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32 results

mixer.c

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  • mixer.c 96.57 KiB
    // SPDX-License-Identifier: GPL-2.0-or-later
    /*
     *   (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)
     */
    
    /*
     * 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 inline int mixer_ctrl_intf(struct usb_mixer_interface *mixer)
    {
    	return get_iface_desc(mixer->hostif)->bInterfaceNumber;
    }
    
    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 = mixer_ctrl_intf(cval->head.mixer) | (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 = mixer_ctrl_intf(cval->head.mixer) | (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 = mixer_ctrl_intf(cval->head.mixer) | (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_control(struct usb_mixer_elem_list *list,
    			      struct snd_kcontrol *kctl)
    {
    	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->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)
    {
    	struct uac2_effect_unit_descriptor *d = p1;
    	int err;
    
    	err = __check_input_term(state, d->bSourceID, term);
    	if (err < 0)
    		return err;
    	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, mixer_ctrl_intf(cval->head.mixer),
    							       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 = mixer_ctrl_intf(cval->head.mixer) | (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 const 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 const 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
     */
    const 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;
    	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 (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 =
    			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"};
    	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, mixer_ctrl_intf(mixer),
    				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;
    
    		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 const struct snd_device_ops dev_ops = {
    		.dev_free = snd_usb_mixer_dev_free
    	};
    	struct usb_mixer_interface *mixer;
    	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_ro_proc_new(chip->card, "usbmixer", 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);
    	if (mixer->private_free)
    		mixer->private_free(mixer);
    	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);
    	if (mixer->private_suspend)
    		mixer->private_suspend(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
    }