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usbmixer.c

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

#include <sound/driver.h>
#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 <sound/core.h>
#include <sound/control.h>

#include "usbaudio.h"


/*
 */

/* ignore error from controls - for debugging */
/* #define IGNORE_CTL_ERROR */

typedef struct usb_mixer_build mixer_build_t;
typedef struct usb_audio_term usb_audio_term_t;
typedef struct usb_mixer_elem_info usb_mixer_elem_info_t;


struct usb_audio_term {
      int id;
      int type;
      int channels;
      unsigned int chconfig;
      int name;
};

struct usbmix_name_map;

struct usb_mixer_build {
      snd_usb_audio_t *chip;
      unsigned char *buffer;
      unsigned int buflen;
      unsigned int ctrlif;
      unsigned short vendor;
      unsigned short product;
      DECLARE_BITMAP(unitbitmap, 32*32);
      usb_audio_term_t oterm;
      const struct usbmix_name_map *map;
};

struct usb_mixer_elem_info {
      snd_usb_audio_t *chip;
      unsigned int ctrlif;
      unsigned int id;
      unsigned int control;   /* CS or ICN (high byte) */
      unsigned int cmask; /* channel mask bitmap: 0 = master */
      int channels;
      int val_type;
      int min, max, res;
      unsigned int initialized: 1;
};


enum {
      USB_FEATURE_NONE = 0,
      USB_FEATURE_MUTE = 1,
      USB_FEATURE_VOLUME,
      USB_FEATURE_BASS,
      USB_FEATURE_MID,
      USB_FEATURE_TREBLE,
      USB_FEATURE_GEQ,
      USB_FEATURE_AGC,
      USB_FEATURE_DELAY,
      USB_FEATURE_BASSBOOST,
      USB_FEATURE_LOUDNESS
};

enum {
      USB_MIXER_BOOLEAN,
      USB_MIXER_INV_BOOLEAN,
      USB_MIXER_S8,
      USB_MIXER_U8,
      USB_MIXER_S16,
      USB_MIXER_U16,
};

enum {
      USB_PROC_UPDOWN = 1,
      USB_PROC_UPDOWN_SWITCH = 1,
      USB_PROC_UPDOWN_MODE_SEL = 2,

      USB_PROC_PROLOGIC = 2,
      USB_PROC_PROLOGIC_SWITCH = 1,
      USB_PROC_PROLOGIC_MODE_SEL = 2,

      USB_PROC_3DENH = 3,
      USB_PROC_3DENH_SWITCH = 1,
      USB_PROC_3DENH_SPACE = 2,

      USB_PROC_REVERB = 4,
      USB_PROC_REVERB_SWITCH = 1,
      USB_PROC_REVERB_LEVEL = 2,
      USB_PROC_REVERB_TIME = 3,
      USB_PROC_REVERB_DELAY = 4,

      USB_PROC_CHORUS = 5,
      USB_PROC_CHORUS_SWITCH = 1,
      USB_PROC_CHORUS_LEVEL = 2,
      USB_PROC_CHORUS_RATE = 3,
      USB_PROC_CHORUS_DEPTH = 4,

      USB_PROC_DCR = 6,
      USB_PROC_DCR_SWITCH = 1,
      USB_PROC_DCR_RATIO = 2,
      USB_PROC_DCR_MAX_AMP = 3,
      USB_PROC_DCR_THRESHOLD = 4,
      USB_PROC_DCR_ATTACK = 5,
      USB_PROC_DCR_RELEASE = 6,
};

#define MAX_CHANNELS    10    /* max logical channels */


/*
 * 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 "usbmixer_maps.c"

/* get the mapped name if the unit matches */
static int check_mapped_name(mixer_build_t *state, int unitid, int control, char *buf, int buflen)
{
      const struct usbmix_name_map *p;

      if (! state->map)
            return 0;

      for (p = state->map; p->id; p++) {
            if (p->id == unitid && p->name &&
                (! control || ! p->control || control == p->control)) {
                  buflen--;
                  return strlcpy(buf, p->name, buflen);
            }
      }
      return 0;
}

/* check whether the control should be ignored */
static int check_ignored_ctl(mixer_build_t *state, int unitid, int control)
{
      const struct usbmix_name_map *p;

      if (! state->map)
            return 0;
      for (p = state->map; p->id; p++) {
            if (p->id == unitid && ! p->name &&
                (! control || ! p->control || control == p->control)) {
                  // printk("ignored control %d:%d\n", unitid, control);
                  return 1;
            }
      }
      return 0;
}

/*
 * find an audio control unit with the given unit id
 */
static void *find_audio_control_unit(mixer_build_t *state, unsigned char unit)
{
      unsigned char *p;

      p = NULL;
      while ((p = snd_usb_find_desc(state->buffer, state->buflen, p,
                              USB_DT_CS_INTERFACE)) != NULL) {
            if (p[0] >= 4 && p[2] >= INPUT_TERMINAL && p[2] <= EXTENSION_UNIT && p[3] == unit)
                  return p;
      }
      return NULL;
}


/*
 * copy a string with the given id
 */
static int snd_usb_copy_string_desc(mixer_build_t *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(usb_mixer_elem_info_t *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(usb_mixer_elem_info_t *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(usb_mixer_elem_info_t *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;
      else
            return (val - cval->min) / cval->res;
}

static int get_abs_value(usb_mixer_elem_info_t *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(usb_mixer_elem_info_t *cval, int request, int validx, int *value_ret)
{
      unsigned char buf[2];
      int val_len = cval->val_type >= USB_MIXER_S16 ? 2 : 1;
      int timeout = 10;

      while (timeout-- > 0) {
            if (snd_usb_ctl_msg(cval->chip->dev, usb_rcvctrlpipe(cval->chip->dev, 0),
                            request,
                            USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_IN,
                            validx, cval->ctrlif | (cval->id << 8),
                            buf, val_len, HZ / 10) >= 0) {
                  *value_ret = convert_signed_value(cval, snd_usb_combine_bytes(buf, val_len));
                  return 0;
            }
      }
      snd_printdd(KERN_ERR "cannot get ctl value: req = 0x%x, wValue = 0x%x, wIndex = 0x%x, type = %d\n", request, validx, cval->ctrlif | (cval->id << 8), cval->val_type);
      return -EINVAL;
}

static int get_cur_ctl_value(usb_mixer_elem_info_t *cval, int validx, int *value)
{
      return get_ctl_value(cval, GET_CUR, validx, value);
}

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

/*
 * set a mixer value
 */

static int set_ctl_value(usb_mixer_elem_info_t *cval, int request, int validx, int value_set)
{
      unsigned char buf[2];
      int val_len = cval->val_type >= USB_MIXER_S16 ? 2 : 1;
      int timeout = 10;

      value_set = convert_bytes_value(cval, value_set);
      buf[0] = value_set & 0xff;
      buf[1] = (value_set >> 8) & 0xff;
      while (timeout -- > 0)
            if (snd_usb_ctl_msg(cval->chip->dev, usb_sndctrlpipe(cval->chip->dev, 0),
                            request,
                            USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_OUT,
                            validx, cval->ctrlif | (cval->id << 8),
                            buf, val_len, HZ / 10) >= 0)
                  return 0;
      snd_printdd(KERN_ERR "cannot set ctl value: req = 0x%x, wValue = 0x%x, wIndex = 0x%x, type = %d, data = 0x%x/0x%x\n", request, validx, cval->ctrlif | (cval->id << 8), cval->val_type, buf[0], buf[1]);
      return -EINVAL;
}

static int set_cur_ctl_value(usb_mixer_elem_info_t *cval, int validx, int value)
{
      return set_ctl_value(cval, SET_CUR, validx, value);
}

inline static int set_cur_mix_value(usb_mixer_elem_info_t *cval, int channel, int value)
{
      return set_ctl_value(cval, SET_CUR, (cval->control << 8) | channel, value);
}


/*
 * parser routines begin here...
 */

static int parse_audio_unit(mixer_build_t *state, int unitid);


/*
 * check if the input/output channel routing is enabled on the given bitmap.
 * used for mixer unit parser
 */
static int check_matrix_bitmap(unsigned char *bmap, int ich, int och, int num_outs)
{
      int idx = ich * num_outs + och;
      return bmap[idx >> 3] & (0x80 >> (idx & 7));
}


/*
 * add an alsa control element
 * search and increment the index until an empty slot is found.
 *
 * if failed, give up and free the control instance.
 */

static int add_control_to_empty(snd_card_t *card, snd_kcontrol_t *kctl)
{
      int err;
      while (snd_ctl_find_id(card, &kctl->id))
            kctl->id.index++;
      if ((err = snd_ctl_add(card, kctl)) < 0) {
            snd_printd(KERN_ERR "cannot add control (err = %d)\n", err);
            snd_ctl_free_one(kctl);
      }
      return err;
}


/*
 * 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(mixer_build_t *state, usb_audio_term_t *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 SELECTOR_UNIT:
                  strcpy(name, "Selector"); return 8;
            case PROCESSING_UNIT:
                  strcpy(name, "Process Unit"); return 12;
            case EXTENSION_UNIT:
                  strcpy(name, "Ext Unit"); return 8;
            case 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(mixer_build_t *state, int id, usb_audio_term_t *term)
{
      unsigned char *p1;

      memset(term, 0, sizeof(*term));
      while ((p1 = find_audio_control_unit(state, id)) != NULL) {
            term->id = id;
            switch (p1[2]) {
            case INPUT_TERMINAL:
                  term->type = combine_word(p1 + 4);
                  term->channels = p1[7];
                  term->chconfig = combine_word(p1 + 8);
                  term->name = p1[11];
                  return 0;
            case FEATURE_UNIT:
                  id = p1[4];
                  break; /* continue to parse */
            case MIXER_UNIT:
                  term->type = p1[2] << 16; /* virtual type */
                  term->channels = p1[5 + p1[4]];
                  term->chconfig = combine_word(p1 + 6 + p1[4]);
                  term->name = p1[p1[0] - 1];
                  return 0;
            case SELECTOR_UNIT:
                  /* call recursively to retrieve the channel info */
                  if (check_input_term(state, p1[5], term) < 0)
                        return -ENODEV;
                  term->type = p1[2] << 16; /* virtual type */
                  term->id = id;
                  term->name = p1[9 + p1[0] - 1];
                  return 0;
            case PROCESSING_UNIT:
            case EXTENSION_UNIT:
                  if (p1[6] == 1) {
                        id = p1[7];
                        break; /* continue to parse */
                  }
                  term->type = p1[2] << 16; /* virtual type */
                  term->channels = p1[7 + p1[6]];
                  term->chconfig = combine_word(p1 + 8 + p1[6]);
                  term->name = p1[12 + p1[6] + p1[11 + p1[6]]];
                  return 0;
            default:
                  return -ENODEV;
            }
      }
      return -ENODEV;
}


/*
 * Feature Unit
 */

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

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


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


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

/*
 * retrieve the minimum and maximum values for the specified control
 */
static int get_min_max(usb_mixer_elem_info_t *cval, int default_min)
{
      /* for failsafe */
      cval->min = default_min;
      cval->max = cval->min + 1;
      cval->res = 1;

      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, GET_MAX, (cval->control << 8) | minchn, &cval->max) < 0 ||
                get_ctl_value(cval, GET_MIN, (cval->control << 8) | minchn, &cval->min) < 0) {
                  snd_printd(KERN_ERR "%d:%d: cannot get min/max values for control %d (id %d)\n", cval->id, cval->ctrlif, cval->control, cval->id);
                  return -EINVAL;
            }
            if (get_ctl_value(cval, GET_RES, (cval->control << 8) | minchn, &cval->res) < 0) {
                  cval->res = 1;
            } else {
                  int last_valid_res = cval->res;

                  while (cval->res > 1) {
                        if (set_ctl_value(cval, SET_RES, (cval->control << 8) | minchn, cval->res / 2) < 0)
                              break;
                        cval->res /= 2;
                  }
                  if (get_ctl_value(cval, GET_RES, (cval->control << 8) | minchn, &cval->res) < 0)
                        cval->res = last_valid_res;
            }
            if (cval->res == 0)
                  cval->res = 1;
            cval->initialized = 1;
      }
      return 0;
}


/* get a feature/mixer unit info */
static int mixer_ctl_feature_info(snd_kcontrol_t *kcontrol, snd_ctl_elem_info_t *uinfo)
{
      usb_mixer_elem_info_t *cval = kcontrol->private_data;

      if (cval->val_type == USB_MIXER_BOOLEAN ||
          cval->val_type == USB_MIXER_INV_BOOLEAN)
            uinfo->type = SNDRV_CTL_ELEM_TYPE_BOOLEAN;
      else
            uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
      uinfo->count = cval->channels;
      if (cval->val_type == USB_MIXER_BOOLEAN ||
          cval->val_type == USB_MIXER_INV_BOOLEAN) {
            uinfo->value.integer.min = 0;
            uinfo->value.integer.max = 1;
      } else {
            if (! cval->initialized)
                  get_min_max(cval,  0);
            uinfo->value.integer.min = 0;
            uinfo->value.integer.max = (cval->max - cval->min) / cval->res;
      }
      return 0;
}

/* get the current value from feature/mixer unit */
static int mixer_ctl_feature_get(snd_kcontrol_t *kcontrol, snd_ctl_elem_value_t *ucontrol)
{
      usb_mixer_elem_info_t *cval = kcontrol->private_data;
      int c, cnt, val, err;

      if (cval->cmask) {
            cnt = 0;
            for (c = 0; c < MAX_CHANNELS; c++) {
                  if (cval->cmask & (1 << c)) {
                        err = get_cur_mix_value(cval, c + 1, &val);
                        if (err < 0) {
                              if (cval->chip->ignore_ctl_error) {
                                    ucontrol->value.integer.value[0] = cval->min;
                                    return 0;
                              }
                              snd_printd(KERN_ERR "cannot get current value for control %d ch %d: err = %d\n", cval->control, c + 1, err);
                              return err;
                        }
                        val = get_relative_value(cval, val);
                        ucontrol->value.integer.value[cnt] = val;
                        cnt++;
                  }
            }
      } else {
            /* master channel */
            err = get_cur_mix_value(cval, 0, &val);
            if (err < 0) {
                  if (cval->chip->ignore_ctl_error) {
                        ucontrol->value.integer.value[0] = cval->min;
                        return 0;
                  }
                  snd_printd(KERN_ERR "cannot get current value for control %d master ch: err = %d\n", cval->control, err);
                  return 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(snd_kcontrol_t *kcontrol, snd_ctl_elem_value_t *ucontrol)
{
      usb_mixer_elem_info_t *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)) {
                        err = get_cur_mix_value(cval, c + 1, &oval);
                        if (err < 0) {
                              if (cval->chip->ignore_ctl_error)
                                    return 0;
                              return err;
                        }
                        val = ucontrol->value.integer.value[cnt];
                        val = get_abs_value(cval, val);
                        if (oval != val) {
                              set_cur_mix_value(cval, c + 1, val);
                              changed = 1;
                        }
                        get_cur_mix_value(cval, c + 1, &val);
                        cnt++;
                  }
            }
      } else {
            /* master channel */
            err = get_cur_mix_value(cval, 0, &oval);
            if (err < 0 && cval->chip->ignore_ctl_error)
                  return 0;
            if (err < 0)
                  return err;
            val = ucontrol->value.integer.value[0];
            val = get_abs_value(cval, val);
            if (val != oval) {
                  set_cur_mix_value(cval, 0, val);
                  changed = 1;
            }
      }
      return changed;
}

static snd_kcontrol_new_t 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,
};


/*
 * build a feature control
 */

static void build_feature_ctl(mixer_build_t *state, unsigned char *desc,
                        unsigned int ctl_mask, int control,
                        usb_audio_term_t *iterm, int unitid)
{
      unsigned int len = 0;
      int mapped_name = 0;
      int nameid = desc[desc[0] - 1];
      snd_kcontrol_t *kctl;
      usb_mixer_elem_info_t *cval;

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

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

      if (check_ignored_ctl(state, unitid, control))
            return;

      cval = kcalloc(1, sizeof(*cval), GFP_KERNEL);
      if (! cval) {
            snd_printk(KERN_ERR "cannot malloc kcontrol\n");
            return;
      }
      cval->chip = state->chip;
      cval->ctrlif = state->ctrlif;
      cval->id = unitid;
      cval->control = control;
      cval->cmask = ctl_mask;
      cval->val_type = audio_feature_info[control-1].type;
      if (ctl_mask == 0)
            cval->channels = 1;     /* master channel */
      else {
            int i, c = 0;
            for (i = 0; i < 16; i++)
                  if (ctl_mask & (1 << i))
                        c++;
            cval->channels = c;
      }

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

      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(state, unitid, control, 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 USB_FEATURE_MUTE:
      case USB_FEATURE_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 = strlcat(kctl->id.name, " Capture", sizeof(kctl->id.name));
                  } else {
                        len = strlcat(kctl->id.name + len, " Playback", sizeof(kctl->id.name));
                  }
            }
            strlcat(kctl->id.name + len, control == USB_FEATURE_MUTE ? " Switch" : " Volume",
                  sizeof(kctl->id.name));
            break;

      default:
            if (! len)
                  strlcpy(kctl->id.name, audio_feature_info[control-1].name,
                        sizeof(kctl->id.name));
            break;
      }

      /* 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 (((state->vendor == 0x471 && (state->product == 0x104 || state->product == 0x105 || state->product == 0x101)) ||
           (state->vendor == 0x672 && state->product == 0x1041)) && !strcmp(kctl->id.name, "PCM Playback Volume") &&
           cval->min == -15616) {
            snd_printk("USB Audio: using volume control quirk for the UDA1321/N101 chip\n");
            cval->max = -256;
      }

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



/*
 * parse a feature unit
 *
 * most of controlls are defined here.
 */
static int parse_audio_feature_unit(mixer_build_t *state, int unitid, unsigned char *ftr)
{
      int channels, i, j;
      usb_audio_term_t iterm;
      unsigned int master_bits, first_ch_bits;
      int err, csize;

      if (ftr[0] < 7 || ! (csize = ftr[5]) || ftr[0] < 7 + csize) {
            snd_printk(KERN_ERR "usbaudio: unit %u: invalid FEATURE_UNIT descriptor\n", unitid);
            return -EINVAL;
      }

      /* parse the source unit */
      if ((err = parse_audio_unit(state, ftr[4])) < 0)
            return err;

      /* determine the input source type and name */
      if (check_input_term(state, ftr[4], &iterm) < 0)
            return -EINVAL;

      channels = (ftr[0] - 7) / csize - 1;

      master_bits = snd_usb_combine_bytes(ftr + 6, csize);
      if (channels > 0)
            first_ch_bits = snd_usb_combine_bytes(ftr + 6 + csize, csize);
      else
            first_ch_bits = 0;
      /* 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(ftr + 6 + csize * (j+1), csize);
                  if (mask & (1 << i))
                        ch_bits |= (1 << j);
            }
            if (ch_bits & 1) /* the first channel must be set (for ease of programming) */
                  build_feature_ctl(state, ftr, ch_bits, i, &iterm, unitid);
            if (master_bits & (1 << i))
                  build_feature_ctl(state, ftr, 0, i, &iterm, unitid);
      }

      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(mixer_build_t *state, unsigned char *desc,
                         int in_pin, int in_ch, int unitid,
                         usb_audio_term_t *iterm)
{
      usb_mixer_elem_info_t *cval;
      unsigned int input_pins = desc[4];
      unsigned int num_outs = desc[5 + input_pins];
      unsigned int i, len;
      snd_kcontrol_t *kctl;

      if (check_ignored_ctl(state, unitid, 0))
            return;

      cval = kcalloc(1, sizeof(*cval), GFP_KERNEL);
      if (! cval)
            return;

      cval->chip = state->chip;
      cval->ctrlif = state->ctrlif;
      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(desc + 9 + input_pins, 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(state, unitid, 0, 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);
      strlcat(kctl->id.name + len, " Volume", sizeof(kctl->id.name));

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


/*
 * parse a mixer unit
 */
static int parse_audio_mixer_unit(mixer_build_t *state, int unitid, unsigned char *desc)
{
      usb_audio_term_t iterm;
      int input_pins, num_ins, num_outs;
      int pin, ich, err;

      if (desc[0] < 11 || ! (input_pins = desc[4]) || ! (num_outs = desc[5 + input_pins])) {
            snd_printk(KERN_ERR "invalid MIXER UNIT descriptor %d\n", unitid);
            return -EINVAL;
      }
      /* no bmControls field (e.g. Maya44) -> ignore */
      if (desc[0] <= 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[5 + pin]);
            if (err < 0)
                  return err;
            err = check_input_term(state, desc[5 + 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(desc + 9 + input_pins,
                                          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(snd_kcontrol_t *kcontrol, snd_ctl_elem_value_t *ucontrol)
{
      usb_mixer_elem_info_t *cval = kcontrol->private_data;
      int err, val;

      err = get_cur_ctl_value(cval, cval->control << 8, &val);
      if (err < 0 && cval->chip->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(snd_kcontrol_t *kcontrol, snd_ctl_elem_value_t *ucontrol)
{
      usb_mixer_elem_info_t *cval = kcontrol->private_data;
      int val, oval, err;

      err = get_cur_ctl_value(cval, cval->control << 8, &oval);
      if (err < 0) {
            if (cval->chip->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 snd_kcontrol_new_t mixer_procunit_ctl = {
      .iface = SNDRV_CTL_ELEM_IFACE_MIXER,
      .name = "", /* will be filled later */
      .info = mixer_ctl_feature_info,
      .get = mixer_ctl_procunit_get,
      .put = mixer_ctl_procunit_put,
};


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

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

static struct procunit_value_info updown_proc_info[] = {
      { USB_PROC_UPDOWN_SWITCH, "Switch", USB_MIXER_BOOLEAN },
      { USB_PROC_UPDOWN_MODE_SEL, "Mode Select", USB_MIXER_U8, 1 },
      { 0 }
};
static struct procunit_value_info prologic_proc_info[] = {
      { USB_PROC_PROLOGIC_SWITCH, "Switch", USB_MIXER_BOOLEAN },
      { USB_PROC_PROLOGIC_MODE_SEL, "Mode Select", USB_MIXER_U8, 1 },
      { 0 }
};
static struct procunit_value_info threed_enh_proc_info[] = {
      { USB_PROC_3DENH_SWITCH, "Switch", USB_MIXER_BOOLEAN },
      { USB_PROC_3DENH_SPACE, "Spaciousness", USB_MIXER_U8 },
      { 0 }
};
static struct procunit_value_info reverb_proc_info[] = {
      { USB_PROC_REVERB_SWITCH, "Switch", USB_MIXER_BOOLEAN },
      { USB_PROC_REVERB_LEVEL, "Level", USB_MIXER_U8 },
      { USB_PROC_REVERB_TIME, "Time", USB_MIXER_U16 },
      { USB_PROC_REVERB_DELAY, "Delay", USB_MIXER_U8 },
      { 0 }
};
static struct procunit_value_info chorus_proc_info[] = {
      { USB_PROC_CHORUS_SWITCH, "Switch", USB_MIXER_BOOLEAN },
      { USB_PROC_CHORUS_LEVEL, "Level", USB_MIXER_U8 },
      { USB_PROC_CHORUS_RATE, "Rate", USB_MIXER_U16 },
      { USB_PROC_CHORUS_DEPTH, "Depth", USB_MIXER_U16 },
      { 0 }
};
static struct procunit_value_info dcr_proc_info[] = {
      { USB_PROC_DCR_SWITCH, "Switch", USB_MIXER_BOOLEAN },
      { USB_PROC_DCR_RATIO, "Ratio", USB_MIXER_U16 },
      { USB_PROC_DCR_MAX_AMP, "Max Amp", USB_MIXER_S16 },
      { USB_PROC_DCR_THRESHOLD, "Threshold", USB_MIXER_S16 },
      { USB_PROC_DCR_ATTACK, "Attack Time", USB_MIXER_U16 },
      { USB_PROC_DCR_RELEASE, "Release Time", USB_MIXER_U16 },
      { 0 }
};

static struct procunit_info procunits[] = {
      { USB_PROC_UPDOWN, "Up Down", updown_proc_info },
      { USB_PROC_PROLOGIC, "Dolby Prologic", prologic_proc_info },
      { USB_PROC_3DENH, "3D Stereo Extender", threed_enh_proc_info },
      { USB_PROC_REVERB, "Reverb", reverb_proc_info },
      { USB_PROC_CHORUS, "Chorus", chorus_proc_info },
      { USB_PROC_DCR, "DCR", dcr_proc_info },
      { 0 },
};

/*
 * build a processing/extension unit
 */
static int build_audio_procunit(mixer_build_t *state, int unitid, unsigned char *dsc, struct procunit_info *list, char *name)
{
      int num_ins = dsc[6];
      usb_mixer_elem_info_t *cval;
      snd_kcontrol_t *kctl;
      int i, err, nameid, type, len;
      struct procunit_info *info;
      struct procunit_value_info *valinfo;
      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 (dsc[0] < 13 || dsc[0] < 13 + num_ins || dsc[0] < num_ins + dsc[11 + num_ins]) {
            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, dsc[7 + i])) < 0)
                  return err;
      }

      type = combine_word(&dsc[4]);
      if (! type)
            return 0; /* undefined? */

      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++) {
            /* FIXME: bitmap might be longer than 8bit */
            if (! (dsc[12 + num_ins] & (1 << (valinfo->control - 1))))
                  continue;
            if (check_ignored_ctl(state, unitid, valinfo->control))
                  continue;
            cval = kcalloc(1, sizeof(*cval), GFP_KERNEL);
            if (! cval) {
                  snd_printk(KERN_ERR "cannot malloc kcontrol\n");
                  return -ENOMEM;
            }
            cval->chip = state->chip;
            cval->ctrlif = state->ctrlif;
            cval->id = unitid;
            cval->control = valinfo->control;
            cval->val_type = valinfo->val_type;
            cval->channels = 1;

            /* get min/max values */
            if (type == USB_PROC_UPDOWN && cval->control == USB_PROC_UPDOWN_MODE_SEL) {
                  /* FIXME: hard-coded */
                  cval->min = 1;
                  cval->max = dsc[15];
                  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(state, unitid, cval->control, kctl->id.name, sizeof(kctl->id.name)))
                  ;
            else if (info->name)
                  strlcpy(kctl->id.name, info->name, sizeof(kctl->id.name));
            else {
                  nameid = dsc[12 + num_ins + dsc[11 + num_ins]];
                  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));
            }
            strlcat(kctl->id.name, " ", sizeof(kctl->id.name));
            strlcat(kctl->id.name, valinfo->suffix, sizeof(kctl->id.name));

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


static int parse_audio_processing_unit(mixer_build_t *state, int unitid, unsigned char *desc)
{
      return build_audio_procunit(state, unitid, desc, procunits, "Processing Unit");
}

static int parse_audio_extension_unit(mixer_build_t *state, int unitid, unsigned char *desc)
{
      return build_audio_procunit(state, unitid, desc, NULL, "Extension Unit");
}


/*
 * Selector Unit
 */

/* info callback for selector unit
 * use an enumerator type for routing
 */
static int mixer_ctl_selector_info(snd_kcontrol_t *kcontrol, snd_ctl_elem_info_t *uinfo)
{
      usb_mixer_elem_info_t *cval = kcontrol->private_data;
      char **itemlist = (char **)kcontrol->private_value;

      snd_assert(itemlist, return -EINVAL);
      uinfo->type = SNDRV_CTL_ELEM_TYPE_ENUMERATED;
      uinfo->count = 1;
      uinfo->value.enumerated.items = cval->max;
      if ((int)uinfo->value.enumerated.item >= cval->max)
            uinfo->value.enumerated.item = cval->max - 1;
      strcpy(uinfo->value.enumerated.name, itemlist[uinfo->value.enumerated.item]);
      return 0;
}

/* get callback for selector unit */
static int mixer_ctl_selector_get(snd_kcontrol_t *kcontrol, snd_ctl_elem_value_t *ucontrol)
{
      usb_mixer_elem_info_t *cval = kcontrol->private_data;
      int val, err;

      err = get_cur_ctl_value(cval, 0, &val);
      if (err < 0) {
            if (cval->chip->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(snd_kcontrol_t *kcontrol, snd_ctl_elem_value_t *ucontrol)
{
      usb_mixer_elem_info_t *cval = kcontrol->private_data;
      int val, oval, err;

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

/* alsa control interface for selector unit */
static snd_kcontrol_new_t 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(snd_kcontrol_t *kctl)
{
      int i, num_ins = 0;

      if (kctl->private_data) {
            usb_mixer_elem_info_t *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(mixer_build_t *state, int unitid, unsigned char *desc)
{
      unsigned int num_ins = desc[4];
      unsigned int i, nameid, len;
      int err;
      usb_mixer_elem_info_t *cval;
      snd_kcontrol_t *kctl;
      char **namelist;

      if (! num_ins || desc[0] < 6 + num_ins) {
            snd_printk(KERN_ERR "invalid SELECTOR UNIT descriptor %d\n", unitid);
            return -EINVAL;
      }

      for (i = 0; i < num_ins; i++) {
            if ((err = parse_audio_unit(state, desc[5 + i])) < 0)
                  return err;
      }

      if (num_ins == 1) /* only one ? nonsense! */
            return 0;

      if (check_ignored_ctl(state, unitid, 0))
            return 0;

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

      namelist = kmalloc(sizeof(char *) * num_ins, 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 < num_ins; i++) {
            usb_audio_term_t iterm;
            len = 0;
            namelist[i] = kmalloc(MAX_ITEM_NAME_LEN, GFP_KERNEL);
            if (! namelist[i]) {
                  snd_printk(KERN_ERR "cannot malloc\n");
                  while (--i > 0)
                        kfree(namelist[i]);
                  kfree(namelist);
                  kfree(cval);
                  return -ENOMEM;
            }
            if (check_input_term(state, desc[5 + 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(cval);
            return -ENOMEM;
      }
      kctl->private_value = (unsigned long)namelist;
      kctl->private_free = usb_mixer_selector_elem_free;

      nameid = desc[desc[0] - 1];
      len = check_mapped_name(state, unitid, 0, kctl->id.name, sizeof(kctl->id.name));
      if (len)
            ;
      else if (nameid)
            snd_usb_copy_string_desc(state, nameid, kctl->id.name, sizeof(kctl->id.name));
      else {
            len = get_term_name(state, &state->oterm,
                            kctl->id.name, sizeof(kctl->id.name), 0);
            if (! len)
                  strlcpy(kctl->id.name, "USB", sizeof(kctl->id.name));

            if ((state->oterm.type & 0xff00) == 0x0100)
                  strlcat(kctl->id.name, " Capture Source", sizeof(kctl->id.name));
            else
                  strlcat(kctl->id.name, " Playback Source", sizeof(kctl->id.name));
      }

      snd_printdd(KERN_INFO "[%d] SU [%s] items = %d\n",
                cval->id, kctl->id.name, num_ins);
      if ((err = add_control_to_empty(state->chip->card, kctl)) < 0)
            return err;

      return 0;
}


/*
 * parse an audio unit recursively
 */

static int parse_audio_unit(mixer_build_t *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 INPUT_TERMINAL:
            return 0; /* NOP */
      case MIXER_UNIT:
            return parse_audio_mixer_unit(state, unitid, p1);
      case SELECTOR_UNIT:
            return parse_audio_selector_unit(state, unitid, p1);
      case FEATURE_UNIT:
            return parse_audio_feature_unit(state, unitid, p1);
      case PROCESSING_UNIT:
            return parse_audio_processing_unit(state, unitid, p1);
      case EXTENSION_UNIT:
            return parse_audio_extension_unit(state, unitid, p1);
      default:
            snd_printk(KERN_ERR "usbaudio: unit %u: unexpected type 0x%02x\n", unitid, p1[2]);
            return -EINVAL;
      }
}

/*
 * create mixer controls
 *
 * walk through all OUTPUT_TERMINAL descriptors to search for mixers
 */
int snd_usb_create_mixer(snd_usb_audio_t *chip, int ctrlif)
{
      unsigned char *desc;
      mixer_build_t state;
      int err;
      const struct usbmix_ctl_map *map;
      struct usb_device_descriptor *dev = &chip->dev->descriptor;
      struct usb_host_interface *hostif = &usb_ifnum_to_if(chip->dev, ctrlif)->altsetting[0];

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

      memset(&state, 0, sizeof(state));
      state.chip = chip;
      state.buffer = hostif->extra;
      state.buflen = hostif->extralen;
      state.ctrlif = ctrlif;
      state.vendor = dev->idVendor;
      state.product = dev->idProduct;

      /* check the mapping table */
      for (map = usbmix_ctl_maps; map->vendor; map++) {
            if (map->vendor == dev->idVendor && map->product == dev->idProduct) {
                  state.map = map->map;
                  chip->ignore_ctl_error = map->ignore_ctl_error;
                  break;
            }
      }
#ifdef IGNORE_CTL_ERROR
      chip->ignore_ctl_error = 1;
#endif

      desc = NULL;
      while ((desc = snd_usb_find_csint_desc(hostif->extra, hostif->extralen, desc, OUTPUT_TERMINAL)) != NULL) {
            if (desc[0] < 9)
                  continue; /* invalid descriptor? */
            set_bit(desc[3], state.unitbitmap);  /* mark terminal ID as visited */
            state.oterm.id = desc[3];
            state.oterm.type = combine_word(&desc[4]);
            state.oterm.name = desc[8];
            err = parse_audio_unit(&state, desc[7]);
            if (err < 0)
                  return err;
      }
      return 0;
}

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