xref: /openbmc/linux/sound/core/control.c (revision c8dbaa22)
1 /*
2  *  Routines for driver control interface
3  *  Copyright (c) by Jaroslav Kysela <perex@perex.cz>
4  *
5  *
6  *   This program is free software; you can redistribute it and/or modify
7  *   it under the terms of the GNU General Public License as published by
8  *   the Free Software Foundation; either version 2 of the License, or
9  *   (at your option) any later version.
10  *
11  *   This program is distributed in the hope that it will be useful,
12  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
13  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14  *   GNU General Public License for more details.
15  *
16  *   You should have received a copy of the GNU General Public License
17  *   along with this program; if not, write to the Free Software
18  *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
19  *
20  */
21 
22 #include <linux/threads.h>
23 #include <linux/interrupt.h>
24 #include <linux/module.h>
25 #include <linux/slab.h>
26 #include <linux/vmalloc.h>
27 #include <linux/time.h>
28 #include <linux/sched/signal.h>
29 #include <sound/core.h>
30 #include <sound/minors.h>
31 #include <sound/info.h>
32 #include <sound/control.h>
33 
34 /* max number of user-defined controls */
35 #define MAX_USER_CONTROLS	32
36 #define MAX_CONTROL_COUNT	1028
37 
38 struct snd_kctl_ioctl {
39 	struct list_head list;		/* list of all ioctls */
40 	snd_kctl_ioctl_func_t fioctl;
41 };
42 
43 static DECLARE_RWSEM(snd_ioctl_rwsem);
44 static LIST_HEAD(snd_control_ioctls);
45 #ifdef CONFIG_COMPAT
46 static LIST_HEAD(snd_control_compat_ioctls);
47 #endif
48 
49 static int snd_ctl_open(struct inode *inode, struct file *file)
50 {
51 	unsigned long flags;
52 	struct snd_card *card;
53 	struct snd_ctl_file *ctl;
54 	int i, err;
55 
56 	err = nonseekable_open(inode, file);
57 	if (err < 0)
58 		return err;
59 
60 	card = snd_lookup_minor_data(iminor(inode), SNDRV_DEVICE_TYPE_CONTROL);
61 	if (!card) {
62 		err = -ENODEV;
63 		goto __error1;
64 	}
65 	err = snd_card_file_add(card, file);
66 	if (err < 0) {
67 		err = -ENODEV;
68 		goto __error1;
69 	}
70 	if (!try_module_get(card->module)) {
71 		err = -EFAULT;
72 		goto __error2;
73 	}
74 	ctl = kzalloc(sizeof(*ctl), GFP_KERNEL);
75 	if (ctl == NULL) {
76 		err = -ENOMEM;
77 		goto __error;
78 	}
79 	INIT_LIST_HEAD(&ctl->events);
80 	init_waitqueue_head(&ctl->change_sleep);
81 	spin_lock_init(&ctl->read_lock);
82 	ctl->card = card;
83 	for (i = 0; i < SND_CTL_SUBDEV_ITEMS; i++)
84 		ctl->preferred_subdevice[i] = -1;
85 	ctl->pid = get_pid(task_pid(current));
86 	file->private_data = ctl;
87 	write_lock_irqsave(&card->ctl_files_rwlock, flags);
88 	list_add_tail(&ctl->list, &card->ctl_files);
89 	write_unlock_irqrestore(&card->ctl_files_rwlock, flags);
90 	snd_card_unref(card);
91 	return 0;
92 
93       __error:
94 	module_put(card->module);
95       __error2:
96 	snd_card_file_remove(card, file);
97       __error1:
98 	if (card)
99 		snd_card_unref(card);
100       	return err;
101 }
102 
103 static void snd_ctl_empty_read_queue(struct snd_ctl_file * ctl)
104 {
105 	unsigned long flags;
106 	struct snd_kctl_event *cread;
107 
108 	spin_lock_irqsave(&ctl->read_lock, flags);
109 	while (!list_empty(&ctl->events)) {
110 		cread = snd_kctl_event(ctl->events.next);
111 		list_del(&cread->list);
112 		kfree(cread);
113 	}
114 	spin_unlock_irqrestore(&ctl->read_lock, flags);
115 }
116 
117 static int snd_ctl_release(struct inode *inode, struct file *file)
118 {
119 	unsigned long flags;
120 	struct snd_card *card;
121 	struct snd_ctl_file *ctl;
122 	struct snd_kcontrol *control;
123 	unsigned int idx;
124 
125 	ctl = file->private_data;
126 	file->private_data = NULL;
127 	card = ctl->card;
128 	write_lock_irqsave(&card->ctl_files_rwlock, flags);
129 	list_del(&ctl->list);
130 	write_unlock_irqrestore(&card->ctl_files_rwlock, flags);
131 	down_write(&card->controls_rwsem);
132 	list_for_each_entry(control, &card->controls, list)
133 		for (idx = 0; idx < control->count; idx++)
134 			if (control->vd[idx].owner == ctl)
135 				control->vd[idx].owner = NULL;
136 	up_write(&card->controls_rwsem);
137 	snd_ctl_empty_read_queue(ctl);
138 	put_pid(ctl->pid);
139 	kfree(ctl);
140 	module_put(card->module);
141 	snd_card_file_remove(card, file);
142 	return 0;
143 }
144 
145 /**
146  * snd_ctl_notify - Send notification to user-space for a control change
147  * @card: the card to send notification
148  * @mask: the event mask, SNDRV_CTL_EVENT_*
149  * @id: the ctl element id to send notification
150  *
151  * This function adds an event record with the given id and mask, appends
152  * to the list and wakes up the user-space for notification.  This can be
153  * called in the atomic context.
154  */
155 void snd_ctl_notify(struct snd_card *card, unsigned int mask,
156 		    struct snd_ctl_elem_id *id)
157 {
158 	unsigned long flags;
159 	struct snd_ctl_file *ctl;
160 	struct snd_kctl_event *ev;
161 
162 	if (snd_BUG_ON(!card || !id))
163 		return;
164 	if (card->shutdown)
165 		return;
166 	read_lock(&card->ctl_files_rwlock);
167 #if IS_ENABLED(CONFIG_SND_MIXER_OSS)
168 	card->mixer_oss_change_count++;
169 #endif
170 	list_for_each_entry(ctl, &card->ctl_files, list) {
171 		if (!ctl->subscribed)
172 			continue;
173 		spin_lock_irqsave(&ctl->read_lock, flags);
174 		list_for_each_entry(ev, &ctl->events, list) {
175 			if (ev->id.numid == id->numid) {
176 				ev->mask |= mask;
177 				goto _found;
178 			}
179 		}
180 		ev = kzalloc(sizeof(*ev), GFP_ATOMIC);
181 		if (ev) {
182 			ev->id = *id;
183 			ev->mask = mask;
184 			list_add_tail(&ev->list, &ctl->events);
185 		} else {
186 			dev_err(card->dev, "No memory available to allocate event\n");
187 		}
188 	_found:
189 		wake_up(&ctl->change_sleep);
190 		spin_unlock_irqrestore(&ctl->read_lock, flags);
191 		kill_fasync(&ctl->fasync, SIGIO, POLL_IN);
192 	}
193 	read_unlock(&card->ctl_files_rwlock);
194 }
195 EXPORT_SYMBOL(snd_ctl_notify);
196 
197 /**
198  * snd_ctl_new - create a new control instance with some elements
199  * @kctl: the pointer to store new control instance
200  * @count: the number of elements in this control
201  * @access: the default access flags for elements in this control
202  * @file: given when locking these elements
203  *
204  * Allocates a memory object for a new control instance. The instance has
205  * elements as many as the given number (@count). Each element has given
206  * access permissions (@access). Each element is locked when @file is given.
207  *
208  * Return: 0 on success, error code on failure
209  */
210 static int snd_ctl_new(struct snd_kcontrol **kctl, unsigned int count,
211 		       unsigned int access, struct snd_ctl_file *file)
212 {
213 	unsigned int size;
214 	unsigned int idx;
215 
216 	if (count == 0 || count > MAX_CONTROL_COUNT)
217 		return -EINVAL;
218 
219 	size  = sizeof(struct snd_kcontrol);
220 	size += sizeof(struct snd_kcontrol_volatile) * count;
221 
222 	*kctl = kzalloc(size, GFP_KERNEL);
223 	if (!*kctl)
224 		return -ENOMEM;
225 
226 	for (idx = 0; idx < count; idx++) {
227 		(*kctl)->vd[idx].access = access;
228 		(*kctl)->vd[idx].owner = file;
229 	}
230 	(*kctl)->count = count;
231 
232 	return 0;
233 }
234 
235 /**
236  * snd_ctl_new1 - create a control instance from the template
237  * @ncontrol: the initialization record
238  * @private_data: the private data to set
239  *
240  * Allocates a new struct snd_kcontrol instance and initialize from the given
241  * template.  When the access field of ncontrol is 0, it's assumed as
242  * READWRITE access. When the count field is 0, it's assumes as one.
243  *
244  * Return: The pointer of the newly generated instance, or %NULL on failure.
245  */
246 struct snd_kcontrol *snd_ctl_new1(const struct snd_kcontrol_new *ncontrol,
247 				  void *private_data)
248 {
249 	struct snd_kcontrol *kctl;
250 	unsigned int count;
251 	unsigned int access;
252 	int err;
253 
254 	if (snd_BUG_ON(!ncontrol || !ncontrol->info))
255 		return NULL;
256 
257 	count = ncontrol->count;
258 	if (count == 0)
259 		count = 1;
260 
261 	access = ncontrol->access;
262 	if (access == 0)
263 		access = SNDRV_CTL_ELEM_ACCESS_READWRITE;
264 	access &= (SNDRV_CTL_ELEM_ACCESS_READWRITE |
265 		   SNDRV_CTL_ELEM_ACCESS_VOLATILE |
266 		   SNDRV_CTL_ELEM_ACCESS_INACTIVE |
267 		   SNDRV_CTL_ELEM_ACCESS_TLV_READWRITE |
268 		   SNDRV_CTL_ELEM_ACCESS_TLV_COMMAND |
269 		   SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK);
270 
271 	err = snd_ctl_new(&kctl, count, access, NULL);
272 	if (err < 0)
273 		return NULL;
274 
275 	/* The 'numid' member is decided when calling snd_ctl_add(). */
276 	kctl->id.iface = ncontrol->iface;
277 	kctl->id.device = ncontrol->device;
278 	kctl->id.subdevice = ncontrol->subdevice;
279 	if (ncontrol->name) {
280 		strlcpy(kctl->id.name, ncontrol->name, sizeof(kctl->id.name));
281 		if (strcmp(ncontrol->name, kctl->id.name) != 0)
282 			pr_warn("ALSA: Control name '%s' truncated to '%s'\n",
283 				ncontrol->name, kctl->id.name);
284 	}
285 	kctl->id.index = ncontrol->index;
286 
287 	kctl->info = ncontrol->info;
288 	kctl->get = ncontrol->get;
289 	kctl->put = ncontrol->put;
290 	kctl->tlv.p = ncontrol->tlv.p;
291 
292 	kctl->private_value = ncontrol->private_value;
293 	kctl->private_data = private_data;
294 
295 	return kctl;
296 }
297 EXPORT_SYMBOL(snd_ctl_new1);
298 
299 /**
300  * snd_ctl_free_one - release the control instance
301  * @kcontrol: the control instance
302  *
303  * Releases the control instance created via snd_ctl_new()
304  * or snd_ctl_new1().
305  * Don't call this after the control was added to the card.
306  */
307 void snd_ctl_free_one(struct snd_kcontrol *kcontrol)
308 {
309 	if (kcontrol) {
310 		if (kcontrol->private_free)
311 			kcontrol->private_free(kcontrol);
312 		kfree(kcontrol);
313 	}
314 }
315 EXPORT_SYMBOL(snd_ctl_free_one);
316 
317 static bool snd_ctl_remove_numid_conflict(struct snd_card *card,
318 					  unsigned int count)
319 {
320 	struct snd_kcontrol *kctl;
321 
322 	/* Make sure that the ids assigned to the control do not wrap around */
323 	if (card->last_numid >= UINT_MAX - count)
324 		card->last_numid = 0;
325 
326 	list_for_each_entry(kctl, &card->controls, list) {
327 		if (kctl->id.numid < card->last_numid + 1 + count &&
328 		    kctl->id.numid + kctl->count > card->last_numid + 1) {
329 		    	card->last_numid = kctl->id.numid + kctl->count - 1;
330 			return true;
331 		}
332 	}
333 	return false;
334 }
335 
336 static int snd_ctl_find_hole(struct snd_card *card, unsigned int count)
337 {
338 	unsigned int iter = 100000;
339 
340 	while (snd_ctl_remove_numid_conflict(card, count)) {
341 		if (--iter == 0) {
342 			/* this situation is very unlikely */
343 			dev_err(card->dev, "unable to allocate new control numid\n");
344 			return -ENOMEM;
345 		}
346 	}
347 	return 0;
348 }
349 
350 /**
351  * snd_ctl_add - add the control instance to the card
352  * @card: the card instance
353  * @kcontrol: the control instance to add
354  *
355  * Adds the control instance created via snd_ctl_new() or
356  * snd_ctl_new1() to the given card. Assigns also an unique
357  * numid used for fast search.
358  *
359  * It frees automatically the control which cannot be added.
360  *
361  * Return: Zero if successful, or a negative error code on failure.
362  *
363  */
364 int snd_ctl_add(struct snd_card *card, struct snd_kcontrol *kcontrol)
365 {
366 	struct snd_ctl_elem_id id;
367 	unsigned int idx;
368 	unsigned int count;
369 	int err = -EINVAL;
370 
371 	if (! kcontrol)
372 		return err;
373 	if (snd_BUG_ON(!card || !kcontrol->info))
374 		goto error;
375 	id = kcontrol->id;
376 	if (id.index > UINT_MAX - kcontrol->count)
377 		goto error;
378 
379 	down_write(&card->controls_rwsem);
380 	if (snd_ctl_find_id(card, &id)) {
381 		up_write(&card->controls_rwsem);
382 		dev_err(card->dev, "control %i:%i:%i:%s:%i is already present\n",
383 					id.iface,
384 					id.device,
385 					id.subdevice,
386 					id.name,
387 					id.index);
388 		err = -EBUSY;
389 		goto error;
390 	}
391 	if (snd_ctl_find_hole(card, kcontrol->count) < 0) {
392 		up_write(&card->controls_rwsem);
393 		err = -ENOMEM;
394 		goto error;
395 	}
396 	list_add_tail(&kcontrol->list, &card->controls);
397 	card->controls_count += kcontrol->count;
398 	kcontrol->id.numid = card->last_numid + 1;
399 	card->last_numid += kcontrol->count;
400 	id = kcontrol->id;
401 	count = kcontrol->count;
402 	up_write(&card->controls_rwsem);
403 	for (idx = 0; idx < count; idx++, id.index++, id.numid++)
404 		snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_ADD, &id);
405 	return 0;
406 
407  error:
408 	snd_ctl_free_one(kcontrol);
409 	return err;
410 }
411 EXPORT_SYMBOL(snd_ctl_add);
412 
413 /**
414  * snd_ctl_replace - replace the control instance of the card
415  * @card: the card instance
416  * @kcontrol: the control instance to replace
417  * @add_on_replace: add the control if not already added
418  *
419  * Replaces the given control.  If the given control does not exist
420  * and the add_on_replace flag is set, the control is added.  If the
421  * control exists, it is destroyed first.
422  *
423  * It frees automatically the control which cannot be added or replaced.
424  *
425  * Return: Zero if successful, or a negative error code on failure.
426  */
427 int snd_ctl_replace(struct snd_card *card, struct snd_kcontrol *kcontrol,
428 		    bool add_on_replace)
429 {
430 	struct snd_ctl_elem_id id;
431 	unsigned int count;
432 	unsigned int idx;
433 	struct snd_kcontrol *old;
434 	int ret;
435 
436 	if (!kcontrol)
437 		return -EINVAL;
438 	if (snd_BUG_ON(!card || !kcontrol->info)) {
439 		ret = -EINVAL;
440 		goto error;
441 	}
442 	id = kcontrol->id;
443 	down_write(&card->controls_rwsem);
444 	old = snd_ctl_find_id(card, &id);
445 	if (!old) {
446 		if (add_on_replace)
447 			goto add;
448 		up_write(&card->controls_rwsem);
449 		ret = -EINVAL;
450 		goto error;
451 	}
452 	ret = snd_ctl_remove(card, old);
453 	if (ret < 0) {
454 		up_write(&card->controls_rwsem);
455 		goto error;
456 	}
457 add:
458 	if (snd_ctl_find_hole(card, kcontrol->count) < 0) {
459 		up_write(&card->controls_rwsem);
460 		ret = -ENOMEM;
461 		goto error;
462 	}
463 	list_add_tail(&kcontrol->list, &card->controls);
464 	card->controls_count += kcontrol->count;
465 	kcontrol->id.numid = card->last_numid + 1;
466 	card->last_numid += kcontrol->count;
467 	id = kcontrol->id;
468 	count = kcontrol->count;
469 	up_write(&card->controls_rwsem);
470 	for (idx = 0; idx < count; idx++, id.index++, id.numid++)
471 		snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_ADD, &id);
472 	return 0;
473 
474 error:
475 	snd_ctl_free_one(kcontrol);
476 	return ret;
477 }
478 EXPORT_SYMBOL(snd_ctl_replace);
479 
480 /**
481  * snd_ctl_remove - remove the control from the card and release it
482  * @card: the card instance
483  * @kcontrol: the control instance to remove
484  *
485  * Removes the control from the card and then releases the instance.
486  * You don't need to call snd_ctl_free_one(). You must be in
487  * the write lock - down_write(&card->controls_rwsem).
488  *
489  * Return: 0 if successful, or a negative error code on failure.
490  */
491 int snd_ctl_remove(struct snd_card *card, struct snd_kcontrol *kcontrol)
492 {
493 	struct snd_ctl_elem_id id;
494 	unsigned int idx;
495 
496 	if (snd_BUG_ON(!card || !kcontrol))
497 		return -EINVAL;
498 	list_del(&kcontrol->list);
499 	card->controls_count -= kcontrol->count;
500 	id = kcontrol->id;
501 	for (idx = 0; idx < kcontrol->count; idx++, id.index++, id.numid++)
502 		snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_REMOVE, &id);
503 	snd_ctl_free_one(kcontrol);
504 	return 0;
505 }
506 EXPORT_SYMBOL(snd_ctl_remove);
507 
508 /**
509  * snd_ctl_remove_id - remove the control of the given id and release it
510  * @card: the card instance
511  * @id: the control id to remove
512  *
513  * Finds the control instance with the given id, removes it from the
514  * card list and releases it.
515  *
516  * Return: 0 if successful, or a negative error code on failure.
517  */
518 int snd_ctl_remove_id(struct snd_card *card, struct snd_ctl_elem_id *id)
519 {
520 	struct snd_kcontrol *kctl;
521 	int ret;
522 
523 	down_write(&card->controls_rwsem);
524 	kctl = snd_ctl_find_id(card, id);
525 	if (kctl == NULL) {
526 		up_write(&card->controls_rwsem);
527 		return -ENOENT;
528 	}
529 	ret = snd_ctl_remove(card, kctl);
530 	up_write(&card->controls_rwsem);
531 	return ret;
532 }
533 EXPORT_SYMBOL(snd_ctl_remove_id);
534 
535 /**
536  * snd_ctl_remove_user_ctl - remove and release the unlocked user control
537  * @file: active control handle
538  * @id: the control id to remove
539  *
540  * Finds the control instance with the given id, removes it from the
541  * card list and releases it.
542  *
543  * Return: 0 if successful, or a negative error code on failure.
544  */
545 static int snd_ctl_remove_user_ctl(struct snd_ctl_file * file,
546 				   struct snd_ctl_elem_id *id)
547 {
548 	struct snd_card *card = file->card;
549 	struct snd_kcontrol *kctl;
550 	int idx, ret;
551 
552 	down_write(&card->controls_rwsem);
553 	kctl = snd_ctl_find_id(card, id);
554 	if (kctl == NULL) {
555 		ret = -ENOENT;
556 		goto error;
557 	}
558 	if (!(kctl->vd[0].access & SNDRV_CTL_ELEM_ACCESS_USER)) {
559 		ret = -EINVAL;
560 		goto error;
561 	}
562 	for (idx = 0; idx < kctl->count; idx++)
563 		if (kctl->vd[idx].owner != NULL && kctl->vd[idx].owner != file) {
564 			ret = -EBUSY;
565 			goto error;
566 		}
567 	ret = snd_ctl_remove(card, kctl);
568 	if (ret < 0)
569 		goto error;
570 	card->user_ctl_count--;
571 error:
572 	up_write(&card->controls_rwsem);
573 	return ret;
574 }
575 
576 /**
577  * snd_ctl_activate_id - activate/inactivate the control of the given id
578  * @card: the card instance
579  * @id: the control id to activate/inactivate
580  * @active: non-zero to activate
581  *
582  * Finds the control instance with the given id, and activate or
583  * inactivate the control together with notification, if changed.
584  * The given ID data is filled with full information.
585  *
586  * Return: 0 if unchanged, 1 if changed, or a negative error code on failure.
587  */
588 int snd_ctl_activate_id(struct snd_card *card, struct snd_ctl_elem_id *id,
589 			int active)
590 {
591 	struct snd_kcontrol *kctl;
592 	struct snd_kcontrol_volatile *vd;
593 	unsigned int index_offset;
594 	int ret;
595 
596 	down_write(&card->controls_rwsem);
597 	kctl = snd_ctl_find_id(card, id);
598 	if (kctl == NULL) {
599 		ret = -ENOENT;
600 		goto unlock;
601 	}
602 	index_offset = snd_ctl_get_ioff(kctl, id);
603 	vd = &kctl->vd[index_offset];
604 	ret = 0;
605 	if (active) {
606 		if (!(vd->access & SNDRV_CTL_ELEM_ACCESS_INACTIVE))
607 			goto unlock;
608 		vd->access &= ~SNDRV_CTL_ELEM_ACCESS_INACTIVE;
609 	} else {
610 		if (vd->access & SNDRV_CTL_ELEM_ACCESS_INACTIVE)
611 			goto unlock;
612 		vd->access |= SNDRV_CTL_ELEM_ACCESS_INACTIVE;
613 	}
614 	snd_ctl_build_ioff(id, kctl, index_offset);
615 	ret = 1;
616  unlock:
617 	up_write(&card->controls_rwsem);
618 	if (ret > 0)
619 		snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_INFO, id);
620 	return ret;
621 }
622 EXPORT_SYMBOL_GPL(snd_ctl_activate_id);
623 
624 /**
625  * snd_ctl_rename_id - replace the id of a control on the card
626  * @card: the card instance
627  * @src_id: the old id
628  * @dst_id: the new id
629  *
630  * Finds the control with the old id from the card, and replaces the
631  * id with the new one.
632  *
633  * Return: Zero if successful, or a negative error code on failure.
634  */
635 int snd_ctl_rename_id(struct snd_card *card, struct snd_ctl_elem_id *src_id,
636 		      struct snd_ctl_elem_id *dst_id)
637 {
638 	struct snd_kcontrol *kctl;
639 
640 	down_write(&card->controls_rwsem);
641 	kctl = snd_ctl_find_id(card, src_id);
642 	if (kctl == NULL) {
643 		up_write(&card->controls_rwsem);
644 		return -ENOENT;
645 	}
646 	kctl->id = *dst_id;
647 	kctl->id.numid = card->last_numid + 1;
648 	card->last_numid += kctl->count;
649 	up_write(&card->controls_rwsem);
650 	return 0;
651 }
652 EXPORT_SYMBOL(snd_ctl_rename_id);
653 
654 /**
655  * snd_ctl_find_numid - find the control instance with the given number-id
656  * @card: the card instance
657  * @numid: the number-id to search
658  *
659  * Finds the control instance with the given number-id from the card.
660  *
661  * The caller must down card->controls_rwsem before calling this function
662  * (if the race condition can happen).
663  *
664  * Return: The pointer of the instance if found, or %NULL if not.
665  *
666  */
667 struct snd_kcontrol *snd_ctl_find_numid(struct snd_card *card, unsigned int numid)
668 {
669 	struct snd_kcontrol *kctl;
670 
671 	if (snd_BUG_ON(!card || !numid))
672 		return NULL;
673 	list_for_each_entry(kctl, &card->controls, list) {
674 		if (kctl->id.numid <= numid && kctl->id.numid + kctl->count > numid)
675 			return kctl;
676 	}
677 	return NULL;
678 }
679 EXPORT_SYMBOL(snd_ctl_find_numid);
680 
681 /**
682  * snd_ctl_find_id - find the control instance with the given id
683  * @card: the card instance
684  * @id: the id to search
685  *
686  * Finds the control instance with the given id from the card.
687  *
688  * The caller must down card->controls_rwsem before calling this function
689  * (if the race condition can happen).
690  *
691  * Return: The pointer of the instance if found, or %NULL if not.
692  *
693  */
694 struct snd_kcontrol *snd_ctl_find_id(struct snd_card *card,
695 				     struct snd_ctl_elem_id *id)
696 {
697 	struct snd_kcontrol *kctl;
698 
699 	if (snd_BUG_ON(!card || !id))
700 		return NULL;
701 	if (id->numid != 0)
702 		return snd_ctl_find_numid(card, id->numid);
703 	list_for_each_entry(kctl, &card->controls, list) {
704 		if (kctl->id.iface != id->iface)
705 			continue;
706 		if (kctl->id.device != id->device)
707 			continue;
708 		if (kctl->id.subdevice != id->subdevice)
709 			continue;
710 		if (strncmp(kctl->id.name, id->name, sizeof(kctl->id.name)))
711 			continue;
712 		if (kctl->id.index > id->index)
713 			continue;
714 		if (kctl->id.index + kctl->count <= id->index)
715 			continue;
716 		return kctl;
717 	}
718 	return NULL;
719 }
720 EXPORT_SYMBOL(snd_ctl_find_id);
721 
722 static int snd_ctl_card_info(struct snd_card *card, struct snd_ctl_file * ctl,
723 			     unsigned int cmd, void __user *arg)
724 {
725 	struct snd_ctl_card_info *info;
726 
727 	info = kzalloc(sizeof(*info), GFP_KERNEL);
728 	if (! info)
729 		return -ENOMEM;
730 	down_read(&snd_ioctl_rwsem);
731 	info->card = card->number;
732 	strlcpy(info->id, card->id, sizeof(info->id));
733 	strlcpy(info->driver, card->driver, sizeof(info->driver));
734 	strlcpy(info->name, card->shortname, sizeof(info->name));
735 	strlcpy(info->longname, card->longname, sizeof(info->longname));
736 	strlcpy(info->mixername, card->mixername, sizeof(info->mixername));
737 	strlcpy(info->components, card->components, sizeof(info->components));
738 	up_read(&snd_ioctl_rwsem);
739 	if (copy_to_user(arg, info, sizeof(struct snd_ctl_card_info))) {
740 		kfree(info);
741 		return -EFAULT;
742 	}
743 	kfree(info);
744 	return 0;
745 }
746 
747 static int snd_ctl_elem_list(struct snd_card *card,
748 			     struct snd_ctl_elem_list __user *_list)
749 {
750 	struct snd_ctl_elem_list list;
751 	struct snd_kcontrol *kctl;
752 	struct snd_ctl_elem_id id;
753 	unsigned int offset, space, jidx;
754 	int err = 0;
755 
756 	if (copy_from_user(&list, _list, sizeof(list)))
757 		return -EFAULT;
758 	offset = list.offset;
759 	space = list.space;
760 
761 	down_read(&card->controls_rwsem);
762 	list.count = card->controls_count;
763 	list.used = 0;
764 	if (space > 0) {
765 		list_for_each_entry(kctl, &card->controls, list) {
766 			if (offset >= kctl->count) {
767 				offset -= kctl->count;
768 				continue;
769 			}
770 			for (jidx = offset; jidx < kctl->count; jidx++) {
771 				snd_ctl_build_ioff(&id, kctl, jidx);
772 				if (copy_to_user(list.pids + list.used, &id,
773 						 sizeof(id))) {
774 					err = -EFAULT;
775 					goto out;
776 				}
777 				list.used++;
778 				if (!--space)
779 					goto out;
780 			}
781 			offset = 0;
782 		}
783 	}
784  out:
785 	up_read(&card->controls_rwsem);
786 	if (!err && copy_to_user(_list, &list, sizeof(list)))
787 		err = -EFAULT;
788 	return err;
789 }
790 
791 static bool validate_element_member_dimension(struct snd_ctl_elem_info *info)
792 {
793 	unsigned int members;
794 	unsigned int i;
795 
796 	if (info->dimen.d[0] == 0)
797 		return true;
798 
799 	members = 1;
800 	for (i = 0; i < ARRAY_SIZE(info->dimen.d); ++i) {
801 		if (info->dimen.d[i] == 0)
802 			break;
803 		members *= info->dimen.d[i];
804 
805 		/*
806 		 * info->count should be validated in advance, to guarantee
807 		 * calculation soundness.
808 		 */
809 		if (members > info->count)
810 			return false;
811 	}
812 
813 	for (++i; i < ARRAY_SIZE(info->dimen.d); ++i) {
814 		if (info->dimen.d[i] > 0)
815 			return false;
816 	}
817 
818 	return members == info->count;
819 }
820 
821 static int snd_ctl_elem_info(struct snd_ctl_file *ctl,
822 			     struct snd_ctl_elem_info *info)
823 {
824 	struct snd_card *card = ctl->card;
825 	struct snd_kcontrol *kctl;
826 	struct snd_kcontrol_volatile *vd;
827 	unsigned int index_offset;
828 	int result;
829 
830 	down_read(&card->controls_rwsem);
831 	kctl = snd_ctl_find_id(card, &info->id);
832 	if (kctl == NULL) {
833 		up_read(&card->controls_rwsem);
834 		return -ENOENT;
835 	}
836 #ifdef CONFIG_SND_DEBUG
837 	info->access = 0;
838 #endif
839 	result = kctl->info(kctl, info);
840 	if (result >= 0) {
841 		snd_BUG_ON(info->access);
842 		index_offset = snd_ctl_get_ioff(kctl, &info->id);
843 		vd = &kctl->vd[index_offset];
844 		snd_ctl_build_ioff(&info->id, kctl, index_offset);
845 		info->access = vd->access;
846 		if (vd->owner) {
847 			info->access |= SNDRV_CTL_ELEM_ACCESS_LOCK;
848 			if (vd->owner == ctl)
849 				info->access |= SNDRV_CTL_ELEM_ACCESS_OWNER;
850 			info->owner = pid_vnr(vd->owner->pid);
851 		} else {
852 			info->owner = -1;
853 		}
854 	}
855 	up_read(&card->controls_rwsem);
856 	return result;
857 }
858 
859 static int snd_ctl_elem_info_user(struct snd_ctl_file *ctl,
860 				  struct snd_ctl_elem_info __user *_info)
861 {
862 	struct snd_ctl_elem_info info;
863 	int result;
864 
865 	if (copy_from_user(&info, _info, sizeof(info)))
866 		return -EFAULT;
867 	snd_power_lock(ctl->card);
868 	result = snd_power_wait(ctl->card, SNDRV_CTL_POWER_D0);
869 	if (result >= 0)
870 		result = snd_ctl_elem_info(ctl, &info);
871 	snd_power_unlock(ctl->card);
872 	if (result >= 0)
873 		if (copy_to_user(_info, &info, sizeof(info)))
874 			return -EFAULT;
875 	return result;
876 }
877 
878 static int snd_ctl_elem_read(struct snd_card *card,
879 			     struct snd_ctl_elem_value *control)
880 {
881 	struct snd_kcontrol *kctl;
882 	struct snd_kcontrol_volatile *vd;
883 	unsigned int index_offset;
884 	int result;
885 
886 	down_read(&card->controls_rwsem);
887 	kctl = snd_ctl_find_id(card, &control->id);
888 	if (kctl == NULL) {
889 		result = -ENOENT;
890 	} else {
891 		index_offset = snd_ctl_get_ioff(kctl, &control->id);
892 		vd = &kctl->vd[index_offset];
893 		if ((vd->access & SNDRV_CTL_ELEM_ACCESS_READ) &&
894 		    kctl->get != NULL) {
895 			snd_ctl_build_ioff(&control->id, kctl, index_offset);
896 			result = kctl->get(kctl, control);
897 		} else
898 			result = -EPERM;
899 	}
900 	up_read(&card->controls_rwsem);
901 	return result;
902 }
903 
904 static int snd_ctl_elem_read_user(struct snd_card *card,
905 				  struct snd_ctl_elem_value __user *_control)
906 {
907 	struct snd_ctl_elem_value *control;
908 	int result;
909 
910 	control = memdup_user(_control, sizeof(*control));
911 	if (IS_ERR(control))
912 		return PTR_ERR(control);
913 
914 	snd_power_lock(card);
915 	result = snd_power_wait(card, SNDRV_CTL_POWER_D0);
916 	if (result >= 0)
917 		result = snd_ctl_elem_read(card, control);
918 	snd_power_unlock(card);
919 	if (result >= 0)
920 		if (copy_to_user(_control, control, sizeof(*control)))
921 			result = -EFAULT;
922 	kfree(control);
923 	return result;
924 }
925 
926 static int snd_ctl_elem_write(struct snd_card *card, struct snd_ctl_file *file,
927 			      struct snd_ctl_elem_value *control)
928 {
929 	struct snd_kcontrol *kctl;
930 	struct snd_kcontrol_volatile *vd;
931 	unsigned int index_offset;
932 	int result;
933 
934 	down_read(&card->controls_rwsem);
935 	kctl = snd_ctl_find_id(card, &control->id);
936 	if (kctl == NULL) {
937 		result = -ENOENT;
938 	} else {
939 		index_offset = snd_ctl_get_ioff(kctl, &control->id);
940 		vd = &kctl->vd[index_offset];
941 		if (!(vd->access & SNDRV_CTL_ELEM_ACCESS_WRITE) ||
942 		    kctl->put == NULL ||
943 		    (file && vd->owner && vd->owner != file)) {
944 			result = -EPERM;
945 		} else {
946 			snd_ctl_build_ioff(&control->id, kctl, index_offset);
947 			result = kctl->put(kctl, control);
948 		}
949 		if (result > 0) {
950 			struct snd_ctl_elem_id id = control->id;
951 			up_read(&card->controls_rwsem);
952 			snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE, &id);
953 			return 0;
954 		}
955 	}
956 	up_read(&card->controls_rwsem);
957 	return result;
958 }
959 
960 static int snd_ctl_elem_write_user(struct snd_ctl_file *file,
961 				   struct snd_ctl_elem_value __user *_control)
962 {
963 	struct snd_ctl_elem_value *control;
964 	struct snd_card *card;
965 	int result;
966 
967 	control = memdup_user(_control, sizeof(*control));
968 	if (IS_ERR(control))
969 		return PTR_ERR(control);
970 
971 	card = file->card;
972 	snd_power_lock(card);
973 	result = snd_power_wait(card, SNDRV_CTL_POWER_D0);
974 	if (result >= 0)
975 		result = snd_ctl_elem_write(card, file, control);
976 	snd_power_unlock(card);
977 	if (result >= 0)
978 		if (copy_to_user(_control, control, sizeof(*control)))
979 			result = -EFAULT;
980 	kfree(control);
981 	return result;
982 }
983 
984 static int snd_ctl_elem_lock(struct snd_ctl_file *file,
985 			     struct snd_ctl_elem_id __user *_id)
986 {
987 	struct snd_card *card = file->card;
988 	struct snd_ctl_elem_id id;
989 	struct snd_kcontrol *kctl;
990 	struct snd_kcontrol_volatile *vd;
991 	int result;
992 
993 	if (copy_from_user(&id, _id, sizeof(id)))
994 		return -EFAULT;
995 	down_write(&card->controls_rwsem);
996 	kctl = snd_ctl_find_id(card, &id);
997 	if (kctl == NULL) {
998 		result = -ENOENT;
999 	} else {
1000 		vd = &kctl->vd[snd_ctl_get_ioff(kctl, &id)];
1001 		if (vd->owner != NULL)
1002 			result = -EBUSY;
1003 		else {
1004 			vd->owner = file;
1005 			result = 0;
1006 		}
1007 	}
1008 	up_write(&card->controls_rwsem);
1009 	return result;
1010 }
1011 
1012 static int snd_ctl_elem_unlock(struct snd_ctl_file *file,
1013 			       struct snd_ctl_elem_id __user *_id)
1014 {
1015 	struct snd_card *card = file->card;
1016 	struct snd_ctl_elem_id id;
1017 	struct snd_kcontrol *kctl;
1018 	struct snd_kcontrol_volatile *vd;
1019 	int result;
1020 
1021 	if (copy_from_user(&id, _id, sizeof(id)))
1022 		return -EFAULT;
1023 	down_write(&card->controls_rwsem);
1024 	kctl = snd_ctl_find_id(card, &id);
1025 	if (kctl == NULL) {
1026 		result = -ENOENT;
1027 	} else {
1028 		vd = &kctl->vd[snd_ctl_get_ioff(kctl, &id)];
1029 		if (vd->owner == NULL)
1030 			result = -EINVAL;
1031 		else if (vd->owner != file)
1032 			result = -EPERM;
1033 		else {
1034 			vd->owner = NULL;
1035 			result = 0;
1036 		}
1037 	}
1038 	up_write(&card->controls_rwsem);
1039 	return result;
1040 }
1041 
1042 struct user_element {
1043 	struct snd_ctl_elem_info info;
1044 	struct snd_card *card;
1045 	char *elem_data;		/* element data */
1046 	unsigned long elem_data_size;	/* size of element data in bytes */
1047 	void *tlv_data;			/* TLV data */
1048 	unsigned long tlv_data_size;	/* TLV data size */
1049 	void *priv_data;		/* private data (like strings for enumerated type) */
1050 };
1051 
1052 static int snd_ctl_elem_user_info(struct snd_kcontrol *kcontrol,
1053 				  struct snd_ctl_elem_info *uinfo)
1054 {
1055 	struct user_element *ue = kcontrol->private_data;
1056 	unsigned int offset;
1057 
1058 	offset = snd_ctl_get_ioff(kcontrol, &uinfo->id);
1059 	*uinfo = ue->info;
1060 	snd_ctl_build_ioff(&uinfo->id, kcontrol, offset);
1061 
1062 	return 0;
1063 }
1064 
1065 static int snd_ctl_elem_user_enum_info(struct snd_kcontrol *kcontrol,
1066 				       struct snd_ctl_elem_info *uinfo)
1067 {
1068 	struct user_element *ue = kcontrol->private_data;
1069 	const char *names;
1070 	unsigned int item;
1071 	unsigned int offset;
1072 
1073 	item = uinfo->value.enumerated.item;
1074 
1075 	offset = snd_ctl_get_ioff(kcontrol, &uinfo->id);
1076 	*uinfo = ue->info;
1077 	snd_ctl_build_ioff(&uinfo->id, kcontrol, offset);
1078 
1079 	item = min(item, uinfo->value.enumerated.items - 1);
1080 	uinfo->value.enumerated.item = item;
1081 
1082 	names = ue->priv_data;
1083 	for (; item > 0; --item)
1084 		names += strlen(names) + 1;
1085 	strcpy(uinfo->value.enumerated.name, names);
1086 
1087 	return 0;
1088 }
1089 
1090 static int snd_ctl_elem_user_get(struct snd_kcontrol *kcontrol,
1091 				 struct snd_ctl_elem_value *ucontrol)
1092 {
1093 	struct user_element *ue = kcontrol->private_data;
1094 	unsigned int size = ue->elem_data_size;
1095 	char *src = ue->elem_data +
1096 			snd_ctl_get_ioff(kcontrol, &ucontrol->id) * size;
1097 
1098 	mutex_lock(&ue->card->user_ctl_lock);
1099 	memcpy(&ucontrol->value, src, size);
1100 	mutex_unlock(&ue->card->user_ctl_lock);
1101 	return 0;
1102 }
1103 
1104 static int snd_ctl_elem_user_put(struct snd_kcontrol *kcontrol,
1105 				 struct snd_ctl_elem_value *ucontrol)
1106 {
1107 	int change;
1108 	struct user_element *ue = kcontrol->private_data;
1109 	unsigned int size = ue->elem_data_size;
1110 	char *dst = ue->elem_data +
1111 			snd_ctl_get_ioff(kcontrol, &ucontrol->id) * size;
1112 
1113 	mutex_lock(&ue->card->user_ctl_lock);
1114 	change = memcmp(&ucontrol->value, dst, size) != 0;
1115 	if (change)
1116 		memcpy(dst, &ucontrol->value, size);
1117 	mutex_unlock(&ue->card->user_ctl_lock);
1118 	return change;
1119 }
1120 
1121 static int snd_ctl_elem_user_tlv(struct snd_kcontrol *kcontrol,
1122 				 int op_flag,
1123 				 unsigned int size,
1124 				 unsigned int __user *tlv)
1125 {
1126 	struct user_element *ue = kcontrol->private_data;
1127 	int change = 0;
1128 	void *new_data;
1129 
1130 	if (op_flag == SNDRV_CTL_TLV_OP_WRITE) {
1131 		if (size > 1024 * 128)	/* sane value */
1132 			return -EINVAL;
1133 
1134 		new_data = memdup_user(tlv, size);
1135 		if (IS_ERR(new_data))
1136 			return PTR_ERR(new_data);
1137 		mutex_lock(&ue->card->user_ctl_lock);
1138 		change = ue->tlv_data_size != size;
1139 		if (!change)
1140 			change = memcmp(ue->tlv_data, new_data, size);
1141 		kfree(ue->tlv_data);
1142 		ue->tlv_data = new_data;
1143 		ue->tlv_data_size = size;
1144 		mutex_unlock(&ue->card->user_ctl_lock);
1145 	} else {
1146 		int ret = 0;
1147 
1148 		mutex_lock(&ue->card->user_ctl_lock);
1149 		if (!ue->tlv_data_size || !ue->tlv_data) {
1150 			ret = -ENXIO;
1151 			goto err_unlock;
1152 		}
1153 		if (size < ue->tlv_data_size) {
1154 			ret = -ENOSPC;
1155 			goto err_unlock;
1156 		}
1157 		if (copy_to_user(tlv, ue->tlv_data, ue->tlv_data_size))
1158 			ret = -EFAULT;
1159 err_unlock:
1160 		mutex_unlock(&ue->card->user_ctl_lock);
1161 		if (ret)
1162 			return ret;
1163 	}
1164 	return change;
1165 }
1166 
1167 static int snd_ctl_elem_init_enum_names(struct user_element *ue)
1168 {
1169 	char *names, *p;
1170 	size_t buf_len, name_len;
1171 	unsigned int i;
1172 	const uintptr_t user_ptrval = ue->info.value.enumerated.names_ptr;
1173 
1174 	if (ue->info.value.enumerated.names_length > 64 * 1024)
1175 		return -EINVAL;
1176 
1177 	names = memdup_user((const void __user *)user_ptrval,
1178 		ue->info.value.enumerated.names_length);
1179 	if (IS_ERR(names))
1180 		return PTR_ERR(names);
1181 
1182 	/* check that there are enough valid names */
1183 	buf_len = ue->info.value.enumerated.names_length;
1184 	p = names;
1185 	for (i = 0; i < ue->info.value.enumerated.items; ++i) {
1186 		name_len = strnlen(p, buf_len);
1187 		if (name_len == 0 || name_len >= 64 || name_len == buf_len) {
1188 			kfree(names);
1189 			return -EINVAL;
1190 		}
1191 		p += name_len + 1;
1192 		buf_len -= name_len + 1;
1193 	}
1194 
1195 	ue->priv_data = names;
1196 	ue->info.value.enumerated.names_ptr = 0;
1197 
1198 	return 0;
1199 }
1200 
1201 static void snd_ctl_elem_user_free(struct snd_kcontrol *kcontrol)
1202 {
1203 	struct user_element *ue = kcontrol->private_data;
1204 
1205 	kfree(ue->tlv_data);
1206 	kfree(ue->priv_data);
1207 	kfree(ue);
1208 }
1209 
1210 static int snd_ctl_elem_add(struct snd_ctl_file *file,
1211 			    struct snd_ctl_elem_info *info, int replace)
1212 {
1213 	/* The capacity of struct snd_ctl_elem_value.value.*/
1214 	static const unsigned int value_sizes[] = {
1215 		[SNDRV_CTL_ELEM_TYPE_BOOLEAN]	= sizeof(long),
1216 		[SNDRV_CTL_ELEM_TYPE_INTEGER]	= sizeof(long),
1217 		[SNDRV_CTL_ELEM_TYPE_ENUMERATED] = sizeof(unsigned int),
1218 		[SNDRV_CTL_ELEM_TYPE_BYTES]	= sizeof(unsigned char),
1219 		[SNDRV_CTL_ELEM_TYPE_IEC958]	= sizeof(struct snd_aes_iec958),
1220 		[SNDRV_CTL_ELEM_TYPE_INTEGER64] = sizeof(long long),
1221 	};
1222 	static const unsigned int max_value_counts[] = {
1223 		[SNDRV_CTL_ELEM_TYPE_BOOLEAN]	= 128,
1224 		[SNDRV_CTL_ELEM_TYPE_INTEGER]	= 128,
1225 		[SNDRV_CTL_ELEM_TYPE_ENUMERATED] = 128,
1226 		[SNDRV_CTL_ELEM_TYPE_BYTES]	= 512,
1227 		[SNDRV_CTL_ELEM_TYPE_IEC958]	= 1,
1228 		[SNDRV_CTL_ELEM_TYPE_INTEGER64] = 64,
1229 	};
1230 	struct snd_card *card = file->card;
1231 	struct snd_kcontrol *kctl;
1232 	unsigned int count;
1233 	unsigned int access;
1234 	long private_size;
1235 	struct user_element *ue;
1236 	unsigned int offset;
1237 	int err;
1238 
1239 	if (!*info->id.name)
1240 		return -EINVAL;
1241 	if (strnlen(info->id.name, sizeof(info->id.name)) >= sizeof(info->id.name))
1242 		return -EINVAL;
1243 
1244 	/* Delete a control to replace them if needed. */
1245 	if (replace) {
1246 		info->id.numid = 0;
1247 		err = snd_ctl_remove_user_ctl(file, &info->id);
1248 		if (err)
1249 			return err;
1250 	}
1251 
1252 	/*
1253 	 * The number of userspace controls are counted control by control,
1254 	 * not element by element.
1255 	 */
1256 	if (card->user_ctl_count + 1 > MAX_USER_CONTROLS)
1257 		return -ENOMEM;
1258 
1259 	/* Check the number of elements for this userspace control. */
1260 	count = info->owner;
1261 	if (count == 0)
1262 		count = 1;
1263 
1264 	/* Arrange access permissions if needed. */
1265 	access = info->access;
1266 	if (access == 0)
1267 		access = SNDRV_CTL_ELEM_ACCESS_READWRITE;
1268 	access &= (SNDRV_CTL_ELEM_ACCESS_READWRITE |
1269 		   SNDRV_CTL_ELEM_ACCESS_INACTIVE |
1270 		   SNDRV_CTL_ELEM_ACCESS_TLV_READWRITE);
1271 	if (access & SNDRV_CTL_ELEM_ACCESS_TLV_READWRITE)
1272 		access |= SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK;
1273 	access |= SNDRV_CTL_ELEM_ACCESS_USER;
1274 
1275 	/*
1276 	 * Check information and calculate the size of data specific to
1277 	 * this userspace control.
1278 	 */
1279 	if (info->type < SNDRV_CTL_ELEM_TYPE_BOOLEAN ||
1280 	    info->type > SNDRV_CTL_ELEM_TYPE_INTEGER64)
1281 		return -EINVAL;
1282 	if (info->type == SNDRV_CTL_ELEM_TYPE_ENUMERATED &&
1283 	    info->value.enumerated.items == 0)
1284 		return -EINVAL;
1285 	if (info->count < 1 ||
1286 	    info->count > max_value_counts[info->type])
1287 		return -EINVAL;
1288 	if (!validate_element_member_dimension(info))
1289 		return -EINVAL;
1290 	private_size = value_sizes[info->type] * info->count;
1291 
1292 	/*
1293 	 * Keep memory object for this userspace control. After passing this
1294 	 * code block, the instance should be freed by snd_ctl_free_one().
1295 	 *
1296 	 * Note that these elements in this control are locked.
1297 	 */
1298 	err = snd_ctl_new(&kctl, count, access, file);
1299 	if (err < 0)
1300 		return err;
1301 	memcpy(&kctl->id, &info->id, sizeof(kctl->id));
1302 	kctl->private_data = kzalloc(sizeof(struct user_element) + private_size * count,
1303 				     GFP_KERNEL);
1304 	if (kctl->private_data == NULL) {
1305 		kfree(kctl);
1306 		return -ENOMEM;
1307 	}
1308 	kctl->private_free = snd_ctl_elem_user_free;
1309 
1310 	/* Set private data for this userspace control. */
1311 	ue = (struct user_element *)kctl->private_data;
1312 	ue->card = card;
1313 	ue->info = *info;
1314 	ue->info.access = 0;
1315 	ue->elem_data = (char *)ue + sizeof(*ue);
1316 	ue->elem_data_size = private_size;
1317 	if (ue->info.type == SNDRV_CTL_ELEM_TYPE_ENUMERATED) {
1318 		err = snd_ctl_elem_init_enum_names(ue);
1319 		if (err < 0) {
1320 			snd_ctl_free_one(kctl);
1321 			return err;
1322 		}
1323 	}
1324 
1325 	/* Set callback functions. */
1326 	if (info->type == SNDRV_CTL_ELEM_TYPE_ENUMERATED)
1327 		kctl->info = snd_ctl_elem_user_enum_info;
1328 	else
1329 		kctl->info = snd_ctl_elem_user_info;
1330 	if (access & SNDRV_CTL_ELEM_ACCESS_READ)
1331 		kctl->get = snd_ctl_elem_user_get;
1332 	if (access & SNDRV_CTL_ELEM_ACCESS_WRITE)
1333 		kctl->put = snd_ctl_elem_user_put;
1334 	if (access & SNDRV_CTL_ELEM_ACCESS_TLV_READWRITE)
1335 		kctl->tlv.c = snd_ctl_elem_user_tlv;
1336 
1337 	/* This function manage to free the instance on failure. */
1338 	err = snd_ctl_add(card, kctl);
1339 	if (err < 0)
1340 		return err;
1341 	offset = snd_ctl_get_ioff(kctl, &info->id);
1342 	snd_ctl_build_ioff(&info->id, kctl, offset);
1343 	/*
1344 	 * Here we cannot fill any field for the number of elements added by
1345 	 * this operation because there're no specific fields. The usage of
1346 	 * 'owner' field for this purpose may cause any bugs to userspace
1347 	 * applications because the field originally means PID of a process
1348 	 * which locks the element.
1349 	 */
1350 
1351 	down_write(&card->controls_rwsem);
1352 	card->user_ctl_count++;
1353 	up_write(&card->controls_rwsem);
1354 
1355 	return 0;
1356 }
1357 
1358 static int snd_ctl_elem_add_user(struct snd_ctl_file *file,
1359 				 struct snd_ctl_elem_info __user *_info, int replace)
1360 {
1361 	struct snd_ctl_elem_info info;
1362 	int err;
1363 
1364 	if (copy_from_user(&info, _info, sizeof(info)))
1365 		return -EFAULT;
1366 	err = snd_ctl_elem_add(file, &info, replace);
1367 	if (err < 0)
1368 		return err;
1369 	if (copy_to_user(_info, &info, sizeof(info))) {
1370 		snd_ctl_remove_user_ctl(file, &info.id);
1371 		return -EFAULT;
1372 	}
1373 
1374 	return 0;
1375 }
1376 
1377 static int snd_ctl_elem_remove(struct snd_ctl_file *file,
1378 			       struct snd_ctl_elem_id __user *_id)
1379 {
1380 	struct snd_ctl_elem_id id;
1381 
1382 	if (copy_from_user(&id, _id, sizeof(id)))
1383 		return -EFAULT;
1384 	return snd_ctl_remove_user_ctl(file, &id);
1385 }
1386 
1387 static int snd_ctl_subscribe_events(struct snd_ctl_file *file, int __user *ptr)
1388 {
1389 	int subscribe;
1390 	if (get_user(subscribe, ptr))
1391 		return -EFAULT;
1392 	if (subscribe < 0) {
1393 		subscribe = file->subscribed;
1394 		if (put_user(subscribe, ptr))
1395 			return -EFAULT;
1396 		return 0;
1397 	}
1398 	if (subscribe) {
1399 		file->subscribed = 1;
1400 		return 0;
1401 	} else if (file->subscribed) {
1402 		snd_ctl_empty_read_queue(file);
1403 		file->subscribed = 0;
1404 	}
1405 	return 0;
1406 }
1407 
1408 static int snd_ctl_tlv_ioctl(struct snd_ctl_file *file,
1409                              struct snd_ctl_tlv __user *_tlv,
1410                              int op_flag)
1411 {
1412 	struct snd_card *card = file->card;
1413 	struct snd_ctl_tlv tlv;
1414 	struct snd_kcontrol *kctl;
1415 	struct snd_kcontrol_volatile *vd;
1416 	unsigned int len;
1417 	int err = 0;
1418 
1419 	if (copy_from_user(&tlv, _tlv, sizeof(tlv)))
1420 		return -EFAULT;
1421 	if (tlv.length < sizeof(unsigned int) * 2)
1422 		return -EINVAL;
1423 	if (!tlv.numid)
1424 		return -EINVAL;
1425 	down_read(&card->controls_rwsem);
1426 	kctl = snd_ctl_find_numid(card, tlv.numid);
1427 	if (kctl == NULL) {
1428 		err = -ENOENT;
1429 		goto __kctl_end;
1430 	}
1431 	if (kctl->tlv.p == NULL) {
1432 		err = -ENXIO;
1433 		goto __kctl_end;
1434 	}
1435 	vd = &kctl->vd[tlv.numid - kctl->id.numid];
1436 	if ((op_flag == SNDRV_CTL_TLV_OP_READ &&
1437 	     (vd->access & SNDRV_CTL_ELEM_ACCESS_TLV_READ) == 0) ||
1438 	    (op_flag == SNDRV_CTL_TLV_OP_WRITE &&
1439 	     (vd->access & SNDRV_CTL_ELEM_ACCESS_TLV_WRITE) == 0) ||
1440 	    (op_flag == SNDRV_CTL_TLV_OP_CMD &&
1441 	     (vd->access & SNDRV_CTL_ELEM_ACCESS_TLV_COMMAND) == 0)) {
1442 	    	err = -ENXIO;
1443 	    	goto __kctl_end;
1444 	}
1445 	if (vd->access & SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK) {
1446 		if (vd->owner != NULL && vd->owner != file) {
1447 			err = -EPERM;
1448 			goto __kctl_end;
1449 		}
1450 		err = kctl->tlv.c(kctl, op_flag, tlv.length, _tlv->tlv);
1451 		if (err > 0) {
1452 			struct snd_ctl_elem_id id = kctl->id;
1453 			up_read(&card->controls_rwsem);
1454 			snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_TLV, &id);
1455 			return 0;
1456 		}
1457 	} else {
1458 		if (op_flag != SNDRV_CTL_TLV_OP_READ) {
1459 			err = -ENXIO;
1460 			goto __kctl_end;
1461 		}
1462 		len = kctl->tlv.p[1] + 2 * sizeof(unsigned int);
1463 		if (tlv.length < len) {
1464 			err = -ENOMEM;
1465 			goto __kctl_end;
1466 		}
1467 		if (copy_to_user(_tlv->tlv, kctl->tlv.p, len))
1468 			err = -EFAULT;
1469 	}
1470       __kctl_end:
1471 	up_read(&card->controls_rwsem);
1472 	return err;
1473 }
1474 
1475 static long snd_ctl_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
1476 {
1477 	struct snd_ctl_file *ctl;
1478 	struct snd_card *card;
1479 	struct snd_kctl_ioctl *p;
1480 	void __user *argp = (void __user *)arg;
1481 	int __user *ip = argp;
1482 	int err;
1483 
1484 	ctl = file->private_data;
1485 	card = ctl->card;
1486 	if (snd_BUG_ON(!card))
1487 		return -ENXIO;
1488 	switch (cmd) {
1489 	case SNDRV_CTL_IOCTL_PVERSION:
1490 		return put_user(SNDRV_CTL_VERSION, ip) ? -EFAULT : 0;
1491 	case SNDRV_CTL_IOCTL_CARD_INFO:
1492 		return snd_ctl_card_info(card, ctl, cmd, argp);
1493 	case SNDRV_CTL_IOCTL_ELEM_LIST:
1494 		return snd_ctl_elem_list(card, argp);
1495 	case SNDRV_CTL_IOCTL_ELEM_INFO:
1496 		return snd_ctl_elem_info_user(ctl, argp);
1497 	case SNDRV_CTL_IOCTL_ELEM_READ:
1498 		return snd_ctl_elem_read_user(card, argp);
1499 	case SNDRV_CTL_IOCTL_ELEM_WRITE:
1500 		return snd_ctl_elem_write_user(ctl, argp);
1501 	case SNDRV_CTL_IOCTL_ELEM_LOCK:
1502 		return snd_ctl_elem_lock(ctl, argp);
1503 	case SNDRV_CTL_IOCTL_ELEM_UNLOCK:
1504 		return snd_ctl_elem_unlock(ctl, argp);
1505 	case SNDRV_CTL_IOCTL_ELEM_ADD:
1506 		return snd_ctl_elem_add_user(ctl, argp, 0);
1507 	case SNDRV_CTL_IOCTL_ELEM_REPLACE:
1508 		return snd_ctl_elem_add_user(ctl, argp, 1);
1509 	case SNDRV_CTL_IOCTL_ELEM_REMOVE:
1510 		return snd_ctl_elem_remove(ctl, argp);
1511 	case SNDRV_CTL_IOCTL_SUBSCRIBE_EVENTS:
1512 		return snd_ctl_subscribe_events(ctl, ip);
1513 	case SNDRV_CTL_IOCTL_TLV_READ:
1514 		return snd_ctl_tlv_ioctl(ctl, argp, SNDRV_CTL_TLV_OP_READ);
1515 	case SNDRV_CTL_IOCTL_TLV_WRITE:
1516 		return snd_ctl_tlv_ioctl(ctl, argp, SNDRV_CTL_TLV_OP_WRITE);
1517 	case SNDRV_CTL_IOCTL_TLV_COMMAND:
1518 		return snd_ctl_tlv_ioctl(ctl, argp, SNDRV_CTL_TLV_OP_CMD);
1519 	case SNDRV_CTL_IOCTL_POWER:
1520 		return -ENOPROTOOPT;
1521 	case SNDRV_CTL_IOCTL_POWER_STATE:
1522 #ifdef CONFIG_PM
1523 		return put_user(card->power_state, ip) ? -EFAULT : 0;
1524 #else
1525 		return put_user(SNDRV_CTL_POWER_D0, ip) ? -EFAULT : 0;
1526 #endif
1527 	}
1528 	down_read(&snd_ioctl_rwsem);
1529 	list_for_each_entry(p, &snd_control_ioctls, list) {
1530 		err = p->fioctl(card, ctl, cmd, arg);
1531 		if (err != -ENOIOCTLCMD) {
1532 			up_read(&snd_ioctl_rwsem);
1533 			return err;
1534 		}
1535 	}
1536 	up_read(&snd_ioctl_rwsem);
1537 	dev_dbg(card->dev, "unknown ioctl = 0x%x\n", cmd);
1538 	return -ENOTTY;
1539 }
1540 
1541 static ssize_t snd_ctl_read(struct file *file, char __user *buffer,
1542 			    size_t count, loff_t * offset)
1543 {
1544 	struct snd_ctl_file *ctl;
1545 	int err = 0;
1546 	ssize_t result = 0;
1547 
1548 	ctl = file->private_data;
1549 	if (snd_BUG_ON(!ctl || !ctl->card))
1550 		return -ENXIO;
1551 	if (!ctl->subscribed)
1552 		return -EBADFD;
1553 	if (count < sizeof(struct snd_ctl_event))
1554 		return -EINVAL;
1555 	spin_lock_irq(&ctl->read_lock);
1556 	while (count >= sizeof(struct snd_ctl_event)) {
1557 		struct snd_ctl_event ev;
1558 		struct snd_kctl_event *kev;
1559 		while (list_empty(&ctl->events)) {
1560 			wait_queue_entry_t wait;
1561 			if ((file->f_flags & O_NONBLOCK) != 0 || result > 0) {
1562 				err = -EAGAIN;
1563 				goto __end_lock;
1564 			}
1565 			init_waitqueue_entry(&wait, current);
1566 			add_wait_queue(&ctl->change_sleep, &wait);
1567 			set_current_state(TASK_INTERRUPTIBLE);
1568 			spin_unlock_irq(&ctl->read_lock);
1569 			schedule();
1570 			remove_wait_queue(&ctl->change_sleep, &wait);
1571 			if (ctl->card->shutdown)
1572 				return -ENODEV;
1573 			if (signal_pending(current))
1574 				return -ERESTARTSYS;
1575 			spin_lock_irq(&ctl->read_lock);
1576 		}
1577 		kev = snd_kctl_event(ctl->events.next);
1578 		ev.type = SNDRV_CTL_EVENT_ELEM;
1579 		ev.data.elem.mask = kev->mask;
1580 		ev.data.elem.id = kev->id;
1581 		list_del(&kev->list);
1582 		spin_unlock_irq(&ctl->read_lock);
1583 		kfree(kev);
1584 		if (copy_to_user(buffer, &ev, sizeof(struct snd_ctl_event))) {
1585 			err = -EFAULT;
1586 			goto __end;
1587 		}
1588 		spin_lock_irq(&ctl->read_lock);
1589 		buffer += sizeof(struct snd_ctl_event);
1590 		count -= sizeof(struct snd_ctl_event);
1591 		result += sizeof(struct snd_ctl_event);
1592 	}
1593       __end_lock:
1594 	spin_unlock_irq(&ctl->read_lock);
1595       __end:
1596       	return result > 0 ? result : err;
1597 }
1598 
1599 static unsigned int snd_ctl_poll(struct file *file, poll_table * wait)
1600 {
1601 	unsigned int mask;
1602 	struct snd_ctl_file *ctl;
1603 
1604 	ctl = file->private_data;
1605 	if (!ctl->subscribed)
1606 		return 0;
1607 	poll_wait(file, &ctl->change_sleep, wait);
1608 
1609 	mask = 0;
1610 	if (!list_empty(&ctl->events))
1611 		mask |= POLLIN | POLLRDNORM;
1612 
1613 	return mask;
1614 }
1615 
1616 /*
1617  * register the device-specific control-ioctls.
1618  * called from each device manager like pcm.c, hwdep.c, etc.
1619  */
1620 static int _snd_ctl_register_ioctl(snd_kctl_ioctl_func_t fcn, struct list_head *lists)
1621 {
1622 	struct snd_kctl_ioctl *pn;
1623 
1624 	pn = kzalloc(sizeof(struct snd_kctl_ioctl), GFP_KERNEL);
1625 	if (pn == NULL)
1626 		return -ENOMEM;
1627 	pn->fioctl = fcn;
1628 	down_write(&snd_ioctl_rwsem);
1629 	list_add_tail(&pn->list, lists);
1630 	up_write(&snd_ioctl_rwsem);
1631 	return 0;
1632 }
1633 
1634 /**
1635  * snd_ctl_register_ioctl - register the device-specific control-ioctls
1636  * @fcn: ioctl callback function
1637  *
1638  * called from each device manager like pcm.c, hwdep.c, etc.
1639  */
1640 int snd_ctl_register_ioctl(snd_kctl_ioctl_func_t fcn)
1641 {
1642 	return _snd_ctl_register_ioctl(fcn, &snd_control_ioctls);
1643 }
1644 EXPORT_SYMBOL(snd_ctl_register_ioctl);
1645 
1646 #ifdef CONFIG_COMPAT
1647 /**
1648  * snd_ctl_register_ioctl_compat - register the device-specific 32bit compat
1649  * control-ioctls
1650  * @fcn: ioctl callback function
1651  */
1652 int snd_ctl_register_ioctl_compat(snd_kctl_ioctl_func_t fcn)
1653 {
1654 	return _snd_ctl_register_ioctl(fcn, &snd_control_compat_ioctls);
1655 }
1656 EXPORT_SYMBOL(snd_ctl_register_ioctl_compat);
1657 #endif
1658 
1659 /*
1660  * de-register the device-specific control-ioctls.
1661  */
1662 static int _snd_ctl_unregister_ioctl(snd_kctl_ioctl_func_t fcn,
1663 				     struct list_head *lists)
1664 {
1665 	struct snd_kctl_ioctl *p;
1666 
1667 	if (snd_BUG_ON(!fcn))
1668 		return -EINVAL;
1669 	down_write(&snd_ioctl_rwsem);
1670 	list_for_each_entry(p, lists, list) {
1671 		if (p->fioctl == fcn) {
1672 			list_del(&p->list);
1673 			up_write(&snd_ioctl_rwsem);
1674 			kfree(p);
1675 			return 0;
1676 		}
1677 	}
1678 	up_write(&snd_ioctl_rwsem);
1679 	snd_BUG();
1680 	return -EINVAL;
1681 }
1682 
1683 /**
1684  * snd_ctl_unregister_ioctl - de-register the device-specific control-ioctls
1685  * @fcn: ioctl callback function to unregister
1686  */
1687 int snd_ctl_unregister_ioctl(snd_kctl_ioctl_func_t fcn)
1688 {
1689 	return _snd_ctl_unregister_ioctl(fcn, &snd_control_ioctls);
1690 }
1691 EXPORT_SYMBOL(snd_ctl_unregister_ioctl);
1692 
1693 #ifdef CONFIG_COMPAT
1694 /**
1695  * snd_ctl_unregister_ioctl - de-register the device-specific compat 32bit
1696  * control-ioctls
1697  * @fcn: ioctl callback function to unregister
1698  */
1699 int snd_ctl_unregister_ioctl_compat(snd_kctl_ioctl_func_t fcn)
1700 {
1701 	return _snd_ctl_unregister_ioctl(fcn, &snd_control_compat_ioctls);
1702 }
1703 EXPORT_SYMBOL(snd_ctl_unregister_ioctl_compat);
1704 #endif
1705 
1706 static int snd_ctl_fasync(int fd, struct file * file, int on)
1707 {
1708 	struct snd_ctl_file *ctl;
1709 
1710 	ctl = file->private_data;
1711 	return fasync_helper(fd, file, on, &ctl->fasync);
1712 }
1713 
1714 /* return the preferred subdevice number if already assigned;
1715  * otherwise return -1
1716  */
1717 int snd_ctl_get_preferred_subdevice(struct snd_card *card, int type)
1718 {
1719 	struct snd_ctl_file *kctl;
1720 	int subdevice = -1;
1721 
1722 	read_lock(&card->ctl_files_rwlock);
1723 	list_for_each_entry(kctl, &card->ctl_files, list) {
1724 		if (kctl->pid == task_pid(current)) {
1725 			subdevice = kctl->preferred_subdevice[type];
1726 			if (subdevice != -1)
1727 				break;
1728 		}
1729 	}
1730 	read_unlock(&card->ctl_files_rwlock);
1731 	return subdevice;
1732 }
1733 EXPORT_SYMBOL_GPL(snd_ctl_get_preferred_subdevice);
1734 
1735 /*
1736  * ioctl32 compat
1737  */
1738 #ifdef CONFIG_COMPAT
1739 #include "control_compat.c"
1740 #else
1741 #define snd_ctl_ioctl_compat	NULL
1742 #endif
1743 
1744 /*
1745  *  INIT PART
1746  */
1747 
1748 static const struct file_operations snd_ctl_f_ops =
1749 {
1750 	.owner =	THIS_MODULE,
1751 	.read =		snd_ctl_read,
1752 	.open =		snd_ctl_open,
1753 	.release =	snd_ctl_release,
1754 	.llseek =	no_llseek,
1755 	.poll =		snd_ctl_poll,
1756 	.unlocked_ioctl =	snd_ctl_ioctl,
1757 	.compat_ioctl =	snd_ctl_ioctl_compat,
1758 	.fasync =	snd_ctl_fasync,
1759 };
1760 
1761 /*
1762  * registration of the control device
1763  */
1764 static int snd_ctl_dev_register(struct snd_device *device)
1765 {
1766 	struct snd_card *card = device->device_data;
1767 
1768 	return snd_register_device(SNDRV_DEVICE_TYPE_CONTROL, card, -1,
1769 				   &snd_ctl_f_ops, card, &card->ctl_dev);
1770 }
1771 
1772 /*
1773  * disconnection of the control device
1774  */
1775 static int snd_ctl_dev_disconnect(struct snd_device *device)
1776 {
1777 	struct snd_card *card = device->device_data;
1778 	struct snd_ctl_file *ctl;
1779 
1780 	read_lock(&card->ctl_files_rwlock);
1781 	list_for_each_entry(ctl, &card->ctl_files, list) {
1782 		wake_up(&ctl->change_sleep);
1783 		kill_fasync(&ctl->fasync, SIGIO, POLL_ERR);
1784 	}
1785 	read_unlock(&card->ctl_files_rwlock);
1786 
1787 	return snd_unregister_device(&card->ctl_dev);
1788 }
1789 
1790 /*
1791  * free all controls
1792  */
1793 static int snd_ctl_dev_free(struct snd_device *device)
1794 {
1795 	struct snd_card *card = device->device_data;
1796 	struct snd_kcontrol *control;
1797 
1798 	down_write(&card->controls_rwsem);
1799 	while (!list_empty(&card->controls)) {
1800 		control = snd_kcontrol(card->controls.next);
1801 		snd_ctl_remove(card, control);
1802 	}
1803 	up_write(&card->controls_rwsem);
1804 	put_device(&card->ctl_dev);
1805 	return 0;
1806 }
1807 
1808 /*
1809  * create control core:
1810  * called from init.c
1811  */
1812 int snd_ctl_create(struct snd_card *card)
1813 {
1814 	static struct snd_device_ops ops = {
1815 		.dev_free = snd_ctl_dev_free,
1816 		.dev_register =	snd_ctl_dev_register,
1817 		.dev_disconnect = snd_ctl_dev_disconnect,
1818 	};
1819 	int err;
1820 
1821 	if (snd_BUG_ON(!card))
1822 		return -ENXIO;
1823 	if (snd_BUG_ON(card->number < 0 || card->number >= SNDRV_CARDS))
1824 		return -ENXIO;
1825 
1826 	snd_device_initialize(&card->ctl_dev, card);
1827 	dev_set_name(&card->ctl_dev, "controlC%d", card->number);
1828 
1829 	err = snd_device_new(card, SNDRV_DEV_CONTROL, card, &ops);
1830 	if (err < 0)
1831 		put_device(&card->ctl_dev);
1832 	return err;
1833 }
1834 
1835 /*
1836  * Frequently used control callbacks/helpers
1837  */
1838 
1839 /**
1840  * snd_ctl_boolean_mono_info - Helper function for a standard boolean info
1841  * callback with a mono channel
1842  * @kcontrol: the kcontrol instance
1843  * @uinfo: info to store
1844  *
1845  * This is a function that can be used as info callback for a standard
1846  * boolean control with a single mono channel.
1847  */
1848 int snd_ctl_boolean_mono_info(struct snd_kcontrol *kcontrol,
1849 			      struct snd_ctl_elem_info *uinfo)
1850 {
1851 	uinfo->type = SNDRV_CTL_ELEM_TYPE_BOOLEAN;
1852 	uinfo->count = 1;
1853 	uinfo->value.integer.min = 0;
1854 	uinfo->value.integer.max = 1;
1855 	return 0;
1856 }
1857 EXPORT_SYMBOL(snd_ctl_boolean_mono_info);
1858 
1859 /**
1860  * snd_ctl_boolean_stereo_info - Helper function for a standard boolean info
1861  * callback with stereo two channels
1862  * @kcontrol: the kcontrol instance
1863  * @uinfo: info to store
1864  *
1865  * This is a function that can be used as info callback for a standard
1866  * boolean control with stereo two channels.
1867  */
1868 int snd_ctl_boolean_stereo_info(struct snd_kcontrol *kcontrol,
1869 				struct snd_ctl_elem_info *uinfo)
1870 {
1871 	uinfo->type = SNDRV_CTL_ELEM_TYPE_BOOLEAN;
1872 	uinfo->count = 2;
1873 	uinfo->value.integer.min = 0;
1874 	uinfo->value.integer.max = 1;
1875 	return 0;
1876 }
1877 EXPORT_SYMBOL(snd_ctl_boolean_stereo_info);
1878 
1879 /**
1880  * snd_ctl_enum_info - fills the info structure for an enumerated control
1881  * @info: the structure to be filled
1882  * @channels: the number of the control's channels; often one
1883  * @items: the number of control values; also the size of @names
1884  * @names: an array containing the names of all control values
1885  *
1886  * Sets all required fields in @info to their appropriate values.
1887  * If the control's accessibility is not the default (readable and writable),
1888  * the caller has to fill @info->access.
1889  *
1890  * Return: Zero.
1891  */
1892 int snd_ctl_enum_info(struct snd_ctl_elem_info *info, unsigned int channels,
1893 		      unsigned int items, const char *const names[])
1894 {
1895 	info->type = SNDRV_CTL_ELEM_TYPE_ENUMERATED;
1896 	info->count = channels;
1897 	info->value.enumerated.items = items;
1898 	if (!items)
1899 		return 0;
1900 	if (info->value.enumerated.item >= items)
1901 		info->value.enumerated.item = items - 1;
1902 	WARN(strlen(names[info->value.enumerated.item]) >= sizeof(info->value.enumerated.name),
1903 	     "ALSA: too long item name '%s'\n",
1904 	     names[info->value.enumerated.item]);
1905 	strlcpy(info->value.enumerated.name,
1906 		names[info->value.enumerated.item],
1907 		sizeof(info->value.enumerated.name));
1908 	return 0;
1909 }
1910 EXPORT_SYMBOL(snd_ctl_enum_info);
1911