sound/core/control.c - pub/scm/linux/kernel/git/joro/linux - Git at Google

 /*
  *  Routines for driver control interface
  *  Copyright (c) by Jaroslav Kysela <perex@suse.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
  *
  */

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

 typedef struct _snd_kctl_ioctl {
 	struct list_head list;		/* list of all ioctls */
 	snd_kctl_ioctl_func_t fioctl;
 } snd_kctl_ioctl_t;

 #define snd_kctl_ioctl(n) list_entry(n, snd_kctl_ioctl_t, list)

 static rwlock_t snd_ioctl_rwlock = RW_LOCK_UNLOCKED;
 static LIST_HEAD(snd_control_ioctls);

 static inline void dec_mod_count(struct module *module)
 {
 	if (module)
 		__MOD_DEC_USE_COUNT(module);
 }

 static int snd_ctl_open(struct inode *inode, struct file *file)
 {
 	int cardnum = SNDRV_MINOR_CARD(minor(inode->i_rdev));
 	unsigned long flags;
 	snd_card_t *card;
 	snd_ctl_file_t *ctl;
 	int err;

 #ifdef LINUX_2_2
 	MOD_INC_USE_COUNT;
 #endif
 	card = snd_cards[cardnum];
 	if (!card) {
 		err = -ENODEV;
 		goto __error1;
 	}
 	if (!try_inc_mod_count(card->module)) {
 		err = -EFAULT;
 		goto __error1;
 	}
 	ctl = snd_magic_kcalloc(snd_ctl_file_t, 0, 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->pid = current->pid;
 	file->private_data = ctl;
 	write_lock_irqsave(&card->control_rwlock, flags);
 	list_add_tail(&ctl->list, &card->ctl_files);
 	write_unlock_irqrestore(&card->control_rwlock, flags);
 	return 0;

       __error:
       	dec_mod_count(card->module);
       __error1:
 #ifdef LINUX_2_2
       	MOD_DEC_USE_COUNT;
 #endif
       	return err;
 }

 static void snd_ctl_empty_read_queue(snd_ctl_file_t * ctl)
 {
 	snd_kctl_event_t *cread;

 	spin_lock(&ctl->read_lock);
 	while (!list_empty(&ctl->events)) {
 		cread = snd_kctl_event(ctl->events.next);
 		list_del(&cread->list);
 		kfree(cread);
 	}
 	spin_unlock(&ctl->read_lock);
 }

 static int snd_ctl_release(struct inode *inode, struct file *file)
 {
 	unsigned long flags;
 	struct list_head *list;
 	snd_card_t *card;
 	snd_ctl_file_t *ctl;
 	snd_kcontrol_t *control;

 	ctl = snd_magic_cast(snd_ctl_file_t, file->private_data, return -ENXIO);
 	fasync_helper(-1, file, 0, &ctl->fasync);
 	file->private_data = NULL;
 	card = ctl->card;
 	write_lock_irqsave(&card->control_rwlock, flags);
 	list_del(&ctl->list);
 	write_unlock_irqrestore(&card->control_rwlock, flags);
 	write_lock(&card->control_owner_lock);
 	list_for_each(list, &card->controls) {
 		control = snd_kcontrol(list);
 		if (control->owner == ctl)
 			control->owner = NULL;
 	}
 	write_unlock(&card->control_owner_lock);
 	snd_ctl_empty_read_queue(ctl);
 	snd_magic_kfree(ctl);
 	dec_mod_count(card->module);
 #ifdef LINUX_2_2
 	MOD_DEC_USE_COUNT;
 #endif
 	return 0;
 }

 void snd_ctl_notify(snd_card_t *card, unsigned int mask, snd_ctl_elem_id_t *id)
 {
 	unsigned long flags;
 	struct list_head *flist;
 	snd_ctl_file_t *ctl;
 	snd_kctl_event_t *ev;

 	snd_runtime_check(card != NULL && id != NULL, return);
 	read_lock_irqsave(&card->control_rwlock, flags);
 #ifdef CONFIG_SND_OSSEMUL
 	card->mixer_oss_change_count++;
 #endif
 	list_for_each(flist, &card->ctl_files) {
 		struct list_head *elist;
 		ctl = snd_ctl_file(flist);
 		if (!ctl->subscribed)
 			continue;
 		spin_lock(&ctl->read_lock);
 		list_for_each(elist, &ctl->events) {
 			ev = snd_kctl_event(elist);
 			if (ev->id.numid == id->numid) {
 				ev->mask |= mask;
 				goto _found;
 			}
 		}
 		ev = snd_kcalloc(sizeof(*ev), in_interrupt() ? GFP_ATOMIC : GFP_KERNEL);
 		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);
 		kill_fasync(&ctl->fasync, SIGIO, POLL_IN);
 		spin_unlock(&ctl->read_lock);
 	}
 	read_unlock_irqrestore(&card->control_rwlock, flags);
 }

 snd_kcontrol_t *snd_ctl_new(snd_kcontrol_t * control)
 {
 	snd_kcontrol_t *kctl;

 	snd_runtime_check(control != NULL, return NULL);
 	kctl = (snd_kcontrol_t *)snd_magic_kmalloc(snd_kcontrol_t, 0, GFP_KERNEL);
 	if (kctl == NULL)
 		return NULL;
 	*kctl = *control;
 	return kctl;
 }

 snd_kcontrol_t *snd_ctl_new1(snd_kcontrol_new_t * ncontrol, void *private_data)
 {
 	snd_kcontrol_t kctl;

 	snd_runtime_check(ncontrol != NULL, return NULL);
 	snd_assert(ncontrol->info != NULL, return NULL);
 	memset(&kctl, 0, sizeof(kctl));
 	kctl.id.iface = ncontrol->iface;
 	kctl.id.device = ncontrol->device;
 	kctl.id.subdevice = ncontrol->subdevice;
 	strncpy(kctl.id.name, ncontrol->name, sizeof(kctl.id.name)-1);
 	kctl.id.index = ncontrol->index;
 	kctl.access = ncontrol->access == 0 ? SNDRV_CTL_ELEM_ACCESS_READWRITE :
 		      (ncontrol->access & (SNDRV_CTL_ELEM_ACCESS_READWRITE|SNDRV_CTL_ELEM_ACCESS_INACTIVE|SNDRV_CTL_ELEM_ACCESS_INDIRECT));
 	kctl.info = ncontrol->info;
 	kctl.get = ncontrol->get;
 	kctl.put = ncontrol->put;
 	kctl.private_value = ncontrol->private_value;
 	kctl.private_data = private_data;
 	return snd_ctl_new(&kctl);
 }

 void snd_ctl_free_one(snd_kcontrol_t * kcontrol)
 {
 	if (kcontrol) {
 		if (kcontrol->private_free)
 			kcontrol->private_free(kcontrol);
 		snd_magic_kfree(kcontrol);
 	}
 }

 int snd_ctl_add(snd_card_t * card, snd_kcontrol_t * kcontrol)
 {
 	snd_runtime_check(card != NULL && kcontrol != NULL, return -EINVAL);
 	snd_assert(kcontrol->info != NULL, return -EINVAL);
 	snd_assert(!(kcontrol->access & SNDRV_CTL_ELEM_ACCESS_READ) || kcontrol->get != NULL, return -EINVAL);
 	snd_assert(!(kcontrol->access & SNDRV_CTL_ELEM_ACCESS_WRITE) || kcontrol->put != NULL, return -EINVAL);
 	write_lock(&card->control_rwlock);
 	list_add_tail(&kcontrol->list, &card->controls);
 	card->controls_count++;
 	kcontrol->id.numid = ++card->last_numid;
 	write_unlock(&card->control_rwlock);
 	snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_ADD, &kcontrol->id);
 	return 0;
 }

 int snd_ctl_remove(snd_card_t * card, snd_kcontrol_t * kcontrol)
 {
 	snd_runtime_check(card != NULL && kcontrol != NULL, return -EINVAL);
 	write_lock(&card->control_rwlock);
 	list_del(&kcontrol->list);
 	card->controls_count--;
 	write_unlock(&card->control_rwlock);
 	snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_REMOVE, &kcontrol->id);
 	snd_ctl_free_one(kcontrol);
 	return 0;
 }

 int snd_ctl_remove_id(snd_card_t * card, snd_ctl_elem_id_t *id)
 {
 	snd_kcontrol_t *kctl;

 	kctl = snd_ctl_find_id(card, id);
 	if (kctl == NULL)
 		return -ENOENT;
 	return snd_ctl_remove(card, kctl);
 }

 int snd_ctl_rename_id(snd_card_t * card, snd_ctl_elem_id_t *src_id, snd_ctl_elem_id_t *dst_id)
 {
 	snd_kcontrol_t *kctl;

 	kctl = snd_ctl_find_id(card, src_id);
 	if (kctl == NULL)
 		return -ENOENT;
 	write_lock(&card->control_rwlock);
 	kctl->id = *dst_id;
 	kctl->id.numid = ++card->last_numid;
 	write_unlock(&card->control_rwlock);
 	return 0;
 }

 snd_kcontrol_t *snd_ctl_find_numid(snd_card_t * card, unsigned int numid)
 {
 	struct list_head *list;
 	snd_kcontrol_t *kctl;

 	snd_runtime_check(card != NULL && numid != 0, return NULL);
 	read_lock(&card->control_rwlock);
 	list_for_each(list, &card->controls) {
 		kctl = snd_kcontrol(list);
 		if (kctl->id.numid == numid) {
 			read_unlock(&card->control_rwlock);
 			return kctl;
 		}
 	}
 	read_unlock(&card->control_rwlock);
 	return NULL;
 }

 snd_kcontrol_t *snd_ctl_find_id(snd_card_t * card, snd_ctl_elem_id_t *id)
 {
 	struct list_head *list;
 	snd_kcontrol_t *kctl;

 	snd_runtime_check(card != NULL && id != NULL, return NULL);
 	if (id->numid != 0)
 		return snd_ctl_find_numid(card, id->numid);
 	read_lock(&card->control_rwlock);
 	list_for_each(list, &card->controls) {
 		kctl = snd_kcontrol(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;
 		read_unlock(&card->control_rwlock);
 		return kctl;
 	}
 	read_unlock(&card->control_rwlock);
 	return NULL;
 }

 static int snd_ctl_card_info(snd_card_t * card, snd_ctl_file_t * ctl,
 			     unsigned int cmd, unsigned long arg)
 {
 	snd_ctl_card_info_t info;

 	memset(&info, 0, sizeof(info));
 	read_lock(&snd_ioctl_rwlock);
 	info.card = card->number;
 	strncpy(info.id, card->id, sizeof(info.id) - 1);
 	strncpy(info.driver, card->driver, sizeof(info.driver) - 1);
 	strncpy(info.name, card->shortname, sizeof(info.name) - 1);
 	strncpy(info.longname, card->longname, sizeof(info.longname) - 1);
 	strncpy(info.mixername, card->mixername, sizeof(info.mixername) - 1);
 	strncpy(info.components, card->components, sizeof(info.components) - 1);
 	read_unlock(&snd_ioctl_rwlock);
 	if (copy_to_user((void *) arg, &info, sizeof(snd_ctl_card_info_t)))
 		return -EFAULT;
 	return 0;
 }

 static int snd_ctl_elem_list(snd_card_t *card, snd_ctl_elem_list_t *_list)
 {
 	struct list_head *plist;
 	snd_ctl_elem_list_t list;
 	snd_kcontrol_t *kctl;
 	snd_ctl_elem_id_t *dst, *id;
 	int offset, space;

 	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(snd_ctl_elem_id_t));
 		if (dst == NULL)
 			return -ENOMEM;
 		read_lock(&card->control_rwlock);
 		list.count = card->controls_count;
 		plist = card->controls.next;
 		while (offset-- > 0 && plist != &card->controls)
 			plist = plist->next;
 		list.used = 0;
 		id = dst;
 		while (space > 0 && plist != &card->controls) {
 			kctl = snd_kcontrol(plist);
 			memcpy(id, &kctl->id, sizeof(snd_ctl_elem_id_t));
 			id++;
 			plist = plist->next;
 			space--;
 			list.used++;
 		}
 		read_unlock(&card->control_rwlock);
 		if (list.used > 0 && copy_to_user(list.pids, dst, list.used * sizeof(snd_ctl_elem_id_t)))
 			return -EFAULT;
 		vfree(dst);
 	} else {
 		read_lock(&card->control_rwlock);
 		list.count = card->controls_count;
 		read_unlock(&card->control_rwlock);
 	}
 	if (copy_to_user(_list, &list, sizeof(list)))
 		return -EFAULT;
 	return 0;
 }

 static int snd_ctl_elem_info(snd_ctl_file_t *ctl, snd_ctl_elem_info_t *_info)
 {
 	snd_card_t *card = ctl->card;
 	snd_ctl_elem_info_t info;
 	snd_kcontrol_t *kctl;
 	int result;

 	if (copy_from_user(&info, _info, sizeof(info)))
 		return -EFAULT;
 	read_lock(&card->control_rwlock);
 	kctl = snd_ctl_find_id(card, &info.id);
 	if (kctl == NULL) {
 		read_unlock(&card->control_rwlock);
 		return -ENOENT;
 	}
 #ifdef CONFIG_SND_DEBUG
 	info.access = 0;
 #endif
 	result = kctl->info(kctl, &info);
 	if (result >= 0) {
 		snd_assert(info.access == 0, );
 		info.id = kctl->id;
 		info.access = kctl->access;
 		if (kctl->owner) {
 			info.access |= SNDRV_CTL_ELEM_ACCESS_LOCK;
 			if (kctl->owner == ctl)
 				info.access |= SNDRV_CTL_ELEM_ACCESS_OWNER;
 			info.owner = kctl->owner_pid;
 		} else {
 			info.owner = -1;
 		}
 	}
 	read_unlock(&card->control_rwlock);
 	if (result >= 0)
 		if (copy_to_user(_info, &info, sizeof(info)))
 			return -EFAULT;
 	return result;
 }

 static int snd_ctl_elem_read(snd_card_t *card, snd_ctl_elem_value_t *_control)
 {
 	snd_ctl_elem_value_t control;
 	snd_kcontrol_t *kctl;
 	int result, indirect;

 	if (copy_from_user(&control, _control, sizeof(control)))
 		return -EFAULT;
 	read_lock(&card->control_rwlock);
 	kctl = snd_ctl_find_id(card, &control.id);
 	if (kctl == NULL) {
 		result = -ENOENT;
 	} else {
 		indirect = kctl->access & SNDRV_CTL_ELEM_ACCESS_INDIRECT ? 1 : 0;
 		if (control.indirect != indirect) {
 			result = -EACCES;
 		} else {
 			if ((kctl->access & SNDRV_CTL_ELEM_ACCESS_READ) && kctl->get != NULL) {
 				result = kctl->get(kctl, &control);
 				if (result >= 0)
 					control.id = kctl->id;
 			} else
 				result = -EPERM;
 		}
 	}
 	read_unlock(&card->control_rwlock);
 	if (result >= 0)
 		if (copy_to_user(_control, &control, sizeof(control)))
 			return -EFAULT;
 	return result;
 }

 static int snd_ctl_elem_write(snd_ctl_file_t *file, snd_ctl_elem_value_t *_control)
 {
 	snd_card_t *card = file->card;
 	snd_ctl_elem_value_t control;
 	snd_kcontrol_t *kctl;
 	int result, indirect;

 	if (copy_from_user(&control, _control, sizeof(control)))
 		return -EFAULT;
 	read_lock(&card->control_rwlock);
 	kctl = snd_ctl_find_id(card, &control.id);
 	if (kctl == NULL) {
 		result = -ENOENT;
 	} else {
 		indirect = kctl->access & SNDRV_CTL_ELEM_ACCESS_INDIRECT ? 1 : 0;
 		if (control.indirect != indirect) {
 			result = -EACCES;
 		} else {
 			read_lock(&card->control_owner_lock);
 			if (!(kctl->access & SNDRV_CTL_ELEM_ACCESS_WRITE) ||
 			    kctl->put == NULL ||
 			    (kctl->owner != NULL && kctl->owner != file)) {
 				result = -EPERM;
 			} else {
 				result = kctl->put(kctl, &control);
 				if (result >= 0)
 					control.id = kctl->id;
 			}
 			read_unlock(&card->control_owner_lock);
 			if (result > 0) {
 				result = 0;
 				snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE, &kctl->id);
 			}
 		}
 	}
 	read_unlock(&card->control_rwlock);
 	if (result >= 0)
 		if (copy_to_user(_control, &control, sizeof(control)))
 			return -EFAULT;
 	return result;
 }

 static int snd_ctl_elem_lock(snd_ctl_file_t *file, snd_ctl_elem_id_t *_id)
 {
 	snd_card_t *card = file->card;
 	snd_ctl_elem_id_t id;
 	snd_kcontrol_t *kctl;
 	int result;

 	if (copy_from_user(&id, _id, sizeof(id)))
 		return -EFAULT;
 	read_lock(&card->control_rwlock);
 	kctl = snd_ctl_find_id(card, &id);
 	if (kctl == NULL) {
 		result = -ENOENT;
 	} else {
 		write_lock(&card->control_owner_lock);
 		if (kctl->owner != NULL)
 			result = -EBUSY;
 		else {
 			kctl->owner = file;
 			kctl->owner_pid = current->pid;
 			result = 0;
 		}
 		write_unlock(&card->control_owner_lock);
 	}
 	read_unlock(&card->control_rwlock);
 	return result;
 }

 static int snd_ctl_elem_unlock(snd_ctl_file_t *file, snd_ctl_elem_id_t *_id)
 {
 	snd_card_t *card = file->card;
 	snd_ctl_elem_id_t id;
 	snd_kcontrol_t *kctl;
 	int result;

 	if (copy_from_user(&id, _id, sizeof(id)))
 		return -EFAULT;
 	read_lock(&card->control_rwlock);
 	kctl = snd_ctl_find_id(card, &id);
 	if (kctl == NULL) {
 		result = -ENOENT;
 	} else {
 		write_lock(&card->control_owner_lock);
 		if (kctl->owner == NULL)
 			result = -EINVAL;
 		else if (kctl->owner != file)
 			result = -EPERM;
 		else {
 			kctl->owner = NULL;
 			kctl->owner_pid = 0;
 			result = 0;
 		}
 		write_unlock(&card->control_owner_lock);
 	}
 	read_unlock(&card->control_rwlock);
 	return result;
 }

 static int snd_ctl_subscribe_events(snd_ctl_file_t *file, int *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_ioctl(struct inode *inode, struct file *file,
 			 unsigned int cmd, unsigned long arg)
 {
 	snd_ctl_file_t *ctl;
 	snd_card_t *card;
 	struct list_head *list;
 	snd_kctl_ioctl_t *p;
 	int err;

 	ctl = snd_magic_cast(snd_ctl_file_t, file->private_data, return -ENXIO);
 	card = ctl->card;
 	snd_assert(card != NULL, return -ENXIO);
 	switch (cmd) {
 	case SNDRV_CTL_IOCTL_PVERSION:
 		return put_user(SNDRV_CTL_VERSION, (int *)arg) ? -EFAULT : 0;
 	case SNDRV_CTL_IOCTL_CARD_INFO:
 		return snd_ctl_card_info(card, ctl, cmd, arg);
 	case SNDRV_CTL_IOCTL_ELEM_LIST:
 		return snd_ctl_elem_list(ctl->card, (snd_ctl_elem_list_t *) arg);
 	case SNDRV_CTL_IOCTL_ELEM_INFO:
 		return snd_ctl_elem_info(ctl, (snd_ctl_elem_info_t *) arg);
 	case SNDRV_CTL_IOCTL_ELEM_READ:
 		return snd_ctl_elem_read(ctl->card, (snd_ctl_elem_value_t *) arg);
 	case SNDRV_CTL_IOCTL_ELEM_WRITE:
 		return snd_ctl_elem_write(ctl, (snd_ctl_elem_value_t *) arg);
 	case SNDRV_CTL_IOCTL_ELEM_LOCK:
 		return snd_ctl_elem_lock(ctl, (snd_ctl_elem_id_t *) arg);
 	case SNDRV_CTL_IOCTL_ELEM_UNLOCK:
 		return snd_ctl_elem_unlock(ctl, (snd_ctl_elem_id_t *) arg);
 	case SNDRV_CTL_IOCTL_SUBSCRIBE_EVENTS:
 		return snd_ctl_subscribe_events(ctl, (int *) arg);
 	case SNDRV_CTL_IOCTL_POWER:
 		if (get_user(err, (int *)arg))
 			return -EFAULT;
 		if (!capable(CAP_SYS_ADMIN))
 			return -EPERM;
 #ifdef CONFIG_PM
 		if (card->set_power_state == NULL)
 			return -ENOPROTOOPT;
 		return card->set_power_state(card, err);
 #else
 		return -ENOPROTOOPT;
 #endif
 	case SNDRV_CTL_IOCTL_POWER_STATE:
 #ifdef CONFIG_PM
 		return put_user(card->power_state, (int *)arg) ? -EFAULT : 0;
 #else
 		return put_user(SNDRV_CTL_POWER_D0, (int *)arg) ? -EFAULT : 0;
 #endif
 	}
 	read_lock(&snd_ioctl_rwlock);
 	list_for_each(list, &snd_control_ioctls) {
 		p = list_entry(list, snd_kctl_ioctl_t, list);
 		err = p->fioctl(card, ctl, cmd, arg);
 		if (err != -ENOIOCTLCMD) {
 			read_unlock(&snd_ioctl_rwlock);
 			return err;
 		}
 	}
 	read_unlock(&snd_ioctl_rwlock);
 	snd_printd("unknown ioctl = 0x%x\n", cmd);
 	return -ENOTTY;
 }

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

 	ctl = snd_magic_cast(snd_ctl_file_t, file->private_data, return -ENXIO);
 	snd_assert(ctl != NULL && ctl->card != NULL, return -ENXIO);
 	if (!ctl->subscribed)
 		return -EBADFD;
 	if (count < sizeof(snd_ctl_event_t))
 		return -EINVAL;
 	spin_lock_irq(&ctl->read_lock);
 	while (count >= sizeof(snd_ctl_event_t)) {
 		snd_ctl_event_t ev;
 		snd_kctl_event_t *kev;
 		while (list_empty(&ctl->events)) {
 			wait_queue_t wait;
 			if (file->f_flags & O_NONBLOCK) {
 				err = -EAGAIN;
 				goto __end;
 			}
 			init_waitqueue_entry(&wait, current);
 			add_wait_queue(&ctl->change_sleep, &wait);
 			spin_unlock_irq(&ctl->read_lock);
 			set_current_state(TASK_INTERRUPTIBLE);
 			schedule();
 			set_current_state(TASK_RUNNING);
 			remove_wait_queue(&ctl->change_sleep, &wait);
 			if (signal_pending(current))
 				return result > 0 ? result : -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(snd_ctl_event_t))) {
 			err = -EFAULT;
 			goto __end;
 		}
 		spin_lock_irq(&ctl->read_lock);
 		buffer += sizeof(snd_ctl_event_t);
 		count -= sizeof(snd_ctl_event_t);
 		result += sizeof(snd_ctl_event_t);
 	}
       __end:
 	spin_unlock_irq(&ctl->read_lock);
       	return result > 0 ? result : err;
 }

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

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

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

 	return mask;
 }

 int snd_ctl_register_ioctl(snd_kctl_ioctl_func_t fcn)
 {
 	snd_kctl_ioctl_t *pn;

 	pn = (snd_kctl_ioctl_t *)
 		snd_kcalloc(sizeof(snd_kctl_ioctl_t), GFP_KERNEL);
 	if (pn == NULL)
 		return -ENOMEM;
 	pn->fioctl = fcn;
 	write_lock(&snd_ioctl_rwlock);
 	list_add_tail(&pn->list, &snd_control_ioctls);
 	write_unlock(&snd_ioctl_rwlock);
 	return 0;
 }

 int snd_ctl_unregister_ioctl(snd_kctl_ioctl_func_t fcn)
 {
 	struct list_head *list;
 	snd_kctl_ioctl_t *p;

 	snd_runtime_check(fcn != NULL, return -EINVAL);
 	write_lock(&snd_ioctl_rwlock);
 	list_for_each(list, &snd_control_ioctls) {
 		p = list_entry(list, snd_kctl_ioctl_t, list);
 		if (p->fioctl == fcn) {
 			list_del(&p->list);
 			write_unlock(&snd_ioctl_rwlock);
 			kfree(p);
 			return 0;
 		}
 	}
 	write_unlock(&snd_ioctl_rwlock);
 	snd_BUG();
 	return -EINVAL;
 }

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

 /*
  *  INIT PART
  */

 static struct file_operations snd_ctl_f_ops =
 {
 #ifndef LINUX_2_2
 	owner:		THIS_MODULE,
 #endif
 	read:		snd_ctl_read,
 	open:		snd_ctl_open,
 	release:	snd_ctl_release,
 	poll:		snd_ctl_poll,
 	ioctl:		snd_ctl_ioctl,
 	fasync:		snd_ctl_fasync,
 };

 static snd_minor_t snd_ctl_reg =
 {
 	comment:	"ctl",
 	f_ops:		&snd_ctl_f_ops,
 };

 int snd_ctl_register(snd_card_t *card)
 {
 	int err, cardnum;
 	char name[16];

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

 int snd_ctl_unregister(snd_card_t *card)
 {
 	int err, cardnum;
 	snd_kcontrol_t *control;

 	snd_assert(card != NULL, return -ENXIO);
 	cardnum = card->number;
 	snd_assert(cardnum >= 0 && cardnum < SNDRV_CARDS, return -ENXIO);
 	if ((err = snd_unregister_device(SNDRV_DEVICE_TYPE_CONTROL, card, 0)) < 0)
 		return err;
 	while (!list_empty(&card->controls)) {
 		control = snd_kcontrol(card->controls.next);
 		snd_ctl_remove(card, control);
 	}
 	return 0;
 }
	/*
	* Routines for driver control interface
	* Copyright (c) by Jaroslav Kysela <perex@suse.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
	*
	*/

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

	typedef struct _snd_kctl_ioctl {
	struct list_head list; /* list of all ioctls */
	snd_kctl_ioctl_func_t fioctl;
	} snd_kctl_ioctl_t;

	#define snd_kctl_ioctl(n) list_entry(n, snd_kctl_ioctl_t, list)

	static rwlock_t snd_ioctl_rwlock = RW_LOCK_UNLOCKED;
	static LIST_HEAD(snd_control_ioctls);

	static inline void dec_mod_count(struct module *module)
	{
	if (module)
	__MOD_DEC_USE_COUNT(module);
	}

	static int snd_ctl_open(struct inode inode, struct file file)
	{
	int cardnum = SNDRV_MINOR_CARD(minor(inode->i_rdev));
	unsigned long flags;
	snd_card_t *card;
	snd_ctl_file_t *ctl;
	int err;

	#ifdef LINUX_2_2
	MOD_INC_USE_COUNT;
	#endif
	card = snd_cards[cardnum];
	if (!card) {
	err = -ENODEV;
	goto __error1;
	}
	if (!try_inc_mod_count(card->module)) {
	err = -EFAULT;
	goto __error1;
	}
	ctl = snd_magic_kcalloc(snd_ctl_file_t, 0, 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->pid = current->pid;
	file->private_data = ctl;
	write_lock_irqsave(&card->control_rwlock, flags);
	list_add_tail(&ctl->list, &card->ctl_files);
	write_unlock_irqrestore(&card->control_rwlock, flags);
	return 0;

	__error:
	dec_mod_count(card->module);
	__error1:
	#ifdef LINUX_2_2
	MOD_DEC_USE_COUNT;
	#endif
	return err;
	}

	static void snd_ctl_empty_read_queue(snd_ctl_file_t * ctl)
	{
	snd_kctl_event_t *cread;

	spin_lock(&ctl->read_lock);
	while (!list_empty(&ctl->events)) {
	cread = snd_kctl_event(ctl->events.next);
	list_del(&cread->list);
	kfree(cread);
	}
	spin_unlock(&ctl->read_lock);
	}

	static int snd_ctl_release(struct inode inode, struct file file)
	{
	unsigned long flags;
	struct list_head *list;
	snd_card_t *card;
	snd_ctl_file_t *ctl;
	snd_kcontrol_t *control;

	ctl = snd_magic_cast(snd_ctl_file_t, file->private_data, return -ENXIO);
	fasync_helper(-1, file, 0, &ctl->fasync);
	file->private_data = NULL;
	card = ctl->card;
	write_lock_irqsave(&card->control_rwlock, flags);
	list_del(&ctl->list);
	write_unlock_irqrestore(&card->control_rwlock, flags);
	write_lock(&card->control_owner_lock);
	list_for_each(list, &card->controls) {
	control = snd_kcontrol(list);
	if (control->owner == ctl)
	control->owner = NULL;
	}
	write_unlock(&card->control_owner_lock);
	snd_ctl_empty_read_queue(ctl);
	snd_magic_kfree(ctl);
	dec_mod_count(card->module);
	#ifdef LINUX_2_2
	MOD_DEC_USE_COUNT;
	#endif
	return 0;
	}

	void snd_ctl_notify(snd_card_t card, unsigned int mask, snd_ctl_elem_id_t id)
	{
	unsigned long flags;
	struct list_head *flist;
	snd_ctl_file_t *ctl;
	snd_kctl_event_t *ev;

	snd_runtime_check(card != NULL && id != NULL, return);
	read_lock_irqsave(&card->control_rwlock, flags);
	#ifdef CONFIG_SND_OSSEMUL
	card->mixer_oss_change_count++;
	#endif
	list_for_each(flist, &card->ctl_files) {
	struct list_head *elist;
	ctl = snd_ctl_file(flist);
	if (!ctl->subscribed)
	continue;
	spin_lock(&ctl->read_lock);
	list_for_each(elist, &ctl->events) {
	ev = snd_kctl_event(elist);
	if (ev->id.numid == id->numid) {
	ev->mask \|= mask;
	goto _found;
	}
	}
	ev = snd_kcalloc(sizeof(*ev), in_interrupt() ? GFP_ATOMIC : GFP_KERNEL);
	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);
	kill_fasync(&ctl->fasync, SIGIO, POLL_IN);
	spin_unlock(&ctl->read_lock);
	}
	read_unlock_irqrestore(&card->control_rwlock, flags);
	}

	snd_kcontrol_t snd_ctl_new(snd_kcontrol_t control)
	{
	snd_kcontrol_t *kctl;

	snd_runtime_check(control != NULL, return NULL);
	kctl = (snd_kcontrol_t *)snd_magic_kmalloc(snd_kcontrol_t, 0, GFP_KERNEL);
	if (kctl == NULL)
	return NULL;
	kctl = control;
	return kctl;
	}

	snd_kcontrol_t snd_ctl_new1(snd_kcontrol_new_t ncontrol, void *private_data)
	{
	snd_kcontrol_t kctl;

	snd_runtime_check(ncontrol != NULL, return NULL);
	snd_assert(ncontrol->info != NULL, return NULL);
	memset(&kctl, 0, sizeof(kctl));
	kctl.id.iface = ncontrol->iface;
	kctl.id.device = ncontrol->device;
	kctl.id.subdevice = ncontrol->subdevice;
	strncpy(kctl.id.name, ncontrol->name, sizeof(kctl.id.name)-1);
	kctl.id.index = ncontrol->index;
	kctl.access = ncontrol->access == 0 ? SNDRV_CTL_ELEM_ACCESS_READWRITE :
	(ncontrol->access & (SNDRV_CTL_ELEM_ACCESS_READWRITE\|SNDRV_CTL_ELEM_ACCESS_INACTIVE\|SNDRV_CTL_ELEM_ACCESS_INDIRECT));
	kctl.info = ncontrol->info;
	kctl.get = ncontrol->get;
	kctl.put = ncontrol->put;
	kctl.private_value = ncontrol->private_value;
	kctl.private_data = private_data;
	return snd_ctl_new(&kctl);
	}

	void snd_ctl_free_one(snd_kcontrol_t * kcontrol)
	{
	if (kcontrol) {
	if (kcontrol->private_free)
	kcontrol->private_free(kcontrol);
	snd_magic_kfree(kcontrol);
	}
	}

	int snd_ctl_add(snd_card_t * card, snd_kcontrol_t * kcontrol)
	{
	snd_runtime_check(card != NULL && kcontrol != NULL, return -EINVAL);
	snd_assert(kcontrol->info != NULL, return -EINVAL);
	snd_assert(!(kcontrol->access & SNDRV_CTL_ELEM_ACCESS_READ) \|\| kcontrol->get != NULL, return -EINVAL);
	snd_assert(!(kcontrol->access & SNDRV_CTL_ELEM_ACCESS_WRITE) \|\| kcontrol->put != NULL, return -EINVAL);
	write_lock(&card->control_rwlock);
	list_add_tail(&kcontrol->list, &card->controls);
	card->controls_count++;
	kcontrol->id.numid = ++card->last_numid;
	write_unlock(&card->control_rwlock);
	snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_ADD, &kcontrol->id);
	return 0;
	}

	int snd_ctl_remove(snd_card_t * card, snd_kcontrol_t * kcontrol)
	{
	snd_runtime_check(card != NULL && kcontrol != NULL, return -EINVAL);
	write_lock(&card->control_rwlock);
	list_del(&kcontrol->list);
	card->controls_count--;
	write_unlock(&card->control_rwlock);
	snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_REMOVE, &kcontrol->id);
	snd_ctl_free_one(kcontrol);
	return 0;
	}

	int snd_ctl_remove_id(snd_card_t * card, snd_ctl_elem_id_t *id)
	{
	snd_kcontrol_t *kctl;

	kctl = snd_ctl_find_id(card, id);
	if (kctl == NULL)
	return -ENOENT;
	return snd_ctl_remove(card, kctl);
	}

	int snd_ctl_rename_id(snd_card_t * card, snd_ctl_elem_id_t src_id, snd_ctl_elem_id_t dst_id)
	{
	snd_kcontrol_t *kctl;

	kctl = snd_ctl_find_id(card, src_id);
	if (kctl == NULL)
	return -ENOENT;
	write_lock(&card->control_rwlock);
	kctl->id = *dst_id;
	kctl->id.numid = ++card->last_numid;
	write_unlock(&card->control_rwlock);
	return 0;
	}

	snd_kcontrol_t snd_ctl_find_numid(snd_card_t card, unsigned int numid)
	{
	struct list_head *list;
	snd_kcontrol_t *kctl;

	snd_runtime_check(card != NULL && numid != 0, return NULL);
	read_lock(&card->control_rwlock);
	list_for_each(list, &card->controls) {
	kctl = snd_kcontrol(list);
	if (kctl->id.numid == numid) {
	read_unlock(&card->control_rwlock);
	return kctl;
	}
	}
	read_unlock(&card->control_rwlock);
	return NULL;
	}

	snd_kcontrol_t snd_ctl_find_id(snd_card_t card, snd_ctl_elem_id_t *id)
	{
	struct list_head *list;
	snd_kcontrol_t *kctl;

	snd_runtime_check(card != NULL && id != NULL, return NULL);
	if (id->numid != 0)
	return snd_ctl_find_numid(card, id->numid);
	read_lock(&card->control_rwlock);
	list_for_each(list, &card->controls) {
	kctl = snd_kcontrol(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;
	read_unlock(&card->control_rwlock);
	return kctl;
	}
	read_unlock(&card->control_rwlock);
	return NULL;
	}

	static int snd_ctl_card_info(snd_card_t * card, snd_ctl_file_t * ctl,
	unsigned int cmd, unsigned long arg)
	{
	snd_ctl_card_info_t info;

	memset(&info, 0, sizeof(info));
	read_lock(&snd_ioctl_rwlock);
	info.card = card->number;
	strncpy(info.id, card->id, sizeof(info.id) - 1);
	strncpy(info.driver, card->driver, sizeof(info.driver) - 1);
	strncpy(info.name, card->shortname, sizeof(info.name) - 1);
	strncpy(info.longname, card->longname, sizeof(info.longname) - 1);
	strncpy(info.mixername, card->mixername, sizeof(info.mixername) - 1);
	strncpy(info.components, card->components, sizeof(info.components) - 1);
	read_unlock(&snd_ioctl_rwlock);
	if (copy_to_user((void *) arg, &info, sizeof(snd_ctl_card_info_t)))
	return -EFAULT;
	return 0;
	}

	static int snd_ctl_elem_list(snd_card_t card, snd_ctl_elem_list_t _list)
	{
	struct list_head *plist;
	snd_ctl_elem_list_t list;
	snd_kcontrol_t *kctl;
	snd_ctl_elem_id_t dst, id;
	int offset, space;

	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(snd_ctl_elem_id_t));
	if (dst == NULL)
	return -ENOMEM;
	read_lock(&card->control_rwlock);
	list.count = card->controls_count;
	plist = card->controls.next;
	while (offset-- > 0 && plist != &card->controls)
	plist = plist->next;
	list.used = 0;
	id = dst;
	while (space > 0 && plist != &card->controls) {
	kctl = snd_kcontrol(plist);
	memcpy(id, &kctl->id, sizeof(snd_ctl_elem_id_t));
	id++;
	plist = plist->next;
	space--;
	list.used++;
	}
	read_unlock(&card->control_rwlock);
	if (list.used > 0 && copy_to_user(list.pids, dst, list.used * sizeof(snd_ctl_elem_id_t)))
	return -EFAULT;
	vfree(dst);
	} else {
	read_lock(&card->control_rwlock);
	list.count = card->controls_count;
	read_unlock(&card->control_rwlock);
	}
	if (copy_to_user(_list, &list, sizeof(list)))
	return -EFAULT;
	return 0;
	}

	static int snd_ctl_elem_info(snd_ctl_file_t ctl, snd_ctl_elem_info_t _info)
	{
	snd_card_t *card = ctl->card;
	snd_ctl_elem_info_t info;
	snd_kcontrol_t *kctl;
	int result;

	if (copy_from_user(&info, _info, sizeof(info)))
	return -EFAULT;
	read_lock(&card->control_rwlock);
	kctl = snd_ctl_find_id(card, &info.id);
	if (kctl == NULL) {
	read_unlock(&card->control_rwlock);
	return -ENOENT;
	}
	#ifdef CONFIG_SND_DEBUG
	info.access = 0;
	#endif
	result = kctl->info(kctl, &info);
	if (result >= 0) {
	snd_assert(info.access == 0, );
	info.id = kctl->id;
	info.access = kctl->access;
	if (kctl->owner) {
	info.access \|= SNDRV_CTL_ELEM_ACCESS_LOCK;
	if (kctl->owner == ctl)
	info.access \|= SNDRV_CTL_ELEM_ACCESS_OWNER;
	info.owner = kctl->owner_pid;
	} else {
	info.owner = -1;
	}
	}
	read_unlock(&card->control_rwlock);
	if (result >= 0)
	if (copy_to_user(_info, &info, sizeof(info)))
	return -EFAULT;
	return result;
	}

	static int snd_ctl_elem_read(snd_card_t card, snd_ctl_elem_value_t _control)
	{
	snd_ctl_elem_value_t control;
	snd_kcontrol_t *kctl;
	int result, indirect;

	if (copy_from_user(&control, _control, sizeof(control)))
	return -EFAULT;
	read_lock(&card->control_rwlock);
	kctl = snd_ctl_find_id(card, &control.id);
	if (kctl == NULL) {
	result = -ENOENT;
	} else {
	indirect = kctl->access & SNDRV_CTL_ELEM_ACCESS_INDIRECT ? 1 : 0;
	if (control.indirect != indirect) {
	result = -EACCES;
	} else {
	if ((kctl->access & SNDRV_CTL_ELEM_ACCESS_READ) && kctl->get != NULL) {
	result = kctl->get(kctl, &control);
	if (result >= 0)
	control.id = kctl->id;
	} else
	result = -EPERM;
	}
	}
	read_unlock(&card->control_rwlock);
	if (result >= 0)
	if (copy_to_user(_control, &control, sizeof(control)))
	return -EFAULT;
	return result;
	}

	static int snd_ctl_elem_write(snd_ctl_file_t file, snd_ctl_elem_value_t _control)
	{
	snd_card_t *card = file->card;
	snd_ctl_elem_value_t control;
	snd_kcontrol_t *kctl;
	int result, indirect;

	if (copy_from_user(&control, _control, sizeof(control)))
	return -EFAULT;
	read_lock(&card->control_rwlock);
	kctl = snd_ctl_find_id(card, &control.id);
	if (kctl == NULL) {
	result = -ENOENT;
	} else {
	indirect = kctl->access & SNDRV_CTL_ELEM_ACCESS_INDIRECT ? 1 : 0;
	if (control.indirect != indirect) {
	result = -EACCES;
	} else {
	read_lock(&card->control_owner_lock);
	if (!(kctl->access & SNDRV_CTL_ELEM_ACCESS_WRITE) \|\|
	kctl->put == NULL \|\|
	(kctl->owner != NULL && kctl->owner != file)) {
	result = -EPERM;
	} else {
	result = kctl->put(kctl, &control);
	if (result >= 0)
	control.id = kctl->id;
	}
	read_unlock(&card->control_owner_lock);
	if (result > 0) {
	result = 0;
	snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE, &kctl->id);
	}
	}
	}
	read_unlock(&card->control_rwlock);
	if (result >= 0)
	if (copy_to_user(_control, &control, sizeof(control)))
	return -EFAULT;
	return result;
	}

	static int snd_ctl_elem_lock(snd_ctl_file_t file, snd_ctl_elem_id_t _id)
	{
	snd_card_t *card = file->card;
	snd_ctl_elem_id_t id;
	snd_kcontrol_t *kctl;
	int result;

	if (copy_from_user(&id, _id, sizeof(id)))
	return -EFAULT;
	read_lock(&card->control_rwlock);
	kctl = snd_ctl_find_id(card, &id);
	if (kctl == NULL) {
	result = -ENOENT;
	} else {
	write_lock(&card->control_owner_lock);
	if (kctl->owner != NULL)
	result = -EBUSY;
	else {
	kctl->owner = file;
	kctl->owner_pid = current->pid;
	result = 0;
	}
	write_unlock(&card->control_owner_lock);
	}
	read_unlock(&card->control_rwlock);
	return result;
	}

	static int snd_ctl_elem_unlock(snd_ctl_file_t file, snd_ctl_elem_id_t _id)
	{
	snd_card_t *card = file->card;
	snd_ctl_elem_id_t id;
	snd_kcontrol_t *kctl;
	int result;

	if (copy_from_user(&id, _id, sizeof(id)))
	return -EFAULT;
	read_lock(&card->control_rwlock);
	kctl = snd_ctl_find_id(card, &id);
	if (kctl == NULL) {
	result = -ENOENT;
	} else {
	write_lock(&card->control_owner_lock);
	if (kctl->owner == NULL)
	result = -EINVAL;
	else if (kctl->owner != file)
	result = -EPERM;
	else {
	kctl->owner = NULL;
	kctl->owner_pid = 0;
	result = 0;
	}
	write_unlock(&card->control_owner_lock);
	}
	read_unlock(&card->control_rwlock);
	return result;
	}

	static int snd_ctl_subscribe_events(snd_ctl_file_t file, int 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_ioctl(struct inode inode, struct file file,
	unsigned int cmd, unsigned long arg)
	{
	snd_ctl_file_t *ctl;
	snd_card_t *card;
	struct list_head *list;
	snd_kctl_ioctl_t *p;
	int err;

	ctl = snd_magic_cast(snd_ctl_file_t, file->private_data, return -ENXIO);
	card = ctl->card;
	snd_assert(card != NULL, return -ENXIO);
	switch (cmd) {
	case SNDRV_CTL_IOCTL_PVERSION:
	return put_user(SNDRV_CTL_VERSION, (int *)arg) ? -EFAULT : 0;
	case SNDRV_CTL_IOCTL_CARD_INFO:
	return snd_ctl_card_info(card, ctl, cmd, arg);
	case SNDRV_CTL_IOCTL_ELEM_LIST:
	return snd_ctl_elem_list(ctl->card, (snd_ctl_elem_list_t *) arg);
	case SNDRV_CTL_IOCTL_ELEM_INFO:
	return snd_ctl_elem_info(ctl, (snd_ctl_elem_info_t *) arg);
	case SNDRV_CTL_IOCTL_ELEM_READ:
	return snd_ctl_elem_read(ctl->card, (snd_ctl_elem_value_t *) arg);
	case SNDRV_CTL_IOCTL_ELEM_WRITE:
	return snd_ctl_elem_write(ctl, (snd_ctl_elem_value_t *) arg);
	case SNDRV_CTL_IOCTL_ELEM_LOCK:
	return snd_ctl_elem_lock(ctl, (snd_ctl_elem_id_t *) arg);
	case SNDRV_CTL_IOCTL_ELEM_UNLOCK:
	return snd_ctl_elem_unlock(ctl, (snd_ctl_elem_id_t *) arg);
	case SNDRV_CTL_IOCTL_SUBSCRIBE_EVENTS:
	return snd_ctl_subscribe_events(ctl, (int *) arg);
	case SNDRV_CTL_IOCTL_POWER:
	if (get_user(err, (int *)arg))
	return -EFAULT;
	if (!capable(CAP_SYS_ADMIN))
	return -EPERM;
	#ifdef CONFIG_PM
	if (card->set_power_state == NULL)
	return -ENOPROTOOPT;
	return card->set_power_state(card, err);
	#else
	return -ENOPROTOOPT;
	#endif
	case SNDRV_CTL_IOCTL_POWER_STATE:
	#ifdef CONFIG_PM
	return put_user(card->power_state, (int *)arg) ? -EFAULT : 0;
	#else
	return put_user(SNDRV_CTL_POWER_D0, (int *)arg) ? -EFAULT : 0;
	#endif
	}
	read_lock(&snd_ioctl_rwlock);
	list_for_each(list, &snd_control_ioctls) {
	p = list_entry(list, snd_kctl_ioctl_t, list);
	err = p->fioctl(card, ctl, cmd, arg);
	if (err != -ENOIOCTLCMD) {
	read_unlock(&snd_ioctl_rwlock);
	return err;
	}
	}
	read_unlock(&snd_ioctl_rwlock);
	snd_printd("unknown ioctl = 0x%x\n", cmd);
	return -ENOTTY;
	}

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

	ctl = snd_magic_cast(snd_ctl_file_t, file->private_data, return -ENXIO);
	snd_assert(ctl != NULL && ctl->card != NULL, return -ENXIO);
	if (!ctl->subscribed)
	return -EBADFD;
	if (count < sizeof(snd_ctl_event_t))
	return -EINVAL;
	spin_lock_irq(&ctl->read_lock);
	while (count >= sizeof(snd_ctl_event_t)) {
	snd_ctl_event_t ev;
	snd_kctl_event_t *kev;
	while (list_empty(&ctl->events)) {
	wait_queue_t wait;
	if (file->f_flags & O_NONBLOCK) {
	err = -EAGAIN;
	goto __end;
	}
	init_waitqueue_entry(&wait, current);
	add_wait_queue(&ctl->change_sleep, &wait);
	spin_unlock_irq(&ctl->read_lock);
	set_current_state(TASK_INTERRUPTIBLE);
	schedule();
	set_current_state(TASK_RUNNING);
	remove_wait_queue(&ctl->change_sleep, &wait);
	if (signal_pending(current))
	return result > 0 ? result : -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(snd_ctl_event_t))) {
	err = -EFAULT;
	goto __end;
	}
	spin_lock_irq(&ctl->read_lock);
	buffer += sizeof(snd_ctl_event_t);
	count -= sizeof(snd_ctl_event_t);
	result += sizeof(snd_ctl_event_t);
	}
	__end:
	spin_unlock_irq(&ctl->read_lock);
	return result > 0 ? result : err;
	}

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

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

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

	return mask;
	}

	int snd_ctl_register_ioctl(snd_kctl_ioctl_func_t fcn)
	{
	snd_kctl_ioctl_t *pn;

	pn = (snd_kctl_ioctl_t *)
	snd_kcalloc(sizeof(snd_kctl_ioctl_t), GFP_KERNEL);
	if (pn == NULL)
	return -ENOMEM;
	pn->fioctl = fcn;
	write_lock(&snd_ioctl_rwlock);
	list_add_tail(&pn->list, &snd_control_ioctls);
	write_unlock(&snd_ioctl_rwlock);
	return 0;
	}

	int snd_ctl_unregister_ioctl(snd_kctl_ioctl_func_t fcn)
	{
	struct list_head *list;
	snd_kctl_ioctl_t *p;

	snd_runtime_check(fcn != NULL, return -EINVAL);
	write_lock(&snd_ioctl_rwlock);
	list_for_each(list, &snd_control_ioctls) {
	p = list_entry(list, snd_kctl_ioctl_t, list);
	if (p->fioctl == fcn) {
	list_del(&p->list);
	write_unlock(&snd_ioctl_rwlock);
	kfree(p);
	return 0;
	}
	}
	write_unlock(&snd_ioctl_rwlock);
	snd_BUG();
	return -EINVAL;
	}

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

	/*
	* INIT PART
	*/

	static struct file_operations snd_ctl_f_ops =
	{
	#ifndef LINUX_2_2
	owner: THIS_MODULE,
	#endif
	read: snd_ctl_read,
	open: snd_ctl_open,
	release: snd_ctl_release,
	poll: snd_ctl_poll,
	ioctl: snd_ctl_ioctl,
	fasync: snd_ctl_fasync,
	};

	static snd_minor_t snd_ctl_reg =
	{
	comment: "ctl",
	f_ops: &snd_ctl_f_ops,
	};

	int snd_ctl_register(snd_card_t *card)
	{
	int err, cardnum;
	char name[16];

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

	int snd_ctl_unregister(snd_card_t *card)
	{
	int err, cardnum;
	snd_kcontrol_t *control;

	snd_assert(card != NULL, return -ENXIO);
	cardnum = card->number;
	snd_assert(cardnum >= 0 && cardnum < SNDRV_CARDS, return -ENXIO);
	if ((err = snd_unregister_device(SNDRV_DEVICE_TYPE_CONTROL, card, 0)) < 0)
	return err;
	while (!list_empty(&card->controls)) {
	control = snd_kcontrol(card->controls.next);
	snd_ctl_remove(card, control);
	}
	return 0;
	}