (info->inputs_per_phantom == 1) {
+		for (i = 0; i < info->phantom_count; i++) {
+			scnprintf(s, sizeof(s), fmt, i + 1,
+				  "Phantom Power", "Switch");
+			err = scarlett2_add_new_ctl(
+				mixer, &scarlett2_phantom_ctl,
+				i, 1, s, &private->phantom_ctls[i]);
+			if (err < 0)
+				return err;
+		}
+	} else if (info->inputs_per_phantom > 1) {
+		for (i = 0; i < info->phantom_count; i++) {
+			int from = i * info->inputs_per_phantom + 1;
+			int to = (i + 1) * info->inputs_per_phantom;
+
+			scnprintf(s, sizeof(s), fmt2, from, to,
+				  "Phantom Power", "Switch");
+			err = scarlett2_add_new_ctl(
+				mixer, &scarlett2_phantom_ctl,
+				i, 1, s, &private->phantom_ctls[i]);
+			if (err < 0)
+				return err;
+		}
+	}
+	if (info->phantom_count) {
+		err = scarlett2_add_new_ctl(
+			mixer, &scarlett2_phantom_persistence_ctl, 0, 1,
+			"Phantom Power Persistence Capture Switch", NULL);
+		if (err < 0)
+			return err;
+	}
+
+	return 0;
+}
+
+/*** Mixer Volume Controls ***/
+
+static int scarlett2_mixer_ctl_info(struct snd_kcontrol *kctl,
+				    struct snd_ctl_elem_info *uinfo)
+{
+	struct usb_mixer_elem_info *elem = kctl->private_data;
+
+	uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
+	uinfo->count = elem->channels;
+	uinfo->value.integer.min = 0;
+	uinfo->value.integer.max = SCARLETT2_MIXER_MAX_VALUE;
+	uinfo->value.integer.step = 1;
+	return 0;
+}
+
+static int scarlett2_mixer_ctl_get(struct snd_kcontrol *kctl,
+				   struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_info *elem = kctl->private_data;
+	struct scarlett2_data *private = elem->head.mixer->private_data;
+
+	ucontrol->value.integer.value[0] = private->mix[elem->control];
+	return 0;
+}
+
+static int scarlett2_mixer_ctl_put(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;
+	const struct scarlett2_device_info *info = private->info;
+	const int (*port_count)[SCARLETT2_PORT_DIRNS] = info->port_count;
+	int oval, val, num_mixer_in, mix_num, err = 0;
+	int index = elem->control;
+
+	mutex_lock(&private->data_mutex);
+
+	oval = private->mix[index];
+	val = clamp(ucontrol->value.integer.value[0],
+		    0L, (long)SCARLETT2_MIXER_MAX_VALUE);
+	num_mixer_in = port_count[SCARLETT2_PORT_TYPE_MIX][SCARLETT2_PORT_OUT];
+	mix_num = index / num_mixer_in;
+
+	if (oval == val)
+		goto unlock;
+
+	private->mix[index] = val;
+	err = scarlett2_usb_set_mix(mixer, mix_num);
+	if (err == 0)
+		err = 1;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static const DECLARE_TLV_DB_MINMAX(
+	db_scale_scarlett2_mixer,
+	SCARLETT2_MIXER_MIN_DB * 100,
+	SCARLETT2_MIXER_MAX_DB * 100
+);
+
+static const struct snd_kcontrol_new scarlett2_mixer_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.access = SNDRV_CTL_ELEM_ACCESS_READWRITE |
+		  SNDRV_CTL_ELEM_ACCESS_TLV_READ,
+	.name = "",
+	.info = scarlett2_mixer_ctl_info,
+	.get  = scarlett2_mixer_ctl_get,
+	.put  = scarlett2_mixer_ctl_put,
+	.private_value = SCARLETT2_MIXER_MAX_DB, /* max value */
+	.tlv = { .p = db_scale_scarlett2_mixer }
+};
+
+static int scarlett2_add_mixer_ctls(struct usb_mixer_interface *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 err, i, j;
+	int index;
+	char s[SNDRV_CTL_ELEM_ID_NAME_MAXLEN];
+
+	int num_inputs =
+		port_count[SCARLETT2_PORT_TYPE_MIX][SCARLETT2_PORT_OUT];
+	int num_outputs =
+		port_count[SCARLETT2_PORT_TYPE_MIX][SCARLETT2_PORT_IN];
+
+	for (i = 0, index = 0; i < num_outputs; i++)
+		for (j = 0; j < num_inputs; j++, index++) {
+			snprintf(s, sizeof(s),
+				 "Mix %c Input %02d Playback Volume",
+				 'A' + i, j + 1);
+			err = scarlett2_add_new_ctl(mixer, &scarlett2_mixer_ctl,
+						    index, 1, s, NULL);
+			if (err < 0)
+				return err;
+		}
+
+	return 0;
+}
+
+/*** Mux Source Selection Controls ***/
+
+static int scarlett2_mux_src_enum_ctl_info(struct snd_kcontrol *kctl,
+					   struct snd_ctl_elem_info *uinfo)
+{
+	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;
+	unsigned int item = uinfo->value.enumerated.item;
+	int items = private->num_mux_srcs;
+	int port_type;
+
+	uinfo->type = SNDRV_CTL_ELEM_TYPE_ENUMERATED;
+	uinfo->count = elem->channels;
+	uinfo->value.enumerated.items = items;
+
+	if (item >= items)
+		item = uinfo->value.enumerated.item = items - 1;
+
+	for (port_type = 0;
+	     port_type < SCARLETT2_PORT_TYPE_COUNT;
+	     port_type++) {
+		if (item < port_count[port_type][SCARLETT2_PORT_IN]) {
+			const struct scarlett2_port *port =
+				&scarlett2_ports[port_type];
+
+			sprintf(uinfo->value.enumerated.name,
+				port->src_descr, item + port->src_num_offset);
+			return 0;
+		}
+		item -= port_count[port_type][SCARLETT2_PORT_IN];
+	}
+
+	return -EINVAL;
+}
+
+static int scarlett2_mux_src_enum_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 = line_out_remap(private, elem->control);
+	int err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	if (private->mux_updated) {
+		err = scarlett2_usb_get_mux(mixer);
+		if (err < 0)
+			goto unlock;
+	}
+	ucontrol->value.enumerated.item[0] = private->mux[index];
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static int scarlett2_mux_src_enum_ctl_put(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 = line_out_remap(private, elem->control);
+	int oval, val, err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	oval = private->mux[index];
+	val = min(ucontrol->value.enumerated.item[0],
+		  private->num_mux_srcs - 1U);
+
+	if (oval == val)
+		goto unlock;
+
+	private->mux[index] = val;
+	err = scarlett2_usb_set_mux(mixer);
+	if (err == 0)
+		err = 1;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static const struct snd_kcontrol_new scarlett2_mux_src_enum_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.name = "",
+	.info = scarlett2_mux_src_enum_ctl_info,
+	.get  = scarlett2_mux_src_enum_ctl_get,
+	.put  = scarlett2_mux_src_enum_ctl_put,
+};
+
+static int scarlett2_add_mux_enums(struct usb_mixer_interface *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 port_type, channel, i;
+
+	for (i = 0, port_type = 0;
+	     port_type < SCARLETT2_PORT_TYPE_COUNT;
+	     port_type++) {
+		for (channel = 0;
+		     channel < port_count[port_type][SCARLETT2_PORT_OUT];
+		     channel++, i++) {
+			int err;
+			char s[SNDRV_CTL_ELEM_ID_NAME_MAXLEN];
+			const char *const descr =
+				scarlett2_ports[port_type].dst_descr;
+
+			snprintf(s, sizeof(s) - 5, descr, channel + 1);
+			strcat(s, " Enum");
+
+			err = scarlett2_add_new_ctl(mixer,
+						    &scarlett2_mux_src_enum_ctl,
+						    i, 1, s,
+						    &private->mux_ctls[i]);
+			if (err < 0)
+				return err;
+		}
+	}
+
+	return 0;
+}
+
+/*** Meter Controls ***/
+
+static int scarlett2_meter_ctl_info(struct snd_kcontrol *kctl,
+				    struct snd_ctl_elem_info *uinfo)
+{
+	struct usb_mixer_elem_info *elem = kctl->private_data;
+
+	uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
+	uinfo->count = elem->channels;
+	uinfo->value.integer.min = 0;
+	uinfo->value.integer.max = 4095;
+	uinfo->value.integer.step = 1;
+	return 0;
+}
+
+static int scarlett2_meter_ctl_get(struct snd_kcontrol *kctl,
+				   struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_info *elem = kctl->private_data;
+	struct scarlett2_data *private = elem->head.mixer->private_data;
+	u8 *meter_level_map = private->meter_level_map;
+	u16 meter_levels[SCARLETT2_MAX_METERS];
+	int i, err;
+
+	mutex_lock(&private->data_mutex);
+
+	err = scarlett2_usb_get_meter_levels(elem->head.mixer, elem->channels,
+					     meter_levels);
+	if (err < 0)
+		goto unlock;
+
+	/* copy & translate from meter_levels[] using meter_level_map[] */
+	for (i = 0; i < elem->channels; i++) {
+		int idx = meter_level_map[i];
+		int value;
+
+		if (idx == 255)
+			value = 0;
+		else
+			value = meter_levels[idx];
+
+		ucontrol->value.integer.value[i] = value;
+	}
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+
+	return err;
+}
+
+static const struct snd_kcontrol_new scarlett2_meter_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_PCM,
+	.access = SNDRV_CTL_ELEM_ACCESS_READ | SNDRV_CTL_ELEM_ACCESS_VOLATILE,
+	.name = "",
+	.info = scarlett2_meter_ctl_info,
+	.get  = scarlett2_meter_ctl_get
+};
+
+static int scarlett2_add_meter_ctl(struct usb_mixer_interface *mixer)
+{
+	struct scarlett2_data *private = mixer->private_data;
+
+	/* devices without a mixer also don't support reporting levels */
+	if (private->info->config_set == SCARLETT2_CONFIG_SET_GEN_3A)
+		return 0;
+
+	return scarlett2_add_new_ctl(mixer, &scarlett2_meter_ctl,
+				     0, private->num_mux_dsts,
+				     "Level Meter", NULL);
+}
+
+/*** MSD Controls ***/
+
+static int scarlett2_msd_ctl_get(struct snd_kcontrol *kctl,
+				 struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_info *elem = kctl->private_data;
+	struct scarlett2_data *private = elem->head.mixer->private_data;
+
+	ucontrol->value.integer.value[0] = private->msd_switch;
+	return 0;
+}
+
+static int scarlett2_msd_ctl_put(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 oval, val, err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	oval = private->msd_switch;
+	val = !!ucontrol->value.integer.value[0];
+
+	if (oval == val)
+		goto unlock;
+
+	private->msd_switch = val;
+
+	/* Send switch change to the device */
+	err = scarlett2_usb_set_config(mixer, SCARLETT2_CONFIG_MSD_SWITCH,
+				       0, val);
+	if (err == 0)
+		err = 1;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static const struct snd_kcontrol_new scarlett2_msd_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.name = "",
+	.info = snd_ctl_boolean_mono_info,
+	.get  = scarlett2_msd_ctl_get,
+	.put  = scarlett2_msd_ctl_put,
+};
+
+static int scarlett2_add_msd_ctl(struct usb_mixer_interface *mixer)
+{
+	struct scarlett2_data *private = mixer->private_data;
+	const struct scarlett2_device_info *info = private->info;
+
+	if (!info->has_msd_mode)
+		return 0;
+
+	/* If MSD mode is off, hide the switch by default */
+	if (!private->msd_switch && !(mixer->chip->setup & SCARLETT2_MSD_ENABLE))
+		return 0;
+
+	/* Add MSD control */
+	return scarlett2_add_new_ctl(mixer, &scarlett2_msd_ctl,
+				     0, 1, "MSD Mode Switch", NULL);
+}
+
+/*** Standalone Control ***/
+
+static int scarlett2_standalone_ctl_get(struct snd_kcontrol *kctl,
+					struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_info *elem = kctl->private_data;
+	struct scarlett2_data *private = elem->head.mixer->private_data;
+
+	ucontrol->value.integer.value[0] = private->standalone_switch;
+	return 0;
+}
+
+static int scarlett2_standalone_ctl_put(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 oval, val, err = 0;
+
+	mutex_lock(&private->data_mutex);
+
+	oval = private->standalone_switch;
+	val = !!ucontrol->value.integer.value[0];
+
+	if (oval == val)
+		goto unlock;
+
+	private->standalone_switch = val;
+
+	/* Send switch change to the device */
+	err = scarlett2_usb_set_config(mixer,
+				       SCARLETT2_CONFIG_STANDALONE_SWITCH,
+				       0, val);
+	if (err == 0)
+		err = 1;
+
+unlock:
+	mutex_unlock(&private->data_mutex);
+	return err;
+}
+
+static const struct snd_kcontrol_new scarlett2_standalone_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.name = "",
+	.info = snd_ctl_boolean_mono_info,
+	.get  = scarlett2_standalone_ctl_get,
+	.put  = scarlett2_standalone_ctl_put,
+};
+
+static int scarlett2_add_standalone_ctl(struct usb_mixer_interface *mixer)
+{
+	struct scarlett2_data *private = mixer->private_data;
+
+	if (private->info->config_set == SCARLETT2_CONFIG_SET_GEN_3A)
+		return 0;
+
+	/* Add standalone control */
+	return scarlett2_add_new_ctl(mixer, &scarlett2_standalone_ctl,
+				     0, 1, "Standalone Switch", NULL);
+}
+
+/*** Cleanup/Suspend Callbacks ***/
+
+static void scarlett2_private_free(struct usb_mixer_interface *mixer)
+{
+	struct scarlett2_data *private = mixer->private_data;
+
+	cancel_delayed_work_sync(&private->work);
+	kfree(private);
+	mixer->private_data = NULL;
+}
+
+static void scarlett2_private_suspend(struct usb_mixer_interface *mixer)
+{
+	struct scarlett2_data *private = mixer->private_data;
+
+	if (cancel_delayed_work_sync(&private->work))
+		scarlett2_config_save(private->mixer);
+}
+
+/*** Initialisation ***/
+
+static void scarlett2_count_mux_io(struct scarlett2_data *private)
+{
+	const struct scarlett2_device_info *info = private->info;
+	const int (*port_count)[SCARLETT2_PORT_DIRNS] = info->port_count;
+	int port_type, srcs = 0, dsts = 0;
+
+	for (port_type = 0;
+	     port_type < SCARLETT2_PORT_TYPE_COUNT;
+	     port_type++) {
+		srcs += port_count[port_type][SCARLETT2_PORT_IN];
+		dsts += port_count[port_type][SCARLETT2_PORT_OUT];
+	}
+
+	private->num_mux_srcs = srcs;
+	private->num_mux_dsts = dsts;
+}
+
+/* Look through the interface descriptors for the Focusrite Control
+ * interface (bInterfaceClass = 255 Vendor Specific Class) and set
+ * bInterfaceNumber, bEndpointAddress, wMaxPacketSize, and bInterval
+ * in private
+ */
+static int scarlett2_find_fc_interface(struct usb_device *dev,
+				       struct scarlett2_data *private)
+{
+	struct usb_host_config *config = dev->actconfig;
+	int i;
+
+	for (i = 0; i < config->desc.bNumInterfaces; i++) {
+		struct usb_interface *intf = config->interface[i];
+		struct usb_interface_descriptor *desc =
+			&intf->altsetting[0].desc;
+		struct usb_endpoint_descriptor *epd;
+
+		if (desc->bInterfaceClass != 255)
+			continue;
+
+		epd = get_endpoint(intf->altsetting, 0);
+		private->bInterfaceNumber = desc->bInterfaceNumber;
+		private->bEndpointAddress = epd->bEndpointAddress &
+			USB_ENDPOINT_NUMBER_MASK;
+		private->wMaxPacketSize = le16_to_cpu(epd->wMaxPacketSize);
+		private->bInterval = epd->bInterval;
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
+/* Initialise private data */
+static int scarlett2_init_private(struct usb_mixer_interface *mixer,
+				  const struct scarlett2_device_entry *entry)
+{
+	struct scarlett2_data *private =
+		kzalloc(sizeof(struct scarlett2_data), GFP_KERNEL);
+
+	if (!private)
+		return -ENOMEM;
+
+	mutex_init(&private->usb_mutex);
+	mutex_init(&private->data_mutex);
+	INIT_DELAYED_WORK(&private->work, scarlett2_config_save_work);
+
+	mixer->private_data = private;
+	mixer->private_free = scarlett2_private_free;
+	mixer->private_suspend = scarlett2_private_suspend;
+
+	private->info = entry->info;
+	private->series_name = entry->series_name;
+	scarlett2_count_mux_io(private);
+	private->scarlett2_seq = 0;
+	private->mixer = mixer;
+
+	return scarlett2_find_fc_interface(mixer->chip->dev, private);
+}
+
+/* Cargo cult proprietary initialisation sequence */
+static int scarlett2_usb_init(struct usb_mixer_interface *mixer)
+{
+	struct usb_device *dev = mixer->chip->dev;
+	struct scarlett2_data *private = mixer->private_data;
+	u8 step0_buf[24];
+	u8 step2_buf[84];
+	int err;
+
+	if (usb_pipe_type_check(dev, usb_sndctrlpipe(dev, 0)))
+		return -EINVAL;
+
+	/* step 0 */
+	err = scarlett2_usb_rx(dev, private->bInterfaceNumber,
+			       SCARLETT2_USB_CMD_INIT,
+			       step0_buf, sizeof(step0_buf));
+	if (err < 0)
+		return err;
+
+	/* step 1 */
+	private->scarlett2_seq = 1;
+	err = scarlett2_usb(mixer, SCARLETT2_USB_INIT_1, NULL, 0, NULL, 0);
+	if (err < 0)
+		return err;
+
+	/* step 2 */
+	private->scarlett2_seq = 1;
+	err = scarlett2_usb(mixer, SCARLETT2_USB_INIT_2,
+			    NULL, 0,
+			    step2_buf, sizeof(step2_buf));
+	if (err < 0)
+		return err;
+
+	/* extract 4-byte firmware version from step2_buf[8] */
+	private->firmware_version = le32_to_cpu(*(__le32 *)(step2_buf + 8));
+	usb_audio_info(mixer->chip,
+		       "Firmware version %d\n",
+		       private->firmware_version);
+
+	return 0;
+}
+
+/* Read configuration from the interface on start */
+static int scarlett2_read_configs(struct usb_mixer_interface *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 num_line_out =
+		port_count[SCARLETT2_PORT_TYPE_ANALOGUE][SCARLETT2_PORT_OUT];
+	int num_mixer_out =
+		port_count[SCARLETT2_PORT_TYPE_MIX][SCARLETT2_PORT_IN];
+	struct scarlett2_usb_volume_status volume_status;
+	int err, i;
+
+	if (info->has_msd_mode) {
+		err = scarlett2_usb_get_config(
+			mixer, SCARLETT2_CONFIG_MSD_SWITCH,
+			1, &private->msd_switch);
+		if (err < 0)
+			return err;
+
+		/* no other controls are created if MSD mode is on */
+		if (private->msd_switch)
+			return 0;
+	}
+
+	err = scarlett2_update_input_other(mixer);
+	if (err < 0)
+		return err;
+
+	err = scarlett2_update_monitor_other(mixer);
+	if (err < 0)
+		return err;
+
+	/* the rest of the configuration is for devices with a mixer */
+	if (info->config_set == SCARLETT2_CONFIG_SET_GEN_3A)
+		return 0;
+
+	err = scarlett2_usb_get_config(
+		mixer, SCARLETT2_CONFIG_STANDALONE_SWITCH,
+		1, &private->standalone_switch);
+	if (err < 0)
+		return err;
+
+	err = scarlett2_update_sync(mixer);
+	if (err < 0)
+		return err;
+
+	err = scarlett2_usb_get_volume_status(mixer, &volume_status);
+	if (err < 0)
+		return err;
+
+	if (info->line_out_hw_vol)
+		for (i = 0; i < SCARLETT2_DIM_MUTE_COUNT; i++)
+			private->dim_mute[i] = !!volume_status.dim_mute[i];
+
+	private->master_vol = clamp(
+		volume_status.master_vol + SCARLETT2_VOLUME_BIAS,
+		0, SCARLETT2_VOLUME_BIAS);
+
+	for (i = 0; i < num_line_out; i++) {
+		int volume, mute;
+
+		private->vol_sw_hw_switch[i] =
+			info->line_out_hw_vol
+				&& volume_status.sw_hw_switch[i];
+
+		volume = private->vol_sw_hw_switch[i]
+			   ? volume_status.master_vol
+			   : volume_status.sw_vol[i];
+		volume = clamp(volume + SCARLETT2_VOLUME_BIAS,
+			       0, SCARLETT2_VOLUME_BIAS);
+		private->vol[i] = volume;
+
+		mute = private->vol_sw_hw_switch[i]
+			 ? private->dim_mute[SCARLETT2_BUTTON_MUTE]
+			 : volume_status.mute_switch[i];
+		private->mute_switch[i] = mute;
+	}
+
+	for (i = 0; i < num_mixer_out; i++) {
+		err = scarlett2_usb_get_mix(mixer, i);
+		if (err < 0)
+			return err;
+	}
+
+	return scarlett2_usb_get_mux(mixer);
+}
+
+/* Notify on sync change */
+static void scarlett2_notify_sync(
+	struct usb_mixer_interface *mixer)
+{
+	struct scarlett2_data *private = mixer->private_data;
+
+	private->sync_updated = 1;
+
+	snd_ctl_notify(mixer->chip->card, SNDRV_CTL_EVENT_MASK_VALUE,
+		       &private->sync_ctl->id);
+}
+
+/* Notify on monitor change */
+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;
+	int num_line_out =
+		port_count[SCARLETT2_PORT_TYPE_ANALOGUE][SCARLETT2_PORT_OUT];
+	int i;
+
+	/* if line_out_hw_vol is 0, there are no controls to update */
+	if (!info->line_out_hw_vol)
+		return;
+
+	private->vol_updated = 1;
+
+	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[line_out_remap(private, i)])
+			snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE,
+				       &private->vol_ctls[i]->id);
+}
+
+/* Notify on dim/mute change */
+static void scarlett2_notify_dim_mute(
+	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;
+	int num_line_out =
+		port_count[SCARLETT2_PORT_TYPE_ANALOGUE][SCARLETT2_PORT_OUT];
+	int i;
+
+	private->vol_updated = 1;
+
+	if (!info->line_out_hw_vol)
+		return;
+
+	for (i = 0; i < SCARLETT2_DIM_MUTE_COUNT; i++)
+		snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE,
+			       &private->dim_mute_ctls[i]->id);
+
+	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->mute_ctls[i]->id);
+}
+
+/* Notify on "input other" change (level/pad/air) */
+static void scarlett2_notify_input_other(
+	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;
+	int i;
+
+	private->input_other_updated = 1;
+
+	for (i = 0; i < info->level_input_count; i++)
+		snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE,
+			       &private->level_ctls[i]->id);
+	for (i = 0; i < info->pad_input_count; i++)
+		snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE,
+			       &private->pad_ctls[i]->id);
+	for (i = 0; i < info->air_input_count; i++)
+		snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE,
+			       &private->air_ctls[i]->id);
+	for (i = 0; i < info->phantom_count; i++)
+		snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE,
+			       &private->phantom_ctls[i]->id);
+}
+
+/* Notify on "monitor other" change (direct monitor, speaker
+ * switching, talkback)
+ */
+static void scarlett2_notify_monitor_other(
+	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;
+
+	private->monitor_other_updated = 1;
+
+	if (info->direct_monitor) {
+		snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE,
+			       &private->direct_monitor_ctl->id);
+		return;
+	}
+
+	if (info->has_speaker_switching)
+		snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE,
+			       &private->speaker_switching_ctl->id);
+
+	if (info->has_talkback)
+		snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE,
+			       &private->talkback_ctl->id);
+
+	/* if speaker switching was recently enabled or disabled,
+	 * invalidate the dim/mute and mux enum controls
+	 */
+	if (private->speaker_switching_switched) {
+		int i;
+
+		scarlett2_notify_dim_mute(mixer);
+
+		private->speaker_switching_switched = 0;
+		private->mux_updated = 1;
+
+		for (i = 0; i < private->num_mux_dsts; i++)
+			snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE,
+				       &private->mux_ctls[i]->id);
+	}
+}
+
+/* Interrupt callback */
+static void scarlett2_notify(struct urb *urb)
+{
+	struct usb_mixer_interface *mixer = urb->context;
+	int len = urb->actual_length;
+	int ustatus = urb->status;
+	u32 data;
+
+	if (ustatus != 0 || len != 8)
+		goto requeue;
+
+	data = le32_to_cpu(*(__le32 *)urb->transfer_buffer);
+	if (data & SCARLETT2_USB_NOTIFY_SYNC)
+		scarlett2_notify_sync(mixer);
+	if (data & SCARLETT2_USB_NOTIFY_MONITOR)
+		scarlett2_notify_monitor(mixer);
+	if (data & SCARLETT2_USB_NOTIFY_DIM_MUTE)
+		scarlett2_notify_dim_mute(mixer);
+	if (data & SCARLETT2_USB_NOTIFY_INPUT_OTHER)
+		scarlett2_notify_input_other(mixer);
+	if (data & SCARLETT2_USB_NOTIFY_MONITOR_OTHER)
+		scarlett2_notify_monitor_other(mixer);
+
+requeue:
+	if (ustatus != -ENOENT &&
+	    ustatus != -ECONNRESET &&
+	    ustatus != -ESHUTDOWN) {
+		urb->dev = mixer->chip->dev;
+		usb_submit_urb(urb, GFP_ATOMIC);
+	}
+}
+
+static int scarlett2_init_notify(struct usb_mixer_interface *mixer)
+{
+	struct usb_device *dev = mixer->chip->dev;
+	struct scarlett2_data *private = mixer->private_data;
+	unsigned int pipe = usb_rcvintpipe(dev, private->bEndpointAddress);
+	void *transfer_buffer;
+
+	if (mixer->urb) {
+		usb_audio_err(mixer->chip,
+			      "%s: mixer urb already in use!\n", __func__);
+		return 0;
+	}
+
+	if (usb_pipe_type_check(dev, pipe))
+		return -EINVAL;
+
+	mixer->urb = usb_alloc_urb(0, GFP_KERNEL);
+	if (!mixer->urb)
+		return -ENOMEM;
+
+	transfer_buffer = kmalloc(private->wMaxPacketSize, GFP_KERNEL);
+	if (!transfer_buffer)
+		return -ENOMEM;
+
+	usb_fill_int_urb(mixer->urb, dev, pipe,
+			 transfer_buffer, private->wMaxPacketSize,
+			 scarlett2_notify, mixer, private->bInterval);
+
+	return usb_submit_urb(mixer->urb, GFP_KERNEL);
+}
+
+static const struct scarlett2_device_entry *get_scarlett2_device_entry(
+	struct usb_mixer_interface *mixer)
+{
+	const struct scarlett2_device_entry *entry = scarlett2_devices;
+
+	/* Find entry in scarlett2_devices */
+	while (entry->usb_id && entry->usb_id != mixer->chip->usb_id)
+		entry++;
+	if (!entry->usb_id)
+		return NULL;
+
+	return entry;
+}
+
+static int snd_scarlett2_controls_create(
+	struct usb_mixer_interface *mixer,
+	const struct scarlett2_device_entry *entry)
+{
+	int err;
+
+	/* Initialise private data */
+	err = scarlett2_init_private(mixer, entry);
+	if (err < 0)
+		return err;
+
+	/* Send proprietary USB initialisation sequence */
+	err = scarlett2_usb_init(mixer);
+	if (err < 0)
+		return err;
+
+	/* Add firmware version control */
+	err = scarlett2_add_firmware_version_ctl(mixer);
+	if (err < 0)
+		return err;
+
+	/* Read volume levels and controls from the interface */
+	err = scarlett2_read_configs(mixer);
+	if (err < 0)
+		return err;
+
+	/* Create the MSD control */
+	err = scarlett2_add_msd_ctl(mixer);
+	if (err < 0)
+		return err;
+
+	/* If MSD mode is enabled, don't create any other controls */
+	if (((struct scarlett2_data *)mixer->private_data)->msd_switch)
+		return 0;
+
+	/* Create the analogue output controls */
+	err = scarlett2_add_line_out_ctls(mixer);
+	if (err < 0)
+		return err;
+
+	/* Create the analogue input controls */
+	err = scarlett2_add_line_in_ctls(mixer);
+	if (err < 0)
+		return err;
+
+	/* Create the input, output, and mixer mux input selections */
+	err = scarlett2_add_mux_enums(mixer);
+	if (err < 0)
+		return err;
+
+	/* Create the matrix mixer controls */
+	err = scarlett2_add_mixer_ctls(mixer);
+	if (err < 0)
+		return err;
+
+	/* Create the level meter controls */
+	err = scarlett2_add_meter_ctl(mixer);
+	if (err < 0)
+		return err;
+
+	/* Create the sync control */
+	err = scarlett2_add_sync_ctl(mixer);
+	if (err < 0)
+		return err;
+
+	/* Create the direct monitor control */
+	err = scarlett2_add_direct_monitor_ctl(mixer);
+	if (err < 0)
+		return err;
+
+	/* Create the speaker switching control */
+	err = scarlett2_add_speaker_switch_ctl(mixer);
+	if (err < 0)
+		return err;
+
+	/* Create the talkback controls */
+	err = scarlett2_add_talkback_ctls(mixer);
+	if (err < 0)
+		return err;
+
+	/* Create the standalone control */
+	err = scarlett2_add_standalone_ctl(mixer);
+	if (err < 0)
+		return err;
+
+	/* Set up the interrupt polling */
+	err = scarlett2_init_notify(mixer);
+	if (err < 0)
+		return err;
+
+	return 0;
+}
+
+int snd_scarlett2_init(struct usb_mixer_interface *mixer)
+{
+	struct snd_usb_audio *chip = mixer->chip;
+	const struct scarlett2_device_entry *entry;
+	int err;
+
+	/* only use UAC_VERSION_2 */
+	if (!mixer->protocol)
+		return 0;
+
+	/* find entry in scarlett2_devices */
+	entry = get_scarlett2_device_entry(mixer);
+	if (!entry) {
+		usb_audio_err(mixer->chip,
+			      "%s: missing device entry for %04x:%04x\n",
+			      __func__,
+			      USB_ID_VENDOR(chip->usb_id),
+			      USB_ID_PRODUCT(chip->usb_id));
+		return 0;
+	}
+
+	if (chip->setup & SCARLETT2_DISABLE) {
+		usb_audio_info(chip,
+			"Focusrite %s Mixer Driver disabled "
+			"by modprobe options (snd_usb_audio "
+			"vid=0x%04x pid=0x%04x device_setup=%d)\n",
+			entry->series_name,
+			USB_ID_VENDOR(chip->usb_id),
+			USB_ID_PRODUCT(chip->usb_id),
+			SCARLETT2_DISABLE);
+		return 0;
+	}
+
+	usb_audio_info(chip,
+		"Focusrite %s Mixer Driver enabled (pid=0x%04x); "
+		"report any issues to g@b4.vu",
+		entry->series_name,
+		USB_ID_PRODUCT(chip->usb_id));
+
+	err = snd_scarlett2_controls_create(mixer, entry);
+	if (err < 0)
+		usb_audio_err(mixer->chip,
+			      "Error initialising %s Mixer Driver: %d",
+			      entry->series_name,
+			      err);
+
+	return err;
+}