control.c

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

#include <linux/threads.h>
#include <linux/interrupt.h>
#include <linux/module.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
#define MAX_CONTROL_COUNT   1028

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;

    err = nonseekable_open(inode, file);
    if (err < 0)
        return 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 = get_pid(task_pid(current));
    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);
    snd_card_unref(card);
    return 0;

      __error:
    module_put(card->module);
      __error2:
    snd_card_file_remove(card, file);
      __error1:
    if (card)
        snd_card_unref(card);
        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;
    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);
    put_pid(ctl->pid);
    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;
    
    if (snd_BUG_ON(!card || !id))
        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);

static struct snd_kcontrol *snd_ctl_new(struct snd_kcontrol *control,
                    unsigned int access)
{
    struct snd_kcontrol *kctl;
    unsigned int idx;
    
    if (snd_BUG_ON(!control || !control->count))
        return NULL;

    if (control->count > MAX_CONTROL_COUNT)
        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;
}

struct snd_kcontrol *snd_ctl_new1(const struct snd_kcontrol_new *ncontrol,
                  void *private_data)
{
    struct snd_kcontrol kctl;
    unsigned int access;
    
    if (snd_BUG_ON(!ncontrol || !ncontrol->info))
        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));
        if (strcmp(ncontrol->name, kctl.id.name) != 0)
            snd_printk(KERN_WARNING
                   "Control name '%s' truncated to '%s'\n",
                   ncontrol->name, 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_VOLATILE|
                      SNDRV_CTL_ELEM_ACCESS_INACTIVE|
                      SNDRV_CTL_ELEM_ACCESS_TLV_READWRITE|
                      SNDRV_CTL_ELEM_ACCESS_TLV_COMMAND|
                      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);

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 bool snd_ctl_remove_numid_conflict(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 + 1 + count &&
            kctl->id.numid + kctl->count > card->last_numid + 1) {
                card->last_numid = kctl->id.numid + kctl->count - 1;
            return true;
        }
    }
    return false;
}

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

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

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;
    if (snd_BUG_ON(!card || !kcontrol->info))
        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);

int snd_ctl_replace(struct snd_card *card, struct snd_kcontrol *kcontrol,
            bool add_on_replace)
{
    struct snd_ctl_elem_id id;
    unsigned int idx;
    struct snd_kcontrol *old;
    int ret;

    if (!kcontrol)
        return -EINVAL;
    if (snd_BUG_ON(!card || !kcontrol->info)) {
        ret = -EINVAL;
        goto error;
    }
    id = kcontrol->id;
    down_write(&card->controls_rwsem);
    old = snd_ctl_find_id(card, &id);
    if (!old) {
        if (add_on_replace)
            goto add;
        up_write(&card->controls_rwsem);
        ret = -EINVAL;
        goto error;
    }
    ret = snd_ctl_remove(card, old);
    if (ret < 0) {
        up_write(&card->controls_rwsem);
        goto error;
    }
add:
    if (snd_ctl_find_hole(card, kcontrol->count) < 0) {
        up_write(&card->controls_rwsem);
        ret = -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 ret;
}
EXPORT_SYMBOL(snd_ctl_replace);

int snd_ctl_remove(struct snd_card *card, struct snd_kcontrol *kcontrol)
{
    struct snd_ctl_elem_id id;
    unsigned int idx;

    if (snd_BUG_ON(!card || !kcontrol))
        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);

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);

static int snd_ctl_remove_user_ctl(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) {
        ret = -ENOENT;
        goto error;
    }
    if (!(kctl->vd[0].access & SNDRV_CTL_ELEM_ACCESS_USER)) {
        ret = -EINVAL;
        goto error;
    }
    for (idx = 0; idx < kctl->count; idx++)
        if (kctl->vd[idx].owner != NULL && kctl->vd[idx].owner != file) {
            ret = -EBUSY;
            goto error;
        }
    ret = snd_ctl_remove(card, kctl);
    if (ret < 0)
        goto error;
    card->user_ctl_count--;
error:
    up_write(&card->controls_rwsem);
    return ret;
}

int snd_ctl_activate_id(struct snd_card *card, struct snd_ctl_elem_id *id,
            int active)
{
    struct snd_kcontrol *kctl;
    struct snd_kcontrol_volatile *vd;
    unsigned int index_offset;
    int ret;

    down_write(&card->controls_rwsem);
    kctl = snd_ctl_find_id(card, id);
    if (kctl == NULL) {
        ret = -ENOENT;
        goto unlock;
    }
    index_offset = snd_ctl_get_ioff(kctl, &kctl->id);
    vd = &kctl->vd[index_offset];
    ret = 0;
    if (active) {
        if (!(vd->access & SNDRV_CTL_ELEM_ACCESS_INACTIVE))
            goto unlock;
        vd->access &= ~SNDRV_CTL_ELEM_ACCESS_INACTIVE;
    } else {
        if (vd->access & SNDRV_CTL_ELEM_ACCESS_INACTIVE)
            goto unlock;
        vd->access |= SNDRV_CTL_ELEM_ACCESS_INACTIVE;
    }
    ret = 1;
 unlock:
    up_write(&card->controls_rwsem);
    if (ret > 0)
        snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_INFO, id);
    return ret;
}
EXPORT_SYMBOL_GPL(snd_ctl_activate_id);

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);

struct snd_kcontrol *snd_ctl_find_numid(struct snd_card *card, unsigned int numid)
{
    struct snd_kcontrol *kctl;

    if (snd_BUG_ON(!card || !numid))
        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);

struct snd_kcontrol *snd_ctl_find_id(struct snd_card *card,
                     struct snd_ctl_elem_id *id)
{
    struct snd_kcontrol *kctl;

    if (snd_BUG_ON(!card || !id))
        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, jidx;
    
    if (copy_from_user(&list, _list, sizeof(list)))
        return -EFAULT;
    offset = list.offset;
    space = list.space;
    /* 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_BUG_ON(info->access);
        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 = pid_vnr(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 = memdup_user(_control, sizeof(*control));
    if (IS_ERR(control))
        return PTR_ERR(control);

    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 = memdup_user(_control, sizeof(*control));
    if (IS_ERR(control))
        return PTR_ERR(control);

    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;
            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;
            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) */
};

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_enum_info(struct snd_kcontrol *kcontrol,
                       struct snd_ctl_elem_info *uinfo)
{
    struct user_element *ue = kcontrol->private_data;
    const char *names;
    unsigned int item;

    item = uinfo->value.enumerated.item;

    *uinfo = ue->info;

    item = min(item, uinfo->value.enumerated.items - 1);
    uinfo->value.enumerated.item = item;

    names = ue->priv_data;
    for (; item > 0; --item)
        names += strlen(names) + 1;
    strcpy(uinfo->value.enumerated.name, names);

    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 = memdup_user(tlv, size);
        if (IS_ERR(new_data))
            return PTR_ERR(new_data);
        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 int snd_ctl_elem_init_enum_names(struct user_element *ue)
{
    char *names, *p;
    size_t buf_len, name_len;
    unsigned int i;
    const uintptr_t user_ptrval = ue->info.value.enumerated.names_ptr;

    if (ue->info.value.enumerated.names_length > 64 * 1024)
        return -EINVAL;

    names = memdup_user((const void __user *)user_ptrval,
        ue->info.value.enumerated.names_length);
    if (IS_ERR(names))
        return PTR_ERR(names);

    /* check that there are enough valid names */
    buf_len = ue->info.value.enumerated.names_length;
    p = names;
    for (i = 0; i < ue->info.value.enumerated.items; ++i) {
        name_len = strnlen(p, buf_len);
        if (name_len == 0 || name_len >= 64 || name_len == buf_len) {
            kfree(names);
            return -EINVAL;
        }
        p += name_len + 1;
        buf_len -= name_len + 1;
    }

    ue->priv_data = names;
    ue->info.value.enumerated.names_ptr = 0;

    return 0;
}

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

    kfree(ue->tlv_data);
    kfree(ue->priv_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 (!replace && card->user_ctl_count >= MAX_USER_CONTROLS)
        return -ENOMEM;
    if (info->count < 1)
        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;
    if (info->type == SNDRV_CTL_ELEM_TYPE_ENUMERATED)
        kctl.info = snd_ctl_elem_user_enum_info;
    else
        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_ENUMERATED:
        private_size = sizeof(unsigned int);
        if (info->count > 128 || info->value.enumerated.items == 0)
            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;
    if (ue->info.type == SNDRV_CTL_ELEM_TYPE_ENUMERATED) {
        err = snd_ctl_elem_init_enum_names(ue);
        if (err < 0) {
            kfree(ue);
            return err;
        }
    }
    kctl.private_free = snd_ctl_elem_user_free;
    _kctl = snd_ctl_new(&kctl, access);
    if (_kctl == NULL) {
        kfree(ue->priv_data);
        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;

    if (copy_from_user(&id, _id, sizeof(id)))
        return -EFAULT;
    return snd_ctl_remove_user_ctl(file, &id);
}

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) * 2)
        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 (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;
    if (snd_BUG_ON(!card))
        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;
    if (snd_BUG_ON(!ctl || !ctl->card))
        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 (ctl->card->shutdown)
                return -ENODEV;
            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;

    if (snd_BUG_ON(!fcn))
        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;

    ctl = file->private_data;
    return fasync_helper(fd, file, on, &ctl->fasync);
}

/*
 * 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,
    .llseek =   no_llseek,
    .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];

    if (snd_BUG_ON(!card))
        return -ENXIO;
    cardnum = card->number;
    if (snd_BUG_ON(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;

    if (snd_BUG_ON(!card))
        return -ENXIO;
    cardnum = card->number;
    if (snd_BUG_ON(cardnum < 0 || cardnum >= SNDRV_CARDS))
        return -ENXIO;

    read_lock(&card->ctl_files_rwlock);
    list_for_each_entry(ctl, &card->ctl_files, list) {
        wake_up(&ctl->change_sleep);
        kill_fasync(&ctl->fasync, SIGIO, POLL_ERR);
    }
    read_unlock(&card->ctl_files_rwlock);

    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,
    };

    if (snd_BUG_ON(!card))
        return -ENXIO;
    return snd_device_new(card, SNDRV_DEV_CONTROL, card, &ops);
}

/*
 * Frequently used control callbacks/helpers
 */
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);

int snd_ctl_enum_info(struct snd_ctl_elem_info *info, unsigned int channels,
              unsigned int items, const char *const names[])
{
    info->type = SNDRV_CTL_ELEM_TYPE_ENUMERATED;
    info->count = channels;
    info->value.enumerated.items = items;
    if (info->value.enumerated.item >= items)
        info->value.enumerated.item = items - 1;
    strlcpy(info->value.enumerated.name,
        names[info->value.enumerated.item],
        sizeof(info->value.enumerated.name));
    return 0;
}
EXPORT_SYMBOL(snd_ctl_enum_info);