Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost

[cris-mirror.git] / sound / core / 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/module.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/time.h>
#include <linux/mm.h>
#include <linux/sched/signal.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 i, 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;
        for (i = 0; i < SND_CTL_SUBDEV_ITEMS; i++)
                ctl->preferred_subdevice[i] = -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;
}

/**
 * snd_ctl_notify - Send notification to user-space for a control change
 * @card: the card to send notification
 * @mask: the event mask, SNDRV_CTL_EVENT_*
 * @id: the ctl element id to send notification
 *
 * This function adds an event record with the given id and mask, appends
 * to the list and wakes up the user-space for notification.  This can be
 * called in the atomic context.
 */
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;
        if (card->shutdown)
                return;
        read_lock(&card->ctl_files_rwlock);
#if IS_ENABLED(CONFIG_SND_MIXER_OSS)
        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 {
                        dev_err(card->dev, "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 new control instance with some elements
 * @kctl: the pointer to store new control instance
 * @count: the number of elements in this control
 * @access: the default access flags for elements in this control
 * @file: given when locking these elements
 *
 * Allocates a memory object for a new control instance. The instance has
 * elements as many as the given number (@count). Each element has given
 * access permissions (@access). Each element is locked when @file is given.
 *
 * Return: 0 on success, error code on failure
 */
static int snd_ctl_new(struct snd_kcontrol **kctl, unsigned int count,
                       unsigned int access, struct snd_ctl_file *file)
{
        unsigned int size;
        unsigned int idx;
        
        if (count == 0 || count > MAX_CONTROL_COUNT)
                return -EINVAL;

        size  = sizeof(struct snd_kcontrol);
        size += sizeof(struct snd_kcontrol_volatile) * count;

        *kctl = kzalloc(size, GFP_KERNEL);
        if (!*kctl)
                return -ENOMEM;

        for (idx = 0; idx < count; idx++) {
                (*kctl)->vd[idx].access = access;
                (*kctl)->vd[idx].owner = file;
        }
        (*kctl)->count = count;

        return 0;
}

/**
 * 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.
 *
 * Return: 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 count;
        unsigned int access;
        int err;
        
        if (snd_BUG_ON(!ncontrol || !ncontrol->info))
                return NULL;

        count = ncontrol->count;
        if (count == 0)
                count = 1;

        access = ncontrol->access;
        if (access == 0)
                access = SNDRV_CTL_ELEM_ACCESS_READWRITE;
        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);

        err = snd_ctl_new(&kctl, count, access, NULL);
        if (err < 0)
                return NULL;

        /* The 'numid' member is decided when calling snd_ctl_add(). */
        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)
                        pr_warn("ALSA: Control name '%s' truncated to '%s'\n",
                                ncontrol->name, kctl->id.name);
        }
        kctl->id.index = ncontrol->index;

        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 kctl;
}
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 bool snd_ctl_remove_numid_conflict(struct snd_card *card,
                                          unsigned int count)
{
        struct snd_kcontrol *kctl;

        /* Make sure that the ids assigned to the control do not wrap around */
        if (card->last_numid >= UINT_MAX - count)
                card->last_numid = 0;

        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 */
                        dev_err(card->dev, "unable to allocate new control numid\n");
                        return -ENOMEM;
                }
        }
        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.
 *
 * It frees automatically the control which cannot be added.
 *
 * Return: Zero if successful, or a negative error code on failure.
 *
 */
int snd_ctl_add(struct snd_card *card, struct snd_kcontrol *kcontrol)
{
        struct snd_ctl_elem_id id;
        unsigned int idx;
        unsigned int count;
        int err = -EINVAL;

        if (! kcontrol)
                return err;
        if (snd_BUG_ON(!card || !kcontrol->info))
                goto error;
        id = kcontrol->id;
        if (id.index > UINT_MAX - kcontrol->count)
                goto error;

        down_write(&card->controls_rwsem);
        if (snd_ctl_find_id(card, &id)) {
                up_write(&card->controls_rwsem);
                dev_err(card->dev, "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;
        id = kcontrol->id;
        count = kcontrol->count;
        up_write(&card->controls_rwsem);
        for (idx = 0; idx < 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_replace - replace the control instance of the card
 * @card: the card instance
 * @kcontrol: the control instance to replace
 * @add_on_replace: add the control if not already added
 *
 * Replaces the given control.  If the given control does not exist
 * and the add_on_replace flag is set, the control is added.  If the
 * control exists, it is destroyed first.
 *
 * It frees automatically the control which cannot be added or replaced.
 *
 * Return: Zero if successful, or a negative error code on failure.
 */
int snd_ctl_replace(struct snd_card *card, struct snd_kcontrol *kcontrol,
                    bool add_on_replace)
{
        struct snd_ctl_elem_id id;
        unsigned int count;
        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;
        id = kcontrol->id;
        count = kcontrol->count;
        up_write(&card->controls_rwsem);
        for (idx = 0; idx < 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);

/**
 * 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).
 *
 * Return: 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;

        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);

/**
 * 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.
 *
 * Return: 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_user_ctl - remove and release the unlocked user control
 * @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.
 *
 * Return: 0 if successful, or a negative error code on failure.
 */
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;
}

/**
 * snd_ctl_activate_id - activate/inactivate the control of the given id
 * @card: the card instance
 * @id: the control id to activate/inactivate
 * @active: non-zero to activate
 *
 * Finds the control instance with the given id, and activate or
 * inactivate the control together with notification, if changed.
 * The given ID data is filled with full information.
 *
 * Return: 0 if unchanged, 1 if changed, or a negative error code on failure.
 */
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, 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;
        }
        snd_ctl_build_ioff(id, kctl, index_offset);
        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);

/**
 * 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.
 *
 * Return: 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.
 *
 * The caller must down card->controls_rwsem before calling this function
 * (if the race condition can happen).
 *
 * Return: The pointer of the instance if found, or %NULL if not.
 *
 */
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);

/**
 * 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.
 *
 * The caller must down card->controls_rwsem before calling this function
 * (if the race condition can happen).
 *
 * Return: The pointer of the instance if found, or %NULL if not.
 *
 */
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 snd_ctl_elem_list list;
        struct snd_kcontrol *kctl;
        struct snd_ctl_elem_id id;
        unsigned int offset, space, jidx;
        int err = 0;
        
        if (copy_from_user(&list, _list, sizeof(list)))
                return -EFAULT;
        offset = list.offset;
        space = list.space;

        down_read(&card->controls_rwsem);
        list.count = card->controls_count;
        list.used = 0;
        if (space > 0) {
                list_for_each_entry(kctl, &card->controls, list) {
                        if (offset >= kctl->count) {
                                offset -= kctl->count;
                                continue;
                        }
                        for (jidx = offset; jidx < kctl->count; jidx++) {
                                snd_ctl_build_ioff(&id, kctl, jidx);
                                if (copy_to_user(list.pids + list.used, &id,
                                                 sizeof(id))) {
                                        err = -EFAULT;
                                        goto out;
                                }
                                list.used++;
                                if (!--space)
                                        goto out;
                        }
                        offset = 0;
                }
        }
 out:
        up_read(&card->controls_rwsem);
        if (!err && copy_to_user(_list, &list, sizeof(list)))
                err = -EFAULT;
        return err;
}

static bool validate_element_member_dimension(struct snd_ctl_elem_info *info)
{
        unsigned int members;
        unsigned int i;

        if (info->dimen.d[0] == 0)
                return true;

        members = 1;
        for (i = 0; i < ARRAY_SIZE(info->dimen.d); ++i) {
                if (info->dimen.d[i] == 0)
                        break;
                members *= info->dimen.d[i];

                /*
                 * info->count should be validated in advance, to guarantee
                 * calculation soundness.
                 */
                if (members > info->count)
                        return false;
        }

        for (++i; i < ARRAY_SIZE(info->dimen.d); ++i) {
                if (info->dimen.d[i] > 0)
                        return false;
        }

        return members == info->count;
}

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;
        result = snd_power_wait(ctl->card, SNDRV_CTL_POWER_D0);
        if (result < 0)
                return result;
        result = snd_ctl_elem_info(ctl, &info);
        if (result < 0)
                return result;
        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;

        kctl = snd_ctl_find_id(card, &control->id);
        if (kctl == NULL)
                return -ENOENT;

        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)
                return -EPERM;

        snd_ctl_build_ioff(&control->id, kctl, index_offset);
        return kctl->get(kctl, control);
}

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);

        result = snd_power_wait(card, SNDRV_CTL_POWER_D0);
        if (result < 0)
                goto error;

        down_read(&card->controls_rwsem);
        result = snd_ctl_elem_read(card, control);
        up_read(&card->controls_rwsem);
        if (result < 0)
                goto error;

        if (copy_to_user(_control, control, sizeof(*control)))
                result = -EFAULT;
 error:
        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;

        kctl = snd_ctl_find_id(card, &control->id);
        if (kctl == NULL)
                return -ENOENT;

        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)) {
                return -EPERM;
        }

        snd_ctl_build_ioff(&control->id, kctl, index_offset);
        result = kctl->put(kctl, control);
        if (result < 0)
                return result;

        if (result > 0) {
                struct snd_ctl_elem_id id = control->id;
                snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE, &id);
        }

        return 0;
}

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;
        result = snd_power_wait(card, SNDRV_CTL_POWER_D0);
        if (result < 0)
                goto error;

        down_write(&card->controls_rwsem);
        result = snd_ctl_elem_write(card, file, control);
        up_write(&card->controls_rwsem);
        if (result < 0)
                goto error;

        if (copy_to_user(_control, control, sizeof(*control)))
                result = -EFAULT;
 error:
        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;
        struct snd_card *card;
        char *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;
        unsigned int offset;

        offset = snd_ctl_get_ioff(kcontrol, &uinfo->id);
        *uinfo = ue->info;
        snd_ctl_build_ioff(&uinfo->id, kcontrol, offset);

        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;
        unsigned int offset;

        item = uinfo->value.enumerated.item;

        offset = snd_ctl_get_ioff(kcontrol, &uinfo->id);
        *uinfo = ue->info;
        snd_ctl_build_ioff(&uinfo->id, kcontrol, offset);

        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;
        unsigned int size = ue->elem_data_size;
        char *src = ue->elem_data +
                        snd_ctl_get_ioff(kcontrol, &ucontrol->id) * size;

        memcpy(&ucontrol->value, src, 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;
        unsigned int size = ue->elem_data_size;
        char *dst = ue->elem_data +
                        snd_ctl_get_ioff(kcontrol, &ucontrol->id) * size;

        change = memcmp(&ucontrol->value, dst, size) != 0;
        if (change)
                memcpy(dst, &ucontrol->value, size);
        return change;
}

static int replace_user_tlv(struct snd_kcontrol *kctl, unsigned int __user *buf,
                            unsigned int size)
{
        struct user_element *ue = kctl->private_data;
        unsigned int *container;
        struct snd_ctl_elem_id id;
        unsigned int mask = 0;
        int i;
        int change;

        if (size > 1024 * 128)  /* sane value */
                return -EINVAL;

        container = vmemdup_user(buf, size);
        if (IS_ERR(container))
                return PTR_ERR(container);

        change = ue->tlv_data_size != size;
        if (!change)
                change = memcmp(ue->tlv_data, container, size) != 0;
        if (!change) {
                kvfree(container);
                return 0;
        }

        if (ue->tlv_data == NULL) {
                /* Now TLV data is available. */
                for (i = 0; i < kctl->count; ++i)
                        kctl->vd[i].access |= SNDRV_CTL_ELEM_ACCESS_TLV_READ;
                mask = SNDRV_CTL_EVENT_MASK_INFO;
        }

        kvfree(ue->tlv_data);
        ue->tlv_data = container;
        ue->tlv_data_size = size;

        mask |= SNDRV_CTL_EVENT_MASK_TLV;
        for (i = 0; i < kctl->count; ++i) {
                snd_ctl_build_ioff(&id, kctl, i);
                snd_ctl_notify(ue->card, mask, &id);
        }

        return change;
}

static int read_user_tlv(struct snd_kcontrol *kctl, unsigned int __user *buf,
                         unsigned int size)
{
        struct user_element *ue = kctl->private_data;

        if (ue->tlv_data_size == 0 || ue->tlv_data == NULL)
                return -ENXIO;

        if (size < ue->tlv_data_size)
                return -ENOSPC;

        if (copy_to_user(buf, ue->tlv_data, ue->tlv_data_size))
                return -EFAULT;

        return 0;
}

static int snd_ctl_elem_user_tlv(struct snd_kcontrol *kctl, int op_flag,
                                 unsigned int size, unsigned int __user *buf)
{
        if (op_flag == SNDRV_CTL_TLV_OP_WRITE)
                return replace_user_tlv(kctl, buf, size);
        else
                return read_user_tlv(kctl, buf, size);
}

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 = vmemdup_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) {
                        kvfree(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;

        kvfree(ue->tlv_data);
        kvfree(ue->priv_data);
        kfree(ue);
}

static int snd_ctl_elem_add(struct snd_ctl_file *file,
                            struct snd_ctl_elem_info *info, int replace)
{
        /* The capacity of struct snd_ctl_elem_value.value.*/
        static const unsigned int value_sizes[] = {
                [SNDRV_CTL_ELEM_TYPE_BOOLEAN]   = sizeof(long),
                [SNDRV_CTL_ELEM_TYPE_INTEGER]   = sizeof(long),
                [SNDRV_CTL_ELEM_TYPE_ENUMERATED] = sizeof(unsigned int),
                [SNDRV_CTL_ELEM_TYPE_BYTES]     = sizeof(unsigned char),
                [SNDRV_CTL_ELEM_TYPE_IEC958]    = sizeof(struct snd_aes_iec958),
                [SNDRV_CTL_ELEM_TYPE_INTEGER64] = sizeof(long long),
        };
        static const unsigned int max_value_counts[] = {
                [SNDRV_CTL_ELEM_TYPE_BOOLEAN]   = 128,
                [SNDRV_CTL_ELEM_TYPE_INTEGER]   = 128,
                [SNDRV_CTL_ELEM_TYPE_ENUMERATED] = 128,
                [SNDRV_CTL_ELEM_TYPE_BYTES]     = 512,
                [SNDRV_CTL_ELEM_TYPE_IEC958]    = 1,
                [SNDRV_CTL_ELEM_TYPE_INTEGER64] = 64,
        };
        struct snd_card *card = file->card;
        struct snd_kcontrol *kctl;
        unsigned int count;
        unsigned int access;
        long private_size;
        struct user_element *ue;
        unsigned int offset;
        int err;

        if (!*info->id.name)
                return -EINVAL;
        if (strnlen(info->id.name, sizeof(info->id.name)) >= sizeof(info->id.name))
                return -EINVAL;

        /* Delete a control to replace them if needed. */
        if (replace) {
                info->id.numid = 0;
                err = snd_ctl_remove_user_ctl(file, &info->id);
                if (err)
                        return err;
        }

        /*
         * The number of userspace controls are counted control by control,
         * not element by element.
         */
        if (card->user_ctl_count + 1 > MAX_USER_CONTROLS)
                return -ENOMEM;

        /* Check the number of elements for this userspace control. */
        count = info->owner;
        if (count == 0)
                count = 1;

        /* Arrange access permissions if needed. */
        access = info->access;
        if (access == 0)
                access = SNDRV_CTL_ELEM_ACCESS_READWRITE;
        access &= (SNDRV_CTL_ELEM_ACCESS_READWRITE |
                   SNDRV_CTL_ELEM_ACCESS_INACTIVE |
                   SNDRV_CTL_ELEM_ACCESS_TLV_WRITE);

        /* In initial state, nothing is available as TLV container. */
        if (access & SNDRV_CTL_ELEM_ACCESS_TLV_WRITE)
                access |= SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK;
        access |= SNDRV_CTL_ELEM_ACCESS_USER;

        /*
         * Check information and calculate the size of data specific to
         * this userspace control.
         */
        if (info->type < SNDRV_CTL_ELEM_TYPE_BOOLEAN ||
            info->type > SNDRV_CTL_ELEM_TYPE_INTEGER64)
                return -EINVAL;
        if (info->type == SNDRV_CTL_ELEM_TYPE_ENUMERATED &&
            info->value.enumerated.items == 0)
                return -EINVAL;
        if (info->count < 1 ||
            info->count > max_value_counts[info->type])
                return -EINVAL;
        if (!validate_element_member_dimension(info))
                return -EINVAL;
        private_size = value_sizes[info->type] * info->count;

        /*
         * Keep memory object for this userspace control. After passing this
         * code block, the instance should be freed by snd_ctl_free_one().
         *
         * Note that these elements in this control are locked.
         */
        err = snd_ctl_new(&kctl, count, access, file);
        if (err < 0)
                return err;
        memcpy(&kctl->id, &info->id, sizeof(kctl->id));
        kctl->private_data = kzalloc(sizeof(struct user_element) + private_size * count,
                                     GFP_KERNEL);
        if (kctl->private_data == NULL) {
                kfree(kctl);
                return -ENOMEM;
        }
        kctl->private_free = snd_ctl_elem_user_free;

        /* Set private data for this userspace control. */
        ue = (struct user_element *)kctl->private_data;
        ue->card = card;
        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) {
                        snd_ctl_free_one(kctl);
                        return err;
                }
        }

        /* Set callback functions. */
        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_WRITE)
                kctl->tlv.c = snd_ctl_elem_user_tlv;

        /* This function manage to free the instance on failure. */
        err = snd_ctl_add(card, kctl);
        if (err < 0)
                return err;
        offset = snd_ctl_get_ioff(kctl, &info->id);
        snd_ctl_build_ioff(&info->id, kctl, offset);
        /*
         * Here we cannot fill any field for the number of elements added by
         * this operation because there're no specific fields. The usage of
         * 'owner' field for this purpose may cause any bugs to userspace
         * applications because the field originally means PID of a process
         * which locks the element.
         */

        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;
        int err;

        if (copy_from_user(&info, _info, sizeof(info)))
                return -EFAULT;
        err = snd_ctl_elem_add(file, &info, replace);
        if (err < 0)
                return err;
        if (copy_to_user(_info, &info, sizeof(info))) {
                snd_ctl_remove_user_ctl(file, &info.id);
                return -EFAULT;
        }

        return 0;
}

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 call_tlv_handler(struct snd_ctl_file *file, int op_flag,
                            struct snd_kcontrol *kctl,
                            struct snd_ctl_elem_id *id,
                            unsigned int __user *buf, unsigned int size)
{
        static const struct {
                int op;
                int perm;
        } pairs[] = {
                {SNDRV_CTL_TLV_OP_READ,  SNDRV_CTL_ELEM_ACCESS_TLV_READ},
                {SNDRV_CTL_TLV_OP_WRITE, SNDRV_CTL_ELEM_ACCESS_TLV_WRITE},
                {SNDRV_CTL_TLV_OP_CMD,   SNDRV_CTL_ELEM_ACCESS_TLV_COMMAND},
        };
        struct snd_kcontrol_volatile *vd = &kctl->vd[snd_ctl_get_ioff(kctl, id)];
        int i;

        /* Check support of the request for this element. */
        for (i = 0; i < ARRAY_SIZE(pairs); ++i) {
                if (op_flag == pairs[i].op && (vd->access & pairs[i].perm))
                        break;
        }
        if (i == ARRAY_SIZE(pairs))
                return -ENXIO;

        if (kctl->tlv.c == NULL)
                return -ENXIO;

        /* When locked, this is unavailable. */
        if (vd->owner != NULL && vd->owner != file)
                return -EPERM;

        return kctl->tlv.c(kctl, op_flag, size, buf);
}

static int read_tlv_buf(struct snd_kcontrol *kctl, struct snd_ctl_elem_id *id,
                        unsigned int __user *buf, unsigned int size)
{
        struct snd_kcontrol_volatile *vd = &kctl->vd[snd_ctl_get_ioff(kctl, id)];
        unsigned int len;

        if (!(vd->access & SNDRV_CTL_ELEM_ACCESS_TLV_READ))
                return -ENXIO;

        if (kctl->tlv.p == NULL)
                return -ENXIO;

        len = sizeof(unsigned int) * 2 + kctl->tlv.p[1];
        if (size < len)
                return -ENOMEM;

        if (copy_to_user(buf, kctl->tlv.p, len))
                return -EFAULT;

        return 0;
}

static int snd_ctl_tlv_ioctl(struct snd_ctl_file *file,
                             struct snd_ctl_tlv __user *buf,
                             int op_flag)
{
        struct snd_ctl_tlv header;
        unsigned int *container;
        unsigned int container_size;
        struct snd_kcontrol *kctl;
        struct snd_ctl_elem_id id;
        struct snd_kcontrol_volatile *vd;

        if (copy_from_user(&header, buf, sizeof(header)))
                return -EFAULT;

        /* In design of control core, numerical ID starts at 1. */
        if (header.numid == 0)
                return -EINVAL;

        /* At least, container should include type and length fields.  */
        if (header.length < sizeof(unsigned int) * 2)
                return -EINVAL;
        container_size = header.length;
        container = buf->tlv;

        kctl = snd_ctl_find_numid(file->card, header.numid);
        if (kctl == NULL)
                return -ENOENT;

        /* Calculate index of the element in this set. */
        id = kctl->id;
        snd_ctl_build_ioff(&id, kctl, header.numid - id.numid);
        vd = &kctl->vd[snd_ctl_get_ioff(kctl, &id)];

        if (vd->access & SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK) {
                return call_tlv_handler(file, op_flag, kctl, &id, container,
                                        container_size);
        } else {
                if (op_flag == SNDRV_CTL_TLV_OP_READ) {
                        return read_tlv_buf(kctl, &id, container,
                                            container_size);
                }
        }

        /* Not supported. */
        return -ENXIO;
}

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:
                down_read(&ctl->card->controls_rwsem);
                err = snd_ctl_tlv_ioctl(ctl, argp, SNDRV_CTL_TLV_OP_READ);
                up_read(&ctl->card->controls_rwsem);
                return err;
        case SNDRV_CTL_IOCTL_TLV_WRITE:
                down_write(&ctl->card->controls_rwsem);
                err = snd_ctl_tlv_ioctl(ctl, argp, SNDRV_CTL_TLV_OP_WRITE);
                up_write(&ctl->card->controls_rwsem);
                return err;
        case SNDRV_CTL_IOCTL_TLV_COMMAND:
                down_write(&ctl->card->controls_rwsem);
                err = snd_ctl_tlv_ioctl(ctl, argp, SNDRV_CTL_TLV_OP_CMD);
                up_write(&ctl->card->controls_rwsem);
                return err;
        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);
        dev_dbg(card->dev, "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_entry_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 __poll_t snd_ctl_poll(struct file *file, poll_table * wait)
{
        __poll_t 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 |= EPOLLIN | EPOLLRDNORM;

        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;
}

/**
 * snd_ctl_register_ioctl - register the device-specific control-ioctls
 * @fcn: ioctl callback function
 *
 * called from each device manager like pcm.c, hwdep.c, etc.
 */
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
/**
 * snd_ctl_register_ioctl_compat - register the device-specific 32bit compat
 * control-ioctls
 * @fcn: ioctl callback function
 */
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;
}

/**
 * snd_ctl_unregister_ioctl - de-register the device-specific control-ioctls
 * @fcn: ioctl callback function to unregister
 */
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
/**
 * snd_ctl_unregister_ioctl - de-register the device-specific compat 32bit
 * control-ioctls
 * @fcn: ioctl callback function to unregister
 */
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);
}

/* return the preferred subdevice number if already assigned;
 * otherwise return -1
 */
int snd_ctl_get_preferred_subdevice(struct snd_card *card, int type)
{
        struct snd_ctl_file *kctl;
        int subdevice = -1;

        read_lock(&card->ctl_files_rwlock);
        list_for_each_entry(kctl, &card->ctl_files, list) {
                if (kctl->pid == task_pid(current)) {
                        subdevice = kctl->preferred_subdevice[type];
                        if (subdevice != -1)
                                break;
                }
        }
        read_unlock(&card->ctl_files_rwlock);
        return subdevice;
}
EXPORT_SYMBOL_GPL(snd_ctl_get_preferred_subdevice);

/*
 * 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;

        return snd_register_device(SNDRV_DEVICE_TYPE_CONTROL, card, -1,
                                   &snd_ctl_f_ops, card, &card->ctl_dev);
}

/*
 * 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;

        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);

        return snd_unregister_device(&card->ctl_dev);
}

/*
 * 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);
        put_device(&card->ctl_dev);
        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,
        };
        int err;

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

        snd_device_initialize(&card->ctl_dev, card);
        dev_set_name(&card->ctl_dev, "controlC%d", card->number);

        err = snd_device_new(card, SNDRV_DEV_CONTROL, card, &ops);
        if (err < 0)
                put_device(&card->ctl_dev);
        return err;
}

/*
 * Frequently used control callbacks/helpers
 */

/**
 * snd_ctl_boolean_mono_info - Helper function for a standard boolean info
 * callback with a mono channel
 * @kcontrol: the kcontrol instance
 * @uinfo: info to store
 *
 * This is a function that can be used as info callback for a standard
 * boolean control with a single mono channel.
 */
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);

/**
 * snd_ctl_boolean_stereo_info - Helper function for a standard boolean info
 * callback with stereo two channels
 * @kcontrol: the kcontrol instance
 * @uinfo: info to store
 *
 * This is a function that can be used as info callback for a standard
 * boolean control with stereo two channels.
 */
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);

/**
 * snd_ctl_enum_info - fills the info structure for an enumerated control
 * @info: the structure to be filled
 * @channels: the number of the control's channels; often one
 * @items: the number of control values; also the size of @names
 * @names: an array containing the names of all control values
 *
 * Sets all required fields in @info to their appropriate values.
 * If the control's accessibility is not the default (readable and writable),
 * the caller has to fill @info->access.
 *
 * Return: Zero.
 */
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 (!items)
                return 0;
        if (info->value.enumerated.item >= items)
                info->value.enumerated.item = items - 1;
        WARN(strlen(names[info->value.enumerated.item]) >= sizeof(info->value.enumerated.name),
             "ALSA: too long item name '%s'\n",
             names[info->value.enumerated.item]);
        strlcpy(info->value.enumerated.name,
                names[info->value.enumerated.item],
                sizeof(info->value.enumerated.name));
        return 0;
}
EXPORT_SYMBOL(snd_ctl_enum_info);