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TOMOYO Linux Cross Reference
Linux/sound/core/init.c

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  1 /*
  2  *  Initialization routines
  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/init.h>
 23 #include <linux/sched.h>
 24 #include <linux/module.h>
 25 #include <linux/device.h>
 26 #include <linux/file.h>
 27 #include <linux/slab.h>
 28 #include <linux/time.h>
 29 #include <linux/ctype.h>
 30 #include <linux/pm.h>
 31 #include <linux/completion.h>
 32 
 33 #include <sound/core.h>
 34 #include <sound/control.h>
 35 #include <sound/info.h>
 36 
 37 /* monitor files for graceful shutdown (hotplug) */
 38 struct snd_monitor_file {
 39         struct file *file;
 40         const struct file_operations *disconnected_f_op;
 41         struct list_head shutdown_list; /* still need to shutdown */
 42         struct list_head list;  /* link of monitor files */
 43 };
 44 
 45 static DEFINE_SPINLOCK(shutdown_lock);
 46 static LIST_HEAD(shutdown_files);
 47 
 48 static const struct file_operations snd_shutdown_f_ops;
 49 
 50 /* locked for registering/using */
 51 static DECLARE_BITMAP(snd_cards_lock, SNDRV_CARDS);
 52 struct snd_card *snd_cards[SNDRV_CARDS];
 53 EXPORT_SYMBOL(snd_cards);
 54 
 55 static DEFINE_MUTEX(snd_card_mutex);
 56 
 57 static char *slots[SNDRV_CARDS];
 58 module_param_array(slots, charp, NULL, 0444);
 59 MODULE_PARM_DESC(slots, "Module names assigned to the slots.");
 60 
 61 /* return non-zero if the given index is reserved for the given
 62  * module via slots option
 63  */
 64 static int module_slot_match(struct module *module, int idx)
 65 {
 66         int match = 1;
 67 #ifdef MODULE
 68         const char *s1, *s2;
 69 
 70         if (!module || !*module->name || !slots[idx])
 71                 return 0;
 72 
 73         s1 = module->name;
 74         s2 = slots[idx];
 75         if (*s2 == '!') {
 76                 match = 0; /* negative match */
 77                 s2++;
 78         }
 79         /* compare module name strings
 80          * hyphens are handled as equivalent with underscore
 81          */
 82         for (;;) {
 83                 char c1 = *s1++;
 84                 char c2 = *s2++;
 85                 if (c1 == '-')
 86                         c1 = '_';
 87                 if (c2 == '-')
 88                         c2 = '_';
 89                 if (c1 != c2)
 90                         return !match;
 91                 if (!c1)
 92                         break;
 93         }
 94 #endif /* MODULE */
 95         return match;
 96 }
 97 
 98 #if IS_ENABLED(CONFIG_SND_MIXER_OSS)
 99 int (*snd_mixer_oss_notify_callback)(struct snd_card *card, int free_flag);
100 EXPORT_SYMBOL(snd_mixer_oss_notify_callback);
101 #endif
102 
103 #ifdef CONFIG_SND_PROC_FS
104 static void snd_card_id_read(struct snd_info_entry *entry,
105                              struct snd_info_buffer *buffer)
106 {
107         snd_iprintf(buffer, "%s\n", entry->card->id);
108 }
109 
110 static int init_info_for_card(struct snd_card *card)
111 {
112         struct snd_info_entry *entry;
113 
114         entry = snd_info_create_card_entry(card, "id", card->proc_root);
115         if (!entry) {
116                 dev_dbg(card->dev, "unable to create card entry\n");
117                 return -ENOMEM;
118         }
119         entry->c.text.read = snd_card_id_read;
120         card->proc_id = entry;
121 
122         return snd_info_card_register(card);
123 }
124 #else /* !CONFIG_SND_PROC_FS */
125 #define init_info_for_card(card)
126 #endif
127 
128 static int check_empty_slot(struct module *module, int slot)
129 {
130         return !slots[slot] || !*slots[slot];
131 }
132 
133 /* return an empty slot number (>= 0) found in the given bitmask @mask.
134  * @mask == -1 == 0xffffffff means: take any free slot up to 32
135  * when no slot is available, return the original @mask as is.
136  */
137 static int get_slot_from_bitmask(int mask, int (*check)(struct module *, int),
138                                  struct module *module)
139 {
140         int slot;
141 
142         for (slot = 0; slot < SNDRV_CARDS; slot++) {
143                 if (slot < 32 && !(mask & (1U << slot)))
144                         continue;
145                 if (!test_bit(slot, snd_cards_lock)) {
146                         if (check(module, slot))
147                                 return slot; /* found */
148                 }
149         }
150         return mask; /* unchanged */
151 }
152 
153 /* the default release callback set in snd_device_initialize() below;
154  * this is just NOP for now, as almost all jobs are already done in
155  * dev_free callback of snd_device chain instead.
156  */
157 static void default_release(struct device *dev)
158 {
159 }
160 
161 /**
162  * snd_device_initialize - Initialize struct device for sound devices
163  * @dev: device to initialize
164  * @card: card to assign, optional
165  */
166 void snd_device_initialize(struct device *dev, struct snd_card *card)
167 {
168         device_initialize(dev);
169         if (card)
170                 dev->parent = &card->card_dev;
171         dev->class = sound_class;
172         dev->release = default_release;
173 }
174 EXPORT_SYMBOL_GPL(snd_device_initialize);
175 
176 static int snd_card_do_free(struct snd_card *card);
177 static const struct attribute_group card_dev_attr_group;
178 
179 static void release_card_device(struct device *dev)
180 {
181         snd_card_do_free(dev_to_snd_card(dev));
182 }
183 
184 /**
185  *  snd_card_new - create and initialize a soundcard structure
186  *  @parent: the parent device object
187  *  @idx: card index (address) [0 ... (SNDRV_CARDS-1)]
188  *  @xid: card identification (ASCII string)
189  *  @module: top level module for locking
190  *  @extra_size: allocate this extra size after the main soundcard structure
191  *  @card_ret: the pointer to store the created card instance
192  *
193  *  Creates and initializes a soundcard structure.
194  *
195  *  The function allocates snd_card instance via kzalloc with the given
196  *  space for the driver to use freely.  The allocated struct is stored
197  *  in the given card_ret pointer.
198  *
199  *  Return: Zero if successful or a negative error code.
200  */
201 int snd_card_new(struct device *parent, int idx, const char *xid,
202                     struct module *module, int extra_size,
203                     struct snd_card **card_ret)
204 {
205         struct snd_card *card;
206         int err;
207 
208         if (snd_BUG_ON(!card_ret))
209                 return -EINVAL;
210         *card_ret = NULL;
211 
212         if (extra_size < 0)
213                 extra_size = 0;
214         card = kzalloc(sizeof(*card) + extra_size, GFP_KERNEL);
215         if (!card)
216                 return -ENOMEM;
217         if (extra_size > 0)
218                 card->private_data = (char *)card + sizeof(struct snd_card);
219         if (xid)
220                 strlcpy(card->id, xid, sizeof(card->id));
221         err = 0;
222         mutex_lock(&snd_card_mutex);
223         if (idx < 0) /* first check the matching module-name slot */
224                 idx = get_slot_from_bitmask(idx, module_slot_match, module);
225         if (idx < 0) /* if not matched, assign an empty slot */
226                 idx = get_slot_from_bitmask(idx, check_empty_slot, module);
227         if (idx < 0)
228                 err = -ENODEV;
229         else if (idx < snd_ecards_limit) {
230                 if (test_bit(idx, snd_cards_lock))
231                         err = -EBUSY;   /* invalid */
232         } else if (idx >= SNDRV_CARDS)
233                 err = -ENODEV;
234         if (err < 0) {
235                 mutex_unlock(&snd_card_mutex);
236                 dev_err(parent, "cannot find the slot for index %d (range 0-%i), error: %d\n",
237                          idx, snd_ecards_limit - 1, err);
238                 kfree(card);
239                 return err;
240         }
241         set_bit(idx, snd_cards_lock);           /* lock it */
242         if (idx >= snd_ecards_limit)
243                 snd_ecards_limit = idx + 1; /* increase the limit */
244         mutex_unlock(&snd_card_mutex);
245         card->dev = parent;
246         card->number = idx;
247         card->module = module;
248         INIT_LIST_HEAD(&card->devices);
249         init_rwsem(&card->controls_rwsem);
250         rwlock_init(&card->ctl_files_rwlock);
251         mutex_init(&card->user_ctl_lock);
252         INIT_LIST_HEAD(&card->controls);
253         INIT_LIST_HEAD(&card->ctl_files);
254         spin_lock_init(&card->files_lock);
255         INIT_LIST_HEAD(&card->files_list);
256 #ifdef CONFIG_PM
257         mutex_init(&card->power_lock);
258         init_waitqueue_head(&card->power_sleep);
259 #endif
260 
261         device_initialize(&card->card_dev);
262         card->card_dev.parent = parent;
263         card->card_dev.class = sound_class;
264         card->card_dev.release = release_card_device;
265         card->card_dev.groups = card->dev_groups;
266         card->dev_groups[0] = &card_dev_attr_group;
267         err = kobject_set_name(&card->card_dev.kobj, "card%d", idx);
268         if (err < 0)
269                 goto __error;
270 
271         /* the control interface cannot be accessed from the user space until */
272         /* snd_cards_bitmask and snd_cards are set with snd_card_register */
273         err = snd_ctl_create(card);
274         if (err < 0) {
275                 dev_err(parent, "unable to register control minors\n");
276                 goto __error;
277         }
278         err = snd_info_card_create(card);
279         if (err < 0) {
280                 dev_err(parent, "unable to create card info\n");
281                 goto __error_ctl;
282         }
283         *card_ret = card;
284         return 0;
285 
286       __error_ctl:
287         snd_device_free_all(card);
288       __error:
289         put_device(&card->card_dev);
290         return err;
291 }
292 EXPORT_SYMBOL(snd_card_new);
293 
294 /* return non-zero if a card is already locked */
295 int snd_card_locked(int card)
296 {
297         int locked;
298 
299         mutex_lock(&snd_card_mutex);
300         locked = test_bit(card, snd_cards_lock);
301         mutex_unlock(&snd_card_mutex);
302         return locked;
303 }
304 
305 static loff_t snd_disconnect_llseek(struct file *file, loff_t offset, int orig)
306 {
307         return -ENODEV;
308 }
309 
310 static ssize_t snd_disconnect_read(struct file *file, char __user *buf,
311                                    size_t count, loff_t *offset)
312 {
313         return -ENODEV;
314 }
315 
316 static ssize_t snd_disconnect_write(struct file *file, const char __user *buf,
317                                     size_t count, loff_t *offset)
318 {
319         return -ENODEV;
320 }
321 
322 static int snd_disconnect_release(struct inode *inode, struct file *file)
323 {
324         struct snd_monitor_file *df = NULL, *_df;
325 
326         spin_lock(&shutdown_lock);
327         list_for_each_entry(_df, &shutdown_files, shutdown_list) {
328                 if (_df->file == file) {
329                         df = _df;
330                         list_del_init(&df->shutdown_list);
331                         break;
332                 }
333         }
334         spin_unlock(&shutdown_lock);
335 
336         if (likely(df)) {
337                 if ((file->f_flags & FASYNC) && df->disconnected_f_op->fasync)
338                         df->disconnected_f_op->fasync(-1, file, 0);
339                 return df->disconnected_f_op->release(inode, file);
340         }
341 
342         panic("%s(%p, %p) failed!", __func__, inode, file);
343 }
344 
345 static unsigned int snd_disconnect_poll(struct file * file, poll_table * wait)
346 {
347         return POLLERR | POLLNVAL;
348 }
349 
350 static long snd_disconnect_ioctl(struct file *file,
351                                  unsigned int cmd, unsigned long arg)
352 {
353         return -ENODEV;
354 }
355 
356 static int snd_disconnect_mmap(struct file *file, struct vm_area_struct *vma)
357 {
358         return -ENODEV;
359 }
360 
361 static int snd_disconnect_fasync(int fd, struct file *file, int on)
362 {
363         return -ENODEV;
364 }
365 
366 static const struct file_operations snd_shutdown_f_ops =
367 {
368         .owner =        THIS_MODULE,
369         .llseek =       snd_disconnect_llseek,
370         .read =         snd_disconnect_read,
371         .write =        snd_disconnect_write,
372         .release =      snd_disconnect_release,
373         .poll =         snd_disconnect_poll,
374         .unlocked_ioctl = snd_disconnect_ioctl,
375 #ifdef CONFIG_COMPAT
376         .compat_ioctl = snd_disconnect_ioctl,
377 #endif
378         .mmap =         snd_disconnect_mmap,
379         .fasync =       snd_disconnect_fasync
380 };
381 
382 /**
383  *  snd_card_disconnect - disconnect all APIs from the file-operations (user space)
384  *  @card: soundcard structure
385  *
386  *  Disconnects all APIs from the file-operations (user space).
387  *
388  *  Return: Zero, otherwise a negative error code.
389  *
390  *  Note: The current implementation replaces all active file->f_op with special
391  *        dummy file operations (they do nothing except release).
392  */
393 int snd_card_disconnect(struct snd_card *card)
394 {
395         struct snd_monitor_file *mfile;
396 
397         if (!card)
398                 return -EINVAL;
399 
400         spin_lock(&card->files_lock);
401         if (card->shutdown) {
402                 spin_unlock(&card->files_lock);
403                 return 0;
404         }
405         card->shutdown = 1;
406         spin_unlock(&card->files_lock);
407 
408         /* phase 1: disable fops (user space) operations for ALSA API */
409         mutex_lock(&snd_card_mutex);
410         snd_cards[card->number] = NULL;
411         clear_bit(card->number, snd_cards_lock);
412         mutex_unlock(&snd_card_mutex);
413         
414         /* phase 2: replace file->f_op with special dummy operations */
415         
416         spin_lock(&card->files_lock);
417         list_for_each_entry(mfile, &card->files_list, list) {
418                 /* it's critical part, use endless loop */
419                 /* we have no room to fail */
420                 mfile->disconnected_f_op = mfile->file->f_op;
421 
422                 spin_lock(&shutdown_lock);
423                 list_add(&mfile->shutdown_list, &shutdown_files);
424                 spin_unlock(&shutdown_lock);
425 
426                 mfile->file->f_op = &snd_shutdown_f_ops;
427                 fops_get(mfile->file->f_op);
428         }
429         spin_unlock(&card->files_lock); 
430 
431         /* phase 3: notify all connected devices about disconnection */
432         /* at this point, they cannot respond to any calls except release() */
433 
434 #if IS_ENABLED(CONFIG_SND_MIXER_OSS)
435         if (snd_mixer_oss_notify_callback)
436                 snd_mixer_oss_notify_callback(card, SND_MIXER_OSS_NOTIFY_DISCONNECT);
437 #endif
438 
439         /* notify all devices that we are disconnected */
440         snd_device_disconnect_all(card);
441 
442         snd_info_card_disconnect(card);
443         if (card->registered) {
444                 device_del(&card->card_dev);
445                 card->registered = false;
446         }
447 #ifdef CONFIG_PM
448         wake_up(&card->power_sleep);
449 #endif
450         return 0;       
451 }
452 
453 EXPORT_SYMBOL(snd_card_disconnect);
454 
455 static int snd_card_do_free(struct snd_card *card)
456 {
457 #if IS_ENABLED(CONFIG_SND_MIXER_OSS)
458         if (snd_mixer_oss_notify_callback)
459                 snd_mixer_oss_notify_callback(card, SND_MIXER_OSS_NOTIFY_FREE);
460 #endif
461         snd_device_free_all(card);
462         if (card->private_free)
463                 card->private_free(card);
464         snd_info_free_entry(card->proc_id);
465         if (snd_info_card_free(card) < 0) {
466                 dev_warn(card->dev, "unable to free card info\n");
467                 /* Not fatal error */
468         }
469         if (card->release_completion)
470                 complete(card->release_completion);
471         kfree(card);
472         return 0;
473 }
474 
475 /**
476  * snd_card_free_when_closed - Disconnect the card, free it later eventually
477  * @card: soundcard structure
478  *
479  * Unlike snd_card_free(), this function doesn't try to release the card
480  * resource immediately, but tries to disconnect at first.  When the card
481  * is still in use, the function returns before freeing the resources.
482  * The card resources will be freed when the refcount gets to zero.
483  */
484 int snd_card_free_when_closed(struct snd_card *card)
485 {
486         int ret = snd_card_disconnect(card);
487         if (ret)
488                 return ret;
489         put_device(&card->card_dev);
490         return 0;
491 }
492 EXPORT_SYMBOL(snd_card_free_when_closed);
493 
494 /**
495  * snd_card_free - frees given soundcard structure
496  * @card: soundcard structure
497  *
498  * This function releases the soundcard structure and the all assigned
499  * devices automatically.  That is, you don't have to release the devices
500  * by yourself.
501  *
502  * This function waits until the all resources are properly released.
503  *
504  * Return: Zero. Frees all associated devices and frees the control
505  * interface associated to given soundcard.
506  */
507 int snd_card_free(struct snd_card *card)
508 {
509         struct completion released;
510         int ret;
511 
512         init_completion(&released);
513         card->release_completion = &released;
514         ret = snd_card_free_when_closed(card);
515         if (ret)
516                 return ret;
517         /* wait, until all devices are ready for the free operation */
518         wait_for_completion(&released);
519         return 0;
520 }
521 EXPORT_SYMBOL(snd_card_free);
522 
523 /* retrieve the last word of shortname or longname */
524 static const char *retrieve_id_from_card_name(const char *name)
525 {
526         const char *spos = name;
527 
528         while (*name) {
529                 if (isspace(*name) && isalnum(name[1]))
530                         spos = name + 1;
531                 name++;
532         }
533         return spos;
534 }
535 
536 /* return true if the given id string doesn't conflict any other card ids */
537 static bool card_id_ok(struct snd_card *card, const char *id)
538 {
539         int i;
540         if (!snd_info_check_reserved_words(id))
541                 return false;
542         for (i = 0; i < snd_ecards_limit; i++) {
543                 if (snd_cards[i] && snd_cards[i] != card &&
544                     !strcmp(snd_cards[i]->id, id))
545                         return false;
546         }
547         return true;
548 }
549 
550 /* copy to card->id only with valid letters from nid */
551 static void copy_valid_id_string(struct snd_card *card, const char *src,
552                                  const char *nid)
553 {
554         char *id = card->id;
555 
556         while (*nid && !isalnum(*nid))
557                 nid++;
558         if (isdigit(*nid))
559                 *id++ = isalpha(*src) ? *src : 'D';
560         while (*nid && (size_t)(id - card->id) < sizeof(card->id) - 1) {
561                 if (isalnum(*nid))
562                         *id++ = *nid;
563                 nid++;
564         }
565         *id = 0;
566 }
567 
568 /* Set card->id from the given string
569  * If the string conflicts with other ids, add a suffix to make it unique.
570  */
571 static void snd_card_set_id_no_lock(struct snd_card *card, const char *src,
572                                     const char *nid)
573 {
574         int len, loops;
575         bool is_default = false;
576         char *id;
577         
578         copy_valid_id_string(card, src, nid);
579         id = card->id;
580 
581  again:
582         /* use "Default" for obviously invalid strings
583          * ("card" conflicts with proc directories)
584          */
585         if (!*id || !strncmp(id, "card", 4)) {
586                 strcpy(id, "Default");
587                 is_default = true;
588         }
589 
590         len = strlen(id);
591         for (loops = 0; loops < SNDRV_CARDS; loops++) {
592                 char *spos;
593                 char sfxstr[5]; /* "_012" */
594                 int sfxlen;
595 
596                 if (card_id_ok(card, id))
597                         return; /* OK */
598 
599                 /* Add _XYZ suffix */
600                 sprintf(sfxstr, "_%X", loops + 1);
601                 sfxlen = strlen(sfxstr);
602                 if (len + sfxlen >= sizeof(card->id))
603                         spos = id + sizeof(card->id) - sfxlen - 1;
604                 else
605                         spos = id + len;
606                 strcpy(spos, sfxstr);
607         }
608         /* fallback to the default id */
609         if (!is_default) {
610                 *id = 0;
611                 goto again;
612         }
613         /* last resort... */
614         dev_err(card->dev, "unable to set card id (%s)\n", id);
615         if (card->proc_root->name)
616                 strlcpy(card->id, card->proc_root->name, sizeof(card->id));
617 }
618 
619 /**
620  *  snd_card_set_id - set card identification name
621  *  @card: soundcard structure
622  *  @nid: new identification string
623  *
624  *  This function sets the card identification and checks for name
625  *  collisions.
626  */
627 void snd_card_set_id(struct snd_card *card, const char *nid)
628 {
629         /* check if user specified own card->id */
630         if (card->id[0] != '\0')
631                 return;
632         mutex_lock(&snd_card_mutex);
633         snd_card_set_id_no_lock(card, nid, nid);
634         mutex_unlock(&snd_card_mutex);
635 }
636 EXPORT_SYMBOL(snd_card_set_id);
637 
638 static ssize_t
639 card_id_show_attr(struct device *dev,
640                   struct device_attribute *attr, char *buf)
641 {
642         struct snd_card *card = container_of(dev, struct snd_card, card_dev);
643         return snprintf(buf, PAGE_SIZE, "%s\n", card->id);
644 }
645 
646 static ssize_t
647 card_id_store_attr(struct device *dev, struct device_attribute *attr,
648                    const char *buf, size_t count)
649 {
650         struct snd_card *card = container_of(dev, struct snd_card, card_dev);
651         char buf1[sizeof(card->id)];
652         size_t copy = count > sizeof(card->id) - 1 ?
653                                         sizeof(card->id) - 1 : count;
654         size_t idx;
655         int c;
656 
657         for (idx = 0; idx < copy; idx++) {
658                 c = buf[idx];
659                 if (!isalnum(c) && c != '_' && c != '-')
660                         return -EINVAL;
661         }
662         memcpy(buf1, buf, copy);
663         buf1[copy] = '\0';
664         mutex_lock(&snd_card_mutex);
665         if (!card_id_ok(NULL, buf1)) {
666                 mutex_unlock(&snd_card_mutex);
667                 return -EEXIST;
668         }
669         strcpy(card->id, buf1);
670         snd_info_card_id_change(card);
671         mutex_unlock(&snd_card_mutex);
672 
673         return count;
674 }
675 
676 static DEVICE_ATTR(id, S_IRUGO | S_IWUSR, card_id_show_attr, card_id_store_attr);
677 
678 static ssize_t
679 card_number_show_attr(struct device *dev,
680                      struct device_attribute *attr, char *buf)
681 {
682         struct snd_card *card = container_of(dev, struct snd_card, card_dev);
683         return snprintf(buf, PAGE_SIZE, "%i\n", card->number);
684 }
685 
686 static DEVICE_ATTR(number, S_IRUGO, card_number_show_attr, NULL);
687 
688 static struct attribute *card_dev_attrs[] = {
689         &dev_attr_id.attr,
690         &dev_attr_number.attr,
691         NULL
692 };
693 
694 static const struct attribute_group card_dev_attr_group = {
695         .attrs  = card_dev_attrs,
696 };
697 
698 /**
699  * snd_card_add_dev_attr - Append a new sysfs attribute group to card
700  * @card: card instance
701  * @group: attribute group to append
702  */
703 int snd_card_add_dev_attr(struct snd_card *card,
704                           const struct attribute_group *group)
705 {
706         int i;
707 
708         /* loop for (arraysize-1) here to keep NULL at the last entry */
709         for (i = 0; i < ARRAY_SIZE(card->dev_groups) - 1; i++) {
710                 if (!card->dev_groups[i]) {
711                         card->dev_groups[i] = group;
712                         return 0;
713                 }
714         }
715 
716         dev_err(card->dev, "Too many groups assigned\n");
717         return -ENOSPC;
718 };
719 EXPORT_SYMBOL_GPL(snd_card_add_dev_attr);
720 
721 /**
722  *  snd_card_register - register the soundcard
723  *  @card: soundcard structure
724  *
725  *  This function registers all the devices assigned to the soundcard.
726  *  Until calling this, the ALSA control interface is blocked from the
727  *  external accesses.  Thus, you should call this function at the end
728  *  of the initialization of the card.
729  *
730  *  Return: Zero otherwise a negative error code if the registration failed.
731  */
732 int snd_card_register(struct snd_card *card)
733 {
734         int err;
735 
736         if (snd_BUG_ON(!card))
737                 return -EINVAL;
738 
739         if (!card->registered) {
740                 err = device_add(&card->card_dev);
741                 if (err < 0)
742                         return err;
743                 card->registered = true;
744         }
745 
746         if ((err = snd_device_register_all(card)) < 0)
747                 return err;
748         mutex_lock(&snd_card_mutex);
749         if (snd_cards[card->number]) {
750                 /* already registered */
751                 mutex_unlock(&snd_card_mutex);
752                 return snd_info_card_register(card); /* register pending info */
753         }
754         if (*card->id) {
755                 /* make a unique id name from the given string */
756                 char tmpid[sizeof(card->id)];
757                 memcpy(tmpid, card->id, sizeof(card->id));
758                 snd_card_set_id_no_lock(card, tmpid, tmpid);
759         } else {
760                 /* create an id from either shortname or longname */
761                 const char *src;
762                 src = *card->shortname ? card->shortname : card->longname;
763                 snd_card_set_id_no_lock(card, src,
764                                         retrieve_id_from_card_name(src));
765         }
766         snd_cards[card->number] = card;
767         mutex_unlock(&snd_card_mutex);
768         init_info_for_card(card);
769 #if IS_ENABLED(CONFIG_SND_MIXER_OSS)
770         if (snd_mixer_oss_notify_callback)
771                 snd_mixer_oss_notify_callback(card, SND_MIXER_OSS_NOTIFY_REGISTER);
772 #endif
773         return 0;
774 }
775 
776 EXPORT_SYMBOL(snd_card_register);
777 
778 #ifdef CONFIG_SND_PROC_FS
779 static void snd_card_info_read(struct snd_info_entry *entry,
780                                struct snd_info_buffer *buffer)
781 {
782         int idx, count;
783         struct snd_card *card;
784 
785         for (idx = count = 0; idx < SNDRV_CARDS; idx++) {
786                 mutex_lock(&snd_card_mutex);
787                 if ((card = snd_cards[idx]) != NULL) {
788                         count++;
789                         snd_iprintf(buffer, "%2i [%-15s]: %s - %s\n",
790                                         idx,
791                                         card->id,
792                                         card->driver,
793                                         card->shortname);
794                         snd_iprintf(buffer, "                      %s\n",
795                                         card->longname);
796                 }
797                 mutex_unlock(&snd_card_mutex);
798         }
799         if (!count)
800                 snd_iprintf(buffer, "--- no soundcards ---\n");
801 }
802 
803 #ifdef CONFIG_SND_OSSEMUL
804 void snd_card_info_read_oss(struct snd_info_buffer *buffer)
805 {
806         int idx, count;
807         struct snd_card *card;
808 
809         for (idx = count = 0; idx < SNDRV_CARDS; idx++) {
810                 mutex_lock(&snd_card_mutex);
811                 if ((card = snd_cards[idx]) != NULL) {
812                         count++;
813                         snd_iprintf(buffer, "%s\n", card->longname);
814                 }
815                 mutex_unlock(&snd_card_mutex);
816         }
817         if (!count) {
818                 snd_iprintf(buffer, "--- no soundcards ---\n");
819         }
820 }
821 
822 #endif
823 
824 #ifdef MODULE
825 static void snd_card_module_info_read(struct snd_info_entry *entry,
826                                       struct snd_info_buffer *buffer)
827 {
828         int idx;
829         struct snd_card *card;
830 
831         for (idx = 0; idx < SNDRV_CARDS; idx++) {
832                 mutex_lock(&snd_card_mutex);
833                 if ((card = snd_cards[idx]) != NULL)
834                         snd_iprintf(buffer, "%2i %s\n",
835                                     idx, card->module->name);
836                 mutex_unlock(&snd_card_mutex);
837         }
838 }
839 #endif
840 
841 int __init snd_card_info_init(void)
842 {
843         struct snd_info_entry *entry;
844 
845         entry = snd_info_create_module_entry(THIS_MODULE, "cards", NULL);
846         if (! entry)
847                 return -ENOMEM;
848         entry->c.text.read = snd_card_info_read;
849         if (snd_info_register(entry) < 0)
850                 return -ENOMEM; /* freed in error path */
851 
852 #ifdef MODULE
853         entry = snd_info_create_module_entry(THIS_MODULE, "modules", NULL);
854         if (!entry)
855                 return -ENOMEM;
856         entry->c.text.read = snd_card_module_info_read;
857         if (snd_info_register(entry) < 0)
858                 return -ENOMEM; /* freed in error path */
859 #endif
860 
861         return 0;
862 }
863 #endif /* CONFIG_SND_PROC_FS */
864 
865 /**
866  *  snd_component_add - add a component string
867  *  @card: soundcard structure
868  *  @component: the component id string
869  *
870  *  This function adds the component id string to the supported list.
871  *  The component can be referred from the alsa-lib.
872  *
873  *  Return: Zero otherwise a negative error code.
874  */
875   
876 int snd_component_add(struct snd_card *card, const char *component)
877 {
878         char *ptr;
879         int len = strlen(component);
880 
881         ptr = strstr(card->components, component);
882         if (ptr != NULL) {
883                 if (ptr[len] == '\0' || ptr[len] == ' ')        /* already there */
884                         return 1;
885         }
886         if (strlen(card->components) + 1 + len + 1 > sizeof(card->components)) {
887                 snd_BUG();
888                 return -ENOMEM;
889         }
890         if (card->components[0] != '\0')
891                 strcat(card->components, " ");
892         strcat(card->components, component);
893         return 0;
894 }
895 
896 EXPORT_SYMBOL(snd_component_add);
897 
898 /**
899  *  snd_card_file_add - add the file to the file list of the card
900  *  @card: soundcard structure
901  *  @file: file pointer
902  *
903  *  This function adds the file to the file linked-list of the card.
904  *  This linked-list is used to keep tracking the connection state,
905  *  and to avoid the release of busy resources by hotplug.
906  *
907  *  Return: zero or a negative error code.
908  */
909 int snd_card_file_add(struct snd_card *card, struct file *file)
910 {
911         struct snd_monitor_file *mfile;
912 
913         mfile = kmalloc(sizeof(*mfile), GFP_KERNEL);
914         if (mfile == NULL)
915                 return -ENOMEM;
916         mfile->file = file;
917         mfile->disconnected_f_op = NULL;
918         INIT_LIST_HEAD(&mfile->shutdown_list);
919         spin_lock(&card->files_lock);
920         if (card->shutdown) {
921                 spin_unlock(&card->files_lock);
922                 kfree(mfile);
923                 return -ENODEV;
924         }
925         list_add(&mfile->list, &card->files_list);
926         get_device(&card->card_dev);
927         spin_unlock(&card->files_lock);
928         return 0;
929 }
930 
931 EXPORT_SYMBOL(snd_card_file_add);
932 
933 /**
934  *  snd_card_file_remove - remove the file from the file list
935  *  @card: soundcard structure
936  *  @file: file pointer
937  *
938  *  This function removes the file formerly added to the card via
939  *  snd_card_file_add() function.
940  *  If all files are removed and snd_card_free_when_closed() was
941  *  called beforehand, it processes the pending release of
942  *  resources.
943  *
944  *  Return: Zero or a negative error code.
945  */
946 int snd_card_file_remove(struct snd_card *card, struct file *file)
947 {
948         struct snd_monitor_file *mfile, *found = NULL;
949 
950         spin_lock(&card->files_lock);
951         list_for_each_entry(mfile, &card->files_list, list) {
952                 if (mfile->file == file) {
953                         list_del(&mfile->list);
954                         spin_lock(&shutdown_lock);
955                         list_del(&mfile->shutdown_list);
956                         spin_unlock(&shutdown_lock);
957                         if (mfile->disconnected_f_op)
958                                 fops_put(mfile->disconnected_f_op);
959                         found = mfile;
960                         break;
961                 }
962         }
963         spin_unlock(&card->files_lock);
964         if (!found) {
965                 dev_err(card->dev, "card file remove problem (%p)\n", file);
966                 return -ENOENT;
967         }
968         kfree(found);
969         put_device(&card->card_dev);
970         return 0;
971 }
972 
973 EXPORT_SYMBOL(snd_card_file_remove);
974 
975 #ifdef CONFIG_PM
976 /**
977  *  snd_power_wait - wait until the power-state is changed.
978  *  @card: soundcard structure
979  *  @power_state: expected power state
980  *
981  *  Waits until the power-state is changed.
982  *
983  *  Return: Zero if successful, or a negative error code.
984  *
985  *  Note: the power lock must be active before call.
986  */
987 int snd_power_wait(struct snd_card *card, unsigned int power_state)
988 {
989         wait_queue_t wait;
990         int result = 0;
991 
992         /* fastpath */
993         if (snd_power_get_state(card) == power_state)
994                 return 0;
995         init_waitqueue_entry(&wait, current);
996         add_wait_queue(&card->power_sleep, &wait);
997         while (1) {
998                 if (card->shutdown) {
999                         result = -ENODEV;
1000                         break;
1001                 }
1002                 if (snd_power_get_state(card) == power_state)
1003                         break;
1004                 set_current_state(TASK_UNINTERRUPTIBLE);
1005                 snd_power_unlock(card);
1006                 schedule_timeout(30 * HZ);
1007                 snd_power_lock(card);
1008         }
1009         remove_wait_queue(&card->power_sleep, &wait);
1010         return result;
1011 }
1012 
1013 EXPORT_SYMBOL(snd_power_wait);
1014 #endif /* CONFIG_PM */
1015 

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