Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2562 insertions, 0 deletions

diff --git a/sound/core/control.c b/sound/core/control.c
new file mode 100644
index 000000000..59c865896
--- /dev/null
+++ b/sound/core/control.c
@@ -0,0 +1,2562 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Routines for driver control interface
+ *  Copyright (c) by Jaroslav Kysela <perex@perex.cz>
+ */
+
+#include <linux/threads.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/time.h>
+#include <linux/mm.h>
+#include <linux/math64.h>
+#include <linux/sched/signal.h>
+#include <sound/core.h>
+#include <sound/minors.h>
+#include <sound/info.h>
+#include <sound/control.h>
+
+// Max allocation size for user controls.
+static int max_user_ctl_alloc_size = 8 * 1024 * 1024;
+module_param_named(max_user_ctl_alloc_size, max_user_ctl_alloc_size, int, 0444);
+MODULE_PARM_DESC(max_user_ctl_alloc_size, "Max allocation size for user controls");
+
+#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 DECLARE_RWSEM(snd_ctl_layer_rwsem);
+static LIST_HEAD(snd_control_ioctls);
+#ifdef CONFIG_COMPAT
+static LIST_HEAD(snd_control_compat_ioctls);
+#endif
+static struct snd_ctl_layer_ops *snd_ctl_layer;
+
+static int snd_ctl_remove_locked(struct snd_card *card,
+				 struct snd_kcontrol *kcontrol);
+
+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 = stream_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_fasync_free(ctl->fasync);
+	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_irqsave(&card->ctl_files_rwlock, flags);
+#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(&ctl->read_lock);
+		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(&ctl->read_lock);
+		snd_kill_fasync(ctl->fasync, SIGIO, POLL_IN);
+	}
+	read_unlock_irqrestore(&card->ctl_files_rwlock, flags);
+}
+EXPORT_SYMBOL(snd_ctl_notify);
+
+/**
+ * snd_ctl_notify_one - Send notification to user-space for a control change
+ * @card: the card to send notification
+ * @mask: the event mask, SNDRV_CTL_EVENT_*
+ * @kctl: the pointer with the control instance
+ * @ioff: the additional offset to the control index
+ *
+ * This function calls snd_ctl_notify() and does additional jobs
+ * like LED state changes.
+ */
+void snd_ctl_notify_one(struct snd_card *card, unsigned int mask,
+			struct snd_kcontrol *kctl, unsigned int ioff)
+{
+	struct snd_ctl_elem_id id = kctl->id;
+	struct snd_ctl_layer_ops *lops;
+
+	id.index += ioff;
+	id.numid += ioff;
+	snd_ctl_notify(card, mask, &id);
+	down_read(&snd_ctl_layer_rwsem);
+	for (lops = snd_ctl_layer; lops; lops = lops->next)
+		lops->lnotify(card, mask, kctl, ioff);
+	up_read(&snd_ctl_layer_rwsem);
+}
+EXPORT_SYMBOL(snd_ctl_notify_one);
+
+/**
+ * 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 idx;
+
+	if (count == 0 || count > MAX_CONTROL_COUNT)
+		return -EINVAL;
+
+	*kctl = kzalloc(struct_size(*kctl, vd, count), 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 |
+		   SNDRV_CTL_ELEM_ACCESS_LED_MASK |
+		   SNDRV_CTL_ELEM_ACCESS_SKIP_CHECK);
+
+	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) {
+		strscpy(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;
+}
+
+/* check whether the given id is contained in the given kctl */
+static bool elem_id_matches(const struct snd_kcontrol *kctl,
+			    const struct snd_ctl_elem_id *id)
+{
+	return kctl->id.iface == id->iface &&
+		kctl->id.device == id->device &&
+		kctl->id.subdevice == id->subdevice &&
+		!strncmp(kctl->id.name, id->name, sizeof(kctl->id.name)) &&
+		kctl->id.index <= id->index &&
+		kctl->id.index + kctl->count > id->index;
+}
+
+#ifdef CONFIG_SND_CTL_FAST_LOOKUP
+/* Compute a hash key for the corresponding ctl id
+ * It's for the name lookup, hence the numid is excluded.
+ * The hash key is bound in LONG_MAX to be used for Xarray key.
+ */
+#define MULTIPLIER	37
+static unsigned long get_ctl_id_hash(const struct snd_ctl_elem_id *id)
+{
+	int i;
+	unsigned long h;
+
+	h = id->iface;
+	h = MULTIPLIER * h + id->device;
+	h = MULTIPLIER * h + id->subdevice;
+	for (i = 0; i < SNDRV_CTL_ELEM_ID_NAME_MAXLEN && id->name[i]; i++)
+		h = MULTIPLIER * h + id->name[i];
+	h = MULTIPLIER * h + id->index;
+	h &= LONG_MAX;
+	return h;
+}
+
+/* add hash entries to numid and ctl xarray tables */
+static void add_hash_entries(struct snd_card *card,
+			     struct snd_kcontrol *kcontrol)
+{
+	struct snd_ctl_elem_id id = kcontrol->id;
+	int i;
+
+	xa_store_range(&card->ctl_numids, kcontrol->id.numid,
+		       kcontrol->id.numid + kcontrol->count - 1,
+		       kcontrol, GFP_KERNEL);
+
+	for (i = 0; i < kcontrol->count; i++) {
+		id.index = kcontrol->id.index + i;
+		if (xa_insert(&card->ctl_hash, get_ctl_id_hash(&id),
+			      kcontrol, GFP_KERNEL)) {
+			/* skip hash for this entry, noting we had collision */
+			card->ctl_hash_collision = true;
+			dev_dbg(card->dev, "ctl_hash collision %d:%s:%d\n",
+				id.iface, id.name, id.index);
+		}
+	}
+}
+
+/* remove hash entries that have been added */
+static void remove_hash_entries(struct snd_card *card,
+				struct snd_kcontrol *kcontrol)
+{
+	struct snd_ctl_elem_id id = kcontrol->id;
+	struct snd_kcontrol *matched;
+	unsigned long h;
+	int i;
+
+	for (i = 0; i < kcontrol->count; i++) {
+		xa_erase(&card->ctl_numids, id.numid);
+		h = get_ctl_id_hash(&id);
+		matched = xa_load(&card->ctl_hash, h);
+		if (matched && (matched == kcontrol ||
+				elem_id_matches(matched, &id)))
+			xa_erase(&card->ctl_hash, h);
+		id.index++;
+		id.numid++;
+	}
+}
+#else /* CONFIG_SND_CTL_FAST_LOOKUP */
+static inline void add_hash_entries(struct snd_card *card,
+				    struct snd_kcontrol *kcontrol)
+{
+}
+static inline void remove_hash_entries(struct snd_card *card,
+				       struct snd_kcontrol *kcontrol)
+{
+}
+#endif /* CONFIG_SND_CTL_FAST_LOOKUP */
+
+enum snd_ctl_add_mode {
+	CTL_ADD_EXCLUSIVE, CTL_REPLACE, CTL_ADD_ON_REPLACE,
+};
+
+/* add/replace a new kcontrol object; call with card->controls_rwsem locked */
+static int __snd_ctl_add_replace(struct snd_card *card,
+				 struct snd_kcontrol *kcontrol,
+				 enum snd_ctl_add_mode mode)
+{
+	struct snd_ctl_elem_id id;
+	unsigned int idx;
+	struct snd_kcontrol *old;
+	int err;
+
+	lockdep_assert_held_write(&card->controls_rwsem);
+
+	id = kcontrol->id;
+	if (id.index > UINT_MAX - kcontrol->count)
+		return -EINVAL;
+
+	old = snd_ctl_find_id_locked(card, &id);
+	if (!old) {
+		if (mode == CTL_REPLACE)
+			return -EINVAL;
+	} else {
+		if (mode == CTL_ADD_EXCLUSIVE) {
+			dev_err(card->dev,
+				"control %i:%i:%i:%s:%i is already present\n",
+				id.iface, id.device, id.subdevice, id.name,
+				id.index);
+			return -EBUSY;
+		}
+
+		err = snd_ctl_remove_locked(card, old);
+		if (err < 0)
+			return err;
+	}
+
+	if (snd_ctl_find_hole(card, kcontrol->count) < 0)
+		return -ENOMEM;
+
+	list_add_tail(&kcontrol->list, &card->controls);
+	card->controls_count += kcontrol->count;
+	kcontrol->id.numid = card->last_numid + 1;
+	card->last_numid += kcontrol->count;
+
+	add_hash_entries(card, kcontrol);
+
+	for (idx = 0; idx < kcontrol->count; idx++)
+		snd_ctl_notify_one(card, SNDRV_CTL_EVENT_MASK_ADD, kcontrol, idx);
+
+	return 0;
+}
+
+static int snd_ctl_add_replace(struct snd_card *card,
+			       struct snd_kcontrol *kcontrol,
+			       enum snd_ctl_add_mode mode)
+{
+	int err = -EINVAL;
+
+	if (! kcontrol)
+		return err;
+	if (snd_BUG_ON(!card || !kcontrol->info))
+		goto error;
+
+	down_write(&card->controls_rwsem);
+	err = __snd_ctl_add_replace(card, kcontrol, mode);
+	up_write(&card->controls_rwsem);
+	if (err < 0)
+		goto error;
+	return 0;
+
+ error:
+	snd_ctl_free_one(kcontrol);
+	return err;
+}
+
+/**
+ * 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)
+{
+	return snd_ctl_add_replace(card, kcontrol, CTL_ADD_EXCLUSIVE);
+}
+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)
+{
+	return snd_ctl_add_replace(card, kcontrol,
+				   add_on_replace ? CTL_ADD_ON_REPLACE : CTL_REPLACE);
+}
+EXPORT_SYMBOL(snd_ctl_replace);
+
+static int __snd_ctl_remove(struct snd_card *card,
+			    struct snd_kcontrol *kcontrol,
+			    bool remove_hash)
+{
+	unsigned int idx;
+
+	lockdep_assert_held_write(&card->controls_rwsem);
+
+	if (snd_BUG_ON(!card || !kcontrol))
+		return -EINVAL;
+	list_del(&kcontrol->list);
+
+	if (remove_hash)
+		remove_hash_entries(card, kcontrol);
+
+	card->controls_count -= kcontrol->count;
+	for (idx = 0; idx < kcontrol->count; idx++)
+		snd_ctl_notify_one(card, SNDRV_CTL_EVENT_MASK_REMOVE, kcontrol, idx);
+	snd_ctl_free_one(kcontrol);
+	return 0;
+}
+
+static inline int snd_ctl_remove_locked(struct snd_card *card,
+					struct snd_kcontrol *kcontrol)
+{
+	return __snd_ctl_remove(card, kcontrol, true);
+}
+
+/**
+ * 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().
+ *
+ * Return: 0 if successful, or a negative error code on failure.
+ *
+ * Note that this function takes card->controls_rwsem lock internally.
+ */
+int snd_ctl_remove(struct snd_card *card, struct snd_kcontrol *kcontrol)
+{
+	int ret;
+
+	down_write(&card->controls_rwsem);
+	ret = snd_ctl_remove_locked(card, kcontrol);
+	up_write(&card->controls_rwsem);
+	return ret;
+}
+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_locked(card, id);
+	if (kctl == NULL) {
+		up_write(&card->controls_rwsem);
+		return -ENOENT;
+	}
+	ret = snd_ctl_remove_locked(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_locked(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_locked(card, kctl);
+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_locked(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);
+	downgrade_write(&card->controls_rwsem);
+	snd_ctl_notify_one(card, SNDRV_CTL_EVENT_MASK_INFO, kctl, index_offset);
+	up_read(&card->controls_rwsem);
+	return 1;
+
+ unlock:
+	up_write(&card->controls_rwsem);
+	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.
+ *
+ * The function tries to keep the already assigned numid while replacing
+ * the rest.
+ *
+ * Note that this function should be used only in the card initialization
+ * phase.  Calling after the card instantiation may cause issues with
+ * user-space expecting persistent numids.
+ *
+ * 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;
+	int saved_numid;
+
+	down_write(&card->controls_rwsem);
+	kctl = snd_ctl_find_id_locked(card, src_id);
+	if (kctl == NULL) {
+		up_write(&card->controls_rwsem);
+		return -ENOENT;
+	}
+	saved_numid = kctl->id.numid;
+	remove_hash_entries(card, kctl);
+	kctl->id = *dst_id;
+	kctl->id.numid = saved_numid;
+	add_hash_entries(card, kctl);
+	up_write(&card->controls_rwsem);
+	return 0;
+}
+EXPORT_SYMBOL(snd_ctl_rename_id);
+
+/**
+ * snd_ctl_rename - rename the control on the card
+ * @card: the card instance
+ * @kctl: the control to rename
+ * @name: the new name
+ *
+ * Renames the specified control on the card to the new name.
+ *
+ * Note that this function takes card->controls_rwsem lock internally.
+ */
+void snd_ctl_rename(struct snd_card *card, struct snd_kcontrol *kctl,
+		    const char *name)
+{
+	down_write(&card->controls_rwsem);
+	remove_hash_entries(card, kctl);
+
+	if (strscpy(kctl->id.name, name, sizeof(kctl->id.name)) < 0)
+		pr_warn("ALSA: Renamed control new name '%s' truncated to '%s'\n",
+			name, kctl->id.name);
+
+	add_hash_entries(card, kctl);
+	up_write(&card->controls_rwsem);
+}
+EXPORT_SYMBOL(snd_ctl_rename);
+
+#ifndef CONFIG_SND_CTL_FAST_LOOKUP
+static struct snd_kcontrol *
+snd_ctl_find_numid_slow(struct snd_card *card, unsigned int numid)
+{
+	struct snd_kcontrol *kctl;
+
+	list_for_each_entry(kctl, &card->controls, list) {
+		if (kctl->id.numid <= numid && kctl->id.numid + kctl->count > numid)
+			return kctl;
+	}
+	return NULL;
+}
+#endif /* !CONFIG_SND_CTL_FAST_LOOKUP */
+
+/**
+ * snd_ctl_find_numid_locked - 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_locked(struct snd_card *card, unsigned int numid)
+{
+	if (snd_BUG_ON(!card || !numid))
+		return NULL;
+	lockdep_assert_held(&card->controls_rwsem);
+#ifdef CONFIG_SND_CTL_FAST_LOOKUP
+	return xa_load(&card->ctl_numids, numid);
+#else
+	return snd_ctl_find_numid_slow(card, numid);
+#endif
+}
+EXPORT_SYMBOL(snd_ctl_find_numid_locked);
+
+/**
+ * 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.
+ *
+ * Return: The pointer of the instance if found, or %NULL if not.
+ *
+ * Note that this function takes card->controls_rwsem lock internally.
+ */
+struct snd_kcontrol *snd_ctl_find_numid(struct snd_card *card,
+					unsigned int numid)
+{
+	struct snd_kcontrol *kctl;
+
+	down_read(&card->controls_rwsem);
+	kctl = snd_ctl_find_numid_locked(card, numid);
+	up_read(&card->controls_rwsem);
+	return kctl;
+}
+EXPORT_SYMBOL(snd_ctl_find_numid);
+
+/**
+ * snd_ctl_find_id_locked - 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_locked(struct snd_card *card,
+					    const struct snd_ctl_elem_id *id)
+{
+	struct snd_kcontrol *kctl;
+
+	if (snd_BUG_ON(!card || !id))
+		return NULL;
+	lockdep_assert_held(&card->controls_rwsem);
+	if (id->numid != 0)
+		return snd_ctl_find_numid_locked(card, id->numid);
+#ifdef CONFIG_SND_CTL_FAST_LOOKUP
+	kctl = xa_load(&card->ctl_hash, get_ctl_id_hash(id));
+	if (kctl && elem_id_matches(kctl, id))
+		return kctl;
+	if (!card->ctl_hash_collision)
+		return NULL; /* we can rely on only hash table */
+#endif
+	/* no matching in hash table - try all as the last resort */
+	list_for_each_entry(kctl, &card->controls, list)
+		if (elem_id_matches(kctl, id))
+			return kctl;
+
+	return NULL;
+}
+EXPORT_SYMBOL(snd_ctl_find_id_locked);
+
+/**
+ * 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.
+ *
+ * Return: The pointer of the instance if found, or %NULL if not.
+ *
+ * Note that this function takes card->controls_rwsem lock internally.
+ */
+struct snd_kcontrol *snd_ctl_find_id(struct snd_card *card,
+				     const struct snd_ctl_elem_id *id)
+{
+	struct snd_kcontrol *kctl;
+
+	down_read(&card->controls_rwsem);
+	kctl = snd_ctl_find_id_locked(card, id);
+	up_read(&card->controls_rwsem);
+	return kctl;
+}
+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;
+	strscpy(info->id, card->id, sizeof(info->id));
+	strscpy(info->driver, card->driver, sizeof(info->driver));
+	strscpy(info->name, card->shortname, sizeof(info->name));
+	strscpy(info->longname, card->longname, sizeof(info->longname));
+	strscpy(info->mixername, card->mixername, sizeof(info->mixername));
+	strscpy(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 *list)
+{
+	struct snd_kcontrol *kctl;
+	struct snd_ctl_elem_id id;
+	unsigned int offset, space, jidx;
+	int err = 0;
+
+	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);
+	return err;
+}
+
+static int snd_ctl_elem_list_user(struct snd_card *card,
+				  struct snd_ctl_elem_list __user *_list)
+{
+	struct snd_ctl_elem_list list;
+	int err;
+
+	if (copy_from_user(&list, _list, sizeof(list)))
+		return -EFAULT;
+	err = snd_ctl_elem_list(card, &list);
+	if (err)
+		return err;
+	if (copy_to_user(_list, &list, sizeof(list)))
+		return -EFAULT;
+
+	return 0;
+}
+
+/* Check whether the given kctl info is valid */
+static int snd_ctl_check_elem_info(struct snd_card *card,
+				   const struct snd_ctl_elem_info *info)
+{
+	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,
+	};
+
+	if (info->type < SNDRV_CTL_ELEM_TYPE_BOOLEAN ||
+	    info->type > SNDRV_CTL_ELEM_TYPE_INTEGER64) {
+		if (card)
+			dev_err(card->dev,
+				"control %i:%i:%i:%s:%i: invalid type %d\n",
+				info->id.iface, info->id.device,
+				info->id.subdevice, info->id.name,
+				info->id.index, info->type);
+		return -EINVAL;
+	}
+	if (info->type == SNDRV_CTL_ELEM_TYPE_ENUMERATED &&
+	    info->value.enumerated.items == 0) {
+		if (card)
+			dev_err(card->dev,
+				"control %i:%i:%i:%s:%i: zero enum items\n",
+				info->id.iface, info->id.device,
+				info->id.subdevice, info->id.name,
+				info->id.index);
+		return -EINVAL;
+	}
+	if (info->count > max_value_counts[info->type]) {
+		if (card)
+			dev_err(card->dev,
+				"control %i:%i:%i:%s:%i: invalid count %d\n",
+				info->id.iface, info->id.device,
+				info->id.subdevice, info->id.name,
+				info->id.index, info->count);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/* 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),
+};
+
+/* fill the remaining snd_ctl_elem_value data with the given pattern */
+static void fill_remaining_elem_value(struct snd_ctl_elem_value *control,
+				      struct snd_ctl_elem_info *info,
+				      u32 pattern)
+{
+	size_t offset = value_sizes[info->type] * info->count;
+
+	offset = DIV_ROUND_UP(offset, sizeof(u32));
+	memset32((u32 *)control->value.bytes.data + offset, pattern,
+		 sizeof(control->value) / sizeof(u32) - offset);
+}
+
+/* check whether the given integer ctl value is valid */
+static int sanity_check_int_value(struct snd_card *card,
+				  const struct snd_ctl_elem_value *control,
+				  const struct snd_ctl_elem_info *info,
+				  int i, bool print_error)
+{
+	long long lval, lmin, lmax, lstep;
+	u64 rem;
+
+	switch (info->type) {
+	default:
+	case SNDRV_CTL_ELEM_TYPE_BOOLEAN:
+		lval = control->value.integer.value[i];
+		lmin = 0;
+		lmax = 1;
+		lstep = 0;
+		break;
+	case SNDRV_CTL_ELEM_TYPE_INTEGER:
+		lval = control->value.integer.value[i];
+		lmin = info->value.integer.min;
+		lmax = info->value.integer.max;
+		lstep = info->value.integer.step;
+		break;
+	case SNDRV_CTL_ELEM_TYPE_INTEGER64:
+		lval = control->value.integer64.value[i];
+		lmin = info->value.integer64.min;
+		lmax = info->value.integer64.max;
+		lstep = info->value.integer64.step;
+		break;
+	case SNDRV_CTL_ELEM_TYPE_ENUMERATED:
+		lval = control->value.enumerated.item[i];
+		lmin = 0;
+		lmax = info->value.enumerated.items - 1;
+		lstep = 0;
+		break;
+	}
+
+	if (lval < lmin || lval > lmax) {
+		if (print_error)
+			dev_err(card->dev,
+				"control %i:%i:%i:%s:%i: value out of range %lld (%lld/%lld) at count %i\n",
+				control->id.iface, control->id.device,
+				control->id.subdevice, control->id.name,
+				control->id.index, lval, lmin, lmax, i);
+		return -EINVAL;
+	}
+	if (lstep) {
+		div64_u64_rem(lval, lstep, &rem);
+		if (rem) {
+			if (print_error)
+				dev_err(card->dev,
+					"control %i:%i:%i:%s:%i: unaligned value %lld (step %lld) at count %i\n",
+					control->id.iface, control->id.device,
+					control->id.subdevice, control->id.name,
+					control->id.index, lval, lstep, i);
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
+/* check whether the all input values are valid for the given elem value */
+static int sanity_check_input_values(struct snd_card *card,
+				     const struct snd_ctl_elem_value *control,
+				     const struct snd_ctl_elem_info *info,
+				     bool print_error)
+{
+	int i, ret;
+
+	switch (info->type) {
+	case SNDRV_CTL_ELEM_TYPE_BOOLEAN:
+	case SNDRV_CTL_ELEM_TYPE_INTEGER:
+	case SNDRV_CTL_ELEM_TYPE_INTEGER64:
+	case SNDRV_CTL_ELEM_TYPE_ENUMERATED:
+		for (i = 0; i < info->count; i++) {
+			ret = sanity_check_int_value(card, control, info, i,
+						     print_error);
+			if (ret < 0)
+				return ret;
+		}
+		break;
+	default:
+		break;
+	}
+
+	return 0;
+}
+
+/* perform sanity checks to the given snd_ctl_elem_value object */
+static int sanity_check_elem_value(struct snd_card *card,
+				   const struct snd_ctl_elem_value *control,
+				   const struct snd_ctl_elem_info *info,
+				   u32 pattern)
+{
+	size_t offset;
+	int ret;
+	u32 *p;
+
+	ret = sanity_check_input_values(card, control, info, true);
+	if (ret < 0)
+		return ret;
+
+	/* check whether the remaining area kept untouched */
+	offset = value_sizes[info->type] * info->count;
+	offset = DIV_ROUND_UP(offset, sizeof(u32));
+	p = (u32 *)control->value.bytes.data + offset;
+	for (; offset < sizeof(control->value) / sizeof(u32); offset++, p++) {
+		if (*p != pattern) {
+			ret = -EINVAL;
+			break;
+		}
+		*p = 0; /* clear the checked area */
+	}
+
+	return ret;
+}
+
+static int __snd_ctl_elem_info(struct snd_card *card,
+			       struct snd_kcontrol *kctl,
+			       struct snd_ctl_elem_info *info,
+			       struct snd_ctl_file *ctl)
+{
+	struct snd_kcontrol_volatile *vd;
+	unsigned int index_offset;
+	int result;
+
+#ifdef CONFIG_SND_DEBUG
+	info->access = 0;
+#endif
+	result = snd_power_ref_and_wait(card);
+	if (!result)
+		result = kctl->info(kctl, info);
+	snd_power_unref(card);
+	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;
+		}
+		if (!snd_ctl_skip_validation(info) &&
+		    snd_ctl_check_elem_info(card, info) < 0)
+			result = -EINVAL;
+	}
+	return result;
+}
+
+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;
+	int result;
+
+	down_read(&card->controls_rwsem);
+	kctl = snd_ctl_find_id_locked(card, &info->id);
+	if (kctl == NULL)
+		result = -ENOENT;
+	else
+		result = __snd_ctl_elem_info(card, kctl, info, ctl);
+	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_ctl_elem_info(ctl, &info);
+	if (result < 0)
+		return result;
+	/* drop internal access flags */
+	info.access &= ~(SNDRV_CTL_ELEM_ACCESS_SKIP_CHECK|
+			 SNDRV_CTL_ELEM_ACCESS_LED_MASK);
+	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;
+	struct snd_ctl_elem_info info;
+	const u32 pattern = 0xdeadbeef;
+	int ret;
+
+	down_read(&card->controls_rwsem);
+	kctl = snd_ctl_find_id_locked(card, &control->id);
+	if (kctl == NULL) {
+		ret = -ENOENT;
+		goto unlock;
+	}
+
+	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) {
+		ret = -EPERM;
+		goto unlock;
+	}
+
+	snd_ctl_build_ioff(&control->id, kctl, index_offset);
+
+#ifdef CONFIG_SND_CTL_DEBUG
+	/* info is needed only for validation */
+	memset(&info, 0, sizeof(info));
+	info.id = control->id;
+	ret = __snd_ctl_elem_info(card, kctl, &info, NULL);
+	if (ret < 0)
+		goto unlock;
+#endif
+
+	if (!snd_ctl_skip_validation(&info))
+		fill_remaining_elem_value(control, &info, pattern);
+	ret = snd_power_ref_and_wait(card);
+	if (!ret)
+		ret = kctl->get(kctl, control);
+	snd_power_unref(card);
+	if (ret < 0)
+		goto unlock;
+	if (!snd_ctl_skip_validation(&info) &&
+	    sanity_check_elem_value(card, control, &info, pattern) < 0) {
+		dev_err(card->dev,
+			"control %i:%i:%i:%s:%i: access overflow\n",
+			control->id.iface, control->id.device,
+			control->id.subdevice, control->id.name,
+			control->id.index);
+		ret = -EINVAL;
+		goto unlock;
+	}
+unlock:
+	up_read(&card->controls_rwsem);
+	return ret;
+}
+
+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_ctl_elem_read(card, control);
+	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;
+
+	down_write(&card->controls_rwsem);
+	kctl = snd_ctl_find_id_locked(card, &control->id);
+	if (kctl == NULL) {
+		up_write(&card->controls_rwsem);
+		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)) {
+		up_write(&card->controls_rwsem);
+		return -EPERM;
+	}
+
+	snd_ctl_build_ioff(&control->id, kctl, index_offset);
+	result = snd_power_ref_and_wait(card);
+	/* validate input values */
+	if (IS_ENABLED(CONFIG_SND_CTL_INPUT_VALIDATION) && !result) {
+		struct snd_ctl_elem_info info;
+
+		memset(&info, 0, sizeof(info));
+		info.id = control->id;
+		result = __snd_ctl_elem_info(card, kctl, &info, NULL);
+		if (!result)
+			result = sanity_check_input_values(card, control, &info,
+							   false);
+	}
+	if (!result)
+		result = kctl->put(kctl, control);
+	snd_power_unref(card);
+	if (result < 0) {
+		up_write(&card->controls_rwsem);
+		return result;
+	}
+
+	if (result > 0) {
+		downgrade_write(&card->controls_rwsem);
+		snd_ctl_notify_one(card, SNDRV_CTL_EVENT_MASK_VALUE, kctl, index_offset);
+		up_read(&card->controls_rwsem);
+	} else {
+		up_write(&card->controls_rwsem);
+	}
+
+	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_ctl_elem_write(card, file, control);
+	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_locked(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_locked(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) */
+};
+
+// check whether the addition (in bytes) of user ctl element may overflow the limit.
+static bool check_user_elem_overflow(struct snd_card *card, ssize_t add)
+{
+	return (ssize_t)card->user_ctl_alloc_size + add > max_user_ctl_alloc_size;
+}
+
+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;
+}
+
+/* called in controls_rwsem write lock */
+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;
+	unsigned int mask = 0;
+	int i;
+	int change;
+
+	lockdep_assert_held_write(&ue->card->controls_rwsem);
+
+	if (size > 1024 * 128)	/* sane value */
+		return -EINVAL;
+
+	// does the TLV size change cause overflow?
+	if (check_user_elem_overflow(ue->card, (ssize_t)(size - ue->tlv_data_size)))
+		return -ENOMEM;
+
+	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;
+	} else {
+		ue->card->user_ctl_alloc_size -= ue->tlv_data_size;
+		ue->tlv_data_size = 0;
+		kvfree(ue->tlv_data);
+	}
+
+	ue->tlv_data = container;
+	ue->tlv_data_size = size;
+	// decremented at private_free.
+	ue->card->user_ctl_alloc_size += size;
+
+	mask |= SNDRV_CTL_EVENT_MASK_TLV;
+	for (i = 0; i < kctl->count; ++i)
+		snd_ctl_notify_one(ue->card, mask, kctl, i);
+
+	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);
+}
+
+/* called in controls_rwsem write lock */
+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;
+
+	lockdep_assert_held_write(&ue->card->controls_rwsem);
+
+	buf_len = ue->info.value.enumerated.names_length;
+	if (buf_len > 64 * 1024)
+		return -EINVAL;
+
+	if (check_user_elem_overflow(ue->card, buf_len))
+		return -ENOMEM;
+	names = vmemdup_user((const void __user *)user_ptrval, buf_len);
+	if (IS_ERR(names))
+		return PTR_ERR(names);
+
+	/* check that there are enough valid names */
+	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;
+	// increment the allocation size; decremented again at private_free.
+	ue->card->user_ctl_alloc_size += ue->info.value.enumerated.names_length;
+
+	return 0;
+}
+
+static size_t compute_user_elem_size(size_t size, unsigned int count)
+{
+	return sizeof(struct user_element) + size * count;
+}
+
+static void snd_ctl_elem_user_free(struct snd_kcontrol *kcontrol)
+{
+	struct user_element *ue = kcontrol->private_data;
+
+	// decrement the allocation size.
+	ue->card->user_ctl_alloc_size -= compute_user_elem_size(ue->elem_data_size, kcontrol->count);
+	ue->card->user_ctl_alloc_size -= ue->tlv_data_size;
+	if (ue->priv_data)
+		ue->card->user_ctl_alloc_size -= ue->info.value.enumerated.names_length;
+
+	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)
+{
+	struct snd_card *card = file->card;
+	struct snd_kcontrol *kctl;
+	unsigned int count;
+	unsigned int access;
+	long private_size;
+	size_t alloc_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;
+	}
+
+	/* 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.
+	 */
+	/* pass NULL to card for suppressing error messages */
+	err = snd_ctl_check_elem_info(NULL, info);
+	if (err < 0)
+		return err;
+	/* user-space control doesn't allow zero-size data */
+	if (info->count < 1)
+		return -EINVAL;
+	private_size = value_sizes[info->type] * info->count;
+	alloc_size = compute_user_elem_size(private_size, count);
+
+	down_write(&card->controls_rwsem);
+	if (check_user_elem_overflow(card, alloc_size)) {
+		err = -ENOMEM;
+		goto unlock;
+	}
+
+	/*
+	 * 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)
+		goto unlock;
+	memcpy(&kctl->id, &info->id, sizeof(kctl->id));
+	ue = kzalloc(alloc_size, GFP_KERNEL);
+	if (!ue) {
+		kfree(kctl);
+		err = -ENOMEM;
+		goto unlock;
+	}
+	kctl->private_data = ue;
+	kctl->private_free = snd_ctl_elem_user_free;
+
+	// increment the allocated size; decremented again at private_free.
+	card->user_ctl_alloc_size += alloc_size;
+
+	/* Set private data for this userspace control. */
+	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);
+			goto unlock;
+		}
+	}
+
+	/* 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_replace(card, kctl, CTL_ADD_EXCLUSIVE);
+	if (err < 0) {
+		snd_ctl_free_one(kctl);
+		goto unlock;
+	}
+	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.
+	 */
+ unlock:
+	up_write(&card->controls_rwsem);
+	return err;
+}
+
+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, ret;
+
+	/* 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;
+
+	/* Write and command operations are not allowed for locked element. */
+	if (op_flag != SNDRV_CTL_TLV_OP_READ &&
+	    vd->owner != NULL && vd->owner != file)
+		return -EPERM;
+
+	ret = snd_power_ref_and_wait(file->card);
+	if (!ret)
+		ret = kctl->tlv.c(kctl, op_flag, size, buf);
+	snd_power_unref(file->card);
+	return ret;
+}
+
+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 __user *container;
+	unsigned int container_size;
+	struct snd_kcontrol *kctl;
+	struct snd_ctl_elem_id id;
+	struct snd_kcontrol_volatile *vd;
+
+	lockdep_assert_held(&file->card->controls_rwsem);
+
+	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_locked(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_user(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:
+		return put_user(SNDRV_CTL_POWER_D0, ip) ? -EFAULT : 0;
+	}
+	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.
+ *
+ * Return: zero if successful, or a negative error code
+ */
+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
+ *
+ * Return: zero if successful, or a negative error code
+ */
+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
+ *
+ * Return: zero if successful, or a negative error code
+ */
+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_compat - de-register the device-specific compat
+ * 32bit control-ioctls
+ * @fcn: ioctl callback function to unregister
+ *
+ * Return: zero if successful, or a negative error code
+ */
+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 snd_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;
+	unsigned long flags;
+
+	read_lock_irqsave(&card->ctl_files_rwlock, flags);
+	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_irqrestore(&card->ctl_files_rwlock, flags);
+	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
+
+/*
+ * control layers (audio LED etc.)
+ */
+
+/**
+ * snd_ctl_request_layer - request to use the layer
+ * @module_name: Name of the kernel module (NULL == build-in)
+ *
+ * Return: zero if successful, or an error code when the module cannot be loaded
+ */
+int snd_ctl_request_layer(const char *module_name)
+{
+	struct snd_ctl_layer_ops *lops;
+
+	if (module_name == NULL)
+		return 0;
+	down_read(&snd_ctl_layer_rwsem);
+	for (lops = snd_ctl_layer; lops; lops = lops->next)
+		if (strcmp(lops->module_name, module_name) == 0)
+			break;
+	up_read(&snd_ctl_layer_rwsem);
+	if (lops)
+		return 0;
+	return request_module(module_name);
+}
+EXPORT_SYMBOL_GPL(snd_ctl_request_layer);
+
+/**
+ * snd_ctl_register_layer - register new control layer
+ * @lops: operation structure
+ *
+ * The new layer can track all control elements and do additional
+ * operations on top (like audio LED handling).
+ */
+void snd_ctl_register_layer(struct snd_ctl_layer_ops *lops)
+{
+	struct snd_card *card;
+	int card_number;
+
+	down_write(&snd_ctl_layer_rwsem);
+	lops->next = snd_ctl_layer;
+	snd_ctl_layer = lops;
+	up_write(&snd_ctl_layer_rwsem);
+	for (card_number = 0; card_number < SNDRV_CARDS; card_number++) {
+		card = snd_card_ref(card_number);
+		if (card) {
+			down_read(&card->controls_rwsem);
+			lops->lregister(card);
+			up_read(&card->controls_rwsem);
+			snd_card_unref(card);
+		}
+	}
+}
+EXPORT_SYMBOL_GPL(snd_ctl_register_layer);
+
+/**
+ * snd_ctl_disconnect_layer - disconnect control layer
+ * @lops: operation structure
+ *
+ * It is expected that the information about tracked cards
+ * is freed before this call (the disconnect callback is
+ * not called here).
+ */
+void snd_ctl_disconnect_layer(struct snd_ctl_layer_ops *lops)
+{
+	struct snd_ctl_layer_ops *lops2, *prev_lops2;
+
+	down_write(&snd_ctl_layer_rwsem);
+	for (lops2 = snd_ctl_layer, prev_lops2 = NULL; lops2; lops2 = lops2->next) {
+		if (lops2 == lops) {
+			if (!prev_lops2)
+				snd_ctl_layer = lops->next;
+			else
+				prev_lops2->next = lops->next;
+			break;
+		}
+		prev_lops2 = lops2;
+	}
+	up_write(&snd_ctl_layer_rwsem);
+}
+EXPORT_SYMBOL_GPL(snd_ctl_disconnect_layer);
+
+/*
+ *  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;
+	struct snd_ctl_layer_ops *lops;
+	int err;
+
+	err = snd_register_device(SNDRV_DEVICE_TYPE_CONTROL, card, -1,
+				  &snd_ctl_f_ops, card, card->ctl_dev);
+	if (err < 0)
+		return err;
+	down_read(&card->controls_rwsem);
+	down_read(&snd_ctl_layer_rwsem);
+	for (lops = snd_ctl_layer; lops; lops = lops->next)
+		lops->lregister(card);
+	up_read(&snd_ctl_layer_rwsem);
+	up_read(&card->controls_rwsem);
+	return 0;
+}
+
+/*
+ * disconnection of the control device
+ */
+static int snd_ctl_dev_disconnect(struct snd_device *device)
+{
+	struct snd_card *card = device->device_data;
+	struct snd_ctl_file *ctl;
+	struct snd_ctl_layer_ops *lops;
+	unsigned long flags;
+
+	read_lock_irqsave(&card->ctl_files_rwlock, flags);
+	list_for_each_entry(ctl, &card->ctl_files, list) {
+		wake_up(&ctl->change_sleep);
+		snd_kill_fasync(ctl->fasync, SIGIO, POLL_ERR);
+	}
+	read_unlock_irqrestore(&card->ctl_files_rwlock, flags);
+
+	down_read(&card->controls_rwsem);
+	down_read(&snd_ctl_layer_rwsem);
+	for (lops = snd_ctl_layer; lops; lops = lops->next)
+		lops->ldisconnect(card);
+	up_read(&snd_ctl_layer_rwsem);
+	up_read(&card->controls_rwsem);
+
+	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, false);
+	}
+
+#ifdef CONFIG_SND_CTL_FAST_LOOKUP
+	xa_destroy(&card->ctl_numids);
+	xa_destroy(&card->ctl_hash);
+#endif
+	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 const 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;
+
+	err = snd_device_alloc(&card->ctl_dev, card);
+	if (err < 0)
+		return err;
+	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.
+ *
+ * Return: Zero (always successful)
+ */
+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.
+ *
+ * Return: Zero (always successful)
+ */
+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 (always successful)
+ */
+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]);
+	strscpy(info->value.enumerated.name,
+		names[info->value.enumerated.item],
+		sizeof(info->value.enumerated.name));
+	return 0;
+}
+EXPORT_SYMBOL(snd_ctl_enum_info);