mixer.c

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/*
 *   (Tentative) USB Audio Driver for ALSA
 *
 *   Mixer control part
 *
 *   Copyright (c) 2002 by Takashi Iwai <[email protected]>
 *
 *   Many codes borrowed from audio.c by
 *      Alan Cox ([email protected])
 *      Thomas Sailer ([email protected])
 *
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 *
 */

/*
 * TODOs, for both the mixer and the streaming interfaces:
 *
 *  - support for UAC2 effect units
 *  - support for graphical equalizers
 *  - RANGE and MEM set commands (UAC2)
 *  - RANGE and MEM interrupt dispatchers (UAC2)
 *  - audio channel clustering (UAC2)
 *  - audio sample rate converter units (UAC2)
 *  - proper handling of clock multipliers (UAC2)
 *  - dispatch clock change notifications (UAC2)
 *      - stop PCM streams which use a clock that became invalid
 *      - stop PCM streams which use a clock selector that has changed
 *      - parse available sample rates again when clock sources changed
 */

#include <linux/bitops.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/usb.h>
#include <linux/usb/audio.h>
#include <linux/usb/audio-v2.h>

#include <sound/core.h>
#include <sound/control.h>
#include <sound/hwdep.h>
#include <sound/info.h>
#include <sound/tlv.h>

#include "usbaudio.h"
#include "mixer.h"
#include "helper.h"
#include "mixer_quirks.h"
#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);
    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(struct mixer_build *state, int unitid, int control)
{
    const struct usbmix_name_map *p = state->map;

    if (!p)
        return NULL;

    for (p = state->map; p->id; p++) {
        if (p->id == unitid &&
            (!control || !p->control || control == p->control))
            return p;
    }
    return NULL;
}

/* get the mapped name if the unit matches */
static int
check_mapped_name(const struct usbmix_name_map *p, char *buf, int buflen)
{
    if (!p || !p->name)
        return 0;

    buflen--;
    return strlcpy(buf, p->name, buflen);
}

/* check whether the control should be ignored */
static inline int
check_ignored_ctl(const struct usbmix_name_map *p)
{
    if (!p || p->name || p->dB)
        return 0;
    return 1;
}

/* dB mapping */
static inline void check_mapped_dB(const struct usbmix_name_map *p,
                   struct usb_mixer_elem_info *cval)
{
    if (p && p->dB) {
        cval->dBmin = p->dB->min;
        cval->dBmax = p->dB->max;
        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 <= UAC2_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 mixer_build *state, int index, char *buf, int maxlen)
{
    int len = usb_string(state->chip->dev, index, buf, maxlen - 1);
    buf[len] = 0;
    return len;
}

/*
 * convert from the byte/word on usb descriptor to the zero-based integer
 */
static int convert_signed_value(struct usb_mixer_elem_info *cval, int val)
{
    switch (cval->val_type) {
    case USB_MIXER_BOOLEAN:
        return !!val;
    case USB_MIXER_INV_BOOLEAN:
        return !val;
    case USB_MIXER_U8:
        val &= 0xff;
        break;
    case USB_MIXER_S8:
        val &= 0xff;
        if (val >= 0x80)
            val -= 0x100;
        break;
    case USB_MIXER_U16:
        val &= 0xffff;
        break;
    case USB_MIXER_S16:
        val &= 0xffff;
        if (val >= 0x8000)
            val -= 0x10000;
        break;
    }
    return val;
}

/*
 * convert from the zero-based int to the byte/word for usb descriptor
 */
static int convert_bytes_value(struct usb_mixer_elem_info *cval, int val)
{
    switch (cval->val_type) {
    case USB_MIXER_BOOLEAN:
        return !!val;
    case USB_MIXER_INV_BOOLEAN:
        return !val;
    case USB_MIXER_S8:
    case USB_MIXER_U8:
        return val & 0xff;
    case USB_MIXER_S16:
    case USB_MIXER_U16:
        return val & 0xffff;
    }
    return 0; /* not reached */
}

static int get_relative_value(struct usb_mixer_elem_info *cval, int val)
{
    if (! cval->res)
        cval->res = 1;
    if (val < cval->min)
        return 0;
    else if (val >= cval->max)
        return (cval->max - cval->min + cval->res - 1) / cval->res;
    else
        return (val - cval->min) / cval->res;
}

static int get_abs_value(struct usb_mixer_elem_info *cval, int val)
{
    if (val < 0)
        return cval->min;
    if (! cval->res)
        cval->res = 1;
    val *= cval->res;
    val += cval->min;
    if (val > cval->max)
        return cval->max;
    return val;
}


/*
 * retrieve a mixer value
 */

static int get_ctl_value_v1(struct usb_mixer_elem_info *cval, int request, int validx, int *value_ret)
{
    struct snd_usb_audio *chip = cval->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_autoresume(cval->mixer->chip);
    if (err < 0)
        return -EIO;
    down_read(&chip->shutdown_rwsem);
    while (timeout-- > 0) {
        if (chip->shutdown)
            break;
        idx = snd_usb_ctrl_intf(chip) | (cval->id << 8);
        if (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) >= val_len) {
            *value_ret = convert_signed_value(cval, snd_usb_combine_bytes(buf, val_len));
            err = 0;
            goto out;
        }
    }
    snd_printdd(KERN_ERR "cannot get ctl value: req = %#x, wValue = %#x, wIndex = %#x, type = %d\n",
            request, validx, idx, cval->val_type);
    err = -EINVAL;

 out:
    up_read(&chip->shutdown_rwsem);
    snd_usb_autosuspend(cval->mixer->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->mixer->chip;
    unsigned char buf[2 + 3*sizeof(__u16)]; /* enough space for one range */
    unsigned char *val;
    int idx = 0, ret, size;
    __u8 bRequest;

    if (request == UAC_GET_CUR) {
        bRequest = UAC2_CS_CUR;
        size = sizeof(__u16);
    } else {
        bRequest = UAC2_CS_RANGE;
        size = sizeof(buf);
    }

    memset(buf, 0, sizeof(buf));

    ret = snd_usb_autoresume(chip) ? -EIO : 0;
    if (ret)
        goto error;

    down_read(&chip->shutdown_rwsem);
    if (chip->shutdown)
        ret = -ENODEV;
    else {
        idx = snd_usb_ctrl_intf(chip) | (cval->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);
    }
    up_read(&chip->shutdown_rwsem);
    snd_usb_autosuspend(chip);

    if (ret < 0) {
error:
        snd_printk(KERN_ERR "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) * 2;
        break;
    case UAC_GET_RES:
        val = buf + sizeof(__u16) * 3;
        break;
    default:
        return -EINVAL;
    }

    *value_ret = convert_signed_value(cval, snd_usb_combine_bytes(val, sizeof(__u16)));

    return 0;
}

static int get_ctl_value(struct usb_mixer_elem_info *cval, int request, int validx, int *value_ret)
{
    return (cval->mixer->protocol == UAC_VERSION_1) ?
        get_ctl_value_v1(cval, request, validx, value_ret) :
        get_ctl_value_v2(cval, request, validx, value_ret);
}

static int get_cur_ctl_value(struct usb_mixer_elem_info *cval, int validx, int *value)
{
    return get_ctl_value(cval, UAC_GET_CUR, validx, value);
}

/* channel = 0: master, 1 = first channel */
static inline int get_cur_mix_raw(struct usb_mixer_elem_info *cval,
                  int channel, int *value)
{
    return get_ctl_value(cval, UAC_GET_CUR, (cval->control << 8) | channel, value);
}

static int get_cur_mix_value(struct usb_mixer_elem_info *cval,
                 int channel, int index, int *value)
{
    int err;

    if (cval->cached & (1 << channel)) {
        *value = cval->cache_val[index];
        return 0;
    }
    err = get_cur_mix_raw(cval, channel, value);
    if (err < 0) {
        if (!cval->mixer->ignore_ctl_error)
            snd_printd(KERN_ERR "cannot get current value for control %d ch %d: err = %d\n",
                   cval->control, channel, err);
        return err;
    }
    cval->cached |= 1 << channel;
    cval->cache_val[index] = *value;
    return 0;
}


/*
 * set a mixer value
 */

int snd_usb_mixer_set_ctl_value(struct usb_mixer_elem_info *cval,
                int request, int validx, int value_set)
{
    struct snd_usb_audio *chip = cval->mixer->chip;
    unsigned char buf[2];
    int idx = 0, val_len, err, timeout = 10;

    if (cval->mixer->protocol == UAC_VERSION_1) {
        val_len = cval->val_type >= USB_MIXER_S16 ? 2 : 1;
    } else { /* UAC_VERSION_2 */
        /* audio class v2 controls are always 2 bytes in size */
        val_len = sizeof(__u16);

        /* FIXME */
        if (request != UAC_SET_CUR) {
            snd_printdd(KERN_WARNING "RANGE setting not yet supported\n");
            return -EINVAL;
        }

        request = UAC2_CS_CUR;
    }

    value_set = convert_bytes_value(cval, value_set);
    buf[0] = value_set & 0xff;
    buf[1] = (value_set >> 8) & 0xff;
    err = snd_usb_autoresume(chip);
    if (err < 0)
        return -EIO;
    down_read(&chip->shutdown_rwsem);
    while (timeout-- > 0) {
        if (chip->shutdown)
            break;
        idx = snd_usb_ctrl_intf(chip) | (cval->id << 8);
        if (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) >= 0) {
            err = 0;
            goto out;
        }
    }
    snd_printdd(KERN_ERR "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:
    up_read(&chip->shutdown_rwsem);
    snd_usb_autosuspend(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);
}

static int 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) {
        snd_printdd(KERN_INFO "%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;
    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_interface *mixer,
                  struct snd_kcontrol *kctl)
{
    struct usb_mixer_elem_info *cval = kctl->private_data;
    int err;

    while (snd_ctl_find_id(mixer->chip->card, &kctl->id))
        kctl->id.index++;
    if ((err = snd_ctl_add(mixer->chip->card, kctl)) < 0) {
        snd_printd(KERN_ERR "cannot add control (err = %d)\n", err);
        return err;
    }
    cval->elem_id = &kctl->id;
    cval->next_id_elem = mixer->id_elems[cval->id];
    mixer->id_elems[cval->id] = cval;
    return 0;
}


/*
 * get a terminal name string
 */

static struct iterm_name_combo {
    int type;
    char *name;
} iterm_names[] = {
    { 0x0300, "Output" },
    { 0x0301, "Speaker" },
    { 0x0302, "Headphone" },
    { 0x0303, "HMD Audio" },
    { 0x0304, "Desktop Speaker" },
    { 0x0305, "Room Speaker" },
    { 0x0306, "Com Speaker" },
    { 0x0307, "LFE" },
    { 0x0600, "External In" },
    { 0x0601, "Analog In" },
    { 0x0602, "Digital In" },
    { 0x0603, "Line" },
    { 0x0604, "Legacy In" },
    { 0x0605, "IEC958 In" },
    { 0x0606, "1394 DA Stream" },
    { 0x0607, "1394 DV Stream" },
    { 0x0700, "Embedded" },
    { 0x0701, "Noise Source" },
    { 0x0702, "Equalization Noise" },
    { 0x0703, "CD" },
    { 0x0704, "DAT" },
    { 0x0705, "DCC" },
    { 0x0706, "MiniDisk" },
    { 0x0707, "Analog Tape" },
    { 0x0708, "Phonograph" },
    { 0x0709, "VCR Audio" },
    { 0x070a, "Video Disk Audio" },
    { 0x070b, "DVD Audio" },
    { 0x070c, "TV Tuner Audio" },
    { 0x070d, "Satellite Rec Audio" },
    { 0x070e, "Cable Tuner Audio" },
    { 0x070f, "DSS Audio" },
    { 0x0710, "Radio Receiver" },
    { 0x0711, "Radio Transmitter" },
    { 0x0712, "Multi-Track Recorder" },
    { 0x0713, "Synthesizer" },
    { 0 },
};

static int get_term_name(struct mixer_build *state, struct usb_audio_term *iterm,
             unsigned char *name, int maxlen, int term_only)
{
    struct iterm_name_combo *names;

    if (iterm->name)
        return snd_usb_copy_string_desc(state, iterm->name, name, maxlen);

    /* virtual type - not a real terminal */
    if (iterm->type >> 16) {
        if (term_only)
            return 0;
        switch (iterm->type >> 16) {
        case UAC_SELECTOR_UNIT:
            strcpy(name, "Selector"); return 8;
        case UAC1_PROCESSING_UNIT:
            strcpy(name, "Process Unit"); return 12;
        case UAC1_EXTENSION_UNIT:
            strcpy(name, "Ext Unit"); return 8;
        case UAC_MIXER_UNIT:
            strcpy(name, "Mixer"); return 5;
        default:
            return sprintf(name, "Unit %d", iterm->id);
        }
    }

    switch (iterm->type & 0xff00) {
    case 0x0100:
        strcpy(name, "PCM"); return 3;
    case 0x0200:
        strcpy(name, "Mic"); return 3;
    case 0x0400:
        strcpy(name, "Headset"); return 7;
    case 0x0500:
        strcpy(name, "Phone"); return 5;
    }

    for (names = iterm_names; names->type; names++)
        if (names->type == iterm->type) {
            strcpy(name, names->name);
            return strlen(names->name);
        }
    return 0;
}


/*
 * parse the source unit recursively until it reaches to a terminal
 * or a branched unit.
 */
static int check_input_term(struct mixer_build *state, int id, struct usb_audio_term *term)
{
    int err;
    void *p1;

    memset(term, 0, sizeof(*term));
    while ((p1 = find_audio_control_unit(state, id)) != NULL) {
        unsigned char *hdr = p1;
        term->id = id;
        switch (hdr[2]) {
        case UAC_INPUT_TERMINAL:
            if (state->mixer->protocol == UAC_VERSION_1) {
                struct uac_input_terminal_descriptor *d = p1;
                term->type = le16_to_cpu(d->wTerminalType);
                term->channels = d->bNrChannels;
                term->chconfig = le16_to_cpu(d->wChannelConfig);
                term->name = d->iTerminal;
            } else { /* UAC_VERSION_2 */
                struct uac2_input_terminal_descriptor *d = p1;
                term->type = le16_to_cpu(d->wTerminalType);
                term->channels = d->bNrChannels;
                term->chconfig = le32_to_cpu(d->bmChannelConfig);
                term->name = d->iTerminal;

                /* call recursively to get the clock selectors */
                err = check_input_term(state, d->bCSourceID, term);
                if (err < 0)
                    return err;
            }
            return 0;
        case UAC_FEATURE_UNIT: {
            /* the header is the same for v1 and v2 */
            struct uac_feature_unit_descriptor *d = p1;
            id = d->bSourceID;
            break; /* continue to parse */
        }
        case UAC_MIXER_UNIT: {
            struct uac_mixer_unit_descriptor *d = p1;
            term->type = d->bDescriptorSubtype << 16; /* virtual type */
            term->channels = uac_mixer_unit_bNrChannels(d);
            term->chconfig = uac_mixer_unit_wChannelConfig(d, state->mixer->protocol);
            term->name = uac_mixer_unit_iMixer(d);
            return 0;
        }
        case UAC_SELECTOR_UNIT:
        case UAC2_CLOCK_SELECTOR: {
            struct uac_selector_unit_descriptor *d = p1;
            /* call recursively to retrieve the channel info */
            if (check_input_term(state, d->baSourceID[0], term) < 0)
                return -ENODEV;
            term->type = d->bDescriptorSubtype << 16; /* virtual type */
            term->id = id;
            term->name = uac_selector_unit_iSelector(d);
            return 0;
        }
        case UAC1_PROCESSING_UNIT:
        case UAC1_EXTENSION_UNIT: {
            struct uac_processing_unit_descriptor *d = p1;
            if (d->bNrInPins) {
                id = d->baSourceID[0];
                break; /* continue to parse */
            }
            term->type = d->bDescriptorSubtype << 16; /* virtual type */
            term->channels = uac_processing_unit_bNrChannels(d);
            term->chconfig = uac_processing_unit_wChannelConfig(d, state->mixer->protocol);
            term->name = uac_processing_unit_iProcessing(d, state->mixer->protocol);
            return 0;
        }
        case UAC2_CLOCK_SOURCE: {
            struct uac_clock_source_descriptor *d = p1;
            term->type = d->bDescriptorSubtype << 16; /* virtual type */
            term->id = id;
            term->name = d->iClockSource;
            return 0;
        }
        default:
            return -ENODEV;
        }
    }
    return -ENODEV;
}


/*
 * Feature Unit
 */

/* feature unit control information */
struct usb_feature_control_info {
    const char *name;
    unsigned int type;  /* control type (mute, volume, etc.) */
};

static struct usb_feature_control_info audio_feature_info[] = {
    { "Mute",           USB_MIXER_INV_BOOLEAN },
    { "Volume",         USB_MIXER_S16 },
    { "Tone Control - Bass",    USB_MIXER_S8 },
    { "Tone Control - Mid",     USB_MIXER_S8 },
    { "Tone Control - Treble",  USB_MIXER_S8 },
    { "Graphic Equalizer",      USB_MIXER_S8 }, /* FIXME: not implemeted yet */
    { "Auto Gain Control",      USB_MIXER_BOOLEAN },
    { "Delay Control",      USB_MIXER_U16 },
    { "Bass Boost",         USB_MIXER_BOOLEAN },
    { "Loudness",           USB_MIXER_BOOLEAN },
    /* UAC2 specific */
    { "Input Gain Control",     USB_MIXER_U16 },
    { "Input Gain Pad Control", USB_MIXER_BOOLEAN },
    { "Phase Inverter Control", USB_MIXER_BOOLEAN },
};


/* private_free callback */
static void usb_mixer_elem_free(struct snd_kcontrol *kctl)
{
    kfree(kctl->private_data);
    kctl->private_data = NULL;
}


/*
 * interface to ALSA control for feature/mixer units
 */

/* volume control quirks */
static void volume_control_quirks(struct usb_mixer_elem_info *cval,
                  struct snd_kcontrol *kctl)
{
    switch (cval->mixer->chip->usb_id) {
    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) {
            snd_printk(KERN_INFO
                "usb-audio: 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) {
            snd_printk(KERN_INFO
                "usb-audio: set quirks for FTU Effect Feedback/Volume\n");
            cval->min = 0x00;
            cval->max = 0x7f;
            break;
        }
        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) {
            snd_printk(KERN_INFO
                 "set volume quirk for UDA1321/N101 chip\n");
            cval->max = -256;
        }
        break;

    case USB_ID(0x046d, 0x09a4):
        if (!strcmp(kctl->id.name, "Mic Capture Volume")) {
            snd_printk(KERN_INFO
                "set volume quirk for QuickCam E3500\n");
            cval->min = 6080;
            cval->max = 8768;
            cval->res = 192;
        }
        break;

    case USB_ID(0x046d, 0x0808):
    case USB_ID(0x046d, 0x0809):
    case USB_ID(0x046d, 0x081d): /* HD Webcam c510 */
    case USB_ID(0x046d, 0x0991):
    /* Most audio usb devices lie about volume resolution.
     * Most Logitech webcams have res = 384.
     * Proboly there is some logitech magic behind this number --fishor
     */
        if (!strcmp(kctl->id.name, "Mic Capture Volume")) {
            snd_printk(KERN_INFO
                "set resolution quirk: cval->res = 384\n");
            cval->res = 384;
        }
        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) {
            snd_printd(KERN_ERR "%d:%d: cannot get min/max values for control %d (id %d)\n",
                   cval->id, snd_usb_ctrl_intf(cval->mixer->chip), cval->control, cval->id);
            return -EINVAL;
        }
        if (get_ctl_value(cval, UAC_GET_RES, (cval->control << 8) | minchn, &cval->res) < 0) {
            cval->res = 1;
        } else {
            int last_valid_res = cval->res;

            while (cval->res > 1) {
                if (snd_usb_mixer_set_ctl_value(cval, UAC_SET_RES,
                                (cval->control << 8) | minchn, cval->res / 2) < 0)
                    break;
                cval->res /= 2;
            }
            if (get_ctl_value(cval, UAC_GET_RES, (cval->control << 8) | minchn, &cval->res) < 0)
                cval->res = last_valid_res;
        }
        if (cval->res == 0)
            cval->res = 1;

        /* Additional checks for the proper resolution
         *
         * Some devices report smaller resolutions than actually
         * reacting.  They don't return errors but simply clip
         * to the lower aligned value.
         */
        if (cval->min + cval->res < cval->max) {
            int last_valid_res = cval->res;
            int saved, test, check;
            get_cur_mix_raw(cval, minchn, &saved);
            for (;;) {
                test = saved;
                if (test < cval->max)
                    test += cval->res;
                else
                    test -= cval->res;
                if (test < cval->min || test > cval->max ||
                    set_cur_mix_value(cval, minchn, 0, test) ||
                    get_cur_mix_raw(cval, minchn, &check)) {
                    cval->res = last_valid_res;
                    break;
                }
                if (test == check)
                    break;
                cval->res *= 2;
            }
            set_cur_mix_value(cval, minchn, 0, saved);
        }

        cval->initialized = 1;
    }

    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->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 = get_cur_mix_value(cval, c + 1, cnt, &val);
            if (err < 0)
                return cval->mixer->ignore_ctl_error ? 0 : err;
            val = get_relative_value(cval, val);
            ucontrol->value.integer.value[cnt] = val;
            cnt++;
        }
        return 0;
    } else {
        /* master channel */
        err = get_cur_mix_value(cval, 0, 0, &val);
        if (err < 0)
            return cval->mixer->ignore_ctl_error ? 0 : err;
        val = get_relative_value(cval, val);
        ucontrol->value.integer.value[0] = val;
    }
    return 0;
}

/* put the current value to feature/mixer unit */
static int mixer_ctl_feature_put(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *ucontrol)
{
    struct usb_mixer_elem_info *cval = kcontrol->private_data;
    int c, cnt, val, oval, err;
    int changed = 0;

    if (cval->cmask) {
        cnt = 0;
        for (c = 0; c < MAX_CHANNELS; c++) {
            if (!(cval->cmask & (1 << c)))
                continue;
            err = get_cur_mix_value(cval, c + 1, cnt, &oval);
            if (err < 0)
                return cval->mixer->ignore_ctl_error ? 0 : err;
            val = ucontrol->value.integer.value[cnt];
            val = get_abs_value(cval, val);
            if (oval != val) {
                set_cur_mix_value(cval, c + 1, cnt, val);
                changed = 1;
            }
            cnt++;
        }
    } else {
        /* master channel */
        err = get_cur_mix_value(cval, 0, 0, &oval);
        if (err < 0)
            return cval->mixer->ignore_ctl_error ? 0 : err;
        val = ucontrol->value.integer.value[0];
        val = get_abs_value(cval, val);
        if (val != oval) {
            set_cur_mix_value(cval, 0, 0, val);
            changed = 1;
        }
    }
    return changed;
}

static struct snd_kcontrol_new usb_feature_unit_ctl = {
    .iface = SNDRV_CTL_ELEM_IFACE_MIXER,
    .name = "", /* will be filled later manually */
    .info = mixer_ctl_feature_info,
    .get = mixer_ctl_feature_get,
    .put = mixer_ctl_feature_put,
};

/* the read-only variant */
static struct snd_kcontrol_new usb_feature_unit_ctl_ro = {
    .iface = SNDRV_CTL_ELEM_IFACE_MIXER,
    .name = "", /* will be filled later manually */
    .info = mixer_ctl_feature_info,
    .get = mixer_ctl_feature_get,
    .put = NULL,
};

/* This symbol is exported in order to allow the mixer quirks to
 * hook up to the standard feature unit control mechanism */
struct snd_kcontrol_new *snd_usb_feature_unit_ctl = &usb_feature_unit_ctl;

/*
 * build a feature control
 */

static size_t append_ctl_name(struct snd_kcontrol *kctl, const char *str)
{
    return strlcat(kctl->id.name, str, sizeof(kctl->id.name));
}

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;
    unsigned int len = 0;
    int mapped_name = 0;
    int nameid = uac_feature_unit_iFeature(desc);
    struct snd_kcontrol *kctl;
    struct usb_mixer_elem_info *cval;
    const struct usbmix_name_map *map;
    unsigned int range;

    control++; /* change from zero-based to 1-based value */

    if (control == UAC_FU_GRAPHIC_EQUALIZER) {
        /* FIXME: not supported yet */
        return;
    }

    map = find_map(state, unitid, control);
    if (check_ignored_ctl(map))
        return;

    cval = kzalloc(sizeof(*cval), GFP_KERNEL);
    if (! cval) {
        snd_printk(KERN_ERR "cannot malloc kcontrol\n");
        return;
    }
    cval->mixer = state->mixer;
    cval->id = unitid;
    cval->control = control;
    cval->cmask = ctl_mask;
    cval->val_type = audio_feature_info[control-1].type;
    if (ctl_mask == 0) {
        cval->channels = 1; /* master channel */
        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. 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) {
        snd_printk(KERN_ERR "cannot malloc kcontrol\n");
        kfree(cval);
        return;
    }
    kctl->private_free = usb_mixer_elem_free;

    len = check_mapped_name(map, kctl->id.name, sizeof(kctl->id.name));
    mapped_name = len != 0;
    if (! len && nameid)
        len = snd_usb_copy_string_desc(state, nameid,
                kctl->id.name, sizeof(kctl->id.name));

    switch (control) {
    case UAC_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) {
            len = get_term_name(state, iterm, kctl->id.name, sizeof(kctl->id.name), 1);
            if (! len)
                len = get_term_name(state, &state->oterm, kctl->id.name, sizeof(kctl->id.name), 1);
            if (! len)
                len = snprintf(kctl->id.name, sizeof(kctl->id.name),
                           "Feature %d", unitid);
        }
        /* determine the stream direction:
         * if the connected output is USB stream, then it's likely a
         * capture stream.  otherwise it should be playback (hopefully :)
         */
        if (! mapped_name && ! (state->oterm.type >> 16)) {
            if ((state->oterm.type & 0xff00) == 0x0100) {
                len = append_ctl_name(kctl, " Capture");
            } else {
                len = append_ctl_name(kctl, " Playback");
            }
        }
        append_ctl_name(kctl, control == UAC_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);

    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;
        }
    }

    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) {
        snd_printk(KERN_WARNING "usb_audio: Warning! Unlikely big "
               "volume range (=%u), cval->res is probably wrong.",
               range);
        snd_printk(KERN_WARNING "usb_audio: [%d] FU [%s] ch = %d, "
               "val = %d/%d/%d", cval->id,
               kctl->id.name, cval->channels,
               cval->min, cval->max, cval->res);
    }

    snd_printdd(KERN_INFO "[%d] FU [%s] ch = %d, val = %d/%d/%d\n",
            cval->id, kctl->id.name, cval->channels, cval->min, cval->max, cval->res);
    snd_usb_mixer_add_control(state->mixer, kctl);
}



/*
 * parse a feature unit
 *
 * most of controls are defined here.
 */
static int parse_audio_feature_unit(struct mixer_build *state, int unitid, void *_ftr)
{
    int channels, i, j;
    struct usb_audio_term iterm;
    unsigned int master_bits, first_ch_bits;
    int err, csize;
    struct uac_feature_unit_descriptor *hdr = _ftr;
    __u8 *bmaControls;

    if (state->mixer->protocol == UAC_VERSION_1) {
        csize = hdr->bControlSize;
        if (!csize) {
            snd_printdd(KERN_ERR "usbaudio: unit %u: "
                    "invalid bControlSize == 0\n", unitid);
            return -EINVAL;
        }
        channels = (hdr->bLength - 7) / csize - 1;
        bmaControls = hdr->bmaControls;
    } else {
        struct uac2_feature_unit_descriptor *ftr = _ftr;
        csize = 4;
        channels = (hdr->bLength - 6) / 4 - 1;
        bmaControls = ftr->bmaControls;
    }

    if (hdr->bLength < 7 || !csize || hdr->bLength < 7 + csize) {
        snd_printk(KERN_ERR "usbaudio: unit %u: invalid UAC_FEATURE_UNIT descriptor\n", unitid);
        return -EINVAL;
    }

    /* parse the source unit */
    if ((err = parse_audio_unit(state, hdr->bSourceID)) < 0)
        return err;

    /* determine the input source type and name */
    if (check_input_term(state, hdr->bSourceID, &iterm) < 0)
        return -EINVAL;

    master_bits = snd_usb_combine_bytes(bmaControls, csize);
    /* master configuration quirks */
    switch (state->chip->usb_id) {
    case USB_ID(0x08bb, 0x2702):
        snd_printk(KERN_INFO
               "usbmixer: master volume quirk for PCM2702 chip\n");
        /* disable non-functional volume control */
        master_bits &= ~UAC_CONTROL_BIT(UAC_FU_VOLUME);
        break;
    case USB_ID(0x1130, 0xf211):
        snd_printk(KERN_INFO
               "usbmixer: volume control quirk for Tenx TP6911 Audio Headset\n");
        /* disable non-functional volume control */
        channels = 0;
        break;

    }
    if (channels > 0)
        first_ch_bits = snd_usb_combine_bytes(bmaControls + csize, csize);
    else
        first_ch_bits = 0;

    if (state->mixer->protocol == UAC_VERSION_1) {
        /* check all control types */
        for (i = 0; i < 10; i++) {
            unsigned int ch_bits = 0;
            for (j = 0; j < channels; j++) {
                unsigned int mask = snd_usb_combine_bytes(bmaControls + csize * (j+1), csize);
                if (mask & (1 << i))
                    ch_bits |= (1 << j);
            }
            /* audio class v1 controls are never read-only */
            if (ch_bits & 1) /* the first channel must be set (for ease of programming) */
                build_feature_ctl(state, _ftr, ch_bits, i, &iterm, unitid, 0);
            if (master_bits & (1 << i))
                build_feature_ctl(state, _ftr, 0, i, &iterm, unitid, 0);
        }
    } else { /* UAC_VERSION_2 */
        for (i = 0; i < ARRAY_SIZE(audio_feature_info); i++) {
            unsigned int ch_bits = 0;
            unsigned int ch_read_only = 0;

            for (j = 0; j < channels; j++) {
                unsigned int mask = snd_usb_combine_bytes(bmaControls + csize * (j+1), csize);
                if (uac2_control_is_readable(mask, i)) {
                    ch_bits |= (1 << j);
                    if (!uac2_control_is_writeable(mask, i))
                        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 */
            if (ch_bits & 1) /* the first channel must be set (for ease of programming) */
                build_feature_ctl(state, _ftr, ch_bits, i, &iterm, unitid, ch_read_only);
            if (uac2_control_is_readable(master_bits, i))
                build_feature_ctl(state, _ftr, 0, i, &iterm, unitid,
                          !uac2_control_is_writeable(master_bits, i));
        }
    }

    return 0;
}


/*
 * Mixer Unit
 */

/*
 * build a mixer unit control
 *
 * the callbacks are identical with feature unit.
 * input channel number (zero based) is given in control field instead.
 */

static void build_mixer_unit_ctl(struct mixer_build *state,
                 struct uac_mixer_unit_descriptor *desc,
                 int in_pin, int in_ch, int unitid,
                 struct usb_audio_term *iterm)
{
    struct usb_mixer_elem_info *cval;
    unsigned int num_outs = uac_mixer_unit_bNrChannels(desc);
    unsigned int i, len;
    struct snd_kcontrol *kctl;
    const struct usbmix_name_map *map;

    map = find_map(state, unitid, 0);
    if (check_ignored_ctl(map))
        return;

    cval = kzalloc(sizeof(*cval), GFP_KERNEL);
    if (! cval)
        return;

    cval->mixer = state->mixer;
    cval->id = unitid;
    cval->control = in_ch + 1; /* based on 1 */
    cval->val_type = USB_MIXER_S16;
    for (i = 0; i < num_outs; i++) {
        if (check_matrix_bitmap(uac_mixer_unit_bmControls(desc, state->mixer->protocol), in_ch, i, num_outs)) {
            cval->cmask |= (1 << i);
            cval->channels++;
        }
    }

    /* get min/max values */
    get_min_max(cval, 0);

    kctl = snd_ctl_new1(&usb_feature_unit_ctl, cval);
    if (! kctl) {
        snd_printk(KERN_ERR "cannot malloc kcontrol\n");
        kfree(cval);
        return;
    }
    kctl->private_free = usb_mixer_elem_free;

    len = check_mapped_name(map, kctl->id.name, sizeof(kctl->id.name));
    if (! len)
        len = get_term_name(state, iterm, kctl->id.name, sizeof(kctl->id.name), 0);
    if (! len)
        len = sprintf(kctl->id.name, "Mixer Source %d", in_ch + 1);
    append_ctl_name(kctl, " Volume");

    snd_printdd(KERN_INFO "[%d] MU [%s] ch = %d, val = %d/%d\n",
            cval->id, kctl->id.name, cval->channels, cval->min, cval->max);
    snd_usb_mixer_add_control(state->mixer, kctl);
}


/*
 * parse a mixer unit
 */
static int parse_audio_mixer_unit(struct mixer_build *state, int unitid, void *raw_desc)
{
    struct uac_mixer_unit_descriptor *desc = raw_desc;
    struct usb_audio_term iterm;
    int input_pins, num_ins, num_outs;
    int pin, ich, err;

    if (desc->bLength < 11 || ! (input_pins = desc->bNrInPins) || ! (num_outs = uac_mixer_unit_bNrChannels(desc))) {
        snd_printk(KERN_ERR "invalid MIXER UNIT descriptor %d\n", unitid);
        return -EINVAL;
    }
    /* no bmControls field (e.g. Maya44) -> ignore */
    if (desc->bLength <= 10 + input_pins) {
        snd_printdd(KERN_INFO "MU %d has no bmControls field\n", unitid);
        return 0;
    }

    num_ins = 0;
    ich = 0;
    for (pin = 0; pin < input_pins; pin++) {
        err = parse_audio_unit(state, desc->baSourceID[pin]);
        if (err < 0)
            continue;
        err = check_input_term(state, desc->baSourceID[pin], &iterm);
        if (err < 0)
            return err;
        num_ins += iterm.channels;
        for (; ich < num_ins; ++ich) {
            int och, ich_has_controls = 0;

            for (och = 0; och < num_outs; ++och) {
                if (check_matrix_bitmap(uac_mixer_unit_bmControls(desc, state->mixer->protocol),
                            ich, och, num_outs)) {
                    ich_has_controls = 1;
                    break;
                }
            }
            if (ich_has_controls)
                build_mixer_unit_ctl(state, desc, pin, ich,
                             unitid, &iterm);
        }
    }
    return 0;
}


/*
 * Processing Unit / Extension Unit
 */

/* get callback for processing/extension unit */
static int mixer_ctl_procunit_get(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *ucontrol)
{
    struct usb_mixer_elem_info *cval = kcontrol->private_data;
    int err, val;

    err = get_cur_ctl_value(cval, cval->control << 8, &val);
    if (err < 0 && cval->mixer->ignore_ctl_error) {
        ucontrol->value.integer.value[0] = cval->min;
        return 0;
    }
    if (err < 0)
        return err;
    val = get_relative_value(cval, val);
    ucontrol->value.integer.value[0] = val;
    return 0;
}

/* put callback for processing/extension unit */
static int mixer_ctl_procunit_put(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *ucontrol)
{
    struct usb_mixer_elem_info *cval = kcontrol->private_data;
    int val, oval, err;

    err = get_cur_ctl_value(cval, cval->control << 8, &oval);
    if (err < 0) {
        if (cval->mixer->ignore_ctl_error)
            return 0;
        return err;
    }
    val = ucontrol->value.integer.value[0];
    val = get_abs_value(cval, val);
    if (val != oval) {
        set_cur_ctl_value(cval, cval->control << 8, val);
        return 1;
    }
    return 0;
}

/* alsa control interface for processing/extension unit */
static struct snd_kcontrol_new mixer_procunit_ctl = {
    .iface = SNDRV_CTL_ELEM_IFACE_MIXER,
    .name = "", /* will be filled later */
    .info = mixer_ctl_feature_info,
    .get = mixer_ctl_procunit_get,
    .put = mixer_ctl_procunit_put,
};


/*
 * predefined data for processing units
 */
struct procunit_value_info {
    int control;
    char *suffix;
    int val_type;
    int min_value;
};

struct procunit_info {
    int type;
    char *name;
    struct procunit_value_info *values;
};

static struct procunit_value_info updown_proc_info[] = {
    { UAC_UD_ENABLE, "Switch", USB_MIXER_BOOLEAN },
    { UAC_UD_MODE_SELECT, "Mode Select", USB_MIXER_U8, 1 },
    { 0 }
};
static 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 struct procunit_value_info threed_enh_proc_info[] = {
    { UAC_3D_ENABLE, "Switch", USB_MIXER_BOOLEAN },
    { UAC_3D_SPACE, "Spaciousness", USB_MIXER_U8 },
    { 0 }
};
static 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 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 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 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 },
};
/*
 * predefined data for extension units
 */
static struct procunit_value_info clock_rate_xu_info[] = {
    { USB_XU_CLOCK_RATE_SELECTOR, "Selector", USB_MIXER_U8, 0 },
    { 0 }
};
static struct procunit_value_info clock_source_xu_info[] = {
    { USB_XU_CLOCK_SOURCE_SELECTOR, "External", USB_MIXER_BOOLEAN },
    { 0 }
};
static struct procunit_value_info spdif_format_xu_info[] = {
    { USB_XU_DIGITAL_FORMAT_SELECTOR, "SPDIF/AC3", USB_MIXER_BOOLEAN },
    { 0 }
};
static struct procunit_value_info soft_limit_xu_info[] = {
    { USB_XU_SOFT_LIMIT_SELECTOR, " ", USB_MIXER_BOOLEAN },
    { 0 }
};
static struct procunit_info extunits[] = {
    { USB_XU_CLOCK_RATE, "Clock rate", clock_rate_xu_info },
    { USB_XU_CLOCK_SOURCE, "DigitalIn CLK source", clock_source_xu_info },
    { USB_XU_DIGITAL_IO_STATUS, "DigitalOut format:", spdif_format_xu_info },
    { USB_XU_DEVICE_OPTIONS, "AnalogueIn Soft Limit", soft_limit_xu_info },
    { 0 }
};
/*
 * build a processing/extension unit
 */
static int build_audio_procunit(struct mixer_build *state, int unitid, void *raw_desc, struct procunit_info *list, char *name)
{
    struct uac_processing_unit_descriptor *desc = raw_desc;
    int num_ins = desc->bNrInPins;
    struct usb_mixer_elem_info *cval;
    struct snd_kcontrol *kctl;
    int i, err, nameid, type, len;
    struct procunit_info *info;
    struct procunit_value_info *valinfo;
    const struct usbmix_name_map *map;
    static struct procunit_value_info default_value_info[] = {
        { 0x01, "Switch", USB_MIXER_BOOLEAN },
        { 0 }
    };
    static struct procunit_info default_info = {
        0, NULL, default_value_info
    };

    if (desc->bLength < 13 || desc->bLength < 13 + num_ins ||
        desc->bLength < num_ins + uac_processing_unit_bControlSize(desc, state->mixer->protocol)) {
        snd_printk(KERN_ERR "invalid %s descriptor (id %d)\n", name, unitid);
        return -EINVAL;
    }

    for (i = 0; i < num_ins; i++) {
        if ((err = parse_audio_unit(state, desc->baSourceID[i])) < 0)
            return err;
    }

    type = le16_to_cpu(desc->wProcessType);
    for (info = list; info && info->type; info++)
        if (info->type == type)
            break;
    if (! info || ! info->type)
        info = &default_info;

    for (valinfo = info->values; valinfo->control; valinfo++) {
        __u8 *controls = uac_processing_unit_bmControls(desc, state->mixer->protocol);

        if (! (controls[valinfo->control / 8] & (1 << ((valinfo->control % 8) - 1))))
            continue;
        map = find_map(state, unitid, valinfo->control);
        if (check_ignored_ctl(map))
            continue;
        cval = kzalloc(sizeof(*cval), GFP_KERNEL);
        if (! cval) {
            snd_printk(KERN_ERR "cannot malloc kcontrol\n");
            return -ENOMEM;
        }
        cval->mixer = state->mixer;
        cval->id = unitid;
        cval->control = valinfo->control;
        cval->val_type = valinfo->val_type;
        cval->channels = 1;

        /* get min/max values */
        if (type == UAC_PROCESS_UP_DOWNMIX && cval->control == UAC_UD_MODE_SELECT) {
            __u8 *control_spec = uac_processing_unit_specific(desc, state->mixer->protocol);
            /* FIXME: hard-coded */
            cval->min = 1;
            cval->max = control_spec[0];
            cval->res = 1;
            cval->initialized = 1;
        } else {
            if (type == USB_XU_CLOCK_RATE) {
                /* E-Mu USB 0404/0202/TrackerPre/0204
                 * samplerate control quirk
                 */
                cval->min = 0;
                cval->max = 5;
                cval->res = 1;
                cval->initialized = 1;
            } else
                get_min_max(cval, valinfo->min_value);
        }

        kctl = snd_ctl_new1(&mixer_procunit_ctl, cval);
        if (! kctl) {
            snd_printk(KERN_ERR "cannot malloc kcontrol\n");
            kfree(cval);
            return -ENOMEM;
        }
        kctl->private_free = usb_mixer_elem_free;

        if (check_mapped_name(map, kctl->id.name,
                        sizeof(kctl->id.name)))
            /* nothing */ ;
        else if (info->name)
            strlcpy(kctl->id.name, info->name, sizeof(kctl->id.name));
        else {
            nameid = uac_processing_unit_iProcessing(desc, state->mixer->protocol);
            len = 0;
            if (nameid)
                len = snd_usb_copy_string_desc(state, nameid, kctl->id.name, sizeof(kctl->id.name));
            if (! len)
                strlcpy(kctl->id.name, name, sizeof(kctl->id.name));
        }
        append_ctl_name(kctl, " ");
        append_ctl_name(kctl, valinfo->suffix);

        snd_printdd(KERN_INFO "[%d] PU [%s] ch = %d, val = %d/%d\n",
                cval->id, kctl->id.name, cval->channels, cval->min, cval->max);
        if ((err = snd_usb_mixer_add_control(state->mixer, kctl)) < 0)
            return err;
    }
    return 0;
}


static int parse_audio_processing_unit(struct mixer_build *state, int unitid, void *raw_desc)
{
    return build_audio_procunit(state, unitid, raw_desc, procunits, "Processing Unit");
}

static int parse_audio_extension_unit(struct mixer_build *state, int unitid, void *raw_desc)
{
    /* Note that we parse extension units with processing unit descriptors.
     * That's ok as the layout is the same */
    return build_audio_procunit(state, unitid, raw_desc, extunits, "Extension Unit");
}


/*
 * Selector Unit
 */

/* info callback for selector unit
 * use an enumerator type for routing
 */
static int mixer_ctl_selector_info(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_info *uinfo)
{
    struct usb_mixer_elem_info *cval = kcontrol->private_data;
    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) {
        if (cval->mixer->ignore_ctl_error) {
            ucontrol->value.enumerated.item[0] = 0;
            return 0;
        }
        return err;
    }
    val = get_relative_value(cval, val);
    ucontrol->value.enumerated.item[0] = val;
    return 0;
}

/* put callback for selector unit */
static int mixer_ctl_selector_put(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *ucontrol)
{
    struct usb_mixer_elem_info *cval = kcontrol->private_data;
    int val, oval, err;

    err = get_cur_ctl_value(cval, cval->control << 8, &oval);
    if (err < 0) {
        if (cval->mixer->ignore_ctl_error)
            return 0;
        return err;
    }
    val = ucontrol->value.enumerated.item[0];
    val = get_abs_value(cval, val);
    if (val != oval) {
        set_cur_ctl_value(cval, cval->control << 8, val);
        return 1;
    }
    return 0;
}

/* alsa control interface for selector unit */
static struct snd_kcontrol_new mixer_selectunit_ctl = {
    .iface = SNDRV_CTL_ELEM_IFACE_MIXER,
    .name = "", /* will be filled later */
    .info = mixer_ctl_selector_info,
    .get = mixer_ctl_selector_get,
    .put = mixer_ctl_selector_put,
};


/* private free callback.
 * free both private_data and private_value
 */
static void usb_mixer_selector_elem_free(struct snd_kcontrol *kctl)
{
    int i, num_ins = 0;

    if (kctl->private_data) {
        struct usb_mixer_elem_info *cval = kctl->private_data;
        num_ins = cval->max;
        kfree(cval);
        kctl->private_data = NULL;
    }
    if (kctl->private_value) {
        char **itemlist = (char **)kctl->private_value;
        for (i = 0; i < num_ins; i++)
            kfree(itemlist[i]);
        kfree(itemlist);
        kctl->private_value = 0;
    }
}

/*
 * parse a selector unit
 */
static int parse_audio_selector_unit(struct mixer_build *state, int unitid, void *raw_desc)
{
    struct uac_selector_unit_descriptor *desc = raw_desc;
    unsigned int i, nameid, len;
    int err;
    struct usb_mixer_elem_info *cval;
    struct snd_kcontrol *kctl;
    const struct usbmix_name_map *map;
    char **namelist;

    if (!desc->bNrInPins || desc->bLength < 5 + desc->bNrInPins) {
        snd_printk(KERN_ERR "invalid SELECTOR UNIT descriptor %d\n", unitid);
        return -EINVAL;
    }

    for (i = 0; i < desc->bNrInPins; i++) {
        if ((err = parse_audio_unit(state, desc->baSourceID[i])) < 0)
            return err;
    }

    if (desc->bNrInPins == 1) /* only one ? nonsense! */
        return 0;

    map = find_map(state, unitid, 0);
    if (check_ignored_ctl(map))
        return 0;

    cval = kzalloc(sizeof(*cval), GFP_KERNEL);
    if (! cval) {
        snd_printk(KERN_ERR "cannot malloc kcontrol\n");
        return -ENOMEM;
    }
    cval->mixer = state->mixer;
    cval->id = unitid;
    cval->val_type = USB_MIXER_U8;
    cval->channels = 1;
    cval->min = 1;
    cval->max = desc->bNrInPins;
    cval->res = 1;
    cval->initialized = 1;

    if (desc->bDescriptorSubtype == UAC2_CLOCK_SELECTOR)
        cval->control = UAC2_CX_CLOCK_SELECTOR;
    else
        cval->control = 0;

    namelist = kmalloc(sizeof(char *) * desc->bNrInPins, GFP_KERNEL);
    if (! namelist) {
        snd_printk(KERN_ERR "cannot malloc\n");
        kfree(cval);
        return -ENOMEM;
    }
#define MAX_ITEM_NAME_LEN   64
    for (i = 0; i < desc->bNrInPins; i++) {
        struct usb_audio_term iterm;
        len = 0;
        namelist[i] = kmalloc(MAX_ITEM_NAME_LEN, GFP_KERNEL);
        if (! namelist[i]) {
            snd_printk(KERN_ERR "cannot malloc\n");
            while (i--)
                kfree(namelist[i]);
            kfree(namelist);
            kfree(cval);
            return -ENOMEM;
        }
        len = check_mapped_selector_name(state, unitid, i, namelist[i],
                         MAX_ITEM_NAME_LEN);
        if (! len && check_input_term(state, desc->baSourceID[i], &iterm) >= 0)
            len = get_term_name(state, &iterm, namelist[i], MAX_ITEM_NAME_LEN, 0);
        if (! len)
            sprintf(namelist[i], "Input %d", i);
    }

    kctl = snd_ctl_new1(&mixer_selectunit_ctl, cval);
    if (! kctl) {
        snd_printk(KERN_ERR "cannot malloc kcontrol\n");
        kfree(namelist);
        kfree(cval);
        return -ENOMEM;
    }
    kctl->private_value = (unsigned long)namelist;
    kctl->private_free = usb_mixer_selector_elem_free;

    nameid = uac_selector_unit_iSelector(desc);
    len = check_mapped_name(map, kctl->id.name, sizeof(kctl->id.name));
    if (len)
        ;
    else if (nameid)
        snd_usb_copy_string_desc(state, nameid, kctl->id.name, sizeof(kctl->id.name));
    else {
        len = get_term_name(state, &state->oterm,
                    kctl->id.name, sizeof(kctl->id.name), 0);
        if (! len)
            strlcpy(kctl->id.name, "USB", sizeof(kctl->id.name));

        if (desc->bDescriptorSubtype == UAC2_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");
    }

    snd_printdd(KERN_INFO "[%d] SU [%s] items = %d\n",
            cval->id, kctl->id.name, desc->bNrInPins);
    if ((err = snd_usb_mixer_add_control(state->mixer, kctl)) < 0)
        return err;

    return 0;
}


/*
 * parse an audio unit recursively
 */

static int parse_audio_unit(struct mixer_build *state, int unitid)
{
    unsigned char *p1;

    if (test_and_set_bit(unitid, state->unitbitmap))
        return 0; /* the unit already visited */

    p1 = find_audio_control_unit(state, unitid);
    if (!p1) {
        snd_printk(KERN_ERR "usbaudio: unit %d not found!\n", unitid);
        return -EINVAL;
    }

    switch (p1[2]) {
    case UAC_INPUT_TERMINAL:
    case UAC2_CLOCK_SOURCE:
        return 0; /* NOP */
    case UAC_MIXER_UNIT:
        return parse_audio_mixer_unit(state, unitid, p1);
    case UAC_SELECTOR_UNIT:
    case UAC2_CLOCK_SELECTOR:
        return parse_audio_selector_unit(state, unitid, p1);
    case UAC_FEATURE_UNIT:
        return parse_audio_feature_unit(state, unitid, p1);
    case UAC1_PROCESSING_UNIT:
    /*   UAC2_EFFECT_UNIT has the same value */
        if (state->mixer->protocol == UAC_VERSION_1)
            return parse_audio_processing_unit(state, unitid, p1);
        else
            return 0; /* FIXME - effect units not implemented yet */
    case UAC1_EXTENSION_UNIT:
    /*   UAC2_PROCESSING_UNIT_V2 has the same value */
        if (state->mixer->protocol == UAC_VERSION_1)
            return parse_audio_extension_unit(state, unitid, p1);
        else /* UAC_VERSION_2 */
            return parse_audio_processing_unit(state, unitid, p1);
    default:
        snd_printk(KERN_ERR "usbaudio: unit %u: unexpected type 0x%02x\n", unitid, p1[2]);
        return -EINVAL;
    }
}

static void snd_usb_mixer_free(struct usb_mixer_interface *mixer)
{
    kfree(mixer->id_elems);
    if (mixer->urb) {
        kfree(mixer->urb->transfer_buffer);
        usb_free_urb(mixer->urb);
    }
    usb_free_urb(mixer->rc_urb);
    kfree(mixer->rc_setup_packet);
    kfree(mixer);
}

static int snd_usb_mixer_dev_free(struct snd_device *device)
{
    struct usb_mixer_interface *mixer = device->device_data;
    snd_usb_mixer_free(mixer);
    return 0;
}

/*
 * create mixer controls
 *
 * walk through all UAC_OUTPUT_TERMINAL descriptors to search for mixers
 */
static int snd_usb_mixer_controls(struct usb_mixer_interface *mixer)
{
    struct mixer_build state;
    int err;
    const struct usbmix_ctl_map *map;
    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->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 (mixer->protocol == UAC_VERSION_1) {
            struct uac1_output_terminal_descriptor *desc = p;

            if (desc->bLength < sizeof(*desc))
                continue; /* invalid descriptor? */
            set_bit(desc->bTerminalID, state.unitbitmap);  /* mark terminal ID as visited */
            state.oterm.id = desc->bTerminalID;
            state.oterm.type = le16_to_cpu(desc->wTerminalType);
            state.oterm.name = desc->iTerminal;
            err = parse_audio_unit(&state, desc->bSourceID);
            if (err < 0)
                return err;
        } else { /* UAC_VERSION_2 */
            struct uac2_output_terminal_descriptor *desc = p;

            if (desc->bLength < sizeof(*desc))
                continue; /* invalid descriptor? */
            set_bit(desc->bTerminalID, state.unitbitmap);  /* mark terminal ID as visited */
            state.oterm.id = desc->bTerminalID;
            state.oterm.type = le16_to_cpu(desc->wTerminalType);
            state.oterm.name = desc->iTerminal;
            err = parse_audio_unit(&state, desc->bSourceID);
            if (err < 0)
                return err;

            /* for UAC2, use the same approach to also add the clock selectors */
            err = parse_audio_unit(&state, desc->bCSourceID);
            if (err < 0)
                return err;
        }
    }

    return 0;
}

void snd_usb_mixer_notify_id(struct usb_mixer_interface *mixer, int unitid)
{
    struct usb_mixer_elem_info *info;

    for (info = mixer->id_elems[unitid]; info; info = info->next_id_elem)
        snd_ctl_notify(mixer->chip->card, SNDRV_CTL_EVENT_MASK_VALUE,
                   info->elem_id);
}

static void snd_usb_mixer_dump_cval(struct snd_info_buffer *buffer,
                    int unitid,
                    struct usb_mixer_elem_info *cval)
{
    static char *val_types[] = {"BOOLEAN", "INV_BOOLEAN",
                    "S8", "U8", "S16", "U16"};
    snd_iprintf(buffer, "  Unit: %i\n", unitid);
    if (cval->elem_id)
        snd_iprintf(buffer, "    Control: name=\"%s\", index=%i\n",
                cval->elem_id->name, cval->elem_id->index);
    snd_iprintf(buffer, "    Info: id=%i, control=%i, cmask=0x%x, "
                "channels=%i, type=\"%s\"\n", cval->id,
                cval->control, cval->cmask, cval->channels,
                val_types[cval->val_type]);
    snd_iprintf(buffer, "    Volume: min=%i, max=%i, dBmin=%i, dBmax=%i\n",
                cval->min, cval->max, cval->dBmin, cval->dBmax);
}

static void snd_usb_mixer_proc_read(struct snd_info_entry *entry,
                    struct snd_info_buffer *buffer)
{
    struct snd_usb_audio *chip = entry->private_data;
    struct usb_mixer_interface *mixer;
    struct usb_mixer_elem_info *cval;
    int unitid;

    list_for_each_entry(mixer, &chip->mixer_list, list) {
        snd_iprintf(buffer,
            "USB Mixer: usb_id=0x%08x, ctrlif=%i, ctlerr=%i\n",
                chip->usb_id, snd_usb_ctrl_intf(chip),
                mixer->ignore_ctl_error);
        snd_iprintf(buffer, "Card: %s\n", chip->card->longname);
        for (unitid = 0; unitid < MAX_ID_ELEMS; unitid++) {
            for (cval = mixer->id_elems[unitid]; cval;
                        cval = cval->next_id_elem)
                snd_usb_mixer_dump_cval(buffer, unitid, cval);
        }
    }
}

static void snd_usb_mixer_interrupt_v2(struct usb_mixer_interface *mixer,
                       int attribute, int value, int index)
{
    struct usb_mixer_elem_info *info;
    __u8 unitid = (index >> 8) & 0xff;
    __u8 control = (value >> 8) & 0xff;
    __u8 channel = value & 0xff;

    if (channel >= MAX_CHANNELS) {
        snd_printk(KERN_DEBUG "%s(): bogus channel number %d\n",
                __func__, channel);
        return;
    }

    for (info = mixer->id_elems[unitid]; info; info = info->next_id_elem) {
        if (info->control != control)
            continue;

        switch (attribute) {
        case UAC2_CS_CUR:
            /* invalidate cache, so the value is read from the device */
            if (channel)
                info->cached &= ~(1 << channel);
            else /* master channel */
                info->cached = 0;

            snd_ctl_notify(mixer->chip->card, SNDRV_CTL_EVENT_MASK_VALUE,
                    info->elem_id);
            break;

        case UAC2_CS_RANGE:
            /* TODO */
            break;

        case UAC2_CS_MEM:
            /* TODO */
            break;

        default:
            snd_printk(KERN_DEBUG "unknown attribute %d in interrupt\n",
                        attribute);
            break;
        } /* switch */
    }
}

static void snd_usb_mixer_interrupt(struct urb *urb)
{
    struct usb_mixer_interface *mixer = urb->context;
    int len = urb->actual_length;
    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++) {
            snd_printd(KERN_DEBUG "status interrupt: %02x %02x\n",
                        status->bStatusType,
                        status->bOriginator);

            /* ignore any notifications not from the control interface */
            if ((status->bStatusType & UAC1_STATUS_TYPE_ORIG_MASK) !=
                UAC1_STATUS_TYPE_ORIG_AUDIO_CONTROL_IF)
                continue;

            if (status->bStatusType & UAC1_STATUS_TYPE_MEM_CHANGED)
                snd_usb_mixer_rc_memory_change(mixer, status->bOriginator);
            else
                snd_usb_mixer_notify_id(mixer, status->bOriginator);
        }
    } else { /* UAC_VERSION_2 */
        struct uac2_interrupt_data_msg *msg;

        for (msg = urb->transfer_buffer;
             len >= sizeof(*msg);
             len -= sizeof(*msg), msg++) {
            /* drop vendor specific and endpoint requests */
            if ((msg->bInfo & UAC2_INTERRUPT_DATA_MSG_VENDOR) ||
                (msg->bInfo & UAC2_INTERRUPT_DATA_MSG_EP))
                continue;

            snd_usb_mixer_interrupt_v2(mixer, msg->bAttribute,
                           le16_to_cpu(msg->wValue),
                           le16_to_cpu(msg->wIndex));
        }
    }

requeue:
    if (ustatus != -ENOENT && ustatus != -ECONNRESET && ustatus != -ESHUTDOWN) {
        urb->dev = mixer->chip->dev;
        usb_submit_urb(urb, GFP_ATOMIC);
    }
}

/* stop any bus activity of a mixer */
void snd_usb_mixer_inactivate(struct usb_mixer_interface *mixer)
{
    usb_kill_urb(mixer->urb);
    usb_kill_urb(mixer->rc_urb);
}

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;
}

/* 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;
}

int snd_usb_create_mixer(struct snd_usb_audio *chip, int ctrlif,
             int ignore_error)
{
    static struct snd_device_ops dev_ops = {
        .dev_free = snd_usb_mixer_dev_free
    };
    struct usb_mixer_interface *mixer;
    struct snd_info_entry *entry;
    int err;

    strcpy(chip->card->mixername, "USB Mixer");

    mixer = kzalloc(sizeof(*mixer), GFP_KERNEL);
    if (!mixer)
        return -ENOMEM;
    mixer->chip = chip;
    mixer->ignore_ctl_error = ignore_error;
    mixer->id_elems = kcalloc(MAX_ID_ELEMS, sizeof(*mixer->id_elems),
                  GFP_KERNEL);
    if (!mixer->id_elems) {
        kfree(mixer);
        return -ENOMEM;
    }

    mixer->hostif = &usb_ifnum_to_if(chip->dev, ctrlif)->altsetting[0];
    switch (get_iface_desc(mixer->hostif)->bInterfaceProtocol) {
    case UAC_VERSION_1:
    default:
        mixer->protocol = UAC_VERSION_1;
        break;
    case UAC_VERSION_2:
        mixer->protocol = UAC_VERSION_2;
        break;
    }

    if ((err = snd_usb_mixer_controls(mixer)) < 0 ||
        (err = snd_usb_mixer_status_create(mixer)) < 0)
        goto _error;

    snd_usb_mixer_apply_create_quirk(mixer);

    err = snd_device_new(chip->card, SNDRV_DEV_LOWLEVEL, mixer, &dev_ops);
    if (err < 0)
        goto _error;

    if (list_empty(&chip->mixer_list) &&
        !snd_card_proc_new(chip->card, "usbmixer", &entry))
        snd_info_set_text_ops(entry, chip, snd_usb_mixer_proc_read);

    list_add(&mixer->list, &chip->mixer_list);
    return 0;

_error:
    snd_usb_mixer_free(mixer);
    return err;
}

void snd_usb_mixer_disconnect(struct list_head *p)
{
    struct usb_mixer_interface *mixer;

    mixer = list_entry(p, struct usb_mixer_interface, list);
    usb_kill_urb(mixer->urb);
    usb_kill_urb(mixer->rc_urb);
}