Merge branch 'master' into for-2.6.35

Conflicts:
	fs/ext3/fsync.c

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 2161 insertions, 0 deletions

diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
new file mode 100644
index 00000000000..97dd1765510
--- /dev/null
+++ b/sound/usb/mixer.c
@@ -0,0 +1,2161 @@
+/*
+ *   (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
+ *
+ */
+
+#include <linux/bitops.h>
+#include <linux/init.h>
+#include <linux/list.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 <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"
+
+#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);
+	struct usb_audio_term oterm;
+	const struct usbmix_name_map *map;
+	const struct usbmix_selector_map *selector_map;
+};
+
+enum {
+	USB_MIXER_BOOLEAN,
+	USB_MIXER_INV_BOOLEAN,
+	USB_MIXER_S8,
+	USB_MIXER_U8,
+	USB_MIXER_S16,
+	USB_MIXER_U16,
+};
+
+enum {
+	USB_PROC_UPDOWN = 1,
+	USB_PROC_UPDOWN_SWITCH = 1,
+	USB_PROC_UPDOWN_MODE_SEL = 2,
+
+	USB_PROC_PROLOGIC = 2,
+	USB_PROC_PROLOGIC_SWITCH = 1,
+	USB_PROC_PROLOGIC_MODE_SEL = 2,
+
+	USB_PROC_3DENH = 3,
+	USB_PROC_3DENH_SWITCH = 1,
+	USB_PROC_3DENH_SPACE = 2,
+
+	USB_PROC_REVERB = 4,
+	USB_PROC_REVERB_SWITCH = 1,
+	USB_PROC_REVERB_LEVEL = 2,
+	USB_PROC_REVERB_TIME = 3,
+	USB_PROC_REVERB_DELAY = 4,
+
+	USB_PROC_CHORUS = 5,
+	USB_PROC_CHORUS_SWITCH = 1,
+	USB_PROC_CHORUS_LEVEL = 2,
+	USB_PROC_CHORUS_RATE = 3,
+	USB_PROC_CHORUS_DEPTH = 4,
+
+	USB_PROC_DCR = 6,
+	USB_PROC_DCR_SWITCH = 1,
+	USB_PROC_DCR_RATIO = 2,
+	USB_PROC_DCR_MAX_AMP = 3,
+	USB_PROC_DCR_THRESHOLD = 4,
+	USB_PROC_DCR_ATTACK = 5,
+	USB_PROC_DCR_RELEASE = 6,
+};
+
+/*E-mu 0202(0404) 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(struct mixer_build *state, int unitid, int control)
+{
+	const struct usbmix_name_map *p = state->map;
+
+	if (!p)
+		return NULL;
+
+	for (p = state->map; 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);
+}
+
+/* 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;
+	}
+}
+
+/* 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
+ * this doesn't return any clock related units, so they need to be handled elsewhere
+ */
+static void *find_audio_control_unit(struct mixer_build *state, unsigned char unit)
+{
+	unsigned char *p;
+
+	p = NULL;
+	while ((p = snd_usb_find_desc(state->buffer, state->buflen, p,
+				      USB_DT_CS_INTERFACE)) != NULL) {
+		if (p[0] >= 4 && p[2] >= UAC_INPUT_TERMINAL && p[2] <= UAC2_EXTENSION_UNIT_V2 && p[3] == unit)
+			return p;
+	}
+	return NULL;
+}
+
+
+/*
+ * copy a string with the given id
+ */
+static int snd_usb_copy_string_desc(struct mixer_build *state, int index, char *buf, int maxlen)
+{
+	int len = usb_string(state->chip->dev, index, buf, maxlen - 1);
+	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;
+}
+
+
+/*
+ * retrieve a mixer value
+ */
+
+static int get_ctl_value_v1(struct usb_mixer_elem_info *cval, int request, int validx, int *value_ret)
+{
+	unsigned char buf[2];
+	int val_len = cval->val_type >= USB_MIXER_S16 ? 2 : 1;
+	int timeout = 10;
+
+	while (timeout-- > 0) {
+		if (snd_usb_ctl_msg(cval->mixer->chip->dev,
+				    usb_rcvctrlpipe(cval->mixer->chip->dev, 0),
+				    request,
+				    USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_IN,
+				    validx, cval->mixer->ctrlif | (cval->id << 8),
+				    buf, val_len, 100) >= val_len) {
+			*value_ret = convert_signed_value(cval, snd_usb_combine_bytes(buf, val_len));
+			return 0;
+		}
+	}
+	snd_printdd(KERN_ERR "cannot get ctl value: req = %#x, wValue = %#x, wIndex = %#x, type = %d\n",
+		    request, validx, cval->mixer->ctrlif | (cval->id << 8), cval->val_type);
+	return -EINVAL;
+}
+
+static int get_ctl_value_v2(struct usb_mixer_elem_info *cval, int request, int validx, int *value_ret)
+{
+	unsigned char buf[14]; /* enough space for one range of 4 bytes */
+	unsigned char *val;
+	int ret;
+	__u8 bRequest;
+
+	bRequest = (request == UAC_GET_CUR) ?
+		UAC2_CS_CUR : UAC2_CS_RANGE;
+
+	ret = snd_usb_ctl_msg(cval->mixer->chip->dev,
+			      usb_rcvctrlpipe(cval->mixer->chip->dev, 0),
+			      bRequest,
+			      USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_IN,
+			      validx, cval->mixer->ctrlif | (cval->id << 8),
+			      buf, sizeof(buf), 1000);
+
+	if (ret < 0) {
+		snd_printdd(KERN_ERR "cannot get ctl value: req = %#x, wValue = %#x, wIndex = %#x, type = %d\n",
+			    request, validx, cval->mixer->ctrlif | (cval->id << 8), cval->val_type);
+		return ret;
+	}
+
+	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) * 2;
+		break;
+	case UAC_GET_RES:
+		val = buf + sizeof(__u16) * 3;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	*value_ret = convert_signed_value(cval, snd_usb_combine_bytes(val, sizeof(__u16)));
+
+	return 0;
+}
+
+static int get_ctl_value(struct usb_mixer_elem_info *cval, int request, int validx, int *value_ret)
+{
+	return (cval->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);
+}
+
+static int 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->mixer->ignore_ctl_error)
+			snd_printd(KERN_ERR "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)
+{
+	unsigned char buf[2];
+	int val_len, timeout = 10;
+
+	if (cval->mixer->protocol == UAC_VERSION_1) {
+		val_len = cval->val_type >= USB_MIXER_S16 ? 2 : 1;
+	} else { /* UAC_VERSION_2 */
+		/* audio class v2 controls are always 2 bytes in size */
+		val_len = sizeof(__u16);
+
+		/* FIXME */
+		if (request != UAC_SET_CUR) {
+			snd_printdd(KERN_WARNING "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;
+	while (timeout-- > 0)
+		if (snd_usb_ctl_msg(cval->mixer->chip->dev,
+				    usb_sndctrlpipe(cval->mixer->chip->dev, 0),
+				    request,
+				    USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_OUT,
+				    validx, cval->mixer->ctrlif | (cval->id << 8),
+				    buf, val_len, 100) >= 0)
+			return 0;
+	snd_printdd(KERN_ERR "cannot set ctl value: req = %#x, wValue = %#x, wIndex = %#x, type = %d, data = %#x/%#x\n",
+		    request, validx, cval->mixer->ctrlif | (cval->id << 8), cval->val_type, buf[0], buf[1]);
+	return -EINVAL;
+}
+
+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);
+}
+
+static int set_cur_mix_value(struct usb_mixer_elem_info *cval, int channel,
+			     int index, int value)
+{
+	int err;
+	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
+ */
+static int 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;
+	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.
+ */
+
+static int add_control_to_empty(struct mixer_build *state, struct snd_kcontrol *kctl)
+{
+	struct usb_mixer_elem_info *cval = kctl->private_data;
+	int err;
+
+	while (snd_ctl_find_id(state->chip->card, &kctl->id))
+		kctl->id.index++;
+	if ((err = snd_ctl_add(state->chip->card, kctl)) < 0) {
+		snd_printd(KERN_ERR "cannot add control (err = %d)\n", err);
+		return err;
+	}
+	cval->elem_id = &kctl->id;
+	cval->next_id_elem = state->mixer->id_elems[cval->id];
+	state->mixer->id_elems[cval->id] = cval;
+	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 mixer_build *state, struct usb_audio_term *iterm,
+			 unsigned char *name, int maxlen, int term_only)
+{
+	struct iterm_name_combo *names;
+
+	if (iterm->name)
+		return snd_usb_copy_string_desc(state, iterm->name, name, maxlen);
+
+	/* virtual type - not a real terminal */
+	if (iterm->type >> 16) {
+		if (term_only)
+			return 0;
+		switch (iterm->type >> 16) {
+		case UAC_SELECTOR_UNIT:
+			strcpy(name, "Selector"); return 8;
+		case UAC_PROCESSING_UNIT_V1:
+			strcpy(name, "Process Unit"); return 12;
+		case UAC_EXTENSION_UNIT_V1:
+			strcpy(name, "Ext Unit"); return 8;
+		case UAC_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;
+}
+
+
+/*
+ * 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)
+{
+	void *p1;
+
+	memset(term, 0, sizeof(*term));
+	while ((p1 = find_audio_control_unit(state, id)) != NULL) {
+		unsigned char *hdr = p1;
+		term->id = id;
+		switch (hdr[2]) {
+		case UAC_INPUT_TERMINAL:
+			if (state->mixer->protocol == UAC_VERSION_1) {
+				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;
+			} else { /* UAC_VERSION_2 */
+				struct uac2_input_terminal_descriptor *d = p1;
+				term->type = le16_to_cpu(d->wTerminalType);
+				term->channels = d->bNrChannels;
+				term->chconfig = le32_to_cpu(d->bmChannelConfig);
+				term->name = d->iTerminal;
+			}
+			return 0;
+		case UAC_FEATURE_UNIT: {
+			/* the header is the same for v1 and v2 */
+			struct uac_feature_unit_descriptor *d = p1;
+			id = d->bSourceID;
+			break; /* continue to parse */
+		}
+		case UAC_MIXER_UNIT: {
+			struct uac_mixer_unit_descriptor *d = p1;
+			term->type = d->bDescriptorSubtype << 16; /* virtual type */
+			term->channels = uac_mixer_unit_bNrChannels(d);
+			term->chconfig = uac_mixer_unit_wChannelConfig(d, state->mixer->protocol);
+			term->name = uac_mixer_unit_iMixer(d);
+			return 0;
+		}
+		case UAC_SELECTOR_UNIT: {
+			struct uac_selector_unit_descriptor *d = p1;
+			/* call recursively to retrieve the channel info */
+			if (check_input_term(state, d->baSourceID[0], term) < 0)
+				return -ENODEV;
+			term->type = d->bDescriptorSubtype << 16; /* virtual type */
+			term->id = id;
+			term->name = uac_selector_unit_iSelector(d);
+			return 0;
+		}
+		case UAC_PROCESSING_UNIT_V1:
+		case UAC_EXTENSION_UNIT_V1: {
+			struct uac_processing_unit_descriptor *d = p1;
+			if (d->bNrInPins) {
+				id = d->baSourceID[0];
+				break; /* continue to parse */
+			}
+			term->type = d->bDescriptorSubtype << 16; /* virtual type */
+			term->channels = uac_processing_unit_bNrChannels(d);
+			term->chconfig = uac_processing_unit_wChannelConfig(d, state->mixer->protocol);
+			term->name = uac_processing_unit_iProcessing(d, state->mixer->protocol);
+			return 0;
+		}
+		default:
+			return -ENODEV;
+		}
+	}
+	return -ENODEV;
+}
+
+
+/*
+ * Feature Unit
+ */
+
+/* feature unit control information */
+struct usb_feature_control_info {
+	const char *name;
+	unsigned int type;	/* control type (mute, volume, etc.) */
+};
+
+static struct usb_feature_control_info audio_feature_info[] = {
+	{ "Mute",		USB_MIXER_INV_BOOLEAN },
+	{ "Volume",		USB_MIXER_S16 },
+	{ "Tone Control - Bass",	USB_MIXER_S8 },
+	{ "Tone Control - Mid",		USB_MIXER_S8 },
+	{ "Tone Control - Treble",	USB_MIXER_S8 },
+	{ "Graphic Equalizer",		USB_MIXER_S8 }, /* FIXME: not implemeted yet */
+	{ "Auto Gain Control",	USB_MIXER_BOOLEAN },
+	{ "Delay Control",	USB_MIXER_U16 },
+	{ "Bass Boost",		USB_MIXER_BOOLEAN },
+	{ "Loudness",		USB_MIXER_BOOLEAN },
+};
+
+
+/* private_free callback */
+static void usb_mixer_elem_free(struct snd_kcontrol *kctl)
+{
+	kfree(kctl->private_data);
+	kctl->private_data = NULL;
+}
+
+
+/*
+ * interface to ALSA control for feature/mixer units
+ */
+
+/*
+ * retrieve the minimum and maximum values for the specified control
+ */
+static int get_min_max(struct usb_mixer_elem_info *cval, int default_min)
+{
+	/* 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) {
+			snd_printd(KERN_ERR "%d:%d: cannot get min/max values for control %d (id %d)\n",
+				   cval->id, cval->mixer->ctrlif, cval->control, cval->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;
+			get_cur_mix_raw(cval, minchn, &saved);
+			for (;;) {
+				test = saved;
+				if (test < cval->max)
+					test += cval->res;
+				else
+					test -= cval->res;
+				if (test < cval->min || test > cval->max ||
+				    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;
+			}
+			set_cur_mix_value(cval, minchn, 0, saved);
+		}
+
+		cval->initialized = 1;
+	}
+
+	/* 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;
+}
+
+
+/* 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(cval,  0);
+		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 = get_cur_mix_value(cval, c + 1, cnt, &val);
+			if (err < 0)
+				return cval->mixer->ignore_ctl_error ? 0 : err;
+			val = get_relative_value(cval, val);
+			ucontrol->value.integer.value[cnt] = val;
+			cnt++;
+		}
+		return 0;
+	} else {
+		/* master channel */
+		err = get_cur_mix_value(cval, 0, 0, &val);
+		if (err < 0)
+			return cval->mixer->ignore_ctl_error ? 0 : 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 = get_cur_mix_value(cval, c + 1, cnt, &oval);
+			if (err < 0)
+				return cval->mixer->ignore_ctl_error ? 0 : err;
+			val = ucontrol->value.integer.value[cnt];
+			val = get_abs_value(cval, val);
+			if (oval != val) {
+				set_cur_mix_value(cval, c + 1, cnt, val);
+				changed = 1;
+			}
+			cnt++;
+		}
+	} else {
+		/* master channel */
+		err = get_cur_mix_value(cval, 0, 0, &oval);
+		if (err < 0)
+			return cval->mixer->ignore_ctl_error ? 0 : err;
+		val = ucontrol->value.integer.value[0];
+		val = get_abs_value(cval, val);
+		if (val != oval) {
+			set_cur_mix_value(cval, 0, 0, val);
+			changed = 1;
+		}
+	}
+	return changed;
+}
+
+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 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,
+};
+
+
+/*
+ * 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));
+}
+
+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 read_only)
+{
+	struct uac_feature_unit_descriptor *desc = raw_desc;
+	unsigned int len = 0;
+	int mapped_name = 0;
+	int nameid = uac_feature_unit_iFeature(desc);
+	struct snd_kcontrol *kctl;
+	struct usb_mixer_elem_info *cval;
+	const struct usbmix_name_map *map;
+
+	control++; /* change from zero-based to 1-based value */
+
+	if (control == UAC_GRAPHIC_EQUALIZER_CONTROL) {
+		/* FIXME: not supported yet */
+		return;
+	}
+
+	map = find_map(state, unitid, control);
+	if (check_ignored_ctl(map))
+		return;
+
+	cval = kzalloc(sizeof(*cval), GFP_KERNEL);
+	if (! cval) {
+		snd_printk(KERN_ERR "cannot malloc kcontrol\n");
+		return;
+	}
+	cval->mixer = state->mixer;
+	cval->id = unitid;
+	cval->control = control;
+	cval->cmask = ctl_mask;
+	cval->val_type = audio_feature_info[control-1].type;
+	if (ctl_mask == 0)
+		cval->channels = 1;	/* master channel */
+	else {
+		int i, c = 0;
+		for (i = 0; i < 16; i++)
+			if (ctl_mask & (1 << i))
+				c++;
+		cval->channels = c;
+	}
+
+	/* get min/max values */
+	get_min_max(cval, 0);
+
+	if (read_only)
+		kctl = snd_ctl_new1(&usb_feature_unit_ctl_ro, cval);
+	else
+		kctl = snd_ctl_new1(&usb_feature_unit_ctl, cval);
+
+	if (! kctl) {
+		snd_printk(KERN_ERR "cannot malloc kcontrol\n");
+		kfree(cval);
+		return;
+	}
+	kctl->private_free = 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(state, nameid,
+				kctl->id.name, sizeof(kctl->id.name));
+
+	switch (control) {
+	case UAC_MUTE_CONTROL:
+	case UAC_VOLUME_CONTROL:
+		/* 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) {
+			len = get_term_name(state, iterm, kctl->id.name, sizeof(kctl->id.name), 1);
+			if (! len)
+				len = get_term_name(state, &state->oterm, kctl->id.name, sizeof(kctl->id.name), 1);
+			if (! len)
+				len = snprintf(kctl->id.name, sizeof(kctl->id.name),
+					       "Feature %d", unitid);
+		}
+		/* 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 && ! (state->oterm.type >> 16)) {
+			if ((state->oterm.type & 0xff00) == 0x0100) {
+				len = append_ctl_name(kctl, " Capture");
+			} else {
+				len = append_ctl_name(kctl, " Playback");
+			}
+		}
+		append_ctl_name(kctl, control == UAC_MUTE_CONTROL ?
+				" Switch" : " Volume");
+		if (control == UAC_VOLUME_CONTROL) {
+			kctl->tlv.c = mixer_vol_tlv;
+			kctl->vd[0].access |= 
+				SNDRV_CTL_ELEM_ACCESS_TLV_READ |
+				SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK;
+			check_mapped_dB(map, cval);
+		}
+		break;
+
+	default:
+		if (! len)
+			strlcpy(kctl->id.name, audio_feature_info[control-1].name,
+				sizeof(kctl->id.name));
+		break;
+	}
+
+	/* volume control quirks */
+	switch (state->chip->usb_id) {
+	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) {
+			snd_printk(KERN_INFO
+				 "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")) {
+			snd_printk(KERN_INFO
+				"set volume quirk for QuickCam E3500\n");
+			cval->min = 6080;
+			cval->max = 8768;
+			cval->res = 192;
+		}
+		break;
+
+	}
+
+	snd_printdd(KERN_INFO "[%d] FU [%s] ch = %d, val = %d/%d/%d\n",
+		    cval->id, kctl->id.name, cval->channels, cval->min, cval->max, cval->res);
+	add_control_to_empty(state, kctl);
+}
+
+
+
+/*
+ * parse a feature unit
+ *
+ * most of controlls 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 {
+		struct uac2_feature_unit_descriptor *ftr = _ftr;
+		csize = 4;
+		channels = (hdr->bLength - 6) / 4;
+		bmaControls = ftr->bmaControls;
+	}
+
+	if (hdr->bLength < 7 || !csize || hdr->bLength < 7 + csize) {
+		snd_printk(KERN_ERR "usbaudio: unit %u: invalid UAC_FEATURE_UNIT descriptor\n", unitid);
+		return -EINVAL;
+	}
+
+	/* parse the source unit */
+	if ((err = parse_audio_unit(state, hdr->bSourceID)) < 0)
+		return err;
+
+	/* determine the input source type and name */
+	if (check_input_term(state, hdr->bSourceID, &iterm) < 0)
+		return -EINVAL;
+
+	master_bits = snd_usb_combine_bytes(bmaControls, csize);
+	/* master configuration quirks */
+	switch (state->chip->usb_id) {
+	case USB_ID(0x08bb, 0x2702):
+		snd_printk(KERN_INFO
+			   "usbmixer: master volume quirk for PCM2702 chip\n");
+		/* disable non-functional volume control */
+		master_bits &= ~UAC_FU_VOLUME;
+		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;
+			for (j = 0; j < channels; j++) {
+				unsigned int 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 */
+			if (ch_bits & 1) /* the first channel must be set (for ease of programming) */
+				build_feature_ctl(state, _ftr, ch_bits, i, &iterm, unitid, 0);
+			if (master_bits & (1 << i))
+				build_feature_ctl(state, _ftr, 0, i, &iterm, unitid, 0);
+		}
+	} else { /* UAC_VERSION_2 */
+		for (i = 0; i < 30/2; i++) {
+			/* From the USB Audio spec v2.0:
+			   bmaControls() is a (ch+1)-element array of 4-byte bitmaps,
+			   each containing a set of bit pairs. If a Control is present,
+			   it must be Host readable. If a certain Control is not
+			   present then the bit pair must be set to 0b00.
+			   If a Control is present but read-only, the bit pair must be
+			   set to 0b01. If a Control is also Host programmable, the bit
+			   pair must be set to 0b11. The value 0b10 is not allowed. */
+			unsigned int ch_bits = 0;
+			unsigned int ch_read_only = 0;
+
+			for (j = 0; j < channels; j++) {
+				unsigned int mask = snd_usb_combine_bytes(bmaControls + csize * (j+1), csize);
+				if (mask & (1 << (i * 2))) {
+					ch_bits |= (1 << j);
+					if (~mask & (1 << ((i * 2) + 1)))
+						ch_read_only |= (1 << j);
+				}
+			}
+
+			/* FIXME: the whole unit is read-only if any of the channels is marked read-only */
+			if (ch_bits & 1) /* the first channel must be set (for ease of programming) */
+				build_feature_ctl(state, _ftr, ch_bits, i, &iterm, unitid, !!ch_read_only);
+			if (master_bits & (1 << i * 2))
+				build_feature_ctl(state, _ftr, 0, i, &iterm, unitid,
+						  ~master_bits & (1 << ((i * 2) + 1)));
+		}
+	}
+
+	return 0;
+}
+
+
+/*
+ * Mixer Unit
+ */
+
+/*
+ * 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 unitid,
+				 struct usb_audio_term *iterm)
+{
+	struct usb_mixer_elem_info *cval;
+	unsigned int num_outs = uac_mixer_unit_bNrChannels(desc);
+	unsigned int i, len;
+	struct snd_kcontrol *kctl;
+	const struct usbmix_name_map *map;
+
+	map = find_map(state, unitid, 0);
+	if (check_ignored_ctl(map))
+		return;
+
+	cval = kzalloc(sizeof(*cval), GFP_KERNEL);
+	if (! cval)
+		return;
+
+	cval->mixer = state->mixer;
+	cval->id = unitid;
+	cval->control = in_ch + 1; /* based on 1 */
+	cval->val_type = USB_MIXER_S16;
+	for (i = 0; i < num_outs; i++) {
+		if (check_matrix_bitmap(uac_mixer_unit_bmControls(desc, state->mixer->protocol), 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) {
+		snd_printk(KERN_ERR "cannot malloc kcontrol\n");
+		kfree(cval);
+		return;
+	}
+	kctl->private_free = usb_mixer_elem_free;
+
+	len = check_mapped_name(map, kctl->id.name, sizeof(kctl->id.name));
+	if (! len)
+		len = get_term_name(state, 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");
+
+	snd_printdd(KERN_INFO "[%d] MU [%s] ch = %d, val = %d/%d\n",
+		    cval->id, kctl->id.name, cval->channels, cval->min, cval->max);
+	add_control_to_empty(state, kctl);
+}
+
+
+/*
+ * 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;
+
+	if (desc->bLength < 11 || ! (input_pins = desc->bNrInPins) || ! (num_outs = uac_mixer_unit_bNrChannels(desc))) {
+		snd_printk(KERN_ERR "invalid MIXER UNIT descriptor %d\n", unitid);
+		return -EINVAL;
+	}
+	/* no bmControls field (e.g. Maya44) -> ignore */
+	if (desc->bLength <= 10 + input_pins) {
+		snd_printdd(KERN_INFO "MU %d has no bmControls field\n", unitid);
+		return 0;
+	}
+
+	num_ins = 0;
+	ich = 0;
+	for (pin = 0; pin < input_pins; pin++) {
+		err = parse_audio_unit(state, desc->baSourceID[pin]);
+		if (err < 0)
+			return err;
+		err = check_input_term(state, desc->baSourceID[pin], &iterm);
+		if (err < 0)
+			return err;
+		num_ins += iterm.channels;
+		for (; ich < num_ins; ++ich) {
+			int och, ich_has_controls = 0;
+
+			for (och = 0; och < num_outs; ++och) {
+				if (check_matrix_bitmap(uac_mixer_unit_bmControls(desc, state->mixer->protocol),
+							ich, och, num_outs)) {
+					ich_has_controls = 1;
+					break;
+				}
+			}
+			if (ich_has_controls)
+				build_mixer_unit_ctl(state, desc, pin, ich,
+						     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 && cval->mixer->ignore_ctl_error) {
+		ucontrol->value.integer.value[0] = cval->min;
+		return 0;
+	}
+	if (err < 0)
+		return 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) {
+		if (cval->mixer->ignore_ctl_error)
+			return 0;
+		return 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 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;
+	char *suffix;
+	int val_type;
+	int min_value;
+};
+
+struct procunit_info {
+	int type;
+	char *name;
+	struct procunit_value_info *values;
+};
+
+static struct procunit_value_info updown_proc_info[] = {
+	{ USB_PROC_UPDOWN_SWITCH, "Switch", USB_MIXER_BOOLEAN },
+	{ USB_PROC_UPDOWN_MODE_SEL, "Mode Select", USB_MIXER_U8, 1 },
+	{ 0 }
+};
+static struct procunit_value_info prologic_proc_info[] = {
+	{ USB_PROC_PROLOGIC_SWITCH, "Switch", USB_MIXER_BOOLEAN },
+	{ USB_PROC_PROLOGIC_MODE_SEL, "Mode Select", USB_MIXER_U8, 1 },
+	{ 0 }
+};
+static struct procunit_value_info threed_enh_proc_info[] = {
+	{ USB_PROC_3DENH_SWITCH, "Switch", USB_MIXER_BOOLEAN },
+	{ USB_PROC_3DENH_SPACE, "Spaciousness", USB_MIXER_U8 },
+	{ 0 }
+};
+static struct procunit_value_info reverb_proc_info[] = {
+	{ USB_PROC_REVERB_SWITCH, "Switch", USB_MIXER_BOOLEAN },
+	{ USB_PROC_REVERB_LEVEL, "Level", USB_MIXER_U8 },
+	{ USB_PROC_REVERB_TIME, "Time", USB_MIXER_U16 },
+	{ USB_PROC_REVERB_DELAY, "Delay", USB_MIXER_U8 },
+	{ 0 }
+};
+static struct procunit_value_info chorus_proc_info[] = {
+	{ USB_PROC_CHORUS_SWITCH, "Switch", USB_MIXER_BOOLEAN },
+	{ USB_PROC_CHORUS_LEVEL, "Level", USB_MIXER_U8 },
+	{ USB_PROC_CHORUS_RATE, "Rate", USB_MIXER_U16 },
+	{ USB_PROC_CHORUS_DEPTH, "Depth", USB_MIXER_U16 },
+	{ 0 }
+};
+static struct procunit_value_info dcr_proc_info[] = {
+	{ USB_PROC_DCR_SWITCH, "Switch", USB_MIXER_BOOLEAN },
+	{ USB_PROC_DCR_RATIO, "Ratio", USB_MIXER_U16 },
+	{ USB_PROC_DCR_MAX_AMP, "Max Amp", USB_MIXER_S16 },
+	{ USB_PROC_DCR_THRESHOLD, "Threshold", USB_MIXER_S16 },
+	{ USB_PROC_DCR_ATTACK, "Attack Time", USB_MIXER_U16 },
+	{ USB_PROC_DCR_RELEASE, "Release Time", USB_MIXER_U16 },
+	{ 0 }
+};
+
+static struct procunit_info procunits[] = {
+	{ USB_PROC_UPDOWN, "Up Down", updown_proc_info },
+	{ USB_PROC_PROLOGIC, "Dolby Prologic", prologic_proc_info },
+	{ USB_PROC_3DENH, "3D Stereo Extender", threed_enh_proc_info },
+	{ USB_PROC_REVERB, "Reverb", reverb_proc_info },
+	{ USB_PROC_CHORUS, "Chorus", chorus_proc_info },
+	{ USB_PROC_DCR, "DCR", dcr_proc_info },
+	{ 0 },
+};
+/*
+ * predefined data for extension units
+ */
+static struct procunit_value_info clock_rate_xu_info[] = {
+	{ USB_XU_CLOCK_RATE_SELECTOR, "Selector", USB_MIXER_U8, 0 },
+	{ 0 }
+};
+static struct procunit_value_info clock_source_xu_info[] = {
+	{ USB_XU_CLOCK_SOURCE_SELECTOR, "External", USB_MIXER_BOOLEAN },
+	{ 0 }
+};
+static struct procunit_value_info spdif_format_xu_info[] = {
+	{ USB_XU_DIGITAL_FORMAT_SELECTOR, "SPDIF/AC3", USB_MIXER_BOOLEAN },
+	{ 0 }
+};
+static struct procunit_value_info soft_limit_xu_info[] = {
+	{ USB_XU_SOFT_LIMIT_SELECTOR, " ", USB_MIXER_BOOLEAN },
+	{ 0 }
+};
+static 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, struct procunit_info *list, char *name)
+{
+	struct uac_processing_unit_descriptor *desc = raw_desc;
+	int num_ins = desc->bNrInPins;
+	struct usb_mixer_elem_info *cval;
+	struct snd_kcontrol *kctl;
+	int i, err, nameid, type, len;
+	struct procunit_info *info;
+	struct procunit_value_info *valinfo;
+	const struct usbmix_name_map *map;
+	static struct procunit_value_info default_value_info[] = {
+		{ 0x01, "Switch", USB_MIXER_BOOLEAN },
+		{ 0 }
+	};
+	static struct procunit_info default_info = {
+		0, NULL, default_value_info
+	};
+
+	if (desc->bLength < 13 || desc->bLength < 13 + num_ins ||
+	    desc->bLength < num_ins + uac_processing_unit_bControlSize(desc, state->mixer->protocol)) {
+		snd_printk(KERN_ERR "invalid %s descriptor (id %d)\n", name, unitid);
+		return -EINVAL;
+	}
+
+	for (i = 0; i < num_ins; i++) {
+		if ((err = parse_audio_unit(state, desc->baSourceID[i])) < 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 (! (controls[valinfo->control / 8] & (1 << ((valinfo->control % 8) - 1))))
+			continue;
+		map = find_map(state, unitid, valinfo->control);
+		if (check_ignored_ctl(map))
+			continue;
+		cval = kzalloc(sizeof(*cval), GFP_KERNEL);
+		if (! cval) {
+			snd_printk(KERN_ERR "cannot malloc kcontrol\n");
+			return -ENOMEM;
+		}
+		cval->mixer = state->mixer;
+		cval->id = unitid;
+		cval->control = valinfo->control;
+		cval->val_type = valinfo->val_type;
+		cval->channels = 1;
+
+		/* get min/max values */
+		if (type == USB_PROC_UPDOWN && cval->control == USB_PROC_UPDOWN_MODE_SEL) {
+			__u8 *control_spec = uac_processing_unit_specific(desc, state->mixer->protocol);
+			/* FIXME: hard-coded */
+			cval->min = 1;
+			cval->max = control_spec[0];
+			cval->res = 1;
+			cval->initialized = 1;
+		} else {
+			if (type == USB_XU_CLOCK_RATE) {
+				/* E-Mu USB 0404/0202/TrackerPre
+				 * samplerate control quirk
+				 */
+				cval->min = 0;
+				cval->max = 5;
+				cval->res = 1;
+				cval->initialized = 1;
+			} else
+				get_min_max(cval, valinfo->min_value);
+		}
+
+		kctl = snd_ctl_new1(&mixer_procunit_ctl, cval);
+		if (! kctl) {
+			snd_printk(KERN_ERR "cannot malloc kcontrol\n");
+			kfree(cval);
+			return -ENOMEM;
+		}
+		kctl->private_free = 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 {
+			nameid = uac_processing_unit_iProcessing(desc, state->mixer->protocol);
+			len = 0;
+			if (nameid)
+				len = snd_usb_copy_string_desc(state, 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);
+
+		snd_printdd(KERN_INFO "[%d] PU [%s] ch = %d, val = %d/%d\n",
+			    cval->id, kctl->id.name, cval->channels, cval->min, cval->max);
+		if ((err = add_control_to_empty(state, kctl)) < 0)
+			return err;
+	}
+	return 0;
+}
+
+
+static int parse_audio_processing_unit(struct mixer_build *state, int unitid, void *raw_desc)
+{
+	return build_audio_procunit(state, unitid, raw_desc, procunits, "Processing Unit");
+}
+
+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, "Extension Unit");
+}
+
+
+/*
+ * 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;
+	char **itemlist = (char **)kcontrol->private_value;
+
+	if (snd_BUG_ON(!itemlist))
+		return -EINVAL;
+	uinfo->type = SNDRV_CTL_ELEM_TYPE_ENUMERATED;
+	uinfo->count = 1;
+	uinfo->value.enumerated.items = cval->max;
+	if ((int)uinfo->value.enumerated.item >= cval->max)
+		uinfo->value.enumerated.item = cval->max - 1;
+	strcpy(uinfo->value.enumerated.name, itemlist[uinfo->value.enumerated.item]);
+	return 0;
+}
+
+/* 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, 0, &val);
+	if (err < 0) {
+		if (cval->mixer->ignore_ctl_error) {
+			ucontrol->value.enumerated.item[0] = 0;
+			return 0;
+		}
+		return 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, 0, &oval);
+	if (err < 0) {
+		if (cval->mixer->ignore_ctl_error)
+			return 0;
+		return err;
+	}
+	val = ucontrol->value.enumerated.item[0];
+	val = get_abs_value(cval, val);
+	if (val != oval) {
+		set_cur_ctl_value(cval, 0, val);
+		return 1;
+	}
+	return 0;
+}
+
+/* alsa control interface for selector unit */
+static 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;
+		kfree(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;
+
+	if (!desc->bNrInPins || desc->bLength < 5 + desc->bNrInPins) {
+		snd_printk(KERN_ERR "invalid SELECTOR UNIT descriptor %d\n", unitid);
+		return -EINVAL;
+	}
+
+	for (i = 0; i < desc->bNrInPins; i++) {
+		if ((err = parse_audio_unit(state, desc->baSourceID[i])) < 0)
+			return err;
+	}
+
+	if (desc->bNrInPins == 1) /* only one ? nonsense! */
+		return 0;
+
+	map = find_map(state, unitid, 0);
+	if (check_ignored_ctl(map))
+		return 0;
+
+	cval = kzalloc(sizeof(*cval), GFP_KERNEL);
+	if (! cval) {
+		snd_printk(KERN_ERR "cannot malloc kcontrol\n");
+		return -ENOMEM;
+	}
+	cval->mixer = state->mixer;
+	cval->id = unitid;
+	cval->val_type = USB_MIXER_U8;
+	cval->channels = 1;
+	cval->min = 1;
+	cval->max = desc->bNrInPins;
+	cval->res = 1;
+	cval->initialized = 1;
+
+	namelist = kmalloc(sizeof(char *) * desc->bNrInPins, GFP_KERNEL);
+	if (! namelist) {
+		snd_printk(KERN_ERR "cannot malloc\n");
+		kfree(cval);
+		return -ENOMEM;
+	}
+#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]) {
+			snd_printk(KERN_ERR "cannot malloc\n");
+			while (i--)
+				kfree(namelist[i]);
+			kfree(namelist);
+			kfree(cval);
+			return -ENOMEM;
+		}
+		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, &iterm, namelist[i], MAX_ITEM_NAME_LEN, 0);
+		if (! len)
+			sprintf(namelist[i], "Input %d", i);
+	}
+
+	kctl = snd_ctl_new1(&mixer_selectunit_ctl, cval);
+	if (! kctl) {
+		snd_printk(KERN_ERR "cannot malloc kcontrol\n");
+		kfree(namelist);
+		kfree(cval);
+		return -ENOMEM;
+	}
+	kctl->private_value = (unsigned long)namelist;
+	kctl->private_free = usb_mixer_selector_elem_free;
+
+	nameid = uac_selector_unit_iSelector(desc);
+	len = check_mapped_name(map, kctl->id.name, sizeof(kctl->id.name));
+	if (len)
+		;
+	else if (nameid)
+		snd_usb_copy_string_desc(state, nameid, kctl->id.name, sizeof(kctl->id.name));
+	else {
+		len = get_term_name(state, &state->oterm,
+				    kctl->id.name, sizeof(kctl->id.name), 0);
+		if (! len)
+			strlcpy(kctl->id.name, "USB", sizeof(kctl->id.name));
+
+		if ((state->oterm.type & 0xff00) == 0x0100)
+			append_ctl_name(kctl, " Capture Source");
+		else
+			append_ctl_name(kctl, " Playback Source");
+	}
+
+	snd_printdd(KERN_INFO "[%d] SU [%s] items = %d\n",
+		    cval->id, kctl->id.name, desc->bNrInPins);
+	if ((err = add_control_to_empty(state, kctl)) < 0)
+		return err;
+
+	return 0;
+}
+
+
+/*
+ * parse an audio unit recursively
+ */
+
+static int parse_audio_unit(struct mixer_build *state, int unitid)
+{
+	unsigned char *p1;
+
+	if (test_and_set_bit(unitid, state->unitbitmap))
+		return 0; /* the unit already visited */
+
+	p1 = find_audio_control_unit(state, unitid);
+	if (!p1) {
+		snd_printk(KERN_ERR "usbaudio: unit %d not found!\n", unitid);
+		return -EINVAL;
+	}
+
+	switch (p1[2]) {
+	case UAC_INPUT_TERMINAL:
+		return 0; /* NOP */
+	case UAC_MIXER_UNIT:
+		return parse_audio_mixer_unit(state, unitid, p1);
+	case UAC_SELECTOR_UNIT:
+		return parse_audio_selector_unit(state, unitid, p1);
+	case UAC_FEATURE_UNIT:
+		return parse_audio_feature_unit(state, unitid, p1);
+	case UAC_PROCESSING_UNIT_V1:
+	/*   UAC2_EFFECT_UNIT has the same value */
+		if (state->mixer->protocol == UAC_VERSION_1)
+			return parse_audio_processing_unit(state, unitid, p1);
+		else
+			return 0; /* FIXME - effect units not implemented yet */
+	case UAC_EXTENSION_UNIT_V1:
+	/*   UAC2_PROCESSING_UNIT_V2 has the same value */
+		if (state->mixer->protocol == UAC_VERSION_1)
+			return parse_audio_extension_unit(state, unitid, p1);
+		else /* UAC_VERSION_2 */
+			return parse_audio_processing_unit(state, unitid, p1);
+	default:
+		snd_printk(KERN_ERR "usbaudio: unit %u: unexpected type 0x%02x\n", unitid, p1[2]);
+		return -EINVAL;
+	}
+}
+
+static void snd_usb_mixer_free(struct usb_mixer_interface *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;
+}
+
+/*
+ * 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;
+	struct usb_host_interface *hostif;
+	void *p;
+
+	hostif = &usb_ifnum_to_if(mixer->chip->dev, mixer->ctrlif)->altsetting[0];
+	memset(&state, 0, sizeof(state));
+	state.chip = mixer->chip;
+	state.mixer = mixer;
+	state.buffer = hostif->extra;
+	state.buflen = 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->ignore_ctl_error = map->ignore_ctl_error;
+			break;
+		}
+	}
+
+	p = NULL;
+	while ((p = snd_usb_find_csint_desc(hostif->extra, hostif->extralen, p, UAC_OUTPUT_TERMINAL)) != NULL) {
+		if (mixer->protocol == UAC_VERSION_1) {
+			struct uac_output_terminal_descriptor_v1 *desc = p;
+
+			if (desc->bLength < sizeof(*desc))
+				continue; /* invalid descriptor? */
+			set_bit(desc->bTerminalID, state.unitbitmap);  /* mark terminal ID as visited */
+			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)
+				return err;
+		} else { /* UAC_VERSION_2 */
+			struct uac2_output_terminal_descriptor *desc = p;
+
+			if (desc->bLength < sizeof(*desc))
+				continue; /* invalid descriptor? */
+			set_bit(desc->bTerminalID, state.unitbitmap);  /* mark terminal ID as visited */
+			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)
+				return err;
+		}
+	}
+
+	return 0;
+}
+
+void snd_usb_mixer_notify_id(struct usb_mixer_interface *mixer, int unitid)
+{
+	struct usb_mixer_elem_info *info;
+
+	for (info = mixer->id_elems[unitid]; info; info = info->next_id_elem)
+		snd_ctl_notify(mixer->chip->card, SNDRV_CTL_EVENT_MASK_VALUE,
+			       info->elem_id);
+}
+
+static void snd_usb_mixer_dump_cval(struct snd_info_buffer *buffer,
+				    int unitid,
+				    struct usb_mixer_elem_info *cval)
+{
+	static char *val_types[] = {"BOOLEAN", "INV_BOOLEAN",
+				    "S8", "U8", "S16", "U16"};
+	snd_iprintf(buffer, "  Unit: %i\n", unitid);
+	if (cval->elem_id)
+		snd_iprintf(buffer, "    Control: name=\"%s\", index=%i\n",
+				cval->elem_id->name, cval->elem_id->index);
+	snd_iprintf(buffer, "    Info: id=%i, control=%i, cmask=0x%x, "
+			    "channels=%i, type=\"%s\"\n", cval->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_info *cval;
+	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, mixer->ctrlif,
+				mixer->ignore_ctl_error);
+		snd_iprintf(buffer, "Card: %s\n", chip->card->longname);
+		for (unitid = 0; unitid < MAX_ID_ELEMS; unitid++) {
+			for (cval = mixer->id_elems[unitid]; cval;
+						cval = cval->next_id_elem)
+				snd_usb_mixer_dump_cval(buffer, unitid, cval);
+		}
+	}
+}
+
+static void snd_usb_mixer_interrupt_v2(struct usb_mixer_interface *mixer,
+				       int attribute, int value, int index)
+{
+	struct usb_mixer_elem_info *info;
+	__u8 unitid = (index >> 8) & 0xff;
+	__u8 control = (value >> 8) & 0xff;
+	__u8 channel = value & 0xff;
+
+	if (channel >= MAX_CHANNELS) {
+		snd_printk(KERN_DEBUG "%s(): bogus channel number %d\n",
+				__func__, channel);
+		return;
+	}
+
+	for (info = mixer->id_elems[unitid]; info; info = info->next_id_elem) {
+		if (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->elem_id);
+			break;
+
+		case UAC2_CS_RANGE:
+			/* TODO */
+			break;
+
+		case UAC2_CS_MEM:
+			/* TODO */
+			break;
+
+		default:
+			snd_printk(KERN_DEBUG "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;
+
+	if (urb->status != 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++) {
+			snd_printd(KERN_DEBUG "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 (urb->status != -ENOENT && urb->status != -ECONNRESET) {
+		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_host_interface *hostif;
+	struct usb_endpoint_descriptor *ep;
+	void *transfer_buffer;
+	int buffer_length;
+	unsigned int epnum;
+
+	hostif = &usb_ifnum_to_if(mixer->chip->dev, mixer->ctrlif)->altsetting[0];
+	/* we need one interrupt input endpoint */
+	if (get_iface_desc(hostif)->bNumEndpoints < 1)
+		return 0;
+	ep = get_endpoint(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;
+}
+
+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;
+	struct usb_host_interface *host_iface;
+	int err;
+
+	strcpy(chip->card->mixername, "USB Mixer");
+
+	mixer = kzalloc(sizeof(*mixer), GFP_KERNEL);
+	if (!mixer)
+		return -ENOMEM;
+	mixer->chip = chip;
+	mixer->ctrlif = ctrlif;
+	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;
+	}
+
+	host_iface = &usb_ifnum_to_if(chip->dev, ctrlif)->altsetting[0];
+	mixer->protocol = get_iface_desc(host_iface)->bInterfaceProtocol;
+
+	if ((err = snd_usb_mixer_controls(mixer)) < 0 ||
+	    (err = snd_usb_mixer_status_create(mixer)) < 0)
+		goto _error;
+
+	snd_usb_mixer_apply_create_quirk(mixer);
+
+	err = snd_device_new(chip->card, SNDRV_DEV_LOWLEVEL, 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 list_head *p)
+{
+	struct usb_mixer_interface *mixer;
+
+	mixer = list_entry(p, struct usb_mixer_interface, list);
+	usb_kill_urb(mixer->urb);
+	usb_kill_urb(mixer->rc_urb);
+}