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control.c

/*
 *  Routines for driver control interface
 *  Copyright (c) by Jaroslav Kysela <perex@perex.cz>
 *
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 *
 */

#include <linux/threads.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/time.h>
#include <sound/core.h>
#include <sound/minors.h>
#include <sound/info.h>
#include <sound/control.h>

/* max number of user-defined controls */
#define MAX_USER_CONTROLS     32

struct snd_kctl_ioctl {
      struct list_head list;        /* list of all ioctls */
      snd_kctl_ioctl_func_t fioctl;
};

static DECLARE_RWSEM(snd_ioctl_rwsem);
static LIST_HEAD(snd_control_ioctls);
#ifdef CONFIG_COMPAT
static LIST_HEAD(snd_control_compat_ioctls);
#endif

static int snd_ctl_open(struct inode *inode, struct file *file)
{
      unsigned long flags;
      struct snd_card *card;
      struct snd_ctl_file *ctl;
      int err;

      card = snd_lookup_minor_data(iminor(inode), SNDRV_DEVICE_TYPE_CONTROL);
      if (!card) {
            err = -ENODEV;
            goto __error1;
      }
      err = snd_card_file_add(card, file);
      if (err < 0) {
            err = -ENODEV;
            goto __error1;
      }
      if (!try_module_get(card->module)) {
            err = -EFAULT;
            goto __error2;
      }
      ctl = kzalloc(sizeof(*ctl), GFP_KERNEL);
      if (ctl == NULL) {
            err = -ENOMEM;
            goto __error;
      }
      INIT_LIST_HEAD(&ctl->events);
      init_waitqueue_head(&ctl->change_sleep);
      spin_lock_init(&ctl->read_lock);
      ctl->card = card;
      ctl->prefer_pcm_subdevice = -1;
      ctl->prefer_rawmidi_subdevice = -1;
      ctl->pid = current->pid;
      file->private_data = ctl;
      write_lock_irqsave(&card->ctl_files_rwlock, flags);
      list_add_tail(&ctl->list, &card->ctl_files);
      write_unlock_irqrestore(&card->ctl_files_rwlock, flags);
      return 0;

      __error:
      module_put(card->module);
      __error2:
      snd_card_file_remove(card, file);
      __error1:
            return err;
}

static void snd_ctl_empty_read_queue(struct snd_ctl_file * ctl)
{
      unsigned long flags;
      struct snd_kctl_event *cread;
      
      spin_lock_irqsave(&ctl->read_lock, flags);
      while (!list_empty(&ctl->events)) {
            cread = snd_kctl_event(ctl->events.next);
            list_del(&cread->list);
            kfree(cread);
      }
      spin_unlock_irqrestore(&ctl->read_lock, flags);
}

static int snd_ctl_release(struct inode *inode, struct file *file)
{
      unsigned long flags;
      struct snd_card *card;
      struct snd_ctl_file *ctl;
      struct snd_kcontrol *control;
      unsigned int idx;

      ctl = file->private_data;
      fasync_helper(-1, file, 0, &ctl->fasync);
      file->private_data = NULL;
      card = ctl->card;
      write_lock_irqsave(&card->ctl_files_rwlock, flags);
      list_del(&ctl->list);
      write_unlock_irqrestore(&card->ctl_files_rwlock, flags);
      down_write(&card->controls_rwsem);
      list_for_each_entry(control, &card->controls, list)
            for (idx = 0; idx < control->count; idx++)
                  if (control->vd[idx].owner == ctl)
                        control->vd[idx].owner = NULL;
      up_write(&card->controls_rwsem);
      snd_ctl_empty_read_queue(ctl);
      kfree(ctl);
      module_put(card->module);
      snd_card_file_remove(card, file);
      return 0;
}

void snd_ctl_notify(struct snd_card *card, unsigned int mask,
                struct snd_ctl_elem_id *id)
{
      unsigned long flags;
      struct snd_ctl_file *ctl;
      struct snd_kctl_event *ev;
      
      snd_assert(card != NULL && id != NULL, return);
      read_lock(&card->ctl_files_rwlock);
#if defined(CONFIG_SND_MIXER_OSS) || defined(CONFIG_SND_MIXER_OSS_MODULE)
      card->mixer_oss_change_count++;
#endif
      list_for_each_entry(ctl, &card->ctl_files, list) {
            if (!ctl->subscribed)
                  continue;
            spin_lock_irqsave(&ctl->read_lock, flags);
            list_for_each_entry(ev, &ctl->events, list) {
                  if (ev->id.numid == id->numid) {
                        ev->mask |= mask;
                        goto _found;
                  }
            }
            ev = kzalloc(sizeof(*ev), GFP_ATOMIC);
            if (ev) {
                  ev->id = *id;
                  ev->mask = mask;
                  list_add_tail(&ev->list, &ctl->events);
            } else {
                  snd_printk(KERN_ERR "No memory available to allocate event\n");
            }
      _found:
            wake_up(&ctl->change_sleep);
            spin_unlock_irqrestore(&ctl->read_lock, flags);
            kill_fasync(&ctl->fasync, SIGIO, POLL_IN);
      }
      read_unlock(&card->ctl_files_rwlock);
}

EXPORT_SYMBOL(snd_ctl_notify);

/**
 * snd_ctl_new - create a control instance from the template
 * @control: the control template
 * @access: the default control access
 *
 * Allocates a new struct snd_kcontrol instance and copies the given template 
 * to the new instance. It does not copy volatile data (access).
 *
 * Returns the pointer of the new instance, or NULL on failure.
 */
static struct snd_kcontrol *snd_ctl_new(struct snd_kcontrol *control,
                              unsigned int access)
{
      struct snd_kcontrol *kctl;
      unsigned int idx;
      
      snd_assert(control != NULL, return NULL);
      snd_assert(control->count > 0, return NULL);
      kctl = kzalloc(sizeof(*kctl) + sizeof(struct snd_kcontrol_volatile) * control->count, GFP_KERNEL);
      if (kctl == NULL) {
            snd_printk(KERN_ERR "Cannot allocate control instance\n");
            return NULL;
      }
      *kctl = *control;
      for (idx = 0; idx < kctl->count; idx++)
            kctl->vd[idx].access = access;
      return kctl;
}

/**
 * snd_ctl_new1 - create a control instance from the template
 * @ncontrol: the initialization record
 * @private_data: the private data to set
 *
 * Allocates a new struct snd_kcontrol instance and initialize from the given 
 * template.  When the access field of ncontrol is 0, it's assumed as
 * READWRITE access. When the count field is 0, it's assumes as one.
 *
 * Returns the pointer of the newly generated instance, or NULL on failure.
 */
struct snd_kcontrol *snd_ctl_new1(const struct snd_kcontrol_new *ncontrol,
                          void *private_data)
{
      struct snd_kcontrol kctl;
      unsigned int access;
      
      snd_assert(ncontrol != NULL, return NULL);
      snd_assert(ncontrol->info != NULL, return NULL);
      memset(&kctl, 0, sizeof(kctl));
      kctl.id.iface = ncontrol->iface;
      kctl.id.device = ncontrol->device;
      kctl.id.subdevice = ncontrol->subdevice;
      if (ncontrol->name)
            strlcpy(kctl.id.name, ncontrol->name, sizeof(kctl.id.name));
      kctl.id.index = ncontrol->index;
      kctl.count = ncontrol->count ? ncontrol->count : 1;
      access = ncontrol->access == 0 ? SNDRV_CTL_ELEM_ACCESS_READWRITE :
             (ncontrol->access & (SNDRV_CTL_ELEM_ACCESS_READWRITE|
                              SNDRV_CTL_ELEM_ACCESS_INACTIVE|
                              SNDRV_CTL_ELEM_ACCESS_TLV_READWRITE|
                              SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK));
      kctl.info = ncontrol->info;
      kctl.get = ncontrol->get;
      kctl.put = ncontrol->put;
      kctl.tlv.p = ncontrol->tlv.p;
      kctl.private_value = ncontrol->private_value;
      kctl.private_data = private_data;
      return snd_ctl_new(&kctl, access);
}

EXPORT_SYMBOL(snd_ctl_new1);

/**
 * snd_ctl_free_one - release the control instance
 * @kcontrol: the control instance
 *
 * Releases the control instance created via snd_ctl_new()
 * or snd_ctl_new1().
 * Don't call this after the control was added to the card.
 */
void snd_ctl_free_one(struct snd_kcontrol *kcontrol)
{
      if (kcontrol) {
            if (kcontrol->private_free)
                  kcontrol->private_free(kcontrol);
            kfree(kcontrol);
      }
}

EXPORT_SYMBOL(snd_ctl_free_one);

static unsigned int snd_ctl_hole_check(struct snd_card *card,
                               unsigned int count)
{
      struct snd_kcontrol *kctl;

      list_for_each_entry(kctl, &card->controls, list) {
            if ((kctl->id.numid <= card->last_numid &&
                 kctl->id.numid + kctl->count > card->last_numid) ||
                (kctl->id.numid <= card->last_numid + count - 1 &&
                 kctl->id.numid + kctl->count > card->last_numid + count - 1))
                  return card->last_numid = kctl->id.numid + kctl->count - 1;
      }
      return card->last_numid;
}

static int snd_ctl_find_hole(struct snd_card *card, unsigned int count)
{
      unsigned int last_numid, iter = 100000;

      last_numid = card->last_numid;
      while (last_numid != snd_ctl_hole_check(card, count)) {
            if (--iter == 0) {
                  /* this situation is very unlikely */
                  snd_printk(KERN_ERR "unable to allocate new control numid\n");
                  return -ENOMEM;
            }
            last_numid = card->last_numid;
      }
      return 0;
}

/**
 * snd_ctl_add - add the control instance to the card
 * @card: the card instance
 * @kcontrol: the control instance to add
 *
 * Adds the control instance created via snd_ctl_new() or
 * snd_ctl_new1() to the given card. Assigns also an unique
 * numid used for fast search.
 *
 * Returns zero if successful, or a negative error code on failure.
 *
 * It frees automatically the control which cannot be added.
 */
int snd_ctl_add(struct snd_card *card, struct snd_kcontrol *kcontrol)
{
      struct snd_ctl_elem_id id;
      unsigned int idx;
      int err = -EINVAL;

      if (! kcontrol)
            return err;
      snd_assert(card != NULL, goto error);
      snd_assert(kcontrol->info != NULL, goto error);
      id = kcontrol->id;
      down_write(&card->controls_rwsem);
      if (snd_ctl_find_id(card, &id)) {
            up_write(&card->controls_rwsem);
            snd_printd(KERN_ERR "control %i:%i:%i:%s:%i is already present\n",
                              id.iface,
                              id.device,
                              id.subdevice,
                              id.name,
                              id.index);
            err = -EBUSY;
            goto error;
      }
      if (snd_ctl_find_hole(card, kcontrol->count) < 0) {
            up_write(&card->controls_rwsem);
            err = -ENOMEM;
            goto error;
      }
      list_add_tail(&kcontrol->list, &card->controls);
      card->controls_count += kcontrol->count;
      kcontrol->id.numid = card->last_numid + 1;
      card->last_numid += kcontrol->count;
      up_write(&card->controls_rwsem);
      for (idx = 0; idx < kcontrol->count; idx++, id.index++, id.numid++)
            snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_ADD, &id);
      return 0;

 error:
      snd_ctl_free_one(kcontrol);
      return err;
}

EXPORT_SYMBOL(snd_ctl_add);

/**
 * snd_ctl_remove - remove the control from the card and release it
 * @card: the card instance
 * @kcontrol: the control instance to remove
 *
 * Removes the control from the card and then releases the instance.
 * You don't need to call snd_ctl_free_one(). You must be in
 * the write lock - down_write(&card->controls_rwsem).
 * 
 * Returns 0 if successful, or a negative error code on failure.
 */
int snd_ctl_remove(struct snd_card *card, struct snd_kcontrol *kcontrol)
{
      struct snd_ctl_elem_id id;
      unsigned int idx;

      snd_assert(card != NULL && kcontrol != NULL, return -EINVAL);
      list_del(&kcontrol->list);
      card->controls_count -= kcontrol->count;
      id = kcontrol->id;
      for (idx = 0; idx < kcontrol->count; idx++, id.index++, id.numid++)
            snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_REMOVE, &id);
      snd_ctl_free_one(kcontrol);
      return 0;
}

EXPORT_SYMBOL(snd_ctl_remove);

/**
 * snd_ctl_remove_id - remove the control of the given id and release it
 * @card: the card instance
 * @id: the control id to remove
 *
 * Finds the control instance with the given id, removes it from the
 * card list and releases it.
 * 
 * Returns 0 if successful, or a negative error code on failure.
 */
int snd_ctl_remove_id(struct snd_card *card, struct snd_ctl_elem_id *id)
{
      struct snd_kcontrol *kctl;
      int ret;

      down_write(&card->controls_rwsem);
      kctl = snd_ctl_find_id(card, id);
      if (kctl == NULL) {
            up_write(&card->controls_rwsem);
            return -ENOENT;
      }
      ret = snd_ctl_remove(card, kctl);
      up_write(&card->controls_rwsem);
      return ret;
}

EXPORT_SYMBOL(snd_ctl_remove_id);

/**
 * snd_ctl_remove_unlocked_id - remove the unlocked control of the given id and release it
 * @file: active control handle
 * @id: the control id to remove
 *
 * Finds the control instance with the given id, removes it from the
 * card list and releases it.
 * 
 * Returns 0 if successful, or a negative error code on failure.
 */
static int snd_ctl_remove_unlocked_id(struct snd_ctl_file * file,
                              struct snd_ctl_elem_id *id)
{
      struct snd_card *card = file->card;
      struct snd_kcontrol *kctl;
      int idx, ret;

      down_write(&card->controls_rwsem);
      kctl = snd_ctl_find_id(card, id);
      if (kctl == NULL) {
            up_write(&card->controls_rwsem);
            return -ENOENT;
      }
      for (idx = 0; idx < kctl->count; idx++)
            if (kctl->vd[idx].owner != NULL && kctl->vd[idx].owner != file) {
                  up_write(&card->controls_rwsem);
                  return -EBUSY;
            }
      ret = snd_ctl_remove(card, kctl);
      up_write(&card->controls_rwsem);
      return ret;
}

/**
 * snd_ctl_rename_id - replace the id of a control on the card
 * @card: the card instance
 * @src_id: the old id
 * @dst_id: the new id
 *
 * Finds the control with the old id from the card, and replaces the
 * id with the new one.
 *
 * Returns zero if successful, or a negative error code on failure.
 */
int snd_ctl_rename_id(struct snd_card *card, struct snd_ctl_elem_id *src_id,
                  struct snd_ctl_elem_id *dst_id)
{
      struct snd_kcontrol *kctl;

      down_write(&card->controls_rwsem);
      kctl = snd_ctl_find_id(card, src_id);
      if (kctl == NULL) {
            up_write(&card->controls_rwsem);
            return -ENOENT;
      }
      kctl->id = *dst_id;
      kctl->id.numid = card->last_numid + 1;
      card->last_numid += kctl->count;
      up_write(&card->controls_rwsem);
      return 0;
}

EXPORT_SYMBOL(snd_ctl_rename_id);

/**
 * snd_ctl_find_numid - find the control instance with the given number-id
 * @card: the card instance
 * @numid: the number-id to search
 *
 * Finds the control instance with the given number-id from the card.
 *
 * Returns the pointer of the instance if found, or NULL if not.
 *
 * The caller must down card->controls_rwsem before calling this function
 * (if the race condition can happen).
 */
struct snd_kcontrol *snd_ctl_find_numid(struct snd_card *card, unsigned int numid)
{
      struct snd_kcontrol *kctl;

      snd_assert(card != NULL && numid != 0, return NULL);
      list_for_each_entry(kctl, &card->controls, list) {
            if (kctl->id.numid <= numid && kctl->id.numid + kctl->count > numid)
                  return kctl;
      }
      return NULL;
}

EXPORT_SYMBOL(snd_ctl_find_numid);

/**
 * snd_ctl_find_id - find the control instance with the given id
 * @card: the card instance
 * @id: the id to search
 *
 * Finds the control instance with the given id from the card.
 *
 * Returns the pointer of the instance if found, or NULL if not.
 *
 * The caller must down card->controls_rwsem before calling this function
 * (if the race condition can happen).
 */
struct snd_kcontrol *snd_ctl_find_id(struct snd_card *card,
                             struct snd_ctl_elem_id *id)
{
      struct snd_kcontrol *kctl;

      snd_assert(card != NULL && id != NULL, return NULL);
      if (id->numid != 0)
            return snd_ctl_find_numid(card, id->numid);
      list_for_each_entry(kctl, &card->controls, list) {
            if (kctl->id.iface != id->iface)
                  continue;
            if (kctl->id.device != id->device)
                  continue;
            if (kctl->id.subdevice != id->subdevice)
                  continue;
            if (strncmp(kctl->id.name, id->name, sizeof(kctl->id.name)))
                  continue;
            if (kctl->id.index > id->index)
                  continue;
            if (kctl->id.index + kctl->count <= id->index)
                  continue;
            return kctl;
      }
      return NULL;
}

EXPORT_SYMBOL(snd_ctl_find_id);

static int snd_ctl_card_info(struct snd_card *card, struct snd_ctl_file * ctl,
                       unsigned int cmd, void __user *arg)
{
      struct snd_ctl_card_info *info;

      info = kzalloc(sizeof(*info), GFP_KERNEL);
      if (! info)
            return -ENOMEM;
      down_read(&snd_ioctl_rwsem);
      info->card = card->number;
      strlcpy(info->id, card->id, sizeof(info->id));
      strlcpy(info->driver, card->driver, sizeof(info->driver));
      strlcpy(info->name, card->shortname, sizeof(info->name));
      strlcpy(info->longname, card->longname, sizeof(info->longname));
      strlcpy(info->mixername, card->mixername, sizeof(info->mixername));
      strlcpy(info->components, card->components, sizeof(info->components));
      up_read(&snd_ioctl_rwsem);
      if (copy_to_user(arg, info, sizeof(struct snd_ctl_card_info))) {
            kfree(info);
            return -EFAULT;
      }
      kfree(info);
      return 0;
}

static int snd_ctl_elem_list(struct snd_card *card,
                       struct snd_ctl_elem_list __user *_list)
{
      struct list_head *plist;
      struct snd_ctl_elem_list list;
      struct snd_kcontrol *kctl;
      struct snd_ctl_elem_id *dst, *id;
      unsigned int offset, space, first, jidx;
      
      if (copy_from_user(&list, _list, sizeof(list)))
            return -EFAULT;
      offset = list.offset;
      space = list.space;
      first = 0;
      /* try limit maximum space */
      if (space > 16384)
            return -ENOMEM;
      if (space > 0) {
            /* allocate temporary buffer for atomic operation */
            dst = vmalloc(space * sizeof(struct snd_ctl_elem_id));
            if (dst == NULL)
                  return -ENOMEM;
            down_read(&card->controls_rwsem);
            list.count = card->controls_count;
            plist = card->controls.next;
            while (plist != &card->controls) {
                  if (offset == 0)
                        break;
                  kctl = snd_kcontrol(plist);
                  if (offset < kctl->count)
                        break;
                  offset -= kctl->count;
                  plist = plist->next;
            }
            list.used = 0;
            id = dst;
            while (space > 0 && plist != &card->controls) {
                  kctl = snd_kcontrol(plist);
                  for (jidx = offset; space > 0 && jidx < kctl->count; jidx++) {
                        snd_ctl_build_ioff(id, kctl, jidx);
                        id++;
                        space--;
                        list.used++;
                  }
                  plist = plist->next;
                  offset = 0;
            }
            up_read(&card->controls_rwsem);
            if (list.used > 0 &&
                copy_to_user(list.pids, dst,
                         list.used * sizeof(struct snd_ctl_elem_id))) {
                  vfree(dst);
                  return -EFAULT;
            }
            vfree(dst);
      } else {
            down_read(&card->controls_rwsem);
            list.count = card->controls_count;
            up_read(&card->controls_rwsem);
      }
      if (copy_to_user(_list, &list, sizeof(list)))
            return -EFAULT;
      return 0;
}

static int snd_ctl_elem_info(struct snd_ctl_file *ctl,
                       struct snd_ctl_elem_info *info)
{
      struct snd_card *card = ctl->card;
      struct snd_kcontrol *kctl;
      struct snd_kcontrol_volatile *vd;
      unsigned int index_offset;
      int result;
      
      down_read(&card->controls_rwsem);
      kctl = snd_ctl_find_id(card, &info->id);
      if (kctl == NULL) {
            up_read(&card->controls_rwsem);
            return -ENOENT;
      }
#ifdef CONFIG_SND_DEBUG
      info->access = 0;
#endif
      result = kctl->info(kctl, info);
      if (result >= 0) {
            snd_assert(info->access == 0, );
            index_offset = snd_ctl_get_ioff(kctl, &info->id);
            vd = &kctl->vd[index_offset];
            snd_ctl_build_ioff(&info->id, kctl, index_offset);
            info->access = vd->access;
            if (vd->owner) {
                  info->access |= SNDRV_CTL_ELEM_ACCESS_LOCK;
                  if (vd->owner == ctl)
                        info->access |= SNDRV_CTL_ELEM_ACCESS_OWNER;
                  info->owner = vd->owner_pid;
            } else {
                  info->owner = -1;
            }
      }
      up_read(&card->controls_rwsem);
      return result;
}

static int snd_ctl_elem_info_user(struct snd_ctl_file *ctl,
                          struct snd_ctl_elem_info __user *_info)
{
      struct snd_ctl_elem_info info;
      int result;

      if (copy_from_user(&info, _info, sizeof(info)))
            return -EFAULT;
      snd_power_lock(ctl->card);
      result = snd_power_wait(ctl->card, SNDRV_CTL_POWER_D0);
      if (result >= 0)
            result = snd_ctl_elem_info(ctl, &info);
      snd_power_unlock(ctl->card);
      if (result >= 0)
            if (copy_to_user(_info, &info, sizeof(info)))
                  return -EFAULT;
      return result;
}

static int snd_ctl_elem_read(struct snd_card *card,
                       struct snd_ctl_elem_value *control)
{
      struct snd_kcontrol *kctl;
      struct snd_kcontrol_volatile *vd;
      unsigned int index_offset;
      int result;

      down_read(&card->controls_rwsem);
      kctl = snd_ctl_find_id(card, &control->id);
      if (kctl == NULL) {
            result = -ENOENT;
      } else {
            index_offset = snd_ctl_get_ioff(kctl, &control->id);
            vd = &kctl->vd[index_offset];
            if ((vd->access & SNDRV_CTL_ELEM_ACCESS_READ) &&
                kctl->get != NULL) {
                  snd_ctl_build_ioff(&control->id, kctl, index_offset);
                  result = kctl->get(kctl, control);
            } else
                  result = -EPERM;
      }
      up_read(&card->controls_rwsem);
      return result;
}

static int snd_ctl_elem_read_user(struct snd_card *card,
                          struct snd_ctl_elem_value __user *_control)
{
      struct snd_ctl_elem_value *control;
      int result;
      
      control = kmalloc(sizeof(*control), GFP_KERNEL);
      if (control == NULL)
            return -ENOMEM;   
      if (copy_from_user(control, _control, sizeof(*control))) {
            kfree(control);
            return -EFAULT;
      }
      snd_power_lock(card);
      result = snd_power_wait(card, SNDRV_CTL_POWER_D0);
      if (result >= 0)
            result = snd_ctl_elem_read(card, control);
      snd_power_unlock(card);
      if (result >= 0)
            if (copy_to_user(_control, control, sizeof(*control)))
                  result = -EFAULT;
      kfree(control);
      return result;
}

static int snd_ctl_elem_write(struct snd_card *card, struct snd_ctl_file *file,
                        struct snd_ctl_elem_value *control)
{
      struct snd_kcontrol *kctl;
      struct snd_kcontrol_volatile *vd;
      unsigned int index_offset;
      int result;

      down_read(&card->controls_rwsem);
      kctl = snd_ctl_find_id(card, &control->id);
      if (kctl == NULL) {
            result = -ENOENT;
      } else {
            index_offset = snd_ctl_get_ioff(kctl, &control->id);
            vd = &kctl->vd[index_offset];
            if (!(vd->access & SNDRV_CTL_ELEM_ACCESS_WRITE) ||
                kctl->put == NULL ||
                (file && vd->owner && vd->owner != file)) {
                  result = -EPERM;
            } else {
                  snd_ctl_build_ioff(&control->id, kctl, index_offset);
                  result = kctl->put(kctl, control);
            }
            if (result > 0) {
                  up_read(&card->controls_rwsem);
                  snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE,
                               &control->id);
                  return 0;
            }
      }
      up_read(&card->controls_rwsem);
      return result;
}

static int snd_ctl_elem_write_user(struct snd_ctl_file *file,
                           struct snd_ctl_elem_value __user *_control)
{
      struct snd_ctl_elem_value *control;
      struct snd_card *card;
      int result;

      control = kmalloc(sizeof(*control), GFP_KERNEL);
      if (control == NULL)
            return -ENOMEM;   
      if (copy_from_user(control, _control, sizeof(*control))) {
            kfree(control);
            return -EFAULT;
      }
      card = file->card;
      snd_power_lock(card);
      result = snd_power_wait(card, SNDRV_CTL_POWER_D0);
      if (result >= 0)
            result = snd_ctl_elem_write(card, file, control);
      snd_power_unlock(card);
      if (result >= 0)
            if (copy_to_user(_control, control, sizeof(*control)))
                  result = -EFAULT;
      kfree(control);
      return result;
}

static int snd_ctl_elem_lock(struct snd_ctl_file *file,
                       struct snd_ctl_elem_id __user *_id)
{
      struct snd_card *card = file->card;
      struct snd_ctl_elem_id id;
      struct snd_kcontrol *kctl;
      struct snd_kcontrol_volatile *vd;
      int result;
      
      if (copy_from_user(&id, _id, sizeof(id)))
            return -EFAULT;
      down_write(&card->controls_rwsem);
      kctl = snd_ctl_find_id(card, &id);
      if (kctl == NULL) {
            result = -ENOENT;
      } else {
            vd = &kctl->vd[snd_ctl_get_ioff(kctl, &id)];
            if (vd->owner != NULL)
                  result = -EBUSY;
            else {
                  vd->owner = file;
                  vd->owner_pid = current->pid;
                  result = 0;
            }
      }
      up_write(&card->controls_rwsem);
      return result;
}

static int snd_ctl_elem_unlock(struct snd_ctl_file *file,
                         struct snd_ctl_elem_id __user *_id)
{
      struct snd_card *card = file->card;
      struct snd_ctl_elem_id id;
      struct snd_kcontrol *kctl;
      struct snd_kcontrol_volatile *vd;
      int result;
      
      if (copy_from_user(&id, _id, sizeof(id)))
            return -EFAULT;
      down_write(&card->controls_rwsem);
      kctl = snd_ctl_find_id(card, &id);
      if (kctl == NULL) {
            result = -ENOENT;
      } else {
            vd = &kctl->vd[snd_ctl_get_ioff(kctl, &id)];
            if (vd->owner == NULL)
                  result = -EINVAL;
            else if (vd->owner != file)
                  result = -EPERM;
            else {
                  vd->owner = NULL;
                  vd->owner_pid = 0;
                  result = 0;
            }
      }
      up_write(&card->controls_rwsem);
      return result;
}

struct user_element {
      struct snd_ctl_elem_info info;
      void *elem_data;        /* element data */
      unsigned long elem_data_size; /* size of element data in bytes */
      void *tlv_data;               /* TLV data */
      unsigned long tlv_data_size;  /* TLV data size */
      void *priv_data;        /* private data (like strings for enumerated type) */
      unsigned long priv_data_size; /* size of private data in bytes */
};

static int snd_ctl_elem_user_info(struct snd_kcontrol *kcontrol,
                          struct snd_ctl_elem_info *uinfo)
{
      struct user_element *ue = kcontrol->private_data;

      *uinfo = ue->info;
      return 0;
}

static int snd_ctl_elem_user_get(struct snd_kcontrol *kcontrol,
                         struct snd_ctl_elem_value *ucontrol)
{
      struct user_element *ue = kcontrol->private_data;

      memcpy(&ucontrol->value, ue->elem_data, ue->elem_data_size);
      return 0;
}

static int snd_ctl_elem_user_put(struct snd_kcontrol *kcontrol,
                         struct snd_ctl_elem_value *ucontrol)
{
      int change;
      struct user_element *ue = kcontrol->private_data;
      
      change = memcmp(&ucontrol->value, ue->elem_data, ue->elem_data_size) != 0;
      if (change)
            memcpy(ue->elem_data, &ucontrol->value, ue->elem_data_size);
      return change;
}

static int snd_ctl_elem_user_tlv(struct snd_kcontrol *kcontrol,
                         int op_flag,
                         unsigned int size,
                         unsigned int __user *tlv)
{
      struct user_element *ue = kcontrol->private_data;
      int change = 0;
      void *new_data;

      if (op_flag > 0) {
            if (size > 1024 * 128)  /* sane value */
                  return -EINVAL;
            new_data = kmalloc(size, GFP_KERNEL);
            if (new_data == NULL)
                  return -ENOMEM;
            if (copy_from_user(new_data, tlv, size)) {
                  kfree(new_data);
                  return -EFAULT;
            }
            change = ue->tlv_data_size != size;
            if (!change)
                  change = memcmp(ue->tlv_data, new_data, size);
            kfree(ue->tlv_data);
            ue->tlv_data = new_data;
            ue->tlv_data_size = size;
      } else {
            if (! ue->tlv_data_size || ! ue->tlv_data)
                  return -ENXIO;
            if (size < ue->tlv_data_size)
                  return -ENOSPC;
            if (copy_to_user(tlv, ue->tlv_data, ue->tlv_data_size))
                  return -EFAULT;
      }
      return change;
}

static void snd_ctl_elem_user_free(struct snd_kcontrol *kcontrol)
{
      struct user_element *ue = kcontrol->private_data;
      if (ue->tlv_data)
            kfree(ue->tlv_data);
      kfree(ue);
}

static int snd_ctl_elem_add(struct snd_ctl_file *file,
                      struct snd_ctl_elem_info *info, int replace)
{
      struct snd_card *card = file->card;
      struct snd_kcontrol kctl, *_kctl;
      unsigned int access;
      long private_size;
      struct user_element *ue;
      int idx, err;
      
      if (card->user_ctl_count >= MAX_USER_CONTROLS)
            return -ENOMEM;
      if (info->count > 1024)
            return -EINVAL;
      access = info->access == 0 ? SNDRV_CTL_ELEM_ACCESS_READWRITE :
            (info->access & (SNDRV_CTL_ELEM_ACCESS_READWRITE|
                         SNDRV_CTL_ELEM_ACCESS_INACTIVE|
                         SNDRV_CTL_ELEM_ACCESS_TLV_READWRITE));
      info->id.numid = 0;
      memset(&kctl, 0, sizeof(kctl));
      down_write(&card->controls_rwsem);
      _kctl = snd_ctl_find_id(card, &info->id);
      err = 0;
      if (_kctl) {
            if (replace)
                  err = snd_ctl_remove(card, _kctl);
            else
                  err = -EBUSY;
      } else {
            if (replace)
                  err = -ENOENT;
      }
      up_write(&card->controls_rwsem);
      if (err < 0)
            return err;
      memcpy(&kctl.id, &info->id, sizeof(info->id));
      kctl.count = info->owner ? info->owner : 1;
      access |= SNDRV_CTL_ELEM_ACCESS_USER;
      kctl.info = snd_ctl_elem_user_info;
      if (access & SNDRV_CTL_ELEM_ACCESS_READ)
            kctl.get = snd_ctl_elem_user_get;
      if (access & SNDRV_CTL_ELEM_ACCESS_WRITE)
            kctl.put = snd_ctl_elem_user_put;
      if (access & SNDRV_CTL_ELEM_ACCESS_TLV_READWRITE) {
            kctl.tlv.c = snd_ctl_elem_user_tlv;
            access |= SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK;
      }
      switch (info->type) {
      case SNDRV_CTL_ELEM_TYPE_BOOLEAN:
      case SNDRV_CTL_ELEM_TYPE_INTEGER:
            private_size = sizeof(long);
            if (info->count > 128)
                  return -EINVAL;
            break;
      case SNDRV_CTL_ELEM_TYPE_INTEGER64:
            private_size = sizeof(long long);
            if (info->count > 64)
                  return -EINVAL;
            break;
      case SNDRV_CTL_ELEM_TYPE_BYTES:
            private_size = sizeof(unsigned char);
            if (info->count > 512)
                  return -EINVAL;
            break;
      case SNDRV_CTL_ELEM_TYPE_IEC958:
            private_size = sizeof(struct snd_aes_iec958);
            if (info->count != 1)
                  return -EINVAL;
            break;
      default:
            return -EINVAL;
      }
      private_size *= info->count;
      ue = kzalloc(sizeof(struct user_element) + private_size, GFP_KERNEL);
      if (ue == NULL)
            return -ENOMEM;
      ue->info = *info;
      ue->info.access = 0;
      ue->elem_data = (char *)ue + sizeof(*ue);
      ue->elem_data_size = private_size;
      kctl.private_free = snd_ctl_elem_user_free;
      _kctl = snd_ctl_new(&kctl, access);
      if (_kctl == NULL) {
            kfree(ue);
            return -ENOMEM;
      }
      _kctl->private_data = ue;
      for (idx = 0; idx < _kctl->count; idx++)
            _kctl->vd[idx].owner = file;
      err = snd_ctl_add(card, _kctl);
      if (err < 0)
            return err;

      down_write(&card->controls_rwsem);
      card->user_ctl_count++;
      up_write(&card->controls_rwsem);

      return 0;
}

static int snd_ctl_elem_add_user(struct snd_ctl_file *file,
                         struct snd_ctl_elem_info __user *_info, int replace)
{
      struct snd_ctl_elem_info info;
      if (copy_from_user(&info, _info, sizeof(info)))
            return -EFAULT;
      return snd_ctl_elem_add(file, &info, replace);
}

static int snd_ctl_elem_remove(struct snd_ctl_file *file,
                         struct snd_ctl_elem_id __user *_id)
{
      struct snd_ctl_elem_id id;
      int err;

      if (copy_from_user(&id, _id, sizeof(id)))
            return -EFAULT;
      err = snd_ctl_remove_unlocked_id(file, &id);
      if (! err) {
            struct snd_card *card = file->card;
            down_write(&card->controls_rwsem);
            card->user_ctl_count--;
            up_write(&card->controls_rwsem);
      }
      return err;
}

static int snd_ctl_subscribe_events(struct snd_ctl_file *file, int __user *ptr)
{
      int subscribe;
      if (get_user(subscribe, ptr))
            return -EFAULT;
      if (subscribe < 0) {
            subscribe = file->subscribed;
            if (put_user(subscribe, ptr))
                  return -EFAULT;
            return 0;
      }
      if (subscribe) {
            file->subscribed = 1;
            return 0;
      } else if (file->subscribed) {
            snd_ctl_empty_read_queue(file);
            file->subscribed = 0;
      }
      return 0;
}

static int snd_ctl_tlv_ioctl(struct snd_ctl_file *file,
                             struct snd_ctl_tlv __user *_tlv,
                             int op_flag)
{
      struct snd_card *card = file->card;
      struct snd_ctl_tlv tlv;
      struct snd_kcontrol *kctl;
      struct snd_kcontrol_volatile *vd;
      unsigned int len;
      int err = 0;

      if (copy_from_user(&tlv, _tlv, sizeof(tlv)))
            return -EFAULT;
      if (tlv.length < sizeof(unsigned int) * 3)
            return -EINVAL;
      down_read(&card->controls_rwsem);
      kctl = snd_ctl_find_numid(card, tlv.numid);
      if (kctl == NULL) {
            err = -ENOENT;
            goto __kctl_end;
      }
      if (kctl->tlv.p == NULL) {
            err = -ENXIO;
            goto __kctl_end;
      }
      vd = &kctl->vd[tlv.numid - kctl->id.numid];
      if ((op_flag == 0 && (vd->access & SNDRV_CTL_ELEM_ACCESS_TLV_READ) == 0) ||
          (op_flag > 0 && (vd->access & SNDRV_CTL_ELEM_ACCESS_TLV_WRITE) == 0) ||
          (op_flag < 0 && (vd->access & SNDRV_CTL_ELEM_ACCESS_TLV_COMMAND) == 0)) {
            err = -ENXIO;
            goto __kctl_end;
      }
      if (vd->access & SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK) {
            if (file && vd->owner != NULL && vd->owner != file) {
                  err = -EPERM;
                  goto __kctl_end;
            }
            err = kctl->tlv.c(kctl, op_flag, tlv.length, _tlv->tlv); 
            if (err > 0) {
                  up_read(&card->controls_rwsem);
                  snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_TLV, &kctl->id);
                  return 0;
            }
      } else {
            if (op_flag) {
                  err = -ENXIO;
                  goto __kctl_end;
            }
            len = kctl->tlv.p[1] + 2 * sizeof(unsigned int);
            if (tlv.length < len) {
                  err = -ENOMEM;
                  goto __kctl_end;
            }
            if (copy_to_user(_tlv->tlv, kctl->tlv.p, len))
                  err = -EFAULT;
      }
      __kctl_end:
      up_read(&card->controls_rwsem);
      return err;
}

static long snd_ctl_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
      struct snd_ctl_file *ctl;
      struct snd_card *card;
      struct snd_kctl_ioctl *p;
      void __user *argp = (void __user *)arg;
      int __user *ip = argp;
      int err;

      ctl = file->private_data;
      card = ctl->card;
      snd_assert(card != NULL, return -ENXIO);
      switch (cmd) {
      case SNDRV_CTL_IOCTL_PVERSION:
            return put_user(SNDRV_CTL_VERSION, ip) ? -EFAULT : 0;
      case SNDRV_CTL_IOCTL_CARD_INFO:
            return snd_ctl_card_info(card, ctl, cmd, argp);
      case SNDRV_CTL_IOCTL_ELEM_LIST:
            return snd_ctl_elem_list(card, argp);
      case SNDRV_CTL_IOCTL_ELEM_INFO:
            return snd_ctl_elem_info_user(ctl, argp);
      case SNDRV_CTL_IOCTL_ELEM_READ:
            return snd_ctl_elem_read_user(card, argp);
      case SNDRV_CTL_IOCTL_ELEM_WRITE:
            return snd_ctl_elem_write_user(ctl, argp);
      case SNDRV_CTL_IOCTL_ELEM_LOCK:
            return snd_ctl_elem_lock(ctl, argp);
      case SNDRV_CTL_IOCTL_ELEM_UNLOCK:
            return snd_ctl_elem_unlock(ctl, argp);
      case SNDRV_CTL_IOCTL_ELEM_ADD:
            return snd_ctl_elem_add_user(ctl, argp, 0);
      case SNDRV_CTL_IOCTL_ELEM_REPLACE:
            return snd_ctl_elem_add_user(ctl, argp, 1);
      case SNDRV_CTL_IOCTL_ELEM_REMOVE:
            return snd_ctl_elem_remove(ctl, argp);
      case SNDRV_CTL_IOCTL_SUBSCRIBE_EVENTS:
            return snd_ctl_subscribe_events(ctl, ip);
      case SNDRV_CTL_IOCTL_TLV_READ:
            return snd_ctl_tlv_ioctl(ctl, argp, 0);
      case SNDRV_CTL_IOCTL_TLV_WRITE:
            return snd_ctl_tlv_ioctl(ctl, argp, 1);
      case SNDRV_CTL_IOCTL_TLV_COMMAND:
            return snd_ctl_tlv_ioctl(ctl, argp, -1);
      case SNDRV_CTL_IOCTL_POWER:
            return -ENOPROTOOPT;
      case SNDRV_CTL_IOCTL_POWER_STATE:
#ifdef CONFIG_PM
            return put_user(card->power_state, ip) ? -EFAULT : 0;
#else
            return put_user(SNDRV_CTL_POWER_D0, ip) ? -EFAULT : 0;
#endif
      }
      down_read(&snd_ioctl_rwsem);
      list_for_each_entry(p, &snd_control_ioctls, list) {
            err = p->fioctl(card, ctl, cmd, arg);
            if (err != -ENOIOCTLCMD) {
                  up_read(&snd_ioctl_rwsem);
                  return err;
            }
      }
      up_read(&snd_ioctl_rwsem);
      snd_printdd("unknown ioctl = 0x%x\n", cmd);
      return -ENOTTY;
}

static ssize_t snd_ctl_read(struct file *file, char __user *buffer,
                      size_t count, loff_t * offset)
{
      struct snd_ctl_file *ctl;
      int err = 0;
      ssize_t result = 0;

      ctl = file->private_data;
      snd_assert(ctl != NULL && ctl->card != NULL, return -ENXIO);
      if (!ctl->subscribed)
            return -EBADFD;
      if (count < sizeof(struct snd_ctl_event))
            return -EINVAL;
      spin_lock_irq(&ctl->read_lock);
      while (count >= sizeof(struct snd_ctl_event)) {
            struct snd_ctl_event ev;
            struct snd_kctl_event *kev;
            while (list_empty(&ctl->events)) {
                  wait_queue_t wait;
                  if ((file->f_flags & O_NONBLOCK) != 0 || result > 0) {
                        err = -EAGAIN;
                        goto __end_lock;
                  }
                  init_waitqueue_entry(&wait, current);
                  add_wait_queue(&ctl->change_sleep, &wait);
                  set_current_state(TASK_INTERRUPTIBLE);
                  spin_unlock_irq(&ctl->read_lock);
                  schedule();
                  remove_wait_queue(&ctl->change_sleep, &wait);
                  if (signal_pending(current))
                        return -ERESTARTSYS;
                  spin_lock_irq(&ctl->read_lock);
            }
            kev = snd_kctl_event(ctl->events.next);
            ev.type = SNDRV_CTL_EVENT_ELEM;
            ev.data.elem.mask = kev->mask;
            ev.data.elem.id = kev->id;
            list_del(&kev->list);
            spin_unlock_irq(&ctl->read_lock);
            kfree(kev);
            if (copy_to_user(buffer, &ev, sizeof(struct snd_ctl_event))) {
                  err = -EFAULT;
                  goto __end;
            }
            spin_lock_irq(&ctl->read_lock);
            buffer += sizeof(struct snd_ctl_event);
            count -= sizeof(struct snd_ctl_event);
            result += sizeof(struct snd_ctl_event);
      }
      __end_lock:
      spin_unlock_irq(&ctl->read_lock);
      __end:
            return result > 0 ? result : err;
}

static unsigned int snd_ctl_poll(struct file *file, poll_table * wait)
{
      unsigned int mask;
      struct snd_ctl_file *ctl;

      ctl = file->private_data;
      if (!ctl->subscribed)
            return 0;
      poll_wait(file, &ctl->change_sleep, wait);

      mask = 0;
      if (!list_empty(&ctl->events))
            mask |= POLLIN | POLLRDNORM;

      return mask;
}

/*
 * register the device-specific control-ioctls.
 * called from each device manager like pcm.c, hwdep.c, etc.
 */
static int _snd_ctl_register_ioctl(snd_kctl_ioctl_func_t fcn, struct list_head *lists)
{
      struct snd_kctl_ioctl *pn;

      pn = kzalloc(sizeof(struct snd_kctl_ioctl), GFP_KERNEL);
      if (pn == NULL)
            return -ENOMEM;
      pn->fioctl = fcn;
      down_write(&snd_ioctl_rwsem);
      list_add_tail(&pn->list, lists);
      up_write(&snd_ioctl_rwsem);
      return 0;
}

int snd_ctl_register_ioctl(snd_kctl_ioctl_func_t fcn)
{
      return _snd_ctl_register_ioctl(fcn, &snd_control_ioctls);
}

EXPORT_SYMBOL(snd_ctl_register_ioctl);

#ifdef CONFIG_COMPAT
int snd_ctl_register_ioctl_compat(snd_kctl_ioctl_func_t fcn)
{
      return _snd_ctl_register_ioctl(fcn, &snd_control_compat_ioctls);
}

EXPORT_SYMBOL(snd_ctl_register_ioctl_compat);
#endif

/*
 * de-register the device-specific control-ioctls.
 */
static int _snd_ctl_unregister_ioctl(snd_kctl_ioctl_func_t fcn,
                             struct list_head *lists)
{
      struct snd_kctl_ioctl *p;

      snd_assert(fcn != NULL, return -EINVAL);
      down_write(&snd_ioctl_rwsem);
      list_for_each_entry(p, lists, list) {
            if (p->fioctl == fcn) {
                  list_del(&p->list);
                  up_write(&snd_ioctl_rwsem);
                  kfree(p);
                  return 0;
            }
      }
      up_write(&snd_ioctl_rwsem);
      snd_BUG();
      return -EINVAL;
}

int snd_ctl_unregister_ioctl(snd_kctl_ioctl_func_t fcn)
{
      return _snd_ctl_unregister_ioctl(fcn, &snd_control_ioctls);
}

EXPORT_SYMBOL(snd_ctl_unregister_ioctl);

#ifdef CONFIG_COMPAT
int snd_ctl_unregister_ioctl_compat(snd_kctl_ioctl_func_t fcn)
{
      return _snd_ctl_unregister_ioctl(fcn, &snd_control_compat_ioctls);
}

EXPORT_SYMBOL(snd_ctl_unregister_ioctl_compat);
#endif

static int snd_ctl_fasync(int fd, struct file * file, int on)
{
      struct snd_ctl_file *ctl;
      int err;
      ctl = file->private_data;
      err = fasync_helper(fd, file, on, &ctl->fasync);
      if (err < 0)
            return err;
      return 0;
}

/*
 * ioctl32 compat
 */
#ifdef CONFIG_COMPAT
#include "control_compat.c"
#else
#define snd_ctl_ioctl_compat  NULL
#endif

/*
 *  INIT PART
 */

static const struct file_operations snd_ctl_f_ops =
{
      .owner =    THIS_MODULE,
      .read =           snd_ctl_read,
      .open =           snd_ctl_open,
      .release =  snd_ctl_release,
      .poll =           snd_ctl_poll,
      .unlocked_ioctl = snd_ctl_ioctl,
      .compat_ioctl =   snd_ctl_ioctl_compat,
      .fasync =   snd_ctl_fasync,
};

/*
 * registration of the control device
 */
static int snd_ctl_dev_register(struct snd_device *device)
{
      struct snd_card *card = device->device_data;
      int err, cardnum;
      char name[16];

      snd_assert(card != NULL, return -ENXIO);
      cardnum = card->number;
      snd_assert(cardnum >= 0 && cardnum < SNDRV_CARDS, return -ENXIO);
      sprintf(name, "controlC%i", cardnum);
      if ((err = snd_register_device(SNDRV_DEVICE_TYPE_CONTROL, card, -1,
                               &snd_ctl_f_ops, card, name)) < 0)
            return err;
      return 0;
}

/*
 * disconnection of the control device
 */
static int snd_ctl_dev_disconnect(struct snd_device *device)
{
      struct snd_card *card = device->device_data;
      struct snd_ctl_file *ctl;
      int err, cardnum;

      snd_assert(card != NULL, return -ENXIO);
      cardnum = card->number;
      snd_assert(cardnum >= 0 && cardnum < SNDRV_CARDS, return -ENXIO);

      down_read(&card->controls_rwsem);
      list_for_each_entry(ctl, &card->ctl_files, list) {
            wake_up(&ctl->change_sleep);
            kill_fasync(&ctl->fasync, SIGIO, POLL_ERR);
      }
      up_read(&card->controls_rwsem);

      if ((err = snd_unregister_device(SNDRV_DEVICE_TYPE_CONTROL,
                               card, -1)) < 0)
            return err;
      return 0;
}

/*
 * free all controls
 */
static int snd_ctl_dev_free(struct snd_device *device)
{
      struct snd_card *card = device->device_data;
      struct snd_kcontrol *control;

      down_write(&card->controls_rwsem);
      while (!list_empty(&card->controls)) {
            control = snd_kcontrol(card->controls.next);
            snd_ctl_remove(card, control);
      }
      up_write(&card->controls_rwsem);
      return 0;
}

/*
 * create control core:
 * called from init.c
 */
int snd_ctl_create(struct snd_card *card)
{
      static struct snd_device_ops ops = {
            .dev_free = snd_ctl_dev_free,
            .dev_register =   snd_ctl_dev_register,
            .dev_disconnect = snd_ctl_dev_disconnect,
      };

      snd_assert(card != NULL, return -ENXIO);
      return snd_device_new(card, SNDRV_DEV_CONTROL, card, &ops);
}

/*
 * Frequently used control callbacks
 */
int snd_ctl_boolean_mono_info(struct snd_kcontrol *kcontrol,
                        struct snd_ctl_elem_info *uinfo)
{
      uinfo->type = SNDRV_CTL_ELEM_TYPE_BOOLEAN;
      uinfo->count = 1;
      uinfo->value.integer.min = 0;
      uinfo->value.integer.max = 1;
      return 0;
}

EXPORT_SYMBOL(snd_ctl_boolean_mono_info);

int snd_ctl_boolean_stereo_info(struct snd_kcontrol *kcontrol,
                        struct snd_ctl_elem_info *uinfo)
{
      uinfo->type = SNDRV_CTL_ELEM_TYPE_BOOLEAN;
      uinfo->count = 2;
      uinfo->value.integer.min = 0;
      uinfo->value.integer.max = 1;
      return 0;
}

EXPORT_SYMBOL(snd_ctl_boolean_stereo_info);

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