Adding upstream version 4.19.249.upstream/4.19.249

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

1 files changed, 3677 insertions, 0 deletions

diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
new file mode 100644
index 000000000..6c8cdce81
--- /dev/null
+++ b/sound/usb/mixer.c
@@ -0,0 +1,3677 @@
+/*
+ *   (Tentative) USB Audio Driver for ALSA
+ *
+ *   Mixer control part
+ *
+ *   Copyright (c) 2002 by Takashi Iwai <tiwai@suse.de>
+ *
+ *   Many codes borrowed from audio.c by
+ *	    Alan Cox (alan@lxorguk.ukuu.org.uk)
+ *	    Thomas Sailer (sailer@ife.ee.ethz.ch)
+ *
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program; if not, write to the Free Software
+ *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
+ *
+ */
+
+/*
+ * TODOs, for both the mixer and the streaming interfaces:
+ *
+ *  - support for UAC2 effect units
+ *  - support for graphical equalizers
+ *  - RANGE and MEM set commands (UAC2)
+ *  - RANGE and MEM interrupt dispatchers (UAC2)
+ *  - audio channel clustering (UAC2)
+ *  - audio sample rate converter units (UAC2)
+ *  - proper handling of clock multipliers (UAC2)
+ *  - dispatch clock change notifications (UAC2)
+ *  	- stop PCM streams which use a clock that became invalid
+ *  	- stop PCM streams which use a clock selector that has changed
+ *  	- parse available sample rates again when clock sources changed
+ */
+
+#include <linux/bitops.h>
+#include <linux/init.h>
+#include <linux/list.h>
+#include <linux/log2.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/usb.h>
+#include <linux/usb/audio.h>
+#include <linux/usb/audio-v2.h>
+#include <linux/usb/audio-v3.h>
+
+#include <sound/core.h>
+#include <sound/control.h>
+#include <sound/hwdep.h>
+#include <sound/info.h>
+#include <sound/tlv.h>
+
+#include "usbaudio.h"
+#include "mixer.h"
+#include "helper.h"
+#include "mixer_quirks.h"
+#include "power.h"
+
+#define MAX_ID_ELEMS	256
+
+struct usb_audio_term {
+	int id;
+	int type;
+	int channels;
+	unsigned int chconfig;
+	int name;
+};
+
+struct usbmix_name_map;
+
+struct mixer_build {
+	struct snd_usb_audio *chip;
+	struct usb_mixer_interface *mixer;
+	unsigned char *buffer;
+	unsigned int buflen;
+	DECLARE_BITMAP(unitbitmap, MAX_ID_ELEMS);
+	DECLARE_BITMAP(termbitmap, MAX_ID_ELEMS);
+	struct usb_audio_term oterm;
+	const struct usbmix_name_map *map;
+	const struct usbmix_selector_map *selector_map;
+};
+
+/*E-mu 0202/0404/0204 eXtension Unit(XU) control*/
+enum {
+	USB_XU_CLOCK_RATE 		= 0xe301,
+	USB_XU_CLOCK_SOURCE		= 0xe302,
+	USB_XU_DIGITAL_IO_STATUS	= 0xe303,
+	USB_XU_DEVICE_OPTIONS		= 0xe304,
+	USB_XU_DIRECT_MONITORING	= 0xe305,
+	USB_XU_METERING			= 0xe306
+};
+enum {
+	USB_XU_CLOCK_SOURCE_SELECTOR = 0x02,	/* clock source*/
+	USB_XU_CLOCK_RATE_SELECTOR = 0x03,	/* clock rate */
+	USB_XU_DIGITAL_FORMAT_SELECTOR = 0x01,	/* the spdif format */
+	USB_XU_SOFT_LIMIT_SELECTOR = 0x03	/* soft limiter */
+};
+
+/*
+ * manual mapping of mixer names
+ * if the mixer topology is too complicated and the parsed names are
+ * ambiguous, add the entries in usbmixer_maps.c.
+ */
+#include "mixer_maps.c"
+
+static const struct usbmix_name_map *
+find_map(const struct usbmix_name_map *p, int unitid, int control)
+{
+	if (!p)
+		return NULL;
+
+	for (; p->id; p++) {
+		if (p->id == unitid &&
+		    (!control || !p->control || control == p->control))
+			return p;
+	}
+	return NULL;
+}
+
+/* get the mapped name if the unit matches */
+static int
+check_mapped_name(const struct usbmix_name_map *p, char *buf, int buflen)
+{
+	if (!p || !p->name)
+		return 0;
+
+	buflen--;
+	return strlcpy(buf, p->name, buflen);
+}
+
+/* ignore the error value if ignore_ctl_error flag is set */
+#define filter_error(cval, err) \
+	((cval)->head.mixer->ignore_ctl_error ? 0 : (err))
+
+/* check whether the control should be ignored */
+static inline int
+check_ignored_ctl(const struct usbmix_name_map *p)
+{
+	if (!p || p->name || p->dB)
+		return 0;
+	return 1;
+}
+
+/* dB mapping */
+static inline void check_mapped_dB(const struct usbmix_name_map *p,
+				   struct usb_mixer_elem_info *cval)
+{
+	if (p && p->dB) {
+		cval->dBmin = p->dB->min;
+		cval->dBmax = p->dB->max;
+		cval->initialized = 1;
+	}
+}
+
+/* get the mapped selector source name */
+static int check_mapped_selector_name(struct mixer_build *state, int unitid,
+				      int index, char *buf, int buflen)
+{
+	const struct usbmix_selector_map *p;
+
+	if (!state->selector_map)
+		return 0;
+	for (p = state->selector_map; p->id; p++) {
+		if (p->id == unitid && index < p->count)
+			return strlcpy(buf, p->names[index], buflen);
+	}
+	return 0;
+}
+
+/*
+ * find an audio control unit with the given unit id
+ */
+static void *find_audio_control_unit(struct mixer_build *state,
+				     unsigned char unit)
+{
+	/* we just parse the header */
+	struct uac_feature_unit_descriptor *hdr = NULL;
+
+	while ((hdr = snd_usb_find_desc(state->buffer, state->buflen, hdr,
+					USB_DT_CS_INTERFACE)) != NULL) {
+		if (hdr->bLength >= 4 &&
+		    hdr->bDescriptorSubtype >= UAC_INPUT_TERMINAL &&
+		    hdr->bDescriptorSubtype <= UAC3_SAMPLE_RATE_CONVERTER &&
+		    hdr->bUnitID == unit)
+			return hdr;
+	}
+
+	return NULL;
+}
+
+/*
+ * copy a string with the given id
+ */
+static int snd_usb_copy_string_desc(struct snd_usb_audio *chip,
+				    int index, char *buf, int maxlen)
+{
+	int len = usb_string(chip->dev, index, buf, maxlen - 1);
+
+	if (len < 0)
+		return 0;
+
+	buf[len] = 0;
+	return len;
+}
+
+/*
+ * convert from the byte/word on usb descriptor to the zero-based integer
+ */
+static int convert_signed_value(struct usb_mixer_elem_info *cval, int val)
+{
+	switch (cval->val_type) {
+	case USB_MIXER_BOOLEAN:
+		return !!val;
+	case USB_MIXER_INV_BOOLEAN:
+		return !val;
+	case USB_MIXER_U8:
+		val &= 0xff;
+		break;
+	case USB_MIXER_S8:
+		val &= 0xff;
+		if (val >= 0x80)
+			val -= 0x100;
+		break;
+	case USB_MIXER_U16:
+		val &= 0xffff;
+		break;
+	case USB_MIXER_S16:
+		val &= 0xffff;
+		if (val >= 0x8000)
+			val -= 0x10000;
+		break;
+	}
+	return val;
+}
+
+/*
+ * convert from the zero-based int to the byte/word for usb descriptor
+ */
+static int convert_bytes_value(struct usb_mixer_elem_info *cval, int val)
+{
+	switch (cval->val_type) {
+	case USB_MIXER_BOOLEAN:
+		return !!val;
+	case USB_MIXER_INV_BOOLEAN:
+		return !val;
+	case USB_MIXER_S8:
+	case USB_MIXER_U8:
+		return val & 0xff;
+	case USB_MIXER_S16:
+	case USB_MIXER_U16:
+		return val & 0xffff;
+	}
+	return 0; /* not reached */
+}
+
+static int get_relative_value(struct usb_mixer_elem_info *cval, int val)
+{
+	if (!cval->res)
+		cval->res = 1;
+	if (val < cval->min)
+		return 0;
+	else if (val >= cval->max)
+		return (cval->max - cval->min + cval->res - 1) / cval->res;
+	else
+		return (val - cval->min) / cval->res;
+}
+
+static int get_abs_value(struct usb_mixer_elem_info *cval, int val)
+{
+	if (val < 0)
+		return cval->min;
+	if (!cval->res)
+		cval->res = 1;
+	val *= cval->res;
+	val += cval->min;
+	if (val > cval->max)
+		return cval->max;
+	return val;
+}
+
+static int uac2_ctl_value_size(int val_type)
+{
+	switch (val_type) {
+	case USB_MIXER_S32:
+	case USB_MIXER_U32:
+		return 4;
+	case USB_MIXER_S16:
+	case USB_MIXER_U16:
+		return 2;
+	default:
+		return 1;
+	}
+	return 0; /* unreachable */
+}
+
+
+/*
+ * retrieve a mixer value
+ */
+
+static int get_ctl_value_v1(struct usb_mixer_elem_info *cval, int request,
+			    int validx, int *value_ret)
+{
+	struct snd_usb_audio *chip = cval->head.mixer->chip;
+	unsigned char buf[2];
+	int val_len = cval->val_type >= USB_MIXER_S16 ? 2 : 1;
+	int timeout = 10;
+	int idx = 0, err;
+
+	err = snd_usb_lock_shutdown(chip);
+	if (err < 0)
+		return -EIO;
+
+	while (timeout-- > 0) {
+		idx = snd_usb_ctrl_intf(chip) | (cval->head.id << 8);
+		err = snd_usb_ctl_msg(chip->dev, usb_rcvctrlpipe(chip->dev, 0), request,
+				      USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_IN,
+				      validx, idx, buf, val_len);
+		if (err >= val_len) {
+			*value_ret = convert_signed_value(cval, snd_usb_combine_bytes(buf, val_len));
+			err = 0;
+			goto out;
+		} else if (err == -ETIMEDOUT) {
+			goto out;
+		}
+	}
+	usb_audio_dbg(chip,
+		"cannot get ctl value: req = %#x, wValue = %#x, wIndex = %#x, type = %d\n",
+		request, validx, idx, cval->val_type);
+	err = -EINVAL;
+
+ out:
+	snd_usb_unlock_shutdown(chip);
+	return err;
+}
+
+static int get_ctl_value_v2(struct usb_mixer_elem_info *cval, int request,
+			    int validx, int *value_ret)
+{
+	struct snd_usb_audio *chip = cval->head.mixer->chip;
+	/* enough space for one range */
+	unsigned char buf[sizeof(__u16) + 3 * sizeof(__u32)];
+	unsigned char *val;
+	int idx = 0, ret, val_size, size;
+	__u8 bRequest;
+
+	val_size = uac2_ctl_value_size(cval->val_type);
+
+	if (request == UAC_GET_CUR) {
+		bRequest = UAC2_CS_CUR;
+		size = val_size;
+	} else {
+		bRequest = UAC2_CS_RANGE;
+		size = sizeof(__u16) + 3 * val_size;
+	}
+
+	memset(buf, 0, sizeof(buf));
+
+	ret = snd_usb_lock_shutdown(chip) ? -EIO : 0;
+	if (ret)
+		goto error;
+
+	idx = snd_usb_ctrl_intf(chip) | (cval->head.id << 8);
+	ret = snd_usb_ctl_msg(chip->dev, usb_rcvctrlpipe(chip->dev, 0), bRequest,
+			      USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_IN,
+			      validx, idx, buf, size);
+	snd_usb_unlock_shutdown(chip);
+
+	if (ret < 0) {
+error:
+		usb_audio_err(chip,
+			"cannot get ctl value: req = %#x, wValue = %#x, wIndex = %#x, type = %d\n",
+			request, validx, idx, cval->val_type);
+		return ret;
+	}
+
+	/* FIXME: how should we handle multiple triplets here? */
+
+	switch (request) {
+	case UAC_GET_CUR:
+		val = buf;
+		break;
+	case UAC_GET_MIN:
+		val = buf + sizeof(__u16);
+		break;
+	case UAC_GET_MAX:
+		val = buf + sizeof(__u16) + val_size;
+		break;
+	case UAC_GET_RES:
+		val = buf + sizeof(__u16) + val_size * 2;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	*value_ret = convert_signed_value(cval,
+					  snd_usb_combine_bytes(val, val_size));
+
+	return 0;
+}
+
+static int get_ctl_value(struct usb_mixer_elem_info *cval, int request,
+			 int validx, int *value_ret)
+{
+	validx += cval->idx_off;
+
+	return (cval->head.mixer->protocol == UAC_VERSION_1) ?
+		get_ctl_value_v1(cval, request, validx, value_ret) :
+		get_ctl_value_v2(cval, request, validx, value_ret);
+}
+
+static int get_cur_ctl_value(struct usb_mixer_elem_info *cval,
+			     int validx, int *value)
+{
+	return get_ctl_value(cval, UAC_GET_CUR, validx, value);
+}
+
+/* channel = 0: master, 1 = first channel */
+static inline int get_cur_mix_raw(struct usb_mixer_elem_info *cval,
+				  int channel, int *value)
+{
+	return get_ctl_value(cval, UAC_GET_CUR,
+			     (cval->control << 8) | channel,
+			     value);
+}
+
+int snd_usb_get_cur_mix_value(struct usb_mixer_elem_info *cval,
+			     int channel, int index, int *value)
+{
+	int err;
+
+	if (cval->cached & (1 << channel)) {
+		*value = cval->cache_val[index];
+		return 0;
+	}
+	err = get_cur_mix_raw(cval, channel, value);
+	if (err < 0) {
+		if (!cval->head.mixer->ignore_ctl_error)
+			usb_audio_dbg(cval->head.mixer->chip,
+				"cannot get current value for control %d ch %d: err = %d\n",
+				      cval->control, channel, err);
+		return err;
+	}
+	cval->cached |= 1 << channel;
+	cval->cache_val[index] = *value;
+	return 0;
+}
+
+/*
+ * set a mixer value
+ */
+
+int snd_usb_mixer_set_ctl_value(struct usb_mixer_elem_info *cval,
+				int request, int validx, int value_set)
+{
+	struct snd_usb_audio *chip = cval->head.mixer->chip;
+	unsigned char buf[4];
+	int idx = 0, val_len, err, timeout = 10;
+
+	validx += cval->idx_off;
+
+
+	if (cval->head.mixer->protocol == UAC_VERSION_1) {
+		val_len = cval->val_type >= USB_MIXER_S16 ? 2 : 1;
+	} else { /* UAC_VERSION_2/3 */
+		val_len = uac2_ctl_value_size(cval->val_type);
+
+		/* FIXME */
+		if (request != UAC_SET_CUR) {
+			usb_audio_dbg(chip, "RANGE setting not yet supported\n");
+			return -EINVAL;
+		}
+
+		request = UAC2_CS_CUR;
+	}
+
+	value_set = convert_bytes_value(cval, value_set);
+	buf[0] = value_set & 0xff;
+	buf[1] = (value_set >> 8) & 0xff;
+	buf[2] = (value_set >> 16) & 0xff;
+	buf[3] = (value_set >> 24) & 0xff;
+
+	err = snd_usb_lock_shutdown(chip);
+	if (err < 0)
+		return -EIO;
+
+	while (timeout-- > 0) {
+		idx = snd_usb_ctrl_intf(chip) | (cval->head.id << 8);
+		err = snd_usb_ctl_msg(chip->dev,
+				      usb_sndctrlpipe(chip->dev, 0), request,
+				      USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_OUT,
+				      validx, idx, buf, val_len);
+		if (err >= 0) {
+			err = 0;
+			goto out;
+		} else if (err == -ETIMEDOUT) {
+			goto out;
+		}
+	}
+	usb_audio_dbg(chip, "cannot set ctl value: req = %#x, wValue = %#x, wIndex = %#x, type = %d, data = %#x/%#x\n",
+		      request, validx, idx, cval->val_type, buf[0], buf[1]);
+	err = -EINVAL;
+
+ out:
+	snd_usb_unlock_shutdown(chip);
+	return err;
+}
+
+static int set_cur_ctl_value(struct usb_mixer_elem_info *cval,
+			     int validx, int value)
+{
+	return snd_usb_mixer_set_ctl_value(cval, UAC_SET_CUR, validx, value);
+}
+
+int snd_usb_set_cur_mix_value(struct usb_mixer_elem_info *cval, int channel,
+			     int index, int value)
+{
+	int err;
+	unsigned int read_only = (channel == 0) ?
+		cval->master_readonly :
+		cval->ch_readonly & (1 << (channel - 1));
+
+	if (read_only) {
+		usb_audio_dbg(cval->head.mixer->chip,
+			      "%s(): channel %d of control %d is read_only\n",
+			    __func__, channel, cval->control);
+		return 0;
+	}
+
+	err = snd_usb_mixer_set_ctl_value(cval,
+					  UAC_SET_CUR, (cval->control << 8) | channel,
+					  value);
+	if (err < 0)
+		return err;
+	cval->cached |= 1 << channel;
+	cval->cache_val[index] = value;
+	return 0;
+}
+
+/*
+ * TLV callback for mixer volume controls
+ */
+int snd_usb_mixer_vol_tlv(struct snd_kcontrol *kcontrol, int op_flag,
+			 unsigned int size, unsigned int __user *_tlv)
+{
+	struct usb_mixer_elem_info *cval = kcontrol->private_data;
+	DECLARE_TLV_DB_MINMAX(scale, 0, 0);
+
+	if (size < sizeof(scale))
+		return -ENOMEM;
+	if (cval->min_mute)
+		scale[0] = SNDRV_CTL_TLVT_DB_MINMAX_MUTE;
+	scale[2] = cval->dBmin;
+	scale[3] = cval->dBmax;
+	if (copy_to_user(_tlv, scale, sizeof(scale)))
+		return -EFAULT;
+	return 0;
+}
+
+/*
+ * parser routines begin here...
+ */
+
+static int parse_audio_unit(struct mixer_build *state, int unitid);
+
+
+/*
+ * check if the input/output channel routing is enabled on the given bitmap.
+ * used for mixer unit parser
+ */
+static int check_matrix_bitmap(unsigned char *bmap,
+			       int ich, int och, int num_outs)
+{
+	int idx = ich * num_outs + och;
+	return bmap[idx >> 3] & (0x80 >> (idx & 7));
+}
+
+/*
+ * add an alsa control element
+ * search and increment the index until an empty slot is found.
+ *
+ * if failed, give up and free the control instance.
+ */
+
+int snd_usb_mixer_add_list(struct usb_mixer_elem_list *list,
+			   struct snd_kcontrol *kctl,
+			   bool is_std_info)
+{
+	struct usb_mixer_interface *mixer = list->mixer;
+	int err;
+
+	while (snd_ctl_find_id(mixer->chip->card, &kctl->id))
+		kctl->id.index++;
+	err = snd_ctl_add(mixer->chip->card, kctl);
+	if (err < 0) {
+		usb_audio_dbg(mixer->chip, "cannot add control (err = %d)\n",
+			      err);
+		return err;
+	}
+	list->kctl = kctl;
+	list->is_std_info = is_std_info;
+	list->next_id_elem = mixer->id_elems[list->id];
+	mixer->id_elems[list->id] = list;
+	return 0;
+}
+
+/*
+ * get a terminal name string
+ */
+
+static struct iterm_name_combo {
+	int type;
+	char *name;
+} iterm_names[] = {
+	{ 0x0300, "Output" },
+	{ 0x0301, "Speaker" },
+	{ 0x0302, "Headphone" },
+	{ 0x0303, "HMD Audio" },
+	{ 0x0304, "Desktop Speaker" },
+	{ 0x0305, "Room Speaker" },
+	{ 0x0306, "Com Speaker" },
+	{ 0x0307, "LFE" },
+	{ 0x0600, "External In" },
+	{ 0x0601, "Analog In" },
+	{ 0x0602, "Digital In" },
+	{ 0x0603, "Line" },
+	{ 0x0604, "Legacy In" },
+	{ 0x0605, "IEC958 In" },
+	{ 0x0606, "1394 DA Stream" },
+	{ 0x0607, "1394 DV Stream" },
+	{ 0x0700, "Embedded" },
+	{ 0x0701, "Noise Source" },
+	{ 0x0702, "Equalization Noise" },
+	{ 0x0703, "CD" },
+	{ 0x0704, "DAT" },
+	{ 0x0705, "DCC" },
+	{ 0x0706, "MiniDisk" },
+	{ 0x0707, "Analog Tape" },
+	{ 0x0708, "Phonograph" },
+	{ 0x0709, "VCR Audio" },
+	{ 0x070a, "Video Disk Audio" },
+	{ 0x070b, "DVD Audio" },
+	{ 0x070c, "TV Tuner Audio" },
+	{ 0x070d, "Satellite Rec Audio" },
+	{ 0x070e, "Cable Tuner Audio" },
+	{ 0x070f, "DSS Audio" },
+	{ 0x0710, "Radio Receiver" },
+	{ 0x0711, "Radio Transmitter" },
+	{ 0x0712, "Multi-Track Recorder" },
+	{ 0x0713, "Synthesizer" },
+	{ 0 },
+};
+
+static int get_term_name(struct snd_usb_audio *chip, struct usb_audio_term *iterm,
+			 unsigned char *name, int maxlen, int term_only)
+{
+	struct iterm_name_combo *names;
+	int len;
+
+	if (iterm->name) {
+		len = snd_usb_copy_string_desc(chip, iterm->name,
+						name, maxlen);
+		if (len)
+			return len;
+	}
+
+	/* virtual type - not a real terminal */
+	if (iterm->type >> 16) {
+		if (term_only)
+			return 0;
+		switch (iterm->type >> 16) {
+		case UAC3_SELECTOR_UNIT:
+			strcpy(name, "Selector");
+			return 8;
+		case UAC3_PROCESSING_UNIT:
+			strcpy(name, "Process Unit");
+			return 12;
+		case UAC3_EXTENSION_UNIT:
+			strcpy(name, "Ext Unit");
+			return 8;
+		case UAC3_MIXER_UNIT:
+			strcpy(name, "Mixer");
+			return 5;
+		default:
+			return sprintf(name, "Unit %d", iterm->id);
+		}
+	}
+
+	switch (iterm->type & 0xff00) {
+	case 0x0100:
+		strcpy(name, "PCM");
+		return 3;
+	case 0x0200:
+		strcpy(name, "Mic");
+		return 3;
+	case 0x0400:
+		strcpy(name, "Headset");
+		return 7;
+	case 0x0500:
+		strcpy(name, "Phone");
+		return 5;
+	}
+
+	for (names = iterm_names; names->type; names++) {
+		if (names->type == iterm->type) {
+			strcpy(name, names->name);
+			return strlen(names->name);
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * Get logical cluster information for UAC3 devices.
+ */
+static int get_cluster_channels_v3(struct mixer_build *state, unsigned int cluster_id)
+{
+	struct uac3_cluster_header_descriptor c_header;
+	int err;
+
+	err = snd_usb_ctl_msg(state->chip->dev,
+			usb_rcvctrlpipe(state->chip->dev, 0),
+			UAC3_CS_REQ_HIGH_CAPABILITY_DESCRIPTOR,
+			USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_IN,
+			cluster_id,
+			snd_usb_ctrl_intf(state->chip),
+			&c_header, sizeof(c_header));
+	if (err < 0)
+		goto error;
+	if (err != sizeof(c_header)) {
+		err = -EIO;
+		goto error;
+	}
+
+	return c_header.bNrChannels;
+
+error:
+	usb_audio_err(state->chip, "cannot request logical cluster ID: %d (err: %d)\n", cluster_id, err);
+	return err;
+}
+
+/*
+ * Get number of channels for a Mixer Unit.
+ */
+static int uac_mixer_unit_get_channels(struct mixer_build *state,
+				       struct uac_mixer_unit_descriptor *desc)
+{
+	int mu_channels;
+
+	switch (state->mixer->protocol) {
+	case UAC_VERSION_1:
+	case UAC_VERSION_2:
+	default:
+		if (desc->bLength < sizeof(*desc) + desc->bNrInPins + 1)
+			return 0; /* no bmControls -> skip */
+		mu_channels = uac_mixer_unit_bNrChannels(desc);
+		break;
+	case UAC_VERSION_3:
+		mu_channels = get_cluster_channels_v3(state,
+				uac3_mixer_unit_wClusterDescrID(desc));
+		break;
+	}
+
+	return mu_channels;
+}
+
+/*
+ * Parse Input Terminal Unit
+ */
+static int __check_input_term(struct mixer_build *state, int id,
+			      struct usb_audio_term *term);
+
+static int parse_term_uac1_iterm_unit(struct mixer_build *state,
+				      struct usb_audio_term *term,
+				      void *p1, int id)
+{
+	struct uac_input_terminal_descriptor *d = p1;
+
+	term->type = le16_to_cpu(d->wTerminalType);
+	term->channels = d->bNrChannels;
+	term->chconfig = le16_to_cpu(d->wChannelConfig);
+	term->name = d->iTerminal;
+	return 0;
+}
+
+static int parse_term_uac2_iterm_unit(struct mixer_build *state,
+				      struct usb_audio_term *term,
+				      void *p1, int id)
+{
+	struct uac2_input_terminal_descriptor *d = p1;
+	int err;
+
+	/* call recursively to verify the referenced clock entity */
+	err = __check_input_term(state, d->bCSourceID, term);
+	if (err < 0)
+		return err;
+
+	/* save input term properties after recursion,
+	 * to ensure they are not overriden by the recursion calls
+	 */
+	term->id = id;
+	term->type = le16_to_cpu(d->wTerminalType);
+	term->channels = d->bNrChannels;
+	term->chconfig = le32_to_cpu(d->bmChannelConfig);
+	term->name = d->iTerminal;
+	return 0;
+}
+
+static int parse_term_uac3_iterm_unit(struct mixer_build *state,
+				      struct usb_audio_term *term,
+				      void *p1, int id)
+{
+	struct uac3_input_terminal_descriptor *d = p1;
+	int err;
+
+	/* call recursively to verify the referenced clock entity */
+	err = __check_input_term(state, d->bCSourceID, term);
+	if (err < 0)
+		return err;
+
+	/* save input term properties after recursion,
+	 * to ensure they are not overriden by the recursion calls
+	 */
+	term->id = id;
+	term->type = le16_to_cpu(d->wTerminalType);
+
+	err = get_cluster_channels_v3(state, le16_to_cpu(d->wClusterDescrID));
+	if (err < 0)
+		return err;
+	term->channels = err;
+
+	/* REVISIT: UAC3 IT doesn't have channels cfg */
+	term->chconfig = 0;
+
+	term->name = le16_to_cpu(d->wTerminalDescrStr);
+	return 0;
+}
+
+static int parse_term_mixer_unit(struct mixer_build *state,
+				 struct usb_audio_term *term,
+				 void *p1, int id)
+{
+	struct uac_mixer_unit_descriptor *d = p1;
+	int protocol = state->mixer->protocol;
+	int err;
+
+	err = uac_mixer_unit_get_channels(state, d);
+	if (err <= 0)
+		return err;
+
+	term->type = UAC3_MIXER_UNIT << 16; /* virtual type */
+	term->channels = err;
+	if (protocol != UAC_VERSION_3) {
+		term->chconfig = uac_mixer_unit_wChannelConfig(d, protocol);
+		term->name = uac_mixer_unit_iMixer(d);
+	}
+	return 0;
+}
+
+static int parse_term_selector_unit(struct mixer_build *state,
+				    struct usb_audio_term *term,
+				    void *p1, int id)
+{
+	struct uac_selector_unit_descriptor *d = p1;
+	int err;
+
+	/* call recursively to retrieve the channel info */
+	err = __check_input_term(state, d->baSourceID[0], term);
+	if (err < 0)
+		return err;
+	term->type = UAC3_SELECTOR_UNIT << 16; /* virtual type */
+	term->id = id;
+	if (state->mixer->protocol != UAC_VERSION_3)
+		term->name = uac_selector_unit_iSelector(d);
+	return 0;
+}
+
+static int parse_term_proc_unit(struct mixer_build *state,
+				struct usb_audio_term *term,
+				void *p1, int id, int vtype)
+{
+	struct uac_processing_unit_descriptor *d = p1;
+	int protocol = state->mixer->protocol;
+	int err;
+
+	if (d->bNrInPins) {
+		/* call recursively to retrieve the channel info */
+		err = __check_input_term(state, d->baSourceID[0], term);
+		if (err < 0)
+			return err;
+	}
+
+	term->type = vtype << 16; /* virtual type */
+	term->id = id;
+
+	if (protocol == UAC_VERSION_3)
+		return 0;
+
+	if (!term->channels) {
+		term->channels = uac_processing_unit_bNrChannels(d);
+		term->chconfig = uac_processing_unit_wChannelConfig(d, protocol);
+	}
+	term->name = uac_processing_unit_iProcessing(d, protocol);
+	return 0;
+}
+
+static int parse_term_effect_unit(struct mixer_build *state,
+				  struct usb_audio_term *term,
+				  void *p1, int id)
+{
+	term->type = UAC3_EFFECT_UNIT << 16; /* virtual type */
+	term->id = id;
+	return 0;
+}
+
+static int parse_term_uac2_clock_source(struct mixer_build *state,
+					struct usb_audio_term *term,
+					void *p1, int id)
+{
+	struct uac_clock_source_descriptor *d = p1;
+
+	term->type = UAC3_CLOCK_SOURCE << 16; /* virtual type */
+	term->id = id;
+	term->name = d->iClockSource;
+	return 0;
+}
+
+static int parse_term_uac3_clock_source(struct mixer_build *state,
+					struct usb_audio_term *term,
+					void *p1, int id)
+{
+	struct uac3_clock_source_descriptor *d = p1;
+
+	term->type = UAC3_CLOCK_SOURCE << 16; /* virtual type */
+	term->id = id;
+	term->name = le16_to_cpu(d->wClockSourceStr);
+	return 0;
+}
+
+#define PTYPE(a, b)	((a) << 8 | (b))
+
+/*
+ * parse the source unit recursively until it reaches to a terminal
+ * or a branched unit.
+ */
+static int __check_input_term(struct mixer_build *state, int id,
+			      struct usb_audio_term *term)
+{
+	int protocol = state->mixer->protocol;
+	void *p1;
+	unsigned char *hdr;
+
+	for (;;) {
+		/* a loop in the terminal chain? */
+		if (test_and_set_bit(id, state->termbitmap))
+			return -EINVAL;
+
+		p1 = find_audio_control_unit(state, id);
+		if (!p1)
+			break;
+		if (!snd_usb_validate_audio_desc(p1, protocol))
+			break; /* bad descriptor */
+
+		hdr = p1;
+		term->id = id;
+
+		switch (PTYPE(protocol, hdr[2])) {
+		case PTYPE(UAC_VERSION_1, UAC_FEATURE_UNIT):
+		case PTYPE(UAC_VERSION_2, UAC_FEATURE_UNIT):
+		case PTYPE(UAC_VERSION_3, UAC3_FEATURE_UNIT): {
+			/* the header is the same for all versions */
+			struct uac_feature_unit_descriptor *d = p1;
+
+			id = d->bSourceID;
+			break; /* continue to parse */
+		}
+		case PTYPE(UAC_VERSION_1, UAC_INPUT_TERMINAL):
+			return parse_term_uac1_iterm_unit(state, term, p1, id);
+		case PTYPE(UAC_VERSION_2, UAC_INPUT_TERMINAL):
+			return parse_term_uac2_iterm_unit(state, term, p1, id);
+		case PTYPE(UAC_VERSION_3, UAC_INPUT_TERMINAL):
+			return parse_term_uac3_iterm_unit(state, term, p1, id);
+		case PTYPE(UAC_VERSION_1, UAC_MIXER_UNIT):
+		case PTYPE(UAC_VERSION_2, UAC_MIXER_UNIT):
+		case PTYPE(UAC_VERSION_3, UAC3_MIXER_UNIT):
+			return parse_term_mixer_unit(state, term, p1, id);
+		case PTYPE(UAC_VERSION_1, UAC_SELECTOR_UNIT):
+		case PTYPE(UAC_VERSION_2, UAC_SELECTOR_UNIT):
+		case PTYPE(UAC_VERSION_2, UAC2_CLOCK_SELECTOR):
+		case PTYPE(UAC_VERSION_3, UAC3_SELECTOR_UNIT):
+		case PTYPE(UAC_VERSION_3, UAC3_CLOCK_SELECTOR):
+			return parse_term_selector_unit(state, term, p1, id);
+		case PTYPE(UAC_VERSION_1, UAC1_PROCESSING_UNIT):
+		case PTYPE(UAC_VERSION_2, UAC2_PROCESSING_UNIT_V2):
+		case PTYPE(UAC_VERSION_3, UAC3_PROCESSING_UNIT):
+			return parse_term_proc_unit(state, term, p1, id,
+						    UAC3_PROCESSING_UNIT);
+		case PTYPE(UAC_VERSION_2, UAC2_EFFECT_UNIT):
+		case PTYPE(UAC_VERSION_3, UAC3_EFFECT_UNIT):
+			return parse_term_effect_unit(state, term, p1, id);
+		case PTYPE(UAC_VERSION_1, UAC1_EXTENSION_UNIT):
+		case PTYPE(UAC_VERSION_2, UAC2_EXTENSION_UNIT_V2):
+		case PTYPE(UAC_VERSION_3, UAC3_EXTENSION_UNIT):
+			return parse_term_proc_unit(state, term, p1, id,
+						    UAC3_EXTENSION_UNIT);
+		case PTYPE(UAC_VERSION_2, UAC2_CLOCK_SOURCE):
+			return parse_term_uac2_clock_source(state, term, p1, id);
+		case PTYPE(UAC_VERSION_3, UAC3_CLOCK_SOURCE):
+			return parse_term_uac3_clock_source(state, term, p1, id);
+		default:
+			return -ENODEV;
+		}
+	}
+	return -ENODEV;
+}
+
+
+static int check_input_term(struct mixer_build *state, int id,
+			    struct usb_audio_term *term)
+{
+	memset(term, 0, sizeof(*term));
+	memset(state->termbitmap, 0, sizeof(state->termbitmap));
+	return __check_input_term(state, id, term);
+}
+
+/*
+ * Feature Unit
+ */
+
+/* feature unit control information */
+struct usb_feature_control_info {
+	int control;
+	const char *name;
+	int type;	/* data type for uac1 */
+	int type_uac2;	/* data type for uac2 if different from uac1, else -1 */
+};
+
+static const struct usb_feature_control_info audio_feature_info[] = {
+	{ UAC_FU_MUTE,			"Mute",			USB_MIXER_INV_BOOLEAN, -1 },
+	{ UAC_FU_VOLUME,		"Volume",		USB_MIXER_S16, -1 },
+	{ UAC_FU_BASS,			"Tone Control - Bass",	USB_MIXER_S8, -1 },
+	{ UAC_FU_MID,			"Tone Control - Mid",	USB_MIXER_S8, -1 },
+	{ UAC_FU_TREBLE,		"Tone Control - Treble", USB_MIXER_S8, -1 },
+	{ UAC_FU_GRAPHIC_EQUALIZER,	"Graphic Equalizer",	USB_MIXER_S8, -1 }, /* FIXME: not implemented yet */
+	{ UAC_FU_AUTOMATIC_GAIN,	"Auto Gain Control",	USB_MIXER_BOOLEAN, -1 },
+	{ UAC_FU_DELAY,			"Delay Control",	USB_MIXER_U16, USB_MIXER_U32 },
+	{ UAC_FU_BASS_BOOST,		"Bass Boost",		USB_MIXER_BOOLEAN, -1 },
+	{ UAC_FU_LOUDNESS,		"Loudness",		USB_MIXER_BOOLEAN, -1 },
+	/* UAC2 specific */
+	{ UAC2_FU_INPUT_GAIN,		"Input Gain Control",	USB_MIXER_S16, -1 },
+	{ UAC2_FU_INPUT_GAIN_PAD,	"Input Gain Pad Control", USB_MIXER_S16, -1 },
+	{ UAC2_FU_PHASE_INVERTER,	 "Phase Inverter Control", USB_MIXER_BOOLEAN, -1 },
+};
+
+static void usb_mixer_elem_info_free(struct usb_mixer_elem_info *cval)
+{
+	kfree(cval);
+}
+
+/* private_free callback */
+void snd_usb_mixer_elem_free(struct snd_kcontrol *kctl)
+{
+	usb_mixer_elem_info_free(kctl->private_data);
+	kctl->private_data = NULL;
+}
+
+/*
+ * interface to ALSA control for feature/mixer units
+ */
+
+/* volume control quirks */
+static void volume_control_quirks(struct usb_mixer_elem_info *cval,
+				  struct snd_kcontrol *kctl)
+{
+	struct snd_usb_audio *chip = cval->head.mixer->chip;
+	switch (chip->usb_id) {
+	case USB_ID(0x0763, 0x2030): /* M-Audio Fast Track C400 */
+	case USB_ID(0x0763, 0x2031): /* M-Audio Fast Track C600 */
+		if (strcmp(kctl->id.name, "Effect Duration") == 0) {
+			cval->min = 0x0000;
+			cval->max = 0xffff;
+			cval->res = 0x00e6;
+			break;
+		}
+		if (strcmp(kctl->id.name, "Effect Volume") == 0 ||
+		    strcmp(kctl->id.name, "Effect Feedback Volume") == 0) {
+			cval->min = 0x00;
+			cval->max = 0xff;
+			break;
+		}
+		if (strstr(kctl->id.name, "Effect Return") != NULL) {
+			cval->min = 0xb706;
+			cval->max = 0xff7b;
+			cval->res = 0x0073;
+			break;
+		}
+		if ((strstr(kctl->id.name, "Playback Volume") != NULL) ||
+			(strstr(kctl->id.name, "Effect Send") != NULL)) {
+			cval->min = 0xb5fb; /* -73 dB = 0xb6ff */
+			cval->max = 0xfcfe;
+			cval->res = 0x0073;
+		}
+		break;
+
+	case USB_ID(0x0763, 0x2081): /* M-Audio Fast Track Ultra 8R */
+	case USB_ID(0x0763, 0x2080): /* M-Audio Fast Track Ultra */
+		if (strcmp(kctl->id.name, "Effect Duration") == 0) {
+			usb_audio_info(chip,
+				       "set quirk for FTU Effect Duration\n");
+			cval->min = 0x0000;
+			cval->max = 0x7f00;
+			cval->res = 0x0100;
+			break;
+		}
+		if (strcmp(kctl->id.name, "Effect Volume") == 0 ||
+		    strcmp(kctl->id.name, "Effect Feedback Volume") == 0) {
+			usb_audio_info(chip,
+				       "set quirks for FTU Effect Feedback/Volume\n");
+			cval->min = 0x00;
+			cval->max = 0x7f;
+			break;
+		}
+		break;
+
+	case USB_ID(0x0d8c, 0x0103):
+		if (!strcmp(kctl->id.name, "PCM Playback Volume")) {
+			usb_audio_info(chip,
+				 "set volume quirk for CM102-A+/102S+\n");
+			cval->min = -256;
+		}
+		break;
+
+	case USB_ID(0x0471, 0x0101):
+	case USB_ID(0x0471, 0x0104):
+	case USB_ID(0x0471, 0x0105):
+	case USB_ID(0x0672, 0x1041):
+	/* quirk for UDA1321/N101.
+	 * note that detection between firmware 2.1.1.7 (N101)
+	 * and later 2.1.1.21 is not very clear from datasheets.
+	 * I hope that the min value is -15360 for newer firmware --jk
+	 */
+		if (!strcmp(kctl->id.name, "PCM Playback Volume") &&
+		    cval->min == -15616) {
+			usb_audio_info(chip,
+				 "set volume quirk for UDA1321/N101 chip\n");
+			cval->max = -256;
+		}
+		break;
+
+	case USB_ID(0x046d, 0x09a4):
+		if (!strcmp(kctl->id.name, "Mic Capture Volume")) {
+			usb_audio_info(chip,
+				"set volume quirk for QuickCam E3500\n");
+			cval->min = 6080;
+			cval->max = 8768;
+			cval->res = 192;
+		}
+		break;
+
+	case USB_ID(0x046d, 0x0807): /* Logitech Webcam C500 */
+	case USB_ID(0x046d, 0x0808):
+	case USB_ID(0x046d, 0x0809):
+	case USB_ID(0x046d, 0x0819): /* Logitech Webcam C210 */
+	case USB_ID(0x046d, 0x081b): /* HD Webcam c310 */
+	case USB_ID(0x046d, 0x081d): /* HD Webcam c510 */
+	case USB_ID(0x046d, 0x0825): /* HD Webcam c270 */
+	case USB_ID(0x046d, 0x0826): /* HD Webcam c525 */
+	case USB_ID(0x046d, 0x08ca): /* Logitech Quickcam Fusion */
+	case USB_ID(0x046d, 0x0991):
+	case USB_ID(0x046d, 0x09a2): /* QuickCam Communicate Deluxe/S7500 */
+	/* Most audio usb devices lie about volume resolution.
+	 * Most Logitech webcams have res = 384.
+	 * Probably there is some logitech magic behind this number --fishor
+	 */
+		if (!strcmp(kctl->id.name, "Mic Capture Volume")) {
+			usb_audio_info(chip,
+				"set resolution quirk: cval->res = 384\n");
+			cval->res = 384;
+		}
+		break;
+	case USB_ID(0x0495, 0x3042): /* ESS Technology Asus USB DAC */
+		if ((strstr(kctl->id.name, "Playback Volume") != NULL) ||
+			strstr(kctl->id.name, "Capture Volume") != NULL) {
+			cval->min >>= 8;
+			cval->max = 0;
+			cval->res = 1;
+		}
+		break;
+	}
+}
+
+/*
+ * retrieve the minimum and maximum values for the specified control
+ */
+static int get_min_max_with_quirks(struct usb_mixer_elem_info *cval,
+				   int default_min, struct snd_kcontrol *kctl)
+{
+	/* for failsafe */
+	cval->min = default_min;
+	cval->max = cval->min + 1;
+	cval->res = 1;
+	cval->dBmin = cval->dBmax = 0;
+
+	if (cval->val_type == USB_MIXER_BOOLEAN ||
+	    cval->val_type == USB_MIXER_INV_BOOLEAN) {
+		cval->initialized = 1;
+	} else {
+		int minchn = 0;
+		if (cval->cmask) {
+			int i;
+			for (i = 0; i < MAX_CHANNELS; i++)
+				if (cval->cmask & (1 << i)) {
+					minchn = i + 1;
+					break;
+				}
+		}
+		if (get_ctl_value(cval, UAC_GET_MAX, (cval->control << 8) | minchn, &cval->max) < 0 ||
+		    get_ctl_value(cval, UAC_GET_MIN, (cval->control << 8) | minchn, &cval->min) < 0) {
+			usb_audio_err(cval->head.mixer->chip,
+				      "%d:%d: cannot get min/max values for control %d (id %d)\n",
+				   cval->head.id, snd_usb_ctrl_intf(cval->head.mixer->chip),
+							       cval->control, cval->head.id);
+			return -EINVAL;
+		}
+		if (get_ctl_value(cval, UAC_GET_RES,
+				  (cval->control << 8) | minchn,
+				  &cval->res) < 0) {
+			cval->res = 1;
+		} else {
+			int last_valid_res = cval->res;
+
+			while (cval->res > 1) {
+				if (snd_usb_mixer_set_ctl_value(cval, UAC_SET_RES,
+								(cval->control << 8) | minchn,
+								cval->res / 2) < 0)
+					break;
+				cval->res /= 2;
+			}
+			if (get_ctl_value(cval, UAC_GET_RES,
+					  (cval->control << 8) | minchn, &cval->res) < 0)
+				cval->res = last_valid_res;
+		}
+		if (cval->res == 0)
+			cval->res = 1;
+
+		/* Additional checks for the proper resolution
+		 *
+		 * Some devices report smaller resolutions than actually
+		 * reacting.  They don't return errors but simply clip
+		 * to the lower aligned value.
+		 */
+		if (cval->min + cval->res < cval->max) {
+			int last_valid_res = cval->res;
+			int saved, test, check;
+			if (get_cur_mix_raw(cval, minchn, &saved) < 0)
+				goto no_res_check;
+			for (;;) {
+				test = saved;
+				if (test < cval->max)
+					test += cval->res;
+				else
+					test -= cval->res;
+				if (test < cval->min || test > cval->max ||
+				    snd_usb_set_cur_mix_value(cval, minchn, 0, test) ||
+				    get_cur_mix_raw(cval, minchn, &check)) {
+					cval->res = last_valid_res;
+					break;
+				}
+				if (test == check)
+					break;
+				cval->res *= 2;
+			}
+			snd_usb_set_cur_mix_value(cval, minchn, 0, saved);
+		}
+
+no_res_check:
+		cval->initialized = 1;
+	}
+
+	if (kctl)
+		volume_control_quirks(cval, kctl);
+
+	/* USB descriptions contain the dB scale in 1/256 dB unit
+	 * while ALSA TLV contains in 1/100 dB unit
+	 */
+	cval->dBmin = (convert_signed_value(cval, cval->min) * 100) / 256;
+	cval->dBmax = (convert_signed_value(cval, cval->max) * 100) / 256;
+	if (cval->dBmin > cval->dBmax) {
+		/* something is wrong; assume it's either from/to 0dB */
+		if (cval->dBmin < 0)
+			cval->dBmax = 0;
+		else if (cval->dBmin > 0)
+			cval->dBmin = 0;
+		if (cval->dBmin > cval->dBmax) {
+			/* totally crap, return an error */
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
+#define get_min_max(cval, def)	get_min_max_with_quirks(cval, def, NULL)
+
+/* get a feature/mixer unit info */
+static int mixer_ctl_feature_info(struct snd_kcontrol *kcontrol,
+				  struct snd_ctl_elem_info *uinfo)
+{
+	struct usb_mixer_elem_info *cval = kcontrol->private_data;
+
+	if (cval->val_type == USB_MIXER_BOOLEAN ||
+	    cval->val_type == USB_MIXER_INV_BOOLEAN)
+		uinfo->type = SNDRV_CTL_ELEM_TYPE_BOOLEAN;
+	else
+		uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
+	uinfo->count = cval->channels;
+	if (cval->val_type == USB_MIXER_BOOLEAN ||
+	    cval->val_type == USB_MIXER_INV_BOOLEAN) {
+		uinfo->value.integer.min = 0;
+		uinfo->value.integer.max = 1;
+	} else {
+		if (!cval->initialized) {
+			get_min_max_with_quirks(cval, 0, kcontrol);
+			if (cval->initialized && cval->dBmin >= cval->dBmax) {
+				kcontrol->vd[0].access &= 
+					~(SNDRV_CTL_ELEM_ACCESS_TLV_READ |
+					  SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK);
+				snd_ctl_notify(cval->head.mixer->chip->card,
+					       SNDRV_CTL_EVENT_MASK_INFO,
+					       &kcontrol->id);
+			}
+		}
+		uinfo->value.integer.min = 0;
+		uinfo->value.integer.max =
+			(cval->max - cval->min + cval->res - 1) / cval->res;
+	}
+	return 0;
+}
+
+/* get the current value from feature/mixer unit */
+static int mixer_ctl_feature_get(struct snd_kcontrol *kcontrol,
+				 struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_info *cval = kcontrol->private_data;
+	int c, cnt, val, err;
+
+	ucontrol->value.integer.value[0] = cval->min;
+	if (cval->cmask) {
+		cnt = 0;
+		for (c = 0; c < MAX_CHANNELS; c++) {
+			if (!(cval->cmask & (1 << c)))
+				continue;
+			err = snd_usb_get_cur_mix_value(cval, c + 1, cnt, &val);
+			if (err < 0)
+				return filter_error(cval, err);
+			val = get_relative_value(cval, val);
+			ucontrol->value.integer.value[cnt] = val;
+			cnt++;
+		}
+		return 0;
+	} else {
+		/* master channel */
+		err = snd_usb_get_cur_mix_value(cval, 0, 0, &val);
+		if (err < 0)
+			return filter_error(cval, err);
+		val = get_relative_value(cval, val);
+		ucontrol->value.integer.value[0] = val;
+	}
+	return 0;
+}
+
+/* put the current value to feature/mixer unit */
+static int mixer_ctl_feature_put(struct snd_kcontrol *kcontrol,
+				 struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_info *cval = kcontrol->private_data;
+	int c, cnt, val, oval, err;
+	int changed = 0;
+
+	if (cval->cmask) {
+		cnt = 0;
+		for (c = 0; c < MAX_CHANNELS; c++) {
+			if (!(cval->cmask & (1 << c)))
+				continue;
+			err = snd_usb_get_cur_mix_value(cval, c + 1, cnt, &oval);
+			if (err < 0)
+				return filter_error(cval, err);
+			val = ucontrol->value.integer.value[cnt];
+			val = get_abs_value(cval, val);
+			if (oval != val) {
+				snd_usb_set_cur_mix_value(cval, c + 1, cnt, val);
+				changed = 1;
+			}
+			cnt++;
+		}
+	} else {
+		/* master channel */
+		err = snd_usb_get_cur_mix_value(cval, 0, 0, &oval);
+		if (err < 0)
+			return filter_error(cval, err);
+		val = ucontrol->value.integer.value[0];
+		val = get_abs_value(cval, val);
+		if (val != oval) {
+			snd_usb_set_cur_mix_value(cval, 0, 0, val);
+			changed = 1;
+		}
+	}
+	return changed;
+}
+
+/* get the boolean value from the master channel of a UAC control */
+static int mixer_ctl_master_bool_get(struct snd_kcontrol *kcontrol,
+				     struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_info *cval = kcontrol->private_data;
+	int val, err;
+
+	err = snd_usb_get_cur_mix_value(cval, 0, 0, &val);
+	if (err < 0)
+		return filter_error(cval, err);
+	val = (val != 0);
+	ucontrol->value.integer.value[0] = val;
+	return 0;
+}
+
+/* get the connectors status and report it as boolean type */
+static int mixer_ctl_connector_get(struct snd_kcontrol *kcontrol,
+				   struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_info *cval = kcontrol->private_data;
+	struct snd_usb_audio *chip = cval->head.mixer->chip;
+	int idx = 0, validx, ret, val;
+
+	validx = cval->control << 8 | 0;
+
+	ret = snd_usb_lock_shutdown(chip) ? -EIO : 0;
+	if (ret)
+		goto error;
+
+	idx = snd_usb_ctrl_intf(chip) | (cval->head.id << 8);
+	if (cval->head.mixer->protocol == UAC_VERSION_2) {
+		struct uac2_connectors_ctl_blk uac2_conn;
+
+		ret = snd_usb_ctl_msg(chip->dev, usb_rcvctrlpipe(chip->dev, 0), UAC2_CS_CUR,
+				      USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_IN,
+				      validx, idx, &uac2_conn, sizeof(uac2_conn));
+		val = !!uac2_conn.bNrChannels;
+	} else { /* UAC_VERSION_3 */
+		struct uac3_insertion_ctl_blk uac3_conn;
+
+		ret = snd_usb_ctl_msg(chip->dev, usb_rcvctrlpipe(chip->dev, 0), UAC2_CS_CUR,
+				      USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_IN,
+				      validx, idx, &uac3_conn, sizeof(uac3_conn));
+		val = !!uac3_conn.bmConInserted;
+	}
+
+	snd_usb_unlock_shutdown(chip);
+
+	if (ret < 0) {
+error:
+		usb_audio_err(chip,
+			"cannot get connectors status: req = %#x, wValue = %#x, wIndex = %#x, type = %d\n",
+			UAC_GET_CUR, validx, idx, cval->val_type);
+		return filter_error(cval, ret);
+	}
+
+	ucontrol->value.integer.value[0] = val;
+	return 0;
+}
+
+static struct snd_kcontrol_new usb_feature_unit_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.name = "", /* will be filled later manually */
+	.info = mixer_ctl_feature_info,
+	.get = mixer_ctl_feature_get,
+	.put = mixer_ctl_feature_put,
+};
+
+/* the read-only variant */
+static const struct snd_kcontrol_new usb_feature_unit_ctl_ro = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.name = "", /* will be filled later manually */
+	.info = mixer_ctl_feature_info,
+	.get = mixer_ctl_feature_get,
+	.put = NULL,
+};
+
+/*
+ * A control which shows the boolean value from reading a UAC control on
+ * the master channel.
+ */
+static struct snd_kcontrol_new usb_bool_master_control_ctl_ro = {
+	.iface = SNDRV_CTL_ELEM_IFACE_CARD,
+	.name = "", /* will be filled later manually */
+	.access = SNDRV_CTL_ELEM_ACCESS_READ,
+	.info = snd_ctl_boolean_mono_info,
+	.get = mixer_ctl_master_bool_get,
+	.put = NULL,
+};
+
+static const struct snd_kcontrol_new usb_connector_ctl_ro = {
+	.iface = SNDRV_CTL_ELEM_IFACE_CARD,
+	.name = "", /* will be filled later manually */
+	.access = SNDRV_CTL_ELEM_ACCESS_READ,
+	.info = snd_ctl_boolean_mono_info,
+	.get = mixer_ctl_connector_get,
+	.put = NULL,
+};
+
+/*
+ * This symbol is exported in order to allow the mixer quirks to
+ * hook up to the standard feature unit control mechanism
+ */
+struct snd_kcontrol_new *snd_usb_feature_unit_ctl = &usb_feature_unit_ctl;
+
+/*
+ * build a feature control
+ */
+static size_t append_ctl_name(struct snd_kcontrol *kctl, const char *str)
+{
+	return strlcat(kctl->id.name, str, sizeof(kctl->id.name));
+}
+
+/*
+ * A lot of headsets/headphones have a "Speaker" mixer. Make sure we
+ * rename it to "Headphone". We determine if something is a headphone
+ * similar to how udev determines form factor.
+ */
+static void check_no_speaker_on_headset(struct snd_kcontrol *kctl,
+					struct snd_card *card)
+{
+	const char *names_to_check[] = {
+		"Headset", "headset", "Headphone", "headphone", NULL};
+	const char **s;
+	bool found = false;
+
+	if (strcmp("Speaker", kctl->id.name))
+		return;
+
+	for (s = names_to_check; *s; s++)
+		if (strstr(card->shortname, *s)) {
+			found = true;
+			break;
+		}
+
+	if (!found)
+		return;
+
+	strlcpy(kctl->id.name, "Headphone", sizeof(kctl->id.name));
+}
+
+static const struct usb_feature_control_info *get_feature_control_info(int control)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(audio_feature_info); ++i) {
+		if (audio_feature_info[i].control == control)
+			return &audio_feature_info[i];
+	}
+	return NULL;
+}
+
+static void __build_feature_ctl(struct usb_mixer_interface *mixer,
+				const struct usbmix_name_map *imap,
+				unsigned int ctl_mask, int control,
+				struct usb_audio_term *iterm,
+				struct usb_audio_term *oterm,
+				int unitid, int nameid, int readonly_mask)
+{
+	const struct usb_feature_control_info *ctl_info;
+	unsigned int len = 0;
+	int mapped_name = 0;
+	struct snd_kcontrol *kctl;
+	struct usb_mixer_elem_info *cval;
+	const struct usbmix_name_map *map;
+	unsigned int range;
+
+	if (control == UAC_FU_GRAPHIC_EQUALIZER) {
+		/* FIXME: not supported yet */
+		return;
+	}
+
+	map = find_map(imap, unitid, control);
+	if (check_ignored_ctl(map))
+		return;
+
+	cval = kzalloc(sizeof(*cval), GFP_KERNEL);
+	if (!cval)
+		return;
+	snd_usb_mixer_elem_init_std(&cval->head, mixer, unitid);
+	cval->control = control;
+	cval->cmask = ctl_mask;
+
+	ctl_info = get_feature_control_info(control);
+	if (!ctl_info) {
+		usb_mixer_elem_info_free(cval);
+		return;
+	}
+	if (mixer->protocol == UAC_VERSION_1)
+		cval->val_type = ctl_info->type;
+	else /* UAC_VERSION_2 */
+		cval->val_type = ctl_info->type_uac2 >= 0 ?
+			ctl_info->type_uac2 : ctl_info->type;
+
+	if (ctl_mask == 0) {
+		cval->channels = 1;	/* master channel */
+		cval->master_readonly = readonly_mask;
+	} else {
+		int i, c = 0;
+		for (i = 0; i < 16; i++)
+			if (ctl_mask & (1 << i))
+				c++;
+		cval->channels = c;
+		cval->ch_readonly = readonly_mask;
+	}
+
+	/*
+	 * If all channels in the mask are marked read-only, make the control
+	 * read-only. snd_usb_set_cur_mix_value() will check the mask again and won't
+	 * issue write commands to read-only channels.
+	 */
+	if (cval->channels == readonly_mask)
+		kctl = snd_ctl_new1(&usb_feature_unit_ctl_ro, cval);
+	else
+		kctl = snd_ctl_new1(&usb_feature_unit_ctl, cval);
+
+	if (!kctl) {
+		usb_audio_err(mixer->chip, "cannot malloc kcontrol\n");
+		usb_mixer_elem_info_free(cval);
+		return;
+	}
+	kctl->private_free = snd_usb_mixer_elem_free;
+
+	len = check_mapped_name(map, kctl->id.name, sizeof(kctl->id.name));
+	mapped_name = len != 0;
+	if (!len && nameid)
+		len = snd_usb_copy_string_desc(mixer->chip, nameid,
+				kctl->id.name, sizeof(kctl->id.name));
+
+	switch (control) {
+	case UAC_FU_MUTE:
+	case UAC_FU_VOLUME:
+		/*
+		 * determine the control name.  the rule is:
+		 * - if a name id is given in descriptor, use it.
+		 * - if the connected input can be determined, then use the name
+		 *   of terminal type.
+		 * - if the connected output can be determined, use it.
+		 * - otherwise, anonymous name.
+		 */
+		if (!len) {
+			if (iterm)
+				len = get_term_name(mixer->chip, iterm,
+						    kctl->id.name,
+						    sizeof(kctl->id.name), 1);
+			if (!len && oterm)
+				len = get_term_name(mixer->chip, oterm,
+						    kctl->id.name,
+						    sizeof(kctl->id.name), 1);
+			if (!len)
+				snprintf(kctl->id.name, sizeof(kctl->id.name),
+					 "Feature %d", unitid);
+		}
+
+		if (!mapped_name)
+			check_no_speaker_on_headset(kctl, mixer->chip->card);
+
+		/*
+		 * determine the stream direction:
+		 * if the connected output is USB stream, then it's likely a
+		 * capture stream.  otherwise it should be playback (hopefully :)
+		 */
+		if (!mapped_name && oterm && !(oterm->type >> 16)) {
+			if ((oterm->type & 0xff00) == 0x0100)
+				append_ctl_name(kctl, " Capture");
+			else
+				append_ctl_name(kctl, " Playback");
+		}
+		append_ctl_name(kctl, control == UAC_FU_MUTE ?
+				" Switch" : " Volume");
+		break;
+	default:
+		if (!len)
+			strlcpy(kctl->id.name, audio_feature_info[control-1].name,
+				sizeof(kctl->id.name));
+		break;
+	}
+
+	/* get min/max values */
+	get_min_max_with_quirks(cval, 0, kctl);
+
+	/* skip a bogus volume range */
+	if (cval->max <= cval->min) {
+		usb_audio_dbg(mixer->chip,
+			      "[%d] FU [%s] skipped due to invalid volume\n",
+			      cval->head.id, kctl->id.name);
+		snd_ctl_free_one(kctl);
+		return;
+	}
+
+
+	if (control == UAC_FU_VOLUME) {
+		check_mapped_dB(map, cval);
+		if (cval->dBmin < cval->dBmax || !cval->initialized) {
+			kctl->tlv.c = snd_usb_mixer_vol_tlv;
+			kctl->vd[0].access |=
+				SNDRV_CTL_ELEM_ACCESS_TLV_READ |
+				SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK;
+		}
+	}
+
+	snd_usb_mixer_fu_apply_quirk(mixer, cval, unitid, kctl);
+
+	range = (cval->max - cval->min) / cval->res;
+	/*
+	 * Are there devices with volume range more than 255? I use a bit more
+	 * to be sure. 384 is a resolution magic number found on Logitech
+	 * devices. It will definitively catch all buggy Logitech devices.
+	 */
+	if (range > 384) {
+		usb_audio_warn(mixer->chip,
+			       "Warning! Unlikely big volume range (=%u), cval->res is probably wrong.",
+			       range);
+		usb_audio_warn(mixer->chip,
+			       "[%d] FU [%s] ch = %d, val = %d/%d/%d",
+			       cval->head.id, kctl->id.name, cval->channels,
+			       cval->min, cval->max, cval->res);
+	}
+
+	usb_audio_dbg(mixer->chip, "[%d] FU [%s] ch = %d, val = %d/%d/%d\n",
+		      cval->head.id, kctl->id.name, cval->channels,
+		      cval->min, cval->max, cval->res);
+	snd_usb_mixer_add_control(&cval->head, kctl);
+}
+
+static void build_feature_ctl(struct mixer_build *state, void *raw_desc,
+			      unsigned int ctl_mask, int control,
+			      struct usb_audio_term *iterm, int unitid,
+			      int readonly_mask)
+{
+	struct uac_feature_unit_descriptor *desc = raw_desc;
+	int nameid = uac_feature_unit_iFeature(desc);
+
+	__build_feature_ctl(state->mixer, state->map, ctl_mask, control,
+			iterm, &state->oterm, unitid, nameid, readonly_mask);
+}
+
+static void build_feature_ctl_badd(struct usb_mixer_interface *mixer,
+			      unsigned int ctl_mask, int control, int unitid,
+			      const struct usbmix_name_map *badd_map)
+{
+	__build_feature_ctl(mixer, badd_map, ctl_mask, control,
+			NULL, NULL, unitid, 0, 0);
+}
+
+static void get_connector_control_name(struct usb_mixer_interface *mixer,
+				       struct usb_audio_term *term,
+				       bool is_input, char *name, int name_size)
+{
+	int name_len = get_term_name(mixer->chip, term, name, name_size, 0);
+
+	if (name_len == 0)
+		strlcpy(name, "Unknown", name_size);
+
+	/*
+	 *  sound/core/ctljack.c has a convention of naming jack controls
+	 * by ending in " Jack".  Make it slightly more useful by
+	 * indicating Input or Output after the terminal name.
+	 */
+	if (is_input)
+		strlcat(name, " - Input Jack", name_size);
+	else
+		strlcat(name, " - Output Jack", name_size);
+}
+
+/* Build a mixer control for a UAC connector control (jack-detect) */
+static void build_connector_control(struct usb_mixer_interface *mixer,
+				    const struct usbmix_name_map *imap,
+				    struct usb_audio_term *term, bool is_input)
+{
+	struct snd_kcontrol *kctl;
+	struct usb_mixer_elem_info *cval;
+	const struct usbmix_name_map *map;
+
+	map = find_map(imap, term->id, 0);
+	if (check_ignored_ctl(map))
+		return;
+
+	cval = kzalloc(sizeof(*cval), GFP_KERNEL);
+	if (!cval)
+		return;
+	snd_usb_mixer_elem_init_std(&cval->head, mixer, term->id);
+	/*
+	 * UAC2: The first byte from reading the UAC2_TE_CONNECTOR control returns the
+	 * number of channels connected.
+	 *
+	 * UAC3: The first byte specifies size of bitmap for the inserted controls. The
+	 * following byte(s) specifies which connectors are inserted.
+	 *
+	 * This boolean ctl will simply report if any channels are connected
+	 * or not.
+	 */
+	if (mixer->protocol == UAC_VERSION_2)
+		cval->control = UAC2_TE_CONNECTOR;
+	else /* UAC_VERSION_3 */
+		cval->control = UAC3_TE_INSERTION;
+
+	cval->val_type = USB_MIXER_BOOLEAN;
+	cval->channels = 1; /* report true if any channel is connected */
+	cval->min = 0;
+	cval->max = 1;
+	kctl = snd_ctl_new1(&usb_connector_ctl_ro, cval);
+	if (!kctl) {
+		usb_audio_err(mixer->chip, "cannot malloc kcontrol\n");
+		usb_mixer_elem_info_free(cval);
+		return;
+	}
+
+	if (check_mapped_name(map, kctl->id.name, sizeof(kctl->id.name)))
+		strlcat(kctl->id.name, " Jack", sizeof(kctl->id.name));
+	else
+		get_connector_control_name(mixer, term, is_input, kctl->id.name,
+					   sizeof(kctl->id.name));
+	kctl->private_free = snd_usb_mixer_elem_free;
+	snd_usb_mixer_add_control(&cval->head, kctl);
+}
+
+static int parse_clock_source_unit(struct mixer_build *state, int unitid,
+				   void *_ftr)
+{
+	struct uac_clock_source_descriptor *hdr = _ftr;
+	struct usb_mixer_elem_info *cval;
+	struct snd_kcontrol *kctl;
+	char name[SNDRV_CTL_ELEM_ID_NAME_MAXLEN];
+	int ret;
+
+	if (state->mixer->protocol != UAC_VERSION_2)
+		return -EINVAL;
+
+	/*
+	 * The only property of this unit we are interested in is the
+	 * clock source validity. If that isn't readable, just bail out.
+	 */
+	if (!uac_v2v3_control_is_readable(hdr->bmControls,
+				      UAC2_CS_CONTROL_CLOCK_VALID))
+		return 0;
+
+	cval = kzalloc(sizeof(*cval), GFP_KERNEL);
+	if (!cval)
+		return -ENOMEM;
+
+	snd_usb_mixer_elem_init_std(&cval->head, state->mixer, hdr->bClockID);
+
+	cval->min = 0;
+	cval->max = 1;
+	cval->channels = 1;
+	cval->val_type = USB_MIXER_BOOLEAN;
+	cval->control = UAC2_CS_CONTROL_CLOCK_VALID;
+
+	cval->master_readonly = 1;
+	/* From UAC2 5.2.5.1.2 "Only the get request is supported." */
+	kctl = snd_ctl_new1(&usb_bool_master_control_ctl_ro, cval);
+
+	if (!kctl) {
+		usb_mixer_elem_info_free(cval);
+		return -ENOMEM;
+	}
+
+	kctl->private_free = snd_usb_mixer_elem_free;
+	ret = snd_usb_copy_string_desc(state->chip, hdr->iClockSource,
+				       name, sizeof(name));
+	if (ret > 0)
+		snprintf(kctl->id.name, sizeof(kctl->id.name),
+			 "%s Validity", name);
+	else
+		snprintf(kctl->id.name, sizeof(kctl->id.name),
+			 "Clock Source %d Validity", hdr->bClockID);
+
+	return snd_usb_mixer_add_control(&cval->head, kctl);
+}
+
+/*
+ * parse a feature unit
+ *
+ * most of controls are defined here.
+ */
+static int parse_audio_feature_unit(struct mixer_build *state, int unitid,
+				    void *_ftr)
+{
+	int channels, i, j;
+	struct usb_audio_term iterm;
+	unsigned int master_bits, first_ch_bits;
+	int err, csize;
+	struct uac_feature_unit_descriptor *hdr = _ftr;
+	__u8 *bmaControls;
+
+	if (state->mixer->protocol == UAC_VERSION_1) {
+		csize = hdr->bControlSize;
+		channels = (hdr->bLength - 7) / csize - 1;
+		bmaControls = hdr->bmaControls;
+	} else if (state->mixer->protocol == UAC_VERSION_2) {
+		struct uac2_feature_unit_descriptor *ftr = _ftr;
+		csize = 4;
+		channels = (hdr->bLength - 6) / 4 - 1;
+		bmaControls = ftr->bmaControls;
+	} else { /* UAC_VERSION_3 */
+		struct uac3_feature_unit_descriptor *ftr = _ftr;
+
+		csize = 4;
+		channels = (ftr->bLength - 7) / 4 - 1;
+		bmaControls = ftr->bmaControls;
+	}
+
+	/* parse the source unit */
+	err = parse_audio_unit(state, hdr->bSourceID);
+	if (err < 0)
+		return err;
+
+	/* determine the input source type and name */
+	err = check_input_term(state, hdr->bSourceID, &iterm);
+	if (err < 0)
+		return err;
+
+	master_bits = snd_usb_combine_bytes(bmaControls, csize);
+	/* master configuration quirks */
+	switch (state->chip->usb_id) {
+	case USB_ID(0x08bb, 0x2702):
+		usb_audio_info(state->chip,
+			       "usbmixer: master volume quirk for PCM2702 chip\n");
+		/* disable non-functional volume control */
+		master_bits &= ~UAC_CONTROL_BIT(UAC_FU_VOLUME);
+		break;
+	case USB_ID(0x1130, 0xf211):
+		usb_audio_info(state->chip,
+			       "usbmixer: volume control quirk for Tenx TP6911 Audio Headset\n");
+		/* disable non-functional volume control */
+		channels = 0;
+		break;
+
+	}
+	if (channels > 0)
+		first_ch_bits = snd_usb_combine_bytes(bmaControls + csize, csize);
+	else
+		first_ch_bits = 0;
+
+	if (state->mixer->protocol == UAC_VERSION_1) {
+		/* check all control types */
+		for (i = 0; i < 10; i++) {
+			unsigned int ch_bits = 0;
+			int control = audio_feature_info[i].control;
+
+			for (j = 0; j < channels; j++) {
+				unsigned int mask;
+
+				mask = snd_usb_combine_bytes(bmaControls +
+							     csize * (j+1), csize);
+				if (mask & (1 << i))
+					ch_bits |= (1 << j);
+			}
+			/* audio class v1 controls are never read-only */
+
+			/*
+			 * The first channel must be set
+			 * (for ease of programming).
+			 */
+			if (ch_bits & 1)
+				build_feature_ctl(state, _ftr, ch_bits, control,
+						  &iterm, unitid, 0);
+			if (master_bits & (1 << i))
+				build_feature_ctl(state, _ftr, 0, control,
+						  &iterm, unitid, 0);
+		}
+	} else { /* UAC_VERSION_2/3 */
+		for (i = 0; i < ARRAY_SIZE(audio_feature_info); i++) {
+			unsigned int ch_bits = 0;
+			unsigned int ch_read_only = 0;
+			int control = audio_feature_info[i].control;
+
+			for (j = 0; j < channels; j++) {
+				unsigned int mask;
+
+				mask = snd_usb_combine_bytes(bmaControls +
+							     csize * (j+1), csize);
+				if (uac_v2v3_control_is_readable(mask, control)) {
+					ch_bits |= (1 << j);
+					if (!uac_v2v3_control_is_writeable(mask, control))
+						ch_read_only |= (1 << j);
+				}
+			}
+
+			/*
+			 * NOTE: build_feature_ctl() will mark the control
+			 * read-only if all channels are marked read-only in
+			 * the descriptors. Otherwise, the control will be
+			 * reported as writeable, but the driver will not
+			 * actually issue a write command for read-only
+			 * channels.
+			 */
+
+			/*
+			 * The first channel must be set
+			 * (for ease of programming).
+			 */
+			if (ch_bits & 1)
+				build_feature_ctl(state, _ftr, ch_bits, control,
+						  &iterm, unitid, ch_read_only);
+			if (uac_v2v3_control_is_readable(master_bits, control))
+				build_feature_ctl(state, _ftr, 0, control,
+						  &iterm, unitid,
+						  !uac_v2v3_control_is_writeable(master_bits,
+										 control));
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * Mixer Unit
+ */
+
+/* check whether the given in/out overflows bmMixerControls matrix */
+static bool mixer_bitmap_overflow(struct uac_mixer_unit_descriptor *desc,
+				  int protocol, int num_ins, int num_outs)
+{
+	u8 *hdr = (u8 *)desc;
+	u8 *c = uac_mixer_unit_bmControls(desc, protocol);
+	size_t rest; /* remaining bytes after bmMixerControls */
+
+	switch (protocol) {
+	case UAC_VERSION_1:
+	default:
+		rest = 1; /* iMixer */
+		break;
+	case UAC_VERSION_2:
+		rest = 2; /* bmControls + iMixer */
+		break;
+	case UAC_VERSION_3:
+		rest = 6; /* bmControls + wMixerDescrStr */
+		break;
+	}
+
+	/* overflow? */
+	return c + (num_ins * num_outs + 7) / 8 + rest > hdr + hdr[0];
+}
+
+/*
+ * build a mixer unit control
+ *
+ * the callbacks are identical with feature unit.
+ * input channel number (zero based) is given in control field instead.
+ */
+static void build_mixer_unit_ctl(struct mixer_build *state,
+				 struct uac_mixer_unit_descriptor *desc,
+				 int in_pin, int in_ch, int num_outs,
+				 int unitid, struct usb_audio_term *iterm)
+{
+	struct usb_mixer_elem_info *cval;
+	unsigned int i, len;
+	struct snd_kcontrol *kctl;
+	const struct usbmix_name_map *map;
+
+	map = find_map(state->map, unitid, 0);
+	if (check_ignored_ctl(map))
+		return;
+
+	cval = kzalloc(sizeof(*cval), GFP_KERNEL);
+	if (!cval)
+		return;
+
+	snd_usb_mixer_elem_init_std(&cval->head, state->mixer, unitid);
+	cval->control = in_ch + 1; /* based on 1 */
+	cval->val_type = USB_MIXER_S16;
+	for (i = 0; i < num_outs; i++) {
+		__u8 *c = uac_mixer_unit_bmControls(desc, state->mixer->protocol);
+
+		if (check_matrix_bitmap(c, in_ch, i, num_outs)) {
+			cval->cmask |= (1 << i);
+			cval->channels++;
+		}
+	}
+
+	/* get min/max values */
+	get_min_max(cval, 0);
+
+	kctl = snd_ctl_new1(&usb_feature_unit_ctl, cval);
+	if (!kctl) {
+		usb_audio_err(state->chip, "cannot malloc kcontrol\n");
+		usb_mixer_elem_info_free(cval);
+		return;
+	}
+	kctl->private_free = snd_usb_mixer_elem_free;
+
+	len = check_mapped_name(map, kctl->id.name, sizeof(kctl->id.name));
+	if (!len)
+		len = get_term_name(state->chip, iterm, kctl->id.name,
+				    sizeof(kctl->id.name), 0);
+	if (!len)
+		len = sprintf(kctl->id.name, "Mixer Source %d", in_ch + 1);
+	append_ctl_name(kctl, " Volume");
+
+	usb_audio_dbg(state->chip, "[%d] MU [%s] ch = %d, val = %d/%d\n",
+		    cval->head.id, kctl->id.name, cval->channels, cval->min, cval->max);
+	snd_usb_mixer_add_control(&cval->head, kctl);
+}
+
+static int parse_audio_input_terminal(struct mixer_build *state, int unitid,
+				      void *raw_desc)
+{
+	struct usb_audio_term iterm;
+	unsigned int control, bmctls, term_id;
+
+	if (state->mixer->protocol == UAC_VERSION_2) {
+		struct uac2_input_terminal_descriptor *d_v2 = raw_desc;
+		control = UAC2_TE_CONNECTOR;
+		term_id = d_v2->bTerminalID;
+		bmctls = le16_to_cpu(d_v2->bmControls);
+	} else if (state->mixer->protocol == UAC_VERSION_3) {
+		struct uac3_input_terminal_descriptor *d_v3 = raw_desc;
+		control = UAC3_TE_INSERTION;
+		term_id = d_v3->bTerminalID;
+		bmctls = le32_to_cpu(d_v3->bmControls);
+	} else {
+		return 0; /* UAC1. No Insertion control */
+	}
+
+	check_input_term(state, term_id, &iterm);
+
+	/* Check for jack detection. */
+	if ((iterm.type & 0xff00) != 0x0100 &&
+	    uac_v2v3_control_is_readable(bmctls, control))
+		build_connector_control(state->mixer, state->map, &iterm, true);
+
+	return 0;
+}
+
+/*
+ * parse a mixer unit
+ */
+static int parse_audio_mixer_unit(struct mixer_build *state, int unitid,
+				  void *raw_desc)
+{
+	struct uac_mixer_unit_descriptor *desc = raw_desc;
+	struct usb_audio_term iterm;
+	int input_pins, num_ins, num_outs;
+	int pin, ich, err;
+
+	err = uac_mixer_unit_get_channels(state, desc);
+	if (err < 0) {
+		usb_audio_err(state->chip,
+			      "invalid MIXER UNIT descriptor %d\n",
+			      unitid);
+		return err;
+	}
+
+	num_outs = err;
+	input_pins = desc->bNrInPins;
+
+	num_ins = 0;
+	ich = 0;
+	for (pin = 0; pin < input_pins; pin++) {
+		err = parse_audio_unit(state, desc->baSourceID[pin]);
+		if (err < 0)
+			continue;
+		/* no bmControls field (e.g. Maya44) -> ignore */
+		if (!num_outs)
+			continue;
+		err = check_input_term(state, desc->baSourceID[pin], &iterm);
+		if (err < 0)
+			return err;
+		num_ins += iterm.channels;
+		if (mixer_bitmap_overflow(desc, state->mixer->protocol,
+					  num_ins, num_outs))
+			break;
+		for (; ich < num_ins; ich++) {
+			int och, ich_has_controls = 0;
+
+			for (och = 0; och < num_outs; och++) {
+				__u8 *c = uac_mixer_unit_bmControls(desc,
+						state->mixer->protocol);
+
+				if (check_matrix_bitmap(c, ich, och, num_outs)) {
+					ich_has_controls = 1;
+					break;
+				}
+			}
+			if (ich_has_controls)
+				build_mixer_unit_ctl(state, desc, pin, ich, num_outs,
+						     unitid, &iterm);
+		}
+	}
+	return 0;
+}
+
+/*
+ * Processing Unit / Extension Unit
+ */
+
+/* get callback for processing/extension unit */
+static int mixer_ctl_procunit_get(struct snd_kcontrol *kcontrol,
+				  struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_info *cval = kcontrol->private_data;
+	int err, val;
+
+	err = get_cur_ctl_value(cval, cval->control << 8, &val);
+	if (err < 0) {
+		ucontrol->value.integer.value[0] = cval->min;
+		return filter_error(cval, err);
+	}
+	val = get_relative_value(cval, val);
+	ucontrol->value.integer.value[0] = val;
+	return 0;
+}
+
+/* put callback for processing/extension unit */
+static int mixer_ctl_procunit_put(struct snd_kcontrol *kcontrol,
+				  struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_info *cval = kcontrol->private_data;
+	int val, oval, err;
+
+	err = get_cur_ctl_value(cval, cval->control << 8, &oval);
+	if (err < 0)
+		return filter_error(cval, err);
+	val = ucontrol->value.integer.value[0];
+	val = get_abs_value(cval, val);
+	if (val != oval) {
+		set_cur_ctl_value(cval, cval->control << 8, val);
+		return 1;
+	}
+	return 0;
+}
+
+/* alsa control interface for processing/extension unit */
+static const struct snd_kcontrol_new mixer_procunit_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.name = "", /* will be filled later */
+	.info = mixer_ctl_feature_info,
+	.get = mixer_ctl_procunit_get,
+	.put = mixer_ctl_procunit_put,
+};
+
+/*
+ * predefined data for processing units
+ */
+struct procunit_value_info {
+	int control;
+	const char *suffix;
+	int val_type;
+	int min_value;
+};
+
+struct procunit_info {
+	int type;
+	char *name;
+	const struct procunit_value_info *values;
+};
+
+static const struct procunit_value_info undefined_proc_info[] = {
+	{ 0x00, "Control Undefined", 0 },
+	{ 0 }
+};
+
+static const struct procunit_value_info updown_proc_info[] = {
+	{ UAC_UD_ENABLE, "Switch", USB_MIXER_BOOLEAN },
+	{ UAC_UD_MODE_SELECT, "Mode Select", USB_MIXER_U8, 1 },
+	{ 0 }
+};
+static const struct procunit_value_info prologic_proc_info[] = {
+	{ UAC_DP_ENABLE, "Switch", USB_MIXER_BOOLEAN },
+	{ UAC_DP_MODE_SELECT, "Mode Select", USB_MIXER_U8, 1 },
+	{ 0 }
+};
+static const struct procunit_value_info threed_enh_proc_info[] = {
+	{ UAC_3D_ENABLE, "Switch", USB_MIXER_BOOLEAN },
+	{ UAC_3D_SPACE, "Spaciousness", USB_MIXER_U8 },
+	{ 0 }
+};
+static const struct procunit_value_info reverb_proc_info[] = {
+	{ UAC_REVERB_ENABLE, "Switch", USB_MIXER_BOOLEAN },
+	{ UAC_REVERB_LEVEL, "Level", USB_MIXER_U8 },
+	{ UAC_REVERB_TIME, "Time", USB_MIXER_U16 },
+	{ UAC_REVERB_FEEDBACK, "Feedback", USB_MIXER_U8 },
+	{ 0 }
+};
+static const struct procunit_value_info chorus_proc_info[] = {
+	{ UAC_CHORUS_ENABLE, "Switch", USB_MIXER_BOOLEAN },
+	{ UAC_CHORUS_LEVEL, "Level", USB_MIXER_U8 },
+	{ UAC_CHORUS_RATE, "Rate", USB_MIXER_U16 },
+	{ UAC_CHORUS_DEPTH, "Depth", USB_MIXER_U16 },
+	{ 0 }
+};
+static const struct procunit_value_info dcr_proc_info[] = {
+	{ UAC_DCR_ENABLE, "Switch", USB_MIXER_BOOLEAN },
+	{ UAC_DCR_RATE, "Ratio", USB_MIXER_U16 },
+	{ UAC_DCR_MAXAMPL, "Max Amp", USB_MIXER_S16 },
+	{ UAC_DCR_THRESHOLD, "Threshold", USB_MIXER_S16 },
+	{ UAC_DCR_ATTACK_TIME, "Attack Time", USB_MIXER_U16 },
+	{ UAC_DCR_RELEASE_TIME, "Release Time", USB_MIXER_U16 },
+	{ 0 }
+};
+
+static const struct procunit_info procunits[] = {
+	{ UAC_PROCESS_UP_DOWNMIX, "Up Down", updown_proc_info },
+	{ UAC_PROCESS_DOLBY_PROLOGIC, "Dolby Prologic", prologic_proc_info },
+	{ UAC_PROCESS_STEREO_EXTENDER, "3D Stereo Extender", threed_enh_proc_info },
+	{ UAC_PROCESS_REVERB, "Reverb", reverb_proc_info },
+	{ UAC_PROCESS_CHORUS, "Chorus", chorus_proc_info },
+	{ UAC_PROCESS_DYN_RANGE_COMP, "DCR", dcr_proc_info },
+	{ 0 },
+};
+
+static const struct procunit_value_info uac3_updown_proc_info[] = {
+	{ UAC3_UD_MODE_SELECT, "Mode Select", USB_MIXER_U8, 1 },
+	{ 0 }
+};
+static const struct procunit_value_info uac3_stereo_ext_proc_info[] = {
+	{ UAC3_EXT_WIDTH_CONTROL, "Width Control", USB_MIXER_U8 },
+	{ 0 }
+};
+
+static const struct procunit_info uac3_procunits[] = {
+	{ UAC3_PROCESS_UP_DOWNMIX, "Up Down", uac3_updown_proc_info },
+	{ UAC3_PROCESS_STEREO_EXTENDER, "3D Stereo Extender", uac3_stereo_ext_proc_info },
+	{ UAC3_PROCESS_MULTI_FUNCTION, "Multi-Function", undefined_proc_info },
+	{ 0 },
+};
+
+/*
+ * predefined data for extension units
+ */
+static const struct procunit_value_info clock_rate_xu_info[] = {
+	{ USB_XU_CLOCK_RATE_SELECTOR, "Selector", USB_MIXER_U8, 0 },
+	{ 0 }
+};
+static const struct procunit_value_info clock_source_xu_info[] = {
+	{ USB_XU_CLOCK_SOURCE_SELECTOR, "External", USB_MIXER_BOOLEAN },
+	{ 0 }
+};
+static const struct procunit_value_info spdif_format_xu_info[] = {
+	{ USB_XU_DIGITAL_FORMAT_SELECTOR, "SPDIF/AC3", USB_MIXER_BOOLEAN },
+	{ 0 }
+};
+static const struct procunit_value_info soft_limit_xu_info[] = {
+	{ USB_XU_SOFT_LIMIT_SELECTOR, " ", USB_MIXER_BOOLEAN },
+	{ 0 }
+};
+static const struct procunit_info extunits[] = {
+	{ USB_XU_CLOCK_RATE, "Clock rate", clock_rate_xu_info },
+	{ USB_XU_CLOCK_SOURCE, "DigitalIn CLK source", clock_source_xu_info },
+	{ USB_XU_DIGITAL_IO_STATUS, "DigitalOut format:", spdif_format_xu_info },
+	{ USB_XU_DEVICE_OPTIONS, "AnalogueIn Soft Limit", soft_limit_xu_info },
+	{ 0 }
+};
+
+/*
+ * build a processing/extension unit
+ */
+static int build_audio_procunit(struct mixer_build *state, int unitid,
+				void *raw_desc, const struct procunit_info *list,
+				bool extension_unit)
+{
+	struct uac_processing_unit_descriptor *desc = raw_desc;
+	int num_ins;
+	struct usb_mixer_elem_info *cval;
+	struct snd_kcontrol *kctl;
+	int i, err, nameid, type, len;
+	const struct procunit_info *info;
+	const struct procunit_value_info *valinfo;
+	const struct usbmix_name_map *map;
+	static const struct procunit_value_info default_value_info[] = {
+		{ 0x01, "Switch", USB_MIXER_BOOLEAN },
+		{ 0 }
+	};
+	static const struct procunit_info default_info = {
+		0, NULL, default_value_info
+	};
+	const char *name = extension_unit ?
+		"Extension Unit" : "Processing Unit";
+
+	num_ins = desc->bNrInPins;
+	for (i = 0; i < num_ins; i++) {
+		err = parse_audio_unit(state, desc->baSourceID[i]);
+		if (err < 0)
+			return err;
+	}
+
+	type = le16_to_cpu(desc->wProcessType);
+	for (info = list; info && info->type; info++)
+		if (info->type == type)
+			break;
+	if (!info || !info->type)
+		info = &default_info;
+
+	for (valinfo = info->values; valinfo->control; valinfo++) {
+		__u8 *controls = uac_processing_unit_bmControls(desc, state->mixer->protocol);
+
+		if (state->mixer->protocol == UAC_VERSION_1) {
+			if (!(controls[valinfo->control / 8] &
+					(1 << ((valinfo->control % 8) - 1))))
+				continue;
+		} else { /* UAC_VERSION_2/3 */
+			if (!uac_v2v3_control_is_readable(controls[valinfo->control / 8],
+							  valinfo->control))
+				continue;
+		}
+
+		map = find_map(state->map, unitid, valinfo->control);
+		if (check_ignored_ctl(map))
+			continue;
+		cval = kzalloc(sizeof(*cval), GFP_KERNEL);
+		if (!cval)
+			return -ENOMEM;
+		snd_usb_mixer_elem_init_std(&cval->head, state->mixer, unitid);
+		cval->control = valinfo->control;
+		cval->val_type = valinfo->val_type;
+		cval->channels = 1;
+
+		if (state->mixer->protocol > UAC_VERSION_1 &&
+		    !uac_v2v3_control_is_writeable(controls[valinfo->control / 8],
+						   valinfo->control))
+			cval->master_readonly = 1;
+
+		/* get min/max values */
+		switch (type) {
+		case UAC_PROCESS_UP_DOWNMIX: {
+			bool mode_sel = false;
+
+			switch (state->mixer->protocol) {
+			case UAC_VERSION_1:
+			case UAC_VERSION_2:
+			default:
+				if (cval->control == UAC_UD_MODE_SELECT)
+					mode_sel = true;
+				break;
+			case UAC_VERSION_3:
+				if (cval->control == UAC3_UD_MODE_SELECT)
+					mode_sel = true;
+				break;
+			}
+
+			if (mode_sel) {
+				__u8 *control_spec = uac_processing_unit_specific(desc,
+								state->mixer->protocol);
+				cval->min = 1;
+				cval->max = control_spec[0];
+				cval->res = 1;
+				cval->initialized = 1;
+				break;
+			}
+
+			get_min_max(cval, valinfo->min_value);
+			break;
+		}
+		case USB_XU_CLOCK_RATE:
+			/*
+			 * E-Mu USB 0404/0202/TrackerPre/0204
+			 * samplerate control quirk
+			 */
+			cval->min = 0;
+			cval->max = 5;
+			cval->res = 1;
+			cval->initialized = 1;
+			break;
+		default:
+			get_min_max(cval, valinfo->min_value);
+			break;
+		}
+
+		kctl = snd_ctl_new1(&mixer_procunit_ctl, cval);
+		if (!kctl) {
+			usb_mixer_elem_info_free(cval);
+			return -ENOMEM;
+		}
+		kctl->private_free = snd_usb_mixer_elem_free;
+
+		if (check_mapped_name(map, kctl->id.name, sizeof(kctl->id.name))) {
+			/* nothing */ ;
+		} else if (info->name) {
+			strlcpy(kctl->id.name, info->name, sizeof(kctl->id.name));
+		} else {
+			if (extension_unit)
+				nameid = uac_extension_unit_iExtension(desc, state->mixer->protocol);
+			else
+				nameid = uac_processing_unit_iProcessing(desc, state->mixer->protocol);
+			len = 0;
+			if (nameid)
+				len = snd_usb_copy_string_desc(state->chip,
+							       nameid,
+							       kctl->id.name,
+							       sizeof(kctl->id.name));
+			if (!len)
+				strlcpy(kctl->id.name, name, sizeof(kctl->id.name));
+		}
+		append_ctl_name(kctl, " ");
+		append_ctl_name(kctl, valinfo->suffix);
+
+		usb_audio_dbg(state->chip,
+			      "[%d] PU [%s] ch = %d, val = %d/%d\n",
+			      cval->head.id, kctl->id.name, cval->channels,
+			      cval->min, cval->max);
+
+		err = snd_usb_mixer_add_control(&cval->head, kctl);
+		if (err < 0)
+			return err;
+	}
+	return 0;
+}
+
+static int parse_audio_processing_unit(struct mixer_build *state, int unitid,
+				       void *raw_desc)
+{
+	switch (state->mixer->protocol) {
+	case UAC_VERSION_1:
+	case UAC_VERSION_2:
+	default:
+		return build_audio_procunit(state, unitid, raw_desc,
+					    procunits, false);
+	case UAC_VERSION_3:
+		return build_audio_procunit(state, unitid, raw_desc,
+					    uac3_procunits, false);
+	}
+}
+
+static int parse_audio_extension_unit(struct mixer_build *state, int unitid,
+				      void *raw_desc)
+{
+	/*
+	 * Note that we parse extension units with processing unit descriptors.
+	 * That's ok as the layout is the same.
+	 */
+	return build_audio_procunit(state, unitid, raw_desc, extunits, true);
+}
+
+/*
+ * Selector Unit
+ */
+
+/*
+ * info callback for selector unit
+ * use an enumerator type for routing
+ */
+static int mixer_ctl_selector_info(struct snd_kcontrol *kcontrol,
+				   struct snd_ctl_elem_info *uinfo)
+{
+	struct usb_mixer_elem_info *cval = kcontrol->private_data;
+	const char **itemlist = (const char **)kcontrol->private_value;
+
+	if (snd_BUG_ON(!itemlist))
+		return -EINVAL;
+	return snd_ctl_enum_info(uinfo, 1, cval->max, itemlist);
+}
+
+/* get callback for selector unit */
+static int mixer_ctl_selector_get(struct snd_kcontrol *kcontrol,
+				  struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_info *cval = kcontrol->private_data;
+	int val, err;
+
+	err = get_cur_ctl_value(cval, cval->control << 8, &val);
+	if (err < 0) {
+		ucontrol->value.enumerated.item[0] = 0;
+		return filter_error(cval, err);
+	}
+	val = get_relative_value(cval, val);
+	ucontrol->value.enumerated.item[0] = val;
+	return 0;
+}
+
+/* put callback for selector unit */
+static int mixer_ctl_selector_put(struct snd_kcontrol *kcontrol,
+				  struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_elem_info *cval = kcontrol->private_data;
+	int val, oval, err;
+
+	err = get_cur_ctl_value(cval, cval->control << 8, &oval);
+	if (err < 0)
+		return filter_error(cval, err);
+	val = ucontrol->value.enumerated.item[0];
+	val = get_abs_value(cval, val);
+	if (val != oval) {
+		set_cur_ctl_value(cval, cval->control << 8, val);
+		return 1;
+	}
+	return 0;
+}
+
+/* alsa control interface for selector unit */
+static const struct snd_kcontrol_new mixer_selectunit_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+	.name = "", /* will be filled later */
+	.info = mixer_ctl_selector_info,
+	.get = mixer_ctl_selector_get,
+	.put = mixer_ctl_selector_put,
+};
+
+/*
+ * private free callback.
+ * free both private_data and private_value
+ */
+static void usb_mixer_selector_elem_free(struct snd_kcontrol *kctl)
+{
+	int i, num_ins = 0;
+
+	if (kctl->private_data) {
+		struct usb_mixer_elem_info *cval = kctl->private_data;
+		num_ins = cval->max;
+		usb_mixer_elem_info_free(cval);
+		kctl->private_data = NULL;
+	}
+	if (kctl->private_value) {
+		char **itemlist = (char **)kctl->private_value;
+		for (i = 0; i < num_ins; i++)
+			kfree(itemlist[i]);
+		kfree(itemlist);
+		kctl->private_value = 0;
+	}
+}
+
+/*
+ * parse a selector unit
+ */
+static int parse_audio_selector_unit(struct mixer_build *state, int unitid,
+				     void *raw_desc)
+{
+	struct uac_selector_unit_descriptor *desc = raw_desc;
+	unsigned int i, nameid, len;
+	int err;
+	struct usb_mixer_elem_info *cval;
+	struct snd_kcontrol *kctl;
+	const struct usbmix_name_map *map;
+	char **namelist;
+
+	for (i = 0; i < desc->bNrInPins; i++) {
+		err = parse_audio_unit(state, desc->baSourceID[i]);
+		if (err < 0)
+			return err;
+	}
+
+	if (desc->bNrInPins == 1) /* only one ? nonsense! */
+		return 0;
+
+	map = find_map(state->map, unitid, 0);
+	if (check_ignored_ctl(map))
+		return 0;
+
+	cval = kzalloc(sizeof(*cval), GFP_KERNEL);
+	if (!cval)
+		return -ENOMEM;
+	snd_usb_mixer_elem_init_std(&cval->head, state->mixer, unitid);
+	cval->val_type = USB_MIXER_U8;
+	cval->channels = 1;
+	cval->min = 1;
+	cval->max = desc->bNrInPins;
+	cval->res = 1;
+	cval->initialized = 1;
+
+	switch (state->mixer->protocol) {
+	case UAC_VERSION_1:
+	default:
+		cval->control = 0;
+		break;
+	case UAC_VERSION_2:
+	case UAC_VERSION_3:
+		if (desc->bDescriptorSubtype == UAC2_CLOCK_SELECTOR ||
+		    desc->bDescriptorSubtype == UAC3_CLOCK_SELECTOR)
+			cval->control = UAC2_CX_CLOCK_SELECTOR;
+		else /* UAC2/3_SELECTOR_UNIT */
+			cval->control = UAC2_SU_SELECTOR;
+		break;
+	}
+
+	namelist = kcalloc(desc->bNrInPins, sizeof(char *), GFP_KERNEL);
+	if (!namelist) {
+		err = -ENOMEM;
+		goto error_cval;
+	}
+#define MAX_ITEM_NAME_LEN	64
+	for (i = 0; i < desc->bNrInPins; i++) {
+		struct usb_audio_term iterm;
+		len = 0;
+		namelist[i] = kmalloc(MAX_ITEM_NAME_LEN, GFP_KERNEL);
+		if (!namelist[i]) {
+			err = -ENOMEM;
+			goto error_name;
+		}
+		len = check_mapped_selector_name(state, unitid, i, namelist[i],
+						 MAX_ITEM_NAME_LEN);
+		if (! len && check_input_term(state, desc->baSourceID[i], &iterm) >= 0)
+			len = get_term_name(state->chip, &iterm, namelist[i],
+					    MAX_ITEM_NAME_LEN, 0);
+		if (! len)
+			sprintf(namelist[i], "Input %u", i);
+	}
+
+	kctl = snd_ctl_new1(&mixer_selectunit_ctl, cval);
+	if (! kctl) {
+		usb_audio_err(state->chip, "cannot malloc kcontrol\n");
+		err = -ENOMEM;
+		goto error_name;
+	}
+	kctl->private_value = (unsigned long)namelist;
+	kctl->private_free = usb_mixer_selector_elem_free;
+
+	/* check the static mapping table at first */
+	len = check_mapped_name(map, kctl->id.name, sizeof(kctl->id.name));
+	if (!len) {
+		/* no mapping ? */
+		switch (state->mixer->protocol) {
+		case UAC_VERSION_1:
+		case UAC_VERSION_2:
+		default:
+		/* if iSelector is given, use it */
+			nameid = uac_selector_unit_iSelector(desc);
+			if (nameid)
+				len = snd_usb_copy_string_desc(state->chip,
+							nameid, kctl->id.name,
+							sizeof(kctl->id.name));
+			break;
+		case UAC_VERSION_3:
+			/* TODO: Class-Specific strings not yet supported */
+			break;
+		}
+
+		/* ... or pick up the terminal name at next */
+		if (!len)
+			len = get_term_name(state->chip, &state->oterm,
+				    kctl->id.name, sizeof(kctl->id.name), 0);
+		/* ... or use the fixed string "USB" as the last resort */
+		if (!len)
+			strlcpy(kctl->id.name, "USB", sizeof(kctl->id.name));
+
+		/* and add the proper suffix */
+		if (desc->bDescriptorSubtype == UAC2_CLOCK_SELECTOR ||
+		    desc->bDescriptorSubtype == UAC3_CLOCK_SELECTOR)
+			append_ctl_name(kctl, " Clock Source");
+		else if ((state->oterm.type & 0xff00) == 0x0100)
+			append_ctl_name(kctl, " Capture Source");
+		else
+			append_ctl_name(kctl, " Playback Source");
+	}
+
+	usb_audio_dbg(state->chip, "[%d] SU [%s] items = %d\n",
+		    cval->head.id, kctl->id.name, desc->bNrInPins);
+	return snd_usb_mixer_add_control(&cval->head, kctl);
+
+ error_name:
+	for (i = 0; i < desc->bNrInPins; i++)
+		kfree(namelist[i]);
+	kfree(namelist);
+ error_cval:
+	usb_mixer_elem_info_free(cval);
+	return err;
+}
+
+/*
+ * parse an audio unit recursively
+ */
+
+static int parse_audio_unit(struct mixer_build *state, int unitid)
+{
+	unsigned char *p1;
+	int protocol = state->mixer->protocol;
+
+	if (test_and_set_bit(unitid, state->unitbitmap))
+		return 0; /* the unit already visited */
+
+	p1 = find_audio_control_unit(state, unitid);
+	if (!p1) {
+		usb_audio_err(state->chip, "unit %d not found!\n", unitid);
+		return -EINVAL;
+	}
+
+	if (!snd_usb_validate_audio_desc(p1, protocol)) {
+		usb_audio_dbg(state->chip, "invalid unit %d\n", unitid);
+		return 0; /* skip invalid unit */
+	}
+
+	switch (PTYPE(protocol, p1[2])) {
+	case PTYPE(UAC_VERSION_1, UAC_INPUT_TERMINAL):
+	case PTYPE(UAC_VERSION_2, UAC_INPUT_TERMINAL):
+	case PTYPE(UAC_VERSION_3, UAC_INPUT_TERMINAL):
+		return parse_audio_input_terminal(state, unitid, p1);
+	case PTYPE(UAC_VERSION_1, UAC_MIXER_UNIT):
+	case PTYPE(UAC_VERSION_2, UAC_MIXER_UNIT):
+	case PTYPE(UAC_VERSION_3, UAC3_MIXER_UNIT):
+		return parse_audio_mixer_unit(state, unitid, p1);
+	case PTYPE(UAC_VERSION_2, UAC2_CLOCK_SOURCE):
+	case PTYPE(UAC_VERSION_3, UAC3_CLOCK_SOURCE):
+		return parse_clock_source_unit(state, unitid, p1);
+	case PTYPE(UAC_VERSION_1, UAC_SELECTOR_UNIT):
+	case PTYPE(UAC_VERSION_2, UAC_SELECTOR_UNIT):
+	case PTYPE(UAC_VERSION_3, UAC3_SELECTOR_UNIT):
+	case PTYPE(UAC_VERSION_2, UAC2_CLOCK_SELECTOR):
+	case PTYPE(UAC_VERSION_3, UAC3_CLOCK_SELECTOR):
+		return parse_audio_selector_unit(state, unitid, p1);
+	case PTYPE(UAC_VERSION_1, UAC_FEATURE_UNIT):
+	case PTYPE(UAC_VERSION_2, UAC_FEATURE_UNIT):
+	case PTYPE(UAC_VERSION_3, UAC3_FEATURE_UNIT):
+		return parse_audio_feature_unit(state, unitid, p1);
+	case PTYPE(UAC_VERSION_1, UAC1_PROCESSING_UNIT):
+	case PTYPE(UAC_VERSION_2, UAC2_PROCESSING_UNIT_V2):
+	case PTYPE(UAC_VERSION_3, UAC3_PROCESSING_UNIT):
+		return parse_audio_processing_unit(state, unitid, p1);
+	case PTYPE(UAC_VERSION_1, UAC1_EXTENSION_UNIT):
+	case PTYPE(UAC_VERSION_2, UAC2_EXTENSION_UNIT_V2):
+	case PTYPE(UAC_VERSION_3, UAC3_EXTENSION_UNIT):
+		return parse_audio_extension_unit(state, unitid, p1);
+	case PTYPE(UAC_VERSION_2, UAC2_EFFECT_UNIT):
+	case PTYPE(UAC_VERSION_3, UAC3_EFFECT_UNIT):
+		return 0; /* FIXME - effect units not implemented yet */
+	default:
+		usb_audio_err(state->chip,
+			      "unit %u: unexpected type 0x%02x\n",
+			      unitid, p1[2]);
+		return -EINVAL;
+	}
+}
+
+static void snd_usb_mixer_free(struct usb_mixer_interface *mixer)
+{
+	/* kill pending URBs */
+	snd_usb_mixer_disconnect(mixer);
+
+	kfree(mixer->id_elems);
+	if (mixer->urb) {
+		kfree(mixer->urb->transfer_buffer);
+		usb_free_urb(mixer->urb);
+	}
+	usb_free_urb(mixer->rc_urb);
+	kfree(mixer->rc_setup_packet);
+	kfree(mixer);
+}
+
+static int snd_usb_mixer_dev_free(struct snd_device *device)
+{
+	struct usb_mixer_interface *mixer = device->device_data;
+	snd_usb_mixer_free(mixer);
+	return 0;
+}
+
+/* UAC3 predefined channels configuration */
+struct uac3_badd_profile {
+	int subclass;
+	const char *name;
+	int c_chmask;	/* capture channels mask */
+	int p_chmask;	/* playback channels mask */
+	int st_chmask;	/* side tone mixing channel mask */
+};
+
+static const struct uac3_badd_profile uac3_badd_profiles[] = {
+	{
+		/*
+		 * BAIF, BAOF or combination of both
+		 * IN: Mono or Stereo cfg, Mono alt possible
+		 * OUT: Mono or Stereo cfg, Mono alt possible
+		 */
+		.subclass = UAC3_FUNCTION_SUBCLASS_GENERIC_IO,
+		.name = "GENERIC IO",
+		.c_chmask = -1,		/* dynamic channels */
+		.p_chmask = -1,		/* dynamic channels */
+	},
+	{
+		/* BAOF; Stereo only cfg, Mono alt possible */
+		.subclass = UAC3_FUNCTION_SUBCLASS_HEADPHONE,
+		.name = "HEADPHONE",
+		.p_chmask = 3,
+	},
+	{
+		/* BAOF; Mono or Stereo cfg, Mono alt possible */
+		.subclass = UAC3_FUNCTION_SUBCLASS_SPEAKER,
+		.name = "SPEAKER",
+		.p_chmask = -1,		/* dynamic channels */
+	},
+	{
+		/* BAIF; Mono or Stereo cfg, Mono alt possible */
+		.subclass = UAC3_FUNCTION_SUBCLASS_MICROPHONE,
+		.name = "MICROPHONE",
+		.c_chmask = -1,		/* dynamic channels */
+	},
+	{
+		/*
+		 * BAIOF topology
+		 * IN: Mono only
+		 * OUT: Mono or Stereo cfg, Mono alt possible
+		 */
+		.subclass = UAC3_FUNCTION_SUBCLASS_HEADSET,
+		.name = "HEADSET",
+		.c_chmask = 1,
+		.p_chmask = -1,		/* dynamic channels */
+		.st_chmask = 1,
+	},
+	{
+		/* BAIOF; IN: Mono only; OUT: Stereo only, Mono alt possible */
+		.subclass = UAC3_FUNCTION_SUBCLASS_HEADSET_ADAPTER,
+		.name = "HEADSET ADAPTER",
+		.c_chmask = 1,
+		.p_chmask = 3,
+		.st_chmask = 1,
+	},
+	{
+		/* BAIF + BAOF; IN: Mono only; OUT: Mono only */
+		.subclass = UAC3_FUNCTION_SUBCLASS_SPEAKERPHONE,
+		.name = "SPEAKERPHONE",
+		.c_chmask = 1,
+		.p_chmask = 1,
+	},
+	{ 0 } /* terminator */
+};
+
+static bool uac3_badd_func_has_valid_channels(struct usb_mixer_interface *mixer,
+					      const struct uac3_badd_profile *f,
+					      int c_chmask, int p_chmask)
+{
+	/*
+	 * If both playback/capture channels are dynamic, make sure
+	 * at least one channel is present
+	 */
+	if (f->c_chmask < 0 && f->p_chmask < 0) {
+		if (!c_chmask && !p_chmask) {
+			usb_audio_warn(mixer->chip, "BAAD %s: no channels?",
+				       f->name);
+			return false;
+		}
+		return true;
+	}
+
+	if ((f->c_chmask < 0 && !c_chmask) ||
+	    (f->c_chmask >= 0 && f->c_chmask != c_chmask)) {
+		usb_audio_warn(mixer->chip, "BAAD %s c_chmask mismatch",
+			       f->name);
+		return false;
+	}
+	if ((f->p_chmask < 0 && !p_chmask) ||
+	    (f->p_chmask >= 0 && f->p_chmask != p_chmask)) {
+		usb_audio_warn(mixer->chip, "BAAD %s p_chmask mismatch",
+			       f->name);
+		return false;
+	}
+	return true;
+}
+
+/*
+ * create mixer controls for UAC3 BADD profiles
+ *
+ * UAC3 BADD device doesn't contain CS descriptors thus we will guess everything
+ *
+ * BADD device may contain Mixer Unit, which doesn't have any controls, skip it
+ */
+static int snd_usb_mixer_controls_badd(struct usb_mixer_interface *mixer,
+				       int ctrlif)
+{
+	struct usb_device *dev = mixer->chip->dev;
+	struct usb_interface_assoc_descriptor *assoc;
+	int badd_profile = mixer->chip->badd_profile;
+	const struct uac3_badd_profile *f;
+	const struct usbmix_ctl_map *map;
+	int p_chmask = 0, c_chmask = 0, st_chmask = 0;
+	int i;
+
+	assoc = usb_ifnum_to_if(dev, ctrlif)->intf_assoc;
+
+	/* Detect BADD capture/playback channels from AS EP descriptors */
+	for (i = 0; i < assoc->bInterfaceCount; i++) {
+		int intf = assoc->bFirstInterface + i;
+
+		struct usb_interface *iface;
+		struct usb_host_interface *alts;
+		struct usb_interface_descriptor *altsd;
+		unsigned int maxpacksize;
+		char dir_in;
+		int chmask, num;
+
+		if (intf == ctrlif)
+			continue;
+
+		iface = usb_ifnum_to_if(dev, intf);
+		if (!iface)
+			continue;
+
+		num = iface->num_altsetting;
+
+		if (num < 2)
+			return -EINVAL;
+
+		/*
+		 * The number of Channels in an AudioStreaming interface
+		 * and the audio sample bit resolution (16 bits or 24
+		 * bits) can be derived from the wMaxPacketSize field in
+		 * the Standard AS Audio Data Endpoint descriptor in
+		 * Alternate Setting 1
+		 */
+		alts = &iface->altsetting[1];
+		altsd = get_iface_desc(alts);
+
+		if (altsd->bNumEndpoints < 1)
+			return -EINVAL;
+
+		/* check direction */
+		dir_in = (get_endpoint(alts, 0)->bEndpointAddress & USB_DIR_IN);
+		maxpacksize = le16_to_cpu(get_endpoint(alts, 0)->wMaxPacketSize);
+
+		switch (maxpacksize) {
+		default:
+			usb_audio_err(mixer->chip,
+				"incorrect wMaxPacketSize 0x%x for BADD profile\n",
+				maxpacksize);
+			return -EINVAL;
+		case UAC3_BADD_EP_MAXPSIZE_SYNC_MONO_16:
+		case UAC3_BADD_EP_MAXPSIZE_ASYNC_MONO_16:
+		case UAC3_BADD_EP_MAXPSIZE_SYNC_MONO_24:
+		case UAC3_BADD_EP_MAXPSIZE_ASYNC_MONO_24:
+			chmask = 1;
+			break;
+		case UAC3_BADD_EP_MAXPSIZE_SYNC_STEREO_16:
+		case UAC3_BADD_EP_MAXPSIZE_ASYNC_STEREO_16:
+		case UAC3_BADD_EP_MAXPSIZE_SYNC_STEREO_24:
+		case UAC3_BADD_EP_MAXPSIZE_ASYNC_STEREO_24:
+			chmask = 3;
+			break;
+		}
+
+		if (dir_in)
+			c_chmask = chmask;
+		else
+			p_chmask = chmask;
+	}
+
+	usb_audio_dbg(mixer->chip,
+		"UAC3 BADD profile 0x%x: detected c_chmask=%d p_chmask=%d\n",
+		badd_profile, c_chmask, p_chmask);
+
+	/* check the mapping table */
+	for (map = uac3_badd_usbmix_ctl_maps; map->id; map++) {
+		if (map->id == badd_profile)
+			break;
+	}
+
+	if (!map->id)
+		return -EINVAL;
+
+	for (f = uac3_badd_profiles; f->name; f++) {
+		if (badd_profile == f->subclass)
+			break;
+	}
+	if (!f->name)
+		return -EINVAL;
+	if (!uac3_badd_func_has_valid_channels(mixer, f, c_chmask, p_chmask))
+		return -EINVAL;
+	st_chmask = f->st_chmask;
+
+	/* Playback */
+	if (p_chmask) {
+		/* Master channel, always writable */
+		build_feature_ctl_badd(mixer, 0, UAC_FU_MUTE,
+				       UAC3_BADD_FU_ID2, map->map);
+		/* Mono/Stereo volume channels, always writable */
+		build_feature_ctl_badd(mixer, p_chmask, UAC_FU_VOLUME,
+				       UAC3_BADD_FU_ID2, map->map);
+	}
+
+	/* Capture */
+	if (c_chmask) {
+		/* Master channel, always writable */
+		build_feature_ctl_badd(mixer, 0, UAC_FU_MUTE,
+				       UAC3_BADD_FU_ID5, map->map);
+		/* Mono/Stereo volume channels, always writable */
+		build_feature_ctl_badd(mixer, c_chmask, UAC_FU_VOLUME,
+				       UAC3_BADD_FU_ID5, map->map);
+	}
+
+	/* Side tone-mixing */
+	if (st_chmask) {
+		/* Master channel, always writable */
+		build_feature_ctl_badd(mixer, 0, UAC_FU_MUTE,
+				       UAC3_BADD_FU_ID7, map->map);
+		/* Mono volume channel, always writable */
+		build_feature_ctl_badd(mixer, 1, UAC_FU_VOLUME,
+				       UAC3_BADD_FU_ID7, map->map);
+	}
+
+	/* Insertion Control */
+	if (f->subclass == UAC3_FUNCTION_SUBCLASS_HEADSET_ADAPTER) {
+		struct usb_audio_term iterm, oterm;
+
+		/* Input Term - Insertion control */
+		memset(&iterm, 0, sizeof(iterm));
+		iterm.id = UAC3_BADD_IT_ID4;
+		iterm.type = UAC_BIDIR_TERMINAL_HEADSET;
+		build_connector_control(mixer, map->map, &iterm, true);
+
+		/* Output Term - Insertion control */
+		memset(&oterm, 0, sizeof(oterm));
+		oterm.id = UAC3_BADD_OT_ID3;
+		oterm.type = UAC_BIDIR_TERMINAL_HEADSET;
+		build_connector_control(mixer, map->map, &oterm, false);
+	}
+
+	return 0;
+}
+
+/*
+ * create mixer controls
+ *
+ * walk through all UAC_OUTPUT_TERMINAL descriptors to search for mixers
+ */
+static int snd_usb_mixer_controls(struct usb_mixer_interface *mixer)
+{
+	struct mixer_build state;
+	int err;
+	const struct usbmix_ctl_map *map;
+	void *p;
+
+	memset(&state, 0, sizeof(state));
+	state.chip = mixer->chip;
+	state.mixer = mixer;
+	state.buffer = mixer->hostif->extra;
+	state.buflen = mixer->hostif->extralen;
+
+	/* check the mapping table */
+	for (map = usbmix_ctl_maps; map->id; map++) {
+		if (map->id == state.chip->usb_id) {
+			state.map = map->map;
+			state.selector_map = map->selector_map;
+			mixer->connector_map = map->connector_map;
+			mixer->ignore_ctl_error |= map->ignore_ctl_error;
+			break;
+		}
+	}
+
+	p = NULL;
+	while ((p = snd_usb_find_csint_desc(mixer->hostif->extra,
+					    mixer->hostif->extralen,
+					    p, UAC_OUTPUT_TERMINAL)) != NULL) {
+		if (!snd_usb_validate_audio_desc(p, mixer->protocol))
+			continue; /* skip invalid descriptor */
+
+		if (mixer->protocol == UAC_VERSION_1) {
+			struct uac1_output_terminal_descriptor *desc = p;
+
+			/* mark terminal ID as visited */
+			set_bit(desc->bTerminalID, state.unitbitmap);
+			state.oterm.id = desc->bTerminalID;
+			state.oterm.type = le16_to_cpu(desc->wTerminalType);
+			state.oterm.name = desc->iTerminal;
+			err = parse_audio_unit(&state, desc->bSourceID);
+			if (err < 0 && err != -EINVAL)
+				return err;
+		} else if (mixer->protocol == UAC_VERSION_2) {
+			struct uac2_output_terminal_descriptor *desc = p;
+
+			/* mark terminal ID as visited */
+			set_bit(desc->bTerminalID, state.unitbitmap);
+			state.oterm.id = desc->bTerminalID;
+			state.oterm.type = le16_to_cpu(desc->wTerminalType);
+			state.oterm.name = desc->iTerminal;
+			err = parse_audio_unit(&state, desc->bSourceID);
+			if (err < 0 && err != -EINVAL)
+				return err;
+
+			/*
+			 * For UAC2, use the same approach to also add the
+			 * clock selectors
+			 */
+			err = parse_audio_unit(&state, desc->bCSourceID);
+			if (err < 0 && err != -EINVAL)
+				return err;
+
+			if ((state.oterm.type & 0xff00) != 0x0100 &&
+			    uac_v2v3_control_is_readable(le16_to_cpu(desc->bmControls),
+							 UAC2_TE_CONNECTOR)) {
+				build_connector_control(state.mixer, state.map,
+							&state.oterm, false);
+			}
+		} else {  /* UAC_VERSION_3 */
+			struct uac3_output_terminal_descriptor *desc = p;
+
+			/* mark terminal ID as visited */
+			set_bit(desc->bTerminalID, state.unitbitmap);
+			state.oterm.id = desc->bTerminalID;
+			state.oterm.type = le16_to_cpu(desc->wTerminalType);
+			state.oterm.name = le16_to_cpu(desc->wTerminalDescrStr);
+			err = parse_audio_unit(&state, desc->bSourceID);
+			if (err < 0 && err != -EINVAL)
+				return err;
+
+			/*
+			 * For UAC3, use the same approach to also add the
+			 * clock selectors
+			 */
+			err = parse_audio_unit(&state, desc->bCSourceID);
+			if (err < 0 && err != -EINVAL)
+				return err;
+
+			if ((state.oterm.type & 0xff00) != 0x0100 &&
+			    uac_v2v3_control_is_readable(le32_to_cpu(desc->bmControls),
+							 UAC3_TE_INSERTION)) {
+				build_connector_control(state.mixer, state.map,
+							&state.oterm, false);
+			}
+		}
+	}
+
+	return 0;
+}
+
+static int delegate_notify(struct usb_mixer_interface *mixer, int unitid,
+			   u8 *control, u8 *channel)
+{
+	const struct usbmix_connector_map *map = mixer->connector_map;
+
+	if (!map)
+		return unitid;
+
+	for (; map->id; map++) {
+		if (map->id == unitid) {
+			if (control && map->control)
+				*control = map->control;
+			if (channel && map->channel)
+				*channel = map->channel;
+			return map->delegated_id;
+		}
+	}
+	return unitid;
+}
+
+void snd_usb_mixer_notify_id(struct usb_mixer_interface *mixer, int unitid)
+{
+	struct usb_mixer_elem_list *list;
+
+	unitid = delegate_notify(mixer, unitid, NULL, NULL);
+
+	for_each_mixer_elem(list, mixer, unitid) {
+		struct usb_mixer_elem_info *info;
+
+		if (!list->is_std_info)
+			continue;
+		info = mixer_elem_list_to_info(list);
+		/* invalidate cache, so the value is read from the device */
+		info->cached = 0;
+		snd_ctl_notify(mixer->chip->card, SNDRV_CTL_EVENT_MASK_VALUE,
+			       &list->kctl->id);
+	}
+}
+
+static void snd_usb_mixer_dump_cval(struct snd_info_buffer *buffer,
+				    struct usb_mixer_elem_list *list)
+{
+	struct usb_mixer_elem_info *cval = mixer_elem_list_to_info(list);
+	static const char * const val_types[] = {
+		"BOOLEAN", "INV_BOOLEAN", "S8", "U8", "S16", "U16", "S32", "U32",
+	};
+	snd_iprintf(buffer, "    Info: id=%i, control=%i, cmask=0x%x, "
+			    "channels=%i, type=\"%s\"\n", cval->head.id,
+			    cval->control, cval->cmask, cval->channels,
+			    val_types[cval->val_type]);
+	snd_iprintf(buffer, "    Volume: min=%i, max=%i, dBmin=%i, dBmax=%i\n",
+			    cval->min, cval->max, cval->dBmin, cval->dBmax);
+}
+
+static void snd_usb_mixer_proc_read(struct snd_info_entry *entry,
+				    struct snd_info_buffer *buffer)
+{
+	struct snd_usb_audio *chip = entry->private_data;
+	struct usb_mixer_interface *mixer;
+	struct usb_mixer_elem_list *list;
+	int unitid;
+
+	list_for_each_entry(mixer, &chip->mixer_list, list) {
+		snd_iprintf(buffer,
+			"USB Mixer: usb_id=0x%08x, ctrlif=%i, ctlerr=%i\n",
+				chip->usb_id, snd_usb_ctrl_intf(chip),
+				mixer->ignore_ctl_error);
+		snd_iprintf(buffer, "Card: %s\n", chip->card->longname);
+		for (unitid = 0; unitid < MAX_ID_ELEMS; unitid++) {
+			for_each_mixer_elem(list, mixer, unitid) {
+				snd_iprintf(buffer, "  Unit: %i\n", list->id);
+				if (list->kctl)
+					snd_iprintf(buffer,
+						    "    Control: name=\"%s\", index=%i\n",
+						    list->kctl->id.name,
+						    list->kctl->id.index);
+				if (list->dump)
+					list->dump(buffer, list);
+			}
+		}
+	}
+}
+
+static void snd_usb_mixer_interrupt_v2(struct usb_mixer_interface *mixer,
+				       int attribute, int value, int index)
+{
+	struct usb_mixer_elem_list *list;
+	__u8 unitid = (index >> 8) & 0xff;
+	__u8 control = (value >> 8) & 0xff;
+	__u8 channel = value & 0xff;
+	unsigned int count = 0;
+
+	if (channel >= MAX_CHANNELS) {
+		usb_audio_dbg(mixer->chip,
+			"%s(): bogus channel number %d\n",
+			__func__, channel);
+		return;
+	}
+
+	unitid = delegate_notify(mixer, unitid, &control, &channel);
+
+	for_each_mixer_elem(list, mixer, unitid)
+		count++;
+
+	if (count == 0)
+		return;
+
+	for_each_mixer_elem(list, mixer, unitid) {
+		struct usb_mixer_elem_info *info;
+
+		if (!list->kctl)
+			continue;
+		if (!list->is_std_info)
+			continue;
+
+		info = mixer_elem_list_to_info(list);
+		if (count > 1 && info->control != control)
+			continue;
+
+		switch (attribute) {
+		case UAC2_CS_CUR:
+			/* invalidate cache, so the value is read from the device */
+			if (channel)
+				info->cached &= ~(1 << channel);
+			else /* master channel */
+				info->cached = 0;
+
+			snd_ctl_notify(mixer->chip->card, SNDRV_CTL_EVENT_MASK_VALUE,
+				       &info->head.kctl->id);
+			break;
+
+		case UAC2_CS_RANGE:
+			/* TODO */
+			break;
+
+		case UAC2_CS_MEM:
+			/* TODO */
+			break;
+
+		default:
+			usb_audio_dbg(mixer->chip,
+				"unknown attribute %d in interrupt\n",
+				attribute);
+			break;
+		} /* switch */
+	}
+}
+
+static void snd_usb_mixer_interrupt(struct urb *urb)
+{
+	struct usb_mixer_interface *mixer = urb->context;
+	int len = urb->actual_length;
+	int ustatus = urb->status;
+
+	if (ustatus != 0)
+		goto requeue;
+
+	if (mixer->protocol == UAC_VERSION_1) {
+		struct uac1_status_word *status;
+
+		for (status = urb->transfer_buffer;
+		     len >= sizeof(*status);
+		     len -= sizeof(*status), status++) {
+			dev_dbg(&urb->dev->dev, "status interrupt: %02x %02x\n",
+						status->bStatusType,
+						status->bOriginator);
+
+			/* ignore any notifications not from the control interface */
+			if ((status->bStatusType & UAC1_STATUS_TYPE_ORIG_MASK) !=
+				UAC1_STATUS_TYPE_ORIG_AUDIO_CONTROL_IF)
+				continue;
+
+			if (status->bStatusType & UAC1_STATUS_TYPE_MEM_CHANGED)
+				snd_usb_mixer_rc_memory_change(mixer, status->bOriginator);
+			else
+				snd_usb_mixer_notify_id(mixer, status->bOriginator);
+		}
+	} else { /* UAC_VERSION_2 */
+		struct uac2_interrupt_data_msg *msg;
+
+		for (msg = urb->transfer_buffer;
+		     len >= sizeof(*msg);
+		     len -= sizeof(*msg), msg++) {
+			/* drop vendor specific and endpoint requests */
+			if ((msg->bInfo & UAC2_INTERRUPT_DATA_MSG_VENDOR) ||
+			    (msg->bInfo & UAC2_INTERRUPT_DATA_MSG_EP))
+				continue;
+
+			snd_usb_mixer_interrupt_v2(mixer, msg->bAttribute,
+						   le16_to_cpu(msg->wValue),
+						   le16_to_cpu(msg->wIndex));
+		}
+	}
+
+requeue:
+	if (ustatus != -ENOENT &&
+	    ustatus != -ECONNRESET &&
+	    ustatus != -ESHUTDOWN) {
+		urb->dev = mixer->chip->dev;
+		usb_submit_urb(urb, GFP_ATOMIC);
+	}
+}
+
+/* create the handler for the optional status interrupt endpoint */
+static int snd_usb_mixer_status_create(struct usb_mixer_interface *mixer)
+{
+	struct usb_endpoint_descriptor *ep;
+	void *transfer_buffer;
+	int buffer_length;
+	unsigned int epnum;
+
+	/* we need one interrupt input endpoint */
+	if (get_iface_desc(mixer->hostif)->bNumEndpoints < 1)
+		return 0;
+	ep = get_endpoint(mixer->hostif, 0);
+	if (!usb_endpoint_dir_in(ep) || !usb_endpoint_xfer_int(ep))
+		return 0;
+
+	epnum = usb_endpoint_num(ep);
+	buffer_length = le16_to_cpu(ep->wMaxPacketSize);
+	transfer_buffer = kmalloc(buffer_length, GFP_KERNEL);
+	if (!transfer_buffer)
+		return -ENOMEM;
+	mixer->urb = usb_alloc_urb(0, GFP_KERNEL);
+	if (!mixer->urb) {
+		kfree(transfer_buffer);
+		return -ENOMEM;
+	}
+	usb_fill_int_urb(mixer->urb, mixer->chip->dev,
+			 usb_rcvintpipe(mixer->chip->dev, epnum),
+			 transfer_buffer, buffer_length,
+			 snd_usb_mixer_interrupt, mixer, ep->bInterval);
+	usb_submit_urb(mixer->urb, GFP_KERNEL);
+	return 0;
+}
+
+static int keep_iface_ctl_get(struct snd_kcontrol *kcontrol,
+			      struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_interface *mixer = snd_kcontrol_chip(kcontrol);
+
+	ucontrol->value.integer.value[0] = mixer->chip->keep_iface;
+	return 0;
+}
+
+static int keep_iface_ctl_put(struct snd_kcontrol *kcontrol,
+			      struct snd_ctl_elem_value *ucontrol)
+{
+	struct usb_mixer_interface *mixer = snd_kcontrol_chip(kcontrol);
+	bool keep_iface = !!ucontrol->value.integer.value[0];
+
+	if (mixer->chip->keep_iface == keep_iface)
+		return 0;
+	mixer->chip->keep_iface = keep_iface;
+	return 1;
+}
+
+static const struct snd_kcontrol_new keep_iface_ctl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_CARD,
+	.name = "Keep Interface",
+	.info = snd_ctl_boolean_mono_info,
+	.get = keep_iface_ctl_get,
+	.put = keep_iface_ctl_put,
+};
+
+static int create_keep_iface_ctl(struct usb_mixer_interface *mixer)
+{
+	struct snd_kcontrol *kctl = snd_ctl_new1(&keep_iface_ctl, mixer);
+
+	/* need only one control per card */
+	if (snd_ctl_find_id(mixer->chip->card, &kctl->id)) {
+		snd_ctl_free_one(kctl);
+		return 0;
+	}
+
+	return snd_ctl_add(mixer->chip->card, kctl);
+}
+
+int snd_usb_create_mixer(struct snd_usb_audio *chip, int ctrlif,
+			 int ignore_error)
+{
+	static struct snd_device_ops dev_ops = {
+		.dev_free = snd_usb_mixer_dev_free
+	};
+	struct usb_mixer_interface *mixer;
+	struct snd_info_entry *entry;
+	int err;
+
+	strcpy(chip->card->mixername, "USB Mixer");
+
+	mixer = kzalloc(sizeof(*mixer), GFP_KERNEL);
+	if (!mixer)
+		return -ENOMEM;
+	mixer->chip = chip;
+	mixer->ignore_ctl_error = ignore_error;
+	mixer->id_elems = kcalloc(MAX_ID_ELEMS, sizeof(*mixer->id_elems),
+				  GFP_KERNEL);
+	if (!mixer->id_elems) {
+		kfree(mixer);
+		return -ENOMEM;
+	}
+
+	mixer->hostif = &usb_ifnum_to_if(chip->dev, ctrlif)->altsetting[0];
+	switch (get_iface_desc(mixer->hostif)->bInterfaceProtocol) {
+	case UAC_VERSION_1:
+	default:
+		mixer->protocol = UAC_VERSION_1;
+		break;
+	case UAC_VERSION_2:
+		mixer->protocol = UAC_VERSION_2;
+		break;
+	case UAC_VERSION_3:
+		mixer->protocol = UAC_VERSION_3;
+		break;
+	}
+
+	if (mixer->protocol == UAC_VERSION_3 &&
+			chip->badd_profile >= UAC3_FUNCTION_SUBCLASS_GENERIC_IO) {
+		err = snd_usb_mixer_controls_badd(mixer, ctrlif);
+		if (err < 0)
+			goto _error;
+	} else {
+		err = snd_usb_mixer_controls(mixer);
+		if (err < 0)
+			goto _error;
+	}
+
+	err = snd_usb_mixer_status_create(mixer);
+	if (err < 0)
+		goto _error;
+
+	err = create_keep_iface_ctl(mixer);
+	if (err < 0)
+		goto _error;
+
+	err = snd_usb_mixer_apply_create_quirk(mixer);
+	if (err < 0)
+		goto _error;
+
+	err = snd_device_new(chip->card, SNDRV_DEV_CODEC, mixer, &dev_ops);
+	if (err < 0)
+		goto _error;
+
+	if (list_empty(&chip->mixer_list) &&
+	    !snd_card_proc_new(chip->card, "usbmixer", &entry))
+		snd_info_set_text_ops(entry, chip, snd_usb_mixer_proc_read);
+
+	list_add(&mixer->list, &chip->mixer_list);
+	return 0;
+
+_error:
+	snd_usb_mixer_free(mixer);
+	return err;
+}
+
+void snd_usb_mixer_disconnect(struct usb_mixer_interface *mixer)
+{
+	if (mixer->disconnected)
+		return;
+	if (mixer->urb)
+		usb_kill_urb(mixer->urb);
+	if (mixer->rc_urb)
+		usb_kill_urb(mixer->rc_urb);
+	mixer->disconnected = true;
+}
+
+#ifdef CONFIG_PM
+/* stop any bus activity of a mixer */
+static void snd_usb_mixer_inactivate(struct usb_mixer_interface *mixer)
+{
+	usb_kill_urb(mixer->urb);
+	usb_kill_urb(mixer->rc_urb);
+}
+
+static int snd_usb_mixer_activate(struct usb_mixer_interface *mixer)
+{
+	int err;
+
+	if (mixer->urb) {
+		err = usb_submit_urb(mixer->urb, GFP_NOIO);
+		if (err < 0)
+			return err;
+	}
+
+	return 0;
+}
+
+int snd_usb_mixer_suspend(struct usb_mixer_interface *mixer)
+{
+	snd_usb_mixer_inactivate(mixer);
+	return 0;
+}
+
+static int restore_mixer_value(struct usb_mixer_elem_list *list)
+{
+	struct usb_mixer_elem_info *cval = mixer_elem_list_to_info(list);
+	int c, err, idx;
+
+	if (cval->cmask) {
+		idx = 0;
+		for (c = 0; c < MAX_CHANNELS; c++) {
+			if (!(cval->cmask & (1 << c)))
+				continue;
+			if (cval->cached & (1 << (c + 1))) {
+				err = snd_usb_set_cur_mix_value(cval, c + 1, idx,
+							cval->cache_val[idx]);
+				if (err < 0)
+					return err;
+			}
+			idx++;
+		}
+	} else {
+		/* master */
+		if (cval->cached) {
+			err = snd_usb_set_cur_mix_value(cval, 0, 0, *cval->cache_val);
+			if (err < 0)
+				return err;
+		}
+	}
+
+	return 0;
+}
+
+int snd_usb_mixer_resume(struct usb_mixer_interface *mixer, bool reset_resume)
+{
+	struct usb_mixer_elem_list *list;
+	int id, err;
+
+	if (reset_resume) {
+		/* restore cached mixer values */
+		for (id = 0; id < MAX_ID_ELEMS; id++) {
+			for_each_mixer_elem(list, mixer, id) {
+				if (list->resume) {
+					err = list->resume(list);
+					if (err < 0)
+						return err;
+				}
+			}
+		}
+	}
+
+	snd_usb_mixer_resume_quirk(mixer);
+
+	return snd_usb_mixer_activate(mixer);
+}
+#endif
+
+void snd_usb_mixer_elem_init_std(struct usb_mixer_elem_list *list,
+				 struct usb_mixer_interface *mixer,
+				 int unitid)
+{
+	list->mixer = mixer;
+	list->id = unitid;
+	list->dump = snd_usb_mixer_dump_cval;
+#ifdef CONFIG_PM
+	list->resume = restore_mixer_value;
+#endif
+}