Free Electrons

Embedded Linux Experts

   1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 110
 111
 112
 113
 114
 115
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129
 130
 131
 132
 133
 134
 135
 136
 137
 138
 139
 140
 141
 142
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 153
 154
 155
 156
 157
 158
 159
 160
 161
 162
 163
 164
 165
 166
 167
 168
 169
 170
 171
 172
 173
 174
 175
 176
 177
 178
 179
 180
 181
 182
 183
 184
 185
 186
 187
 188
 189
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 223
 224
 225
 226
 227
 228
 229
 230
 231
 232
 233
 234
 235
 236
 237
 238
 239
 240
 241
 242
 243
 244
 245
 246
 247
 248
 249
 250
 251
 252
 253
 254
 255
 256
 257
 258
 259
 260
 261
 262
 263
 264
 265
 266
 267
 268
 269
 270
 271
 272
 273
 274
 275
 276
 277
 278
 279
 280
 281
 282
 283
 284
 285
 286
 287
 288
 289
 290
 291
 292
 293
 294
 295
 296
 297
 298
 299
 300
 301
 302
 303
 304
 305
 306
 307
 308
 309
 310
 311
 312
 313
 314
 315
 316
 317
 318
 319
 320
 321
 322
 323
 324
 325
 326
 327
 328
 329
 330
 331
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341
 342
 343
 344
 345
 346
 347
 348
 349
 350
 351
 352
 353
 354
 355
 356
 357
 358
 359
 360
 361
 362
 363
 364
 365
 366
 367
 368
 369
 370
 371
 372
 373
 374
 375
 376
 377
 378
 379
 380
 381
 382
 383
 384
 385
 386
 387
 388
 389
 390
 391
 392
 393
 394
 395
 396
 397
 398
 399
 400
 401
 402
 403
 404
 405
 406
 407
 408
 409
 410
 411
 412
 413
 414
 415
 416
 417
 418
 419
 420
 421
 422
 423
 424
 425
 426
 427
 428
 429
 430
 431
 432
 433
 434
 435
 436
 437
 438
 439
 440
 441
 442
 443
 444
 445
 446
 447
 448
 449
 450
 451
 452
 453
 454
 455
 456
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
/*
 *  Initialization routines
 *  Copyright (c) by Jaroslav Kysela <perex@perex.cz>
 *
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 *
 */

#include <linux/init.h>
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/file.h>
#include <linux/slab.h>
#include <linux/time.h>
#include <linux/ctype.h>
#include <linux/pm.h>
#include <linux/completion.h>

#include <sound/core.h>
#include <sound/control.h>
#include <sound/info.h>

/* monitor files for graceful shutdown (hotplug) */
struct snd_monitor_file {
	struct file *file;
	const struct file_operations *disconnected_f_op;
	struct list_head shutdown_list;	/* still need to shutdown */
	struct list_head list;	/* link of monitor files */
};

static DEFINE_SPINLOCK(shutdown_lock);
static LIST_HEAD(shutdown_files);

static const struct file_operations snd_shutdown_f_ops;

/* locked for registering/using */
static DECLARE_BITMAP(snd_cards_lock, SNDRV_CARDS);
struct snd_card *snd_cards[SNDRV_CARDS];
EXPORT_SYMBOL(snd_cards);

static DEFINE_MUTEX(snd_card_mutex);

static char *slots[SNDRV_CARDS];
module_param_array(slots, charp, NULL, 0444);
MODULE_PARM_DESC(slots, "Module names assigned to the slots.");

/* return non-zero if the given index is reserved for the given
 * module via slots option
 */
static int module_slot_match(struct module *module, int idx)
{
	int match = 1;
#ifdef MODULE
	const char *s1, *s2;

	if (!module || !*module->name || !slots[idx])
		return 0;

	s1 = module->name;
	s2 = slots[idx];
	if (*s2 == '!') {
		match = 0; /* negative match */
		s2++;
	}
	/* compare module name strings
	 * hyphens are handled as equivalent with underscore
	 */
	for (;;) {
		char c1 = *s1++;
		char c2 = *s2++;
		if (c1 == '-')
			c1 = '_';
		if (c2 == '-')
			c2 = '_';
		if (c1 != c2)
			return !match;
		if (!c1)
			break;
	}
#endif /* MODULE */
	return match;
}

#if IS_ENABLED(CONFIG_SND_MIXER_OSS)
int (*snd_mixer_oss_notify_callback)(struct snd_card *card, int free_flag);
EXPORT_SYMBOL(snd_mixer_oss_notify_callback);
#endif

#ifdef CONFIG_SND_PROC_FS
static void snd_card_id_read(struct snd_info_entry *entry,
			     struct snd_info_buffer *buffer)
{
	snd_iprintf(buffer, "%s\n", entry->card->id);
}

static int init_info_for_card(struct snd_card *card)
{
	struct snd_info_entry *entry;

	entry = snd_info_create_card_entry(card, "id", card->proc_root);
	if (!entry) {
		dev_dbg(card->dev, "unable to create card entry\n");
		return -ENOMEM;
	}
	entry->c.text.read = snd_card_id_read;
	card->proc_id = entry;

	return snd_info_card_register(card);
}
#else /* !CONFIG_SND_PROC_FS */
#define init_info_for_card(card)
#endif

static int check_empty_slot(struct module *module, int slot)
{
	return !slots[slot] || !*slots[slot];
}

/* return an empty slot number (>= 0) found in the given bitmask @mask.
 * @mask == -1 == 0xffffffff means: take any free slot up to 32
 * when no slot is available, return the original @mask as is.
 */
static int get_slot_from_bitmask(int mask, int (*check)(struct module *, int),
				 struct module *module)
{
	int slot;

	for (slot = 0; slot < SNDRV_CARDS; slot++) {
		if (slot < 32 && !(mask & (1U << slot)))
			continue;
		if (!test_bit(slot, snd_cards_lock)) {
			if (check(module, slot))
				return slot; /* found */
		}
	}
	return mask; /* unchanged */
}

/* the default release callback set in snd_device_initialize() below;
 * this is just NOP for now, as almost all jobs are already done in
 * dev_free callback of snd_device chain instead.
 */
static void default_release(struct device *dev)
{
}

/**
 * snd_device_initialize - Initialize struct device for sound devices
 * @dev: device to initialize
 * @card: card to assign, optional
 */
void snd_device_initialize(struct device *dev, struct snd_card *card)
{
	device_initialize(dev);
	if (card)
		dev->parent = &card->card_dev;
	dev->class = sound_class;
	dev->release = default_release;
}
EXPORT_SYMBOL_GPL(snd_device_initialize);

static int snd_card_do_free(struct snd_card *card);
static const struct attribute_group card_dev_attr_group;

static void release_card_device(struct device *dev)
{
	snd_card_do_free(dev_to_snd_card(dev));
}

/**
 *  snd_card_new - create and initialize a soundcard structure
 *  @parent: the parent device object
 *  @idx: card index (address) [0 ... (SNDRV_CARDS-1)]
 *  @xid: card identification (ASCII string)
 *  @module: top level module for locking
 *  @extra_size: allocate this extra size after the main soundcard structure
 *  @card_ret: the pointer to store the created card instance
 *
 *  Creates and initializes a soundcard structure.
 *
 *  The function allocates snd_card instance via kzalloc with the given
 *  space for the driver to use freely.  The allocated struct is stored
 *  in the given card_ret pointer.
 *
 *  Return: Zero if successful or a negative error code.
 */
int snd_card_new(struct device *parent, int idx, const char *xid,
		    struct module *module, int extra_size,
		    struct snd_card **card_ret)
{
	struct snd_card *card;
	int err;

	if (snd_BUG_ON(!card_ret))
		return -EINVAL;
	*card_ret = NULL;

	if (extra_size < 0)
		extra_size = 0;
	card = kzalloc(sizeof(*card) + extra_size, GFP_KERNEL);
	if (!card)
		return -ENOMEM;
	if (extra_size > 0)
		card->private_data = (char *)card + sizeof(struct snd_card);
	if (xid)
		strlcpy(card->id, xid, sizeof(card->id));
	err = 0;
	mutex_lock(&snd_card_mutex);
	if (idx < 0) /* first check the matching module-name slot */
		idx = get_slot_from_bitmask(idx, module_slot_match, module);
	if (idx < 0) /* if not matched, assign an empty slot */
		idx = get_slot_from_bitmask(idx, check_empty_slot, module);
	if (idx < 0)
		err = -ENODEV;
	else if (idx < snd_ecards_limit) {
		if (test_bit(idx, snd_cards_lock))
			err = -EBUSY;	/* invalid */
	} else if (idx >= SNDRV_CARDS)
		err = -ENODEV;
	if (err < 0) {
		mutex_unlock(&snd_card_mutex);
		dev_err(parent, "cannot find the slot for index %d (range 0-%i), error: %d\n",
			 idx, snd_ecards_limit - 1, err);
		kfree(card);
		return err;
	}
	set_bit(idx, snd_cards_lock);		/* lock it */
	if (idx >= snd_ecards_limit)
		snd_ecards_limit = idx + 1; /* increase the limit */
	mutex_unlock(&snd_card_mutex);
	card->dev = parent;
	card->number = idx;
	card->module = module;
	INIT_LIST_HEAD(&card->devices);
	init_rwsem(&card->controls_rwsem);
	rwlock_init(&card->ctl_files_rwlock);
	INIT_LIST_HEAD(&card->controls);
	INIT_LIST_HEAD(&card->ctl_files);
	spin_lock_init(&card->files_lock);
	INIT_LIST_HEAD(&card->files_list);
#ifdef CONFIG_PM
	init_waitqueue_head(&card->power_sleep);
#endif

	device_initialize(&card->card_dev);
	card->card_dev.parent = parent;
	card->card_dev.class = sound_class;
	card->card_dev.release = release_card_device;
	card->card_dev.groups = card->dev_groups;
	card->dev_groups[0] = &card_dev_attr_group;
	err = kobject_set_name(&card->card_dev.kobj, "card%d", idx);
	if (err < 0)
		goto __error;

	snprintf(card->irq_descr, sizeof(card->irq_descr), "%s:%s",
		 dev_driver_string(card->dev), dev_name(&card->card_dev));

	/* the control interface cannot be accessed from the user space until */
	/* snd_cards_bitmask and snd_cards are set with snd_card_register */
	err = snd_ctl_create(card);
	if (err < 0) {
		dev_err(parent, "unable to register control minors\n");
		goto __error;
	}
	err = snd_info_card_create(card);
	if (err < 0) {
		dev_err(parent, "unable to create card info\n");
		goto __error_ctl;
	}
	*card_ret = card;
	return 0;

      __error_ctl:
	snd_device_free_all(card);
      __error:
	put_device(&card->card_dev);
  	return err;
}
EXPORT_SYMBOL(snd_card_new);

/* return non-zero if a card is already locked */
int snd_card_locked(int card)
{
	int locked;

	mutex_lock(&snd_card_mutex);
	locked = test_bit(card, snd_cards_lock);
	mutex_unlock(&snd_card_mutex);
	return locked;
}

static loff_t snd_disconnect_llseek(struct file *file, loff_t offset, int orig)
{
	return -ENODEV;
}

static ssize_t snd_disconnect_read(struct file *file, char __user *buf,
				   size_t count, loff_t *offset)
{
	return -ENODEV;
}

static ssize_t snd_disconnect_write(struct file *file, const char __user *buf,
				    size_t count, loff_t *offset)
{
	return -ENODEV;
}

static int snd_disconnect_release(struct inode *inode, struct file *file)
{
	struct snd_monitor_file *df = NULL, *_df;

	spin_lock(&shutdown_lock);
	list_for_each_entry(_df, &shutdown_files, shutdown_list) {
		if (_df->file == file) {
			df = _df;
			list_del_init(&df->shutdown_list);
			break;
		}
	}
	spin_unlock(&shutdown_lock);

	if (likely(df)) {
		if ((file->f_flags & FASYNC) && df->disconnected_f_op->fasync)
			df->disconnected_f_op->fasync(-1, file, 0);
		return df->disconnected_f_op->release(inode, file);
	}

	panic("%s(%p, %p) failed!", __func__, inode, file);
}

static unsigned int snd_disconnect_poll(struct file * file, poll_table * wait)
{
	return POLLERR | POLLNVAL;
}

static long snd_disconnect_ioctl(struct file *file,
				 unsigned int cmd, unsigned long arg)
{
	return -ENODEV;
}

static int snd_disconnect_mmap(struct file *file, struct vm_area_struct *vma)
{
	return -ENODEV;
}

static int snd_disconnect_fasync(int fd, struct file *file, int on)
{
	return -ENODEV;
}

static const struct file_operations snd_shutdown_f_ops =
{
	.owner = 	THIS_MODULE,
	.llseek =	snd_disconnect_llseek,
	.read = 	snd_disconnect_read,
	.write =	snd_disconnect_write,
	.release =	snd_disconnect_release,
	.poll =		snd_disconnect_poll,
	.unlocked_ioctl = snd_disconnect_ioctl,
#ifdef CONFIG_COMPAT
	.compat_ioctl = snd_disconnect_ioctl,
#endif
	.mmap =		snd_disconnect_mmap,
	.fasync =	snd_disconnect_fasync
};

/**
 *  snd_card_disconnect - disconnect all APIs from the file-operations (user space)
 *  @card: soundcard structure
 *
 *  Disconnects all APIs from the file-operations (user space).
 *
 *  Return: Zero, otherwise a negative error code.
 *
 *  Note: The current implementation replaces all active file->f_op with special
 *        dummy file operations (they do nothing except release).
 */
int snd_card_disconnect(struct snd_card *card)
{
	struct snd_monitor_file *mfile;

	if (!card)
		return -EINVAL;

	spin_lock(&card->files_lock);
	if (card->shutdown) {
		spin_unlock(&card->files_lock);
		return 0;
	}
	card->shutdown = 1;
	spin_unlock(&card->files_lock);

	/* phase 1: disable fops (user space) operations for ALSA API */
	mutex_lock(&snd_card_mutex);
	snd_cards[card->number] = NULL;
	clear_bit(card->number, snd_cards_lock);
	mutex_unlock(&snd_card_mutex);
	
	/* phase 2: replace file->f_op with special dummy operations */
	
	spin_lock(&card->files_lock);
	list_for_each_entry(mfile, &card->files_list, list) {
		/* it's critical part, use endless loop */
		/* we have no room to fail */
		mfile->disconnected_f_op = mfile->file->f_op;

		spin_lock(&shutdown_lock);
		list_add(&mfile->shutdown_list, &shutdown_files);
		spin_unlock(&shutdown_lock);

		mfile->file->f_op = &snd_shutdown_f_ops;
		fops_get(mfile->file->f_op);
	}
	spin_unlock(&card->files_lock);	

	/* phase 3: notify all connected devices about disconnection */
	/* at this point, they cannot respond to any calls except release() */

#if IS_ENABLED(CONFIG_SND_MIXER_OSS)
	if (snd_mixer_oss_notify_callback)
		snd_mixer_oss_notify_callback(card, SND_MIXER_OSS_NOTIFY_DISCONNECT);
#endif

	/* notify all devices that we are disconnected */
	snd_device_disconnect_all(card);

	snd_info_card_disconnect(card);
	if (card->registered) {
		device_del(&card->card_dev);
		card->registered = false;
	}
#ifdef CONFIG_PM
	wake_up(&card->power_sleep);
#endif
	return 0;	
}
EXPORT_SYMBOL(snd_card_disconnect);

static int snd_card_do_free(struct snd_card *card)
{
#if IS_ENABLED(CONFIG_SND_MIXER_OSS)
	if (snd_mixer_oss_notify_callback)
		snd_mixer_oss_notify_callback(card, SND_MIXER_OSS_NOTIFY_FREE);
#endif
	snd_device_free_all(card);
	if (card->private_free)
		card->private_free(card);
	snd_info_free_entry(card->proc_id);
	if (snd_info_card_free(card) < 0) {
		dev_warn(card->dev, "unable to free card info\n");
		/* Not fatal error */
	}
	if (card->release_completion)
		complete(card->release_completion);
	kfree(card);
	return 0;
}

/**
 * snd_card_free_when_closed - Disconnect the card, free it later eventually
 * @card: soundcard structure
 *
 * Unlike snd_card_free(), this function doesn't try to release the card
 * resource immediately, but tries to disconnect at first.  When the card
 * is still in use, the function returns before freeing the resources.
 * The card resources will be freed when the refcount gets to zero.
 */
int snd_card_free_when_closed(struct snd_card *card)
{
	int ret = snd_card_disconnect(card);
	if (ret)
		return ret;
	put_device(&card->card_dev);
	return 0;
}
EXPORT_SYMBOL(snd_card_free_when_closed);

/**
 * snd_card_free - frees given soundcard structure
 * @card: soundcard structure
 *
 * This function releases the soundcard structure and the all assigned
 * devices automatically.  That is, you don't have to release the devices
 * by yourself.
 *
 * This function waits until the all resources are properly released.
 *
 * Return: Zero. Frees all associated devices and frees the control
 * interface associated to given soundcard.
 */
int snd_card_free(struct snd_card *card)
{
	struct completion released;
	int ret;

	init_completion(&released);
	card->release_completion = &released;
	ret = snd_card_free_when_closed(card);
	if (ret)
		return ret;
	/* wait, until all devices are ready for the free operation */
	wait_for_completion(&released);
	return 0;
}
EXPORT_SYMBOL(snd_card_free);

/* retrieve the last word of shortname or longname */
static const char *retrieve_id_from_card_name(const char *name)
{
	const char *spos = name;

	while (*name) {
		if (isspace(*name) && isalnum(name[1]))
			spos = name + 1;
		name++;
	}
	return spos;
}

/* return true if the given id string doesn't conflict any other card ids */
static bool card_id_ok(struct snd_card *card, const char *id)
{
	int i;
	if (!snd_info_check_reserved_words(id))
		return false;
	for (i = 0; i < snd_ecards_limit; i++) {
		if (snd_cards[i] && snd_cards[i] != card &&
		    !strcmp(snd_cards[i]->id, id))
			return false;
	}
	return true;
}

/* copy to card->id only with valid letters from nid */
static void copy_valid_id_string(struct snd_card *card, const char *src,
				 const char *nid)
{
	char *id = card->id;

	while (*nid && !isalnum(*nid))
		nid++;
	if (isdigit(*nid))
		*id++ = isalpha(*src) ? *src : 'D';
	while (*nid && (size_t)(id - card->id) < sizeof(card->id) - 1) {
		if (isalnum(*nid))
			*id++ = *nid;
		nid++;
	}
	*id = 0;
}

/* Set card->id from the given string
 * If the string conflicts with other ids, add a suffix to make it unique.
 */
static void snd_card_set_id_no_lock(struct snd_card *card, const char *src,
				    const char *nid)
{
	int len, loops;
	bool is_default = false;
	char *id;
	
	copy_valid_id_string(card, src, nid);
	id = card->id;

 again:
	/* use "Default" for obviously invalid strings
	 * ("card" conflicts with proc directories)
	 */
	if (!*id || !strncmp(id, "card", 4)) {
		strcpy(id, "Default");
		is_default = true;
	}

	len = strlen(id);
	for (loops = 0; loops < SNDRV_CARDS; loops++) {
		char *spos;
		char sfxstr[5]; /* "_012" */
		int sfxlen;

		if (card_id_ok(card, id))
			return; /* OK */

		/* Add _XYZ suffix */
		sprintf(sfxstr, "_%X", loops + 1);
		sfxlen = strlen(sfxstr);
		if (len + sfxlen >= sizeof(card->id))
			spos = id + sizeof(card->id) - sfxlen - 1;
		else
			spos = id + len;
		strcpy(spos, sfxstr);
	}
	/* fallback to the default id */
	if (!is_default) {
		*id = 0;
		goto again;
	}
	/* last resort... */
	dev_err(card->dev, "unable to set card id (%s)\n", id);
	if (card->proc_root->name)
		strlcpy(card->id, card->proc_root->name, sizeof(card->id));
}

/**
 *  snd_card_set_id - set card identification name
 *  @card: soundcard structure
 *  @nid: new identification string
 *
 *  This function sets the card identification and checks for name
 *  collisions.
 */
void snd_card_set_id(struct snd_card *card, const char *nid)
{
	/* check if user specified own card->id */
	if (card->id[0] != '\0')
		return;
	mutex_lock(&snd_card_mutex);
	snd_card_set_id_no_lock(card, nid, nid);
	mutex_unlock(&snd_card_mutex);
}
EXPORT_SYMBOL(snd_card_set_id);

static ssize_t
card_id_show_attr(struct device *dev,
		  struct device_attribute *attr, char *buf)
{
	struct snd_card *card = container_of(dev, struct snd_card, card_dev);
	return snprintf(buf, PAGE_SIZE, "%s\n", card->id);
}

static ssize_t
card_id_store_attr(struct device *dev, struct device_attribute *attr,
		   const char *buf, size_t count)
{
	struct snd_card *card = container_of(dev, struct snd_card, card_dev);
	char buf1[sizeof(card->id)];
	size_t copy = count > sizeof(card->id) - 1 ?
					sizeof(card->id) - 1 : count;
	size_t idx;
	int c;

	for (idx = 0; idx < copy; idx++) {
		c = buf[idx];
		if (!isalnum(c) && c != '_' && c != '-')
			return -EINVAL;
	}
	memcpy(buf1, buf, copy);
	buf1[copy] = '\0';
	mutex_lock(&snd_card_mutex);
	if (!card_id_ok(NULL, buf1)) {
		mutex_unlock(&snd_card_mutex);
		return -EEXIST;
	}
	strcpy(card->id, buf1);
	snd_info_card_id_change(card);
	mutex_unlock(&snd_card_mutex);

	return count;
}

static DEVICE_ATTR(id, S_IRUGO | S_IWUSR, card_id_show_attr, card_id_store_attr);

static ssize_t
card_number_show_attr(struct device *dev,
		     struct device_attribute *attr, char *buf)
{
	struct snd_card *card = container_of(dev, struct snd_card, card_dev);
	return snprintf(buf, PAGE_SIZE, "%i\n", card->number);
}

static DEVICE_ATTR(number, S_IRUGO, card_number_show_attr, NULL);

static struct attribute *card_dev_attrs[] = {
	&dev_attr_id.attr,
	&dev_attr_number.attr,
	NULL
};

static const struct attribute_group card_dev_attr_group = {
	.attrs	= card_dev_attrs,
};

/**
 * snd_card_add_dev_attr - Append a new sysfs attribute group to card
 * @card: card instance
 * @group: attribute group to append
 */
int snd_card_add_dev_attr(struct snd_card *card,
			  const struct attribute_group *group)
{
	int i;

	/* loop for (arraysize-1) here to keep NULL at the last entry */
	for (i = 0; i < ARRAY_SIZE(card->dev_groups) - 1; i++) {
		if (!card->dev_groups[i]) {
			card->dev_groups[i] = group;
			return 0;
		}
	}

	dev_err(card->dev, "Too many groups assigned\n");
	return -ENOSPC;
}
EXPORT_SYMBOL_GPL(snd_card_add_dev_attr);

/**
 *  snd_card_register - register the soundcard
 *  @card: soundcard structure
 *
 *  This function registers all the devices assigned to the soundcard.
 *  Until calling this, the ALSA control interface is blocked from the
 *  external accesses.  Thus, you should call this function at the end
 *  of the initialization of the card.
 *
 *  Return: Zero otherwise a negative error code if the registration failed.
 */
int snd_card_register(struct snd_card *card)
{
	int err;

	if (snd_BUG_ON(!card))
		return -EINVAL;

	if (!card->registered) {
		err = device_add(&card->card_dev);
		if (err < 0)
			return err;
		card->registered = true;
	}

	if ((err = snd_device_register_all(card)) < 0)
		return err;
	mutex_lock(&snd_card_mutex);
	if (snd_cards[card->number]) {
		/* already registered */
		mutex_unlock(&snd_card_mutex);
		return snd_info_card_register(card); /* register pending info */
	}
	if (*card->id) {
		/* make a unique id name from the given string */
		char tmpid[sizeof(card->id)];
		memcpy(tmpid, card->id, sizeof(card->id));
		snd_card_set_id_no_lock(card, tmpid, tmpid);
	} else {
		/* create an id from either shortname or longname */
		const char *src;
		src = *card->shortname ? card->shortname : card->longname;
		snd_card_set_id_no_lock(card, src,
					retrieve_id_from_card_name(src));
	}
	snd_cards[card->number] = card;
	mutex_unlock(&snd_card_mutex);
	init_info_for_card(card);
#if IS_ENABLED(CONFIG_SND_MIXER_OSS)
	if (snd_mixer_oss_notify_callback)
		snd_mixer_oss_notify_callback(card, SND_MIXER_OSS_NOTIFY_REGISTER);
#endif
	return 0;
}
EXPORT_SYMBOL(snd_card_register);

#ifdef CONFIG_SND_PROC_FS
static void snd_card_info_read(struct snd_info_entry *entry,
			       struct snd_info_buffer *buffer)
{
	int idx, count;
	struct snd_card *card;

	for (idx = count = 0; idx < SNDRV_CARDS; idx++) {
		mutex_lock(&snd_card_mutex);
		if ((card = snd_cards[idx]) != NULL) {
			count++;
			snd_iprintf(buffer, "%2i [%-15s]: %s - %s\n",
					idx,
					card->id,
					card->driver,
					card->shortname);
			snd_iprintf(buffer, "                      %s\n",
					card->longname);
		}
		mutex_unlock(&snd_card_mutex);
	}
	if (!count)
		snd_iprintf(buffer, "--- no soundcards ---\n");
}

#ifdef CONFIG_SND_OSSEMUL
void snd_card_info_read_oss(struct snd_info_buffer *buffer)
{
	int idx, count;
	struct snd_card *card;

	for (idx = count = 0; idx < SNDRV_CARDS; idx++) {
		mutex_lock(&snd_card_mutex);
		if ((card = snd_cards[idx]) != NULL) {
			count++;
			snd_iprintf(buffer, "%s\n", card->longname);
		}
		mutex_unlock(&snd_card_mutex);
	}
	if (!count) {
		snd_iprintf(buffer, "--- no soundcards ---\n");
	}
}

#endif

#ifdef MODULE
static void snd_card_module_info_read(struct snd_info_entry *entry,
				      struct snd_info_buffer *buffer)
{
	int idx;
	struct snd_card *card;

	for (idx = 0; idx < SNDRV_CARDS; idx++) {
		mutex_lock(&snd_card_mutex);
		if ((card = snd_cards[idx]) != NULL)
			snd_iprintf(buffer, "%2i %s\n",
				    idx, card->module->name);
		mutex_unlock(&snd_card_mutex);
	}
}
#endif

int __init snd_card_info_init(void)
{
	struct snd_info_entry *entry;

	entry = snd_info_create_module_entry(THIS_MODULE, "cards", NULL);
	if (! entry)
		return -ENOMEM;
	entry->c.text.read = snd_card_info_read;
	if (snd_info_register(entry) < 0)
		return -ENOMEM; /* freed in error path */

#ifdef MODULE
	entry = snd_info_create_module_entry(THIS_MODULE, "modules", NULL);
	if (!entry)
		return -ENOMEM;
	entry->c.text.read = snd_card_module_info_read;
	if (snd_info_register(entry) < 0)
		return -ENOMEM; /* freed in error path */
#endif

	return 0;
}
#endif /* CONFIG_SND_PROC_FS */

/**
 *  snd_component_add - add a component string
 *  @card: soundcard structure
 *  @component: the component id string
 *
 *  This function adds the component id string to the supported list.
 *  The component can be referred from the alsa-lib.
 *
 *  Return: Zero otherwise a negative error code.
 */
  
int snd_component_add(struct snd_card *card, const char *component)
{
	char *ptr;
	int len = strlen(component);

	ptr = strstr(card->components, component);
	if (ptr != NULL) {
		if (ptr[len] == '\0' || ptr[len] == ' ')	/* already there */
			return 1;
	}
	if (strlen(card->components) + 1 + len + 1 > sizeof(card->components)) {
		snd_BUG();
		return -ENOMEM;
	}
	if (card->components[0] != '\0')
		strcat(card->components, " ");
	strcat(card->components, component);
	return 0;
}
EXPORT_SYMBOL(snd_component_add);

/**
 *  snd_card_file_add - add the file to the file list of the card
 *  @card: soundcard structure
 *  @file: file pointer
 *
 *  This function adds the file to the file linked-list of the card.
 *  This linked-list is used to keep tracking the connection state,
 *  and to avoid the release of busy resources by hotplug.
 *
 *  Return: zero or a negative error code.
 */
int snd_card_file_add(struct snd_card *card, struct file *file)
{
	struct snd_monitor_file *mfile;

	mfile = kmalloc(sizeof(*mfile), GFP_KERNEL);
	if (mfile == NULL)
		return -ENOMEM;
	mfile->file = file;
	mfile->disconnected_f_op = NULL;
	INIT_LIST_HEAD(&mfile->shutdown_list);
	spin_lock(&card->files_lock);
	if (card->shutdown) {
		spin_unlock(&card->files_lock);
		kfree(mfile);
		return -ENODEV;
	}
	list_add(&mfile->list, &card->files_list);
	get_device(&card->card_dev);
	spin_unlock(&card->files_lock);
	return 0;
}
EXPORT_SYMBOL(snd_card_file_add);

/**
 *  snd_card_file_remove - remove the file from the file list
 *  @card: soundcard structure
 *  @file: file pointer
 *
 *  This function removes the file formerly added to the card via
 *  snd_card_file_add() function.
 *  If all files are removed and snd_card_free_when_closed() was
 *  called beforehand, it processes the pending release of
 *  resources.
 *
 *  Return: Zero or a negative error code.
 */
int snd_card_file_remove(struct snd_card *card, struct file *file)
{
	struct snd_monitor_file *mfile, *found = NULL;

	spin_lock(&card->files_lock);
	list_for_each_entry(mfile, &card->files_list, list) {
		if (mfile->file == file) {
			list_del(&mfile->list);
			spin_lock(&shutdown_lock);
			list_del(&mfile->shutdown_list);
			spin_unlock(&shutdown_lock);
			if (mfile->disconnected_f_op)
				fops_put(mfile->disconnected_f_op);
			found = mfile;
			break;
		}
	}
	spin_unlock(&card->files_lock);
	if (!found) {
		dev_err(card->dev, "card file remove problem (%p)\n", file);
		return -ENOENT;
	}
	kfree(found);
	put_device(&card->card_dev);
	return 0;
}
EXPORT_SYMBOL(snd_card_file_remove);

#ifdef CONFIG_PM
/**
 *  snd_power_wait - wait until the power-state is changed.
 *  @card: soundcard structure
 *  @power_state: expected power state
 *
 *  Waits until the power-state is changed.
 *
 *  Return: Zero if successful, or a negative error code.
 */
int snd_power_wait(struct snd_card *card, unsigned int power_state)
{
	wait_queue_entry_t wait;
	int result = 0;

	/* fastpath */
	if (snd_power_get_state(card) == power_state)
		return 0;
	init_waitqueue_entry(&wait, current);
	add_wait_queue(&card->power_sleep, &wait);
	while (1) {
		if (card->shutdown) {
			result = -ENODEV;
			break;
		}
		if (snd_power_get_state(card) == power_state)
			break;
		set_current_state(TASK_UNINTERRUPTIBLE);
		schedule_timeout(30 * HZ);
	}
	remove_wait_queue(&card->power_sleep, &wait);
	return result;
}
EXPORT_SYMBOL(snd_power_wait);
#endif /* CONFIG_PM */