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
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
/*
 *  The Serio abstraction module
 *
 *  Copyright (c) 1999-2004 Vojtech Pavlik
 *  Copyright (c) 2004 Dmitry Torokhov
 *  Copyright (c) 2003 Daniele Bellucci
 */

/*
 * 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
 *
 * Should you need to contact me, the author, you can do so either by
 * e-mail - mail your message to <vojtech@ucw.cz>, or by paper mail:
 * Vojtech Pavlik, Simunkova 1594, Prague 8, 182 00 Czech Republic
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/stddef.h>
#include <linux/module.h>
#include <linux/serio.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/workqueue.h>
#include <linux/mutex.h>

MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
MODULE_DESCRIPTION("Serio abstraction core");
MODULE_LICENSE("GPL");

/*
 * serio_mutex protects entire serio subsystem and is taken every time
 * serio port or driver registered or unregistered.
 */
static DEFINE_MUTEX(serio_mutex);

static LIST_HEAD(serio_list);

static void serio_add_port(struct serio *serio);
static int serio_reconnect_port(struct serio *serio);
static void serio_disconnect_port(struct serio *serio);
static void serio_reconnect_subtree(struct serio *serio);
static void serio_attach_driver(struct serio_driver *drv);

static int serio_connect_driver(struct serio *serio, struct serio_driver *drv)
{
	int retval;

	mutex_lock(&serio->drv_mutex);
	retval = drv->connect(serio, drv);
	mutex_unlock(&serio->drv_mutex);

	return retval;
}

static int serio_reconnect_driver(struct serio *serio)
{
	int retval = -1;

	mutex_lock(&serio->drv_mutex);
	if (serio->drv && serio->drv->reconnect)
		retval = serio->drv->reconnect(serio);
	mutex_unlock(&serio->drv_mutex);

	return retval;
}

static void serio_disconnect_driver(struct serio *serio)
{
	mutex_lock(&serio->drv_mutex);
	if (serio->drv)
		serio->drv->disconnect(serio);
	mutex_unlock(&serio->drv_mutex);
}

static int serio_match_port(const struct serio_device_id *ids, struct serio *serio)
{
	while (ids->type || ids->proto) {
		if ((ids->type == SERIO_ANY || ids->type == serio->id.type) &&
		    (ids->proto == SERIO_ANY || ids->proto == serio->id.proto) &&
		    (ids->extra == SERIO_ANY || ids->extra == serio->id.extra) &&
		    (ids->id == SERIO_ANY || ids->id == serio->id.id))
			return 1;
		ids++;
	}
	return 0;
}

/*
 * Basic serio -> driver core mappings
 */

static int serio_bind_driver(struct serio *serio, struct serio_driver *drv)
{
	int error;

	if (serio_match_port(drv->id_table, serio)) {

		serio->dev.driver = &drv->driver;
		if (serio_connect_driver(serio, drv)) {
			serio->dev.driver = NULL;
			return -ENODEV;
		}

		error = device_bind_driver(&serio->dev);
		if (error) {
			dev_warn(&serio->dev,
				 "device_bind_driver() failed for %s (%s) and %s, error: %d\n",
				 serio->phys, serio->name,
				 drv->description, error);
			serio_disconnect_driver(serio);
			serio->dev.driver = NULL;
			return error;
		}
	}
	return 0;
}

static void serio_find_driver(struct serio *serio)
{
	int error;

	error = device_attach(&serio->dev);
	if (error < 0)
		dev_warn(&serio->dev,
			 "device_attach() failed for %s (%s), error: %d\n",
			 serio->phys, serio->name, error);
}


/*
 * Serio event processing.
 */

enum serio_event_type {
	SERIO_RESCAN_PORT,
	SERIO_RECONNECT_PORT,
	SERIO_RECONNECT_SUBTREE,
	SERIO_REGISTER_PORT,
	SERIO_ATTACH_DRIVER,
};

struct serio_event {
	enum serio_event_type type;
	void *object;
	struct module *owner;
	struct list_head node;
};

static DEFINE_SPINLOCK(serio_event_lock);	/* protects serio_event_list */
static LIST_HEAD(serio_event_list);

static struct serio_event *serio_get_event(void)
{
	struct serio_event *event = NULL;
	unsigned long flags;

	spin_lock_irqsave(&serio_event_lock, flags);

	if (!list_empty(&serio_event_list)) {
		event = list_first_entry(&serio_event_list,
					 struct serio_event, node);
		list_del_init(&event->node);
	}

	spin_unlock_irqrestore(&serio_event_lock, flags);
	return event;
}

static void serio_free_event(struct serio_event *event)
{
	module_put(event->owner);
	kfree(event);
}

static void serio_remove_duplicate_events(void *object,
					  enum serio_event_type type)
{
	struct serio_event *e, *next;
	unsigned long flags;

	spin_lock_irqsave(&serio_event_lock, flags);

	list_for_each_entry_safe(e, next, &serio_event_list, node) {
		if (object == e->object) {
			/*
			 * If this event is of different type we should not
			 * look further - we only suppress duplicate events
			 * that were sent back-to-back.
			 */
			if (type != e->type)
				break;

			list_del_init(&e->node);
			serio_free_event(e);
		}
	}

	spin_unlock_irqrestore(&serio_event_lock, flags);
}

static void serio_handle_event(struct work_struct *work)
{
	struct serio_event *event;

	mutex_lock(&serio_mutex);

	while ((event = serio_get_event())) {

		switch (event->type) {

		case SERIO_REGISTER_PORT:
			serio_add_port(event->object);
			break;

		case SERIO_RECONNECT_PORT:
			serio_reconnect_port(event->object);
			break;

		case SERIO_RESCAN_PORT:
			serio_disconnect_port(event->object);
			serio_find_driver(event->object);
			break;

		case SERIO_RECONNECT_SUBTREE:
			serio_reconnect_subtree(event->object);
			break;

		case SERIO_ATTACH_DRIVER:
			serio_attach_driver(event->object);
			break;
		}

		serio_remove_duplicate_events(event->object, event->type);
		serio_free_event(event);
	}

	mutex_unlock(&serio_mutex);
}

static DECLARE_WORK(serio_event_work, serio_handle_event);

static int serio_queue_event(void *object, struct module *owner,
			     enum serio_event_type event_type)
{
	unsigned long flags;
	struct serio_event *event;
	int retval = 0;

	spin_lock_irqsave(&serio_event_lock, flags);

	/*
	 * Scan event list for the other events for the same serio port,
	 * starting with the most recent one. If event is the same we
	 * do not need add new one. If event is of different type we
	 * need to add this event and should not look further because
	 * we need to preseve sequence of distinct events.
	 */
	list_for_each_entry_reverse(event, &serio_event_list, node) {
		if (event->object == object) {
			if (event->type == event_type)
				goto out;
			break;
		}
	}

	event = kmalloc(sizeof(struct serio_event), GFP_ATOMIC);
	if (!event) {
		pr_err("Not enough memory to queue event %d\n", event_type);
		retval = -ENOMEM;
		goto out;
	}

	if (!try_module_get(owner)) {
		pr_warning("Can't get module reference, dropping event %d\n",
			   event_type);
		kfree(event);
		retval = -EINVAL;
		goto out;
	}

	event->type = event_type;
	event->object = object;
	event->owner = owner;

	list_add_tail(&event->node, &serio_event_list);
	queue_work(system_long_wq, &serio_event_work);

out:
	spin_unlock_irqrestore(&serio_event_lock, flags);
	return retval;
}

/*
 * Remove all events that have been submitted for a given
 * object, be it serio port or driver.
 */
static void serio_remove_pending_events(void *object)
{
	struct serio_event *event, *next;
	unsigned long flags;

	spin_lock_irqsave(&serio_event_lock, flags);

	list_for_each_entry_safe(event, next, &serio_event_list, node) {
		if (event->object == object) {
			list_del_init(&event->node);
			serio_free_event(event);
		}
	}

	spin_unlock_irqrestore(&serio_event_lock, flags);
}

/*
 * Locate child serio port (if any) that has not been fully registered yet.
 *
 * Children are registered by driver's connect() handler so there can't be a
 * grandchild pending registration together with a child.
 */
static struct serio *serio_get_pending_child(struct serio *parent)
{
	struct serio_event *event;
	struct serio *serio, *child = NULL;
	unsigned long flags;

	spin_lock_irqsave(&serio_event_lock, flags);

	list_for_each_entry(event, &serio_event_list, node) {
		if (event->type == SERIO_REGISTER_PORT) {
			serio = event->object;
			if (serio->parent == parent) {
				child = serio;
				break;
			}
		}
	}

	spin_unlock_irqrestore(&serio_event_lock, flags);
	return child;
}

/*
 * Serio port operations
 */

static ssize_t serio_show_description(struct device *dev, struct device_attribute *attr, char *buf)
{
	struct serio *serio = to_serio_port(dev);
	return sprintf(buf, "%s\n", serio->name);
}

static ssize_t modalias_show(struct device *dev, struct device_attribute *attr, char *buf)
{
	struct serio *serio = to_serio_port(dev);

	return sprintf(buf, "serio:ty%02Xpr%02Xid%02Xex%02X\n",
			serio->id.type, serio->id.proto, serio->id.id, serio->id.extra);
}

static ssize_t type_show(struct device *dev, struct device_attribute *attr, char *buf)
{
	struct serio *serio = to_serio_port(dev);
	return sprintf(buf, "%02x\n", serio->id.type);
}

static ssize_t proto_show(struct device *dev, struct device_attribute *attr, char *buf)
{
	struct serio *serio = to_serio_port(dev);
	return sprintf(buf, "%02x\n", serio->id.proto);
}

static ssize_t id_show(struct device *dev, struct device_attribute *attr, char *buf)
{
	struct serio *serio = to_serio_port(dev);
	return sprintf(buf, "%02x\n", serio->id.id);
}

static ssize_t extra_show(struct device *dev, struct device_attribute *attr, char *buf)
{
	struct serio *serio = to_serio_port(dev);
	return sprintf(buf, "%02x\n", serio->id.extra);
}

static ssize_t drvctl_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
	struct serio *serio = to_serio_port(dev);
	struct device_driver *drv;
	int error;

	error = mutex_lock_interruptible(&serio_mutex);
	if (error)
		return error;

	if (!strncmp(buf, "none", count)) {
		serio_disconnect_port(serio);
	} else if (!strncmp(buf, "reconnect", count)) {
		serio_reconnect_subtree(serio);
	} else if (!strncmp(buf, "rescan", count)) {
		serio_disconnect_port(serio);
		serio_find_driver(serio);
		serio_remove_duplicate_events(serio, SERIO_RESCAN_PORT);
	} else if ((drv = driver_find(buf, &serio_bus)) != NULL) {
		serio_disconnect_port(serio);
		error = serio_bind_driver(serio, to_serio_driver(drv));
		serio_remove_duplicate_events(serio, SERIO_RESCAN_PORT);
	} else {
		error = -EINVAL;
	}

	mutex_unlock(&serio_mutex);

	return error ? error : count;
}

static ssize_t serio_show_bind_mode(struct device *dev, struct device_attribute *attr, char *buf)
{
	struct serio *serio = to_serio_port(dev);
	return sprintf(buf, "%s\n", serio->manual_bind ? "manual" : "auto");
}

static ssize_t serio_set_bind_mode(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
	struct serio *serio = to_serio_port(dev);
	int retval;

	retval = count;
	if (!strncmp(buf, "manual", count)) {
		serio->manual_bind = true;
	} else if (!strncmp(buf, "auto", count)) {
		serio->manual_bind = false;
	} else {
		retval = -EINVAL;
	}

	return retval;
}

static ssize_t firmware_id_show(struct device *dev, struct device_attribute *attr, char *buf)
{
	struct serio *serio = to_serio_port(dev);

	return sprintf(buf, "%s\n", serio->firmware_id);
}

static DEVICE_ATTR_RO(type);
static DEVICE_ATTR_RO(proto);
static DEVICE_ATTR_RO(id);
static DEVICE_ATTR_RO(extra);

static struct attribute *serio_device_id_attrs[] = {
	&dev_attr_type.attr,
	&dev_attr_proto.attr,
	&dev_attr_id.attr,
	&dev_attr_extra.attr,
	NULL
};

static struct attribute_group serio_id_attr_group = {
	.name	= "id",
	.attrs	= serio_device_id_attrs,
};

static DEVICE_ATTR_RO(modalias);
static DEVICE_ATTR_WO(drvctl);
static DEVICE_ATTR(description, S_IRUGO, serio_show_description, NULL);
static DEVICE_ATTR(bind_mode, S_IWUSR | S_IRUGO, serio_show_bind_mode, serio_set_bind_mode);
static DEVICE_ATTR_RO(firmware_id);

static struct attribute *serio_device_attrs[] = {
	&dev_attr_modalias.attr,
	&dev_attr_description.attr,
	&dev_attr_drvctl.attr,
	&dev_attr_bind_mode.attr,
	&dev_attr_firmware_id.attr,
	NULL
};

static struct attribute_group serio_device_attr_group = {
	.attrs	= serio_device_attrs,
};

static const struct attribute_group *serio_device_attr_groups[] = {
	&serio_id_attr_group,
	&serio_device_attr_group,
	NULL
};

static void serio_release_port(struct device *dev)
{
	struct serio *serio = to_serio_port(dev);

	kfree(serio);
	module_put(THIS_MODULE);
}

/*
 * Prepare serio port for registration.
 */
static void serio_init_port(struct serio *serio)
{
	static atomic_t serio_no = ATOMIC_INIT(-1);

	__module_get(THIS_MODULE);

	INIT_LIST_HEAD(&serio->node);
	INIT_LIST_HEAD(&serio->child_node);
	INIT_LIST_HEAD(&serio->children);
	spin_lock_init(&serio->lock);
	mutex_init(&serio->drv_mutex);
	device_initialize(&serio->dev);
	dev_set_name(&serio->dev, "serio%lu",
		     (unsigned long)atomic_inc_return(&serio_no));
	serio->dev.bus = &serio_bus;
	serio->dev.release = serio_release_port;
	serio->dev.groups = serio_device_attr_groups;
	if (serio->parent) {
		serio->dev.parent = &serio->parent->dev;
		serio->depth = serio->parent->depth + 1;
	} else
		serio->depth = 0;
	lockdep_set_subclass(&serio->lock, serio->depth);
}

/*
 * Complete serio port registration.
 * Driver core will attempt to find appropriate driver for the port.
 */
static void serio_add_port(struct serio *serio)
{
	struct serio *parent = serio->parent;
	int error;

	if (parent) {
		serio_pause_rx(parent);
		list_add_tail(&serio->child_node, &parent->children);
		serio_continue_rx(parent);
	}

	list_add_tail(&serio->node, &serio_list);

	if (serio->start)
		serio->start(serio);

	error = device_add(&serio->dev);
	if (error)
		dev_err(&serio->dev,
			"device_add() failed for %s (%s), error: %d\n",
			serio->phys, serio->name, error);
}

/*
 * serio_destroy_port() completes unregistration process and removes
 * port from the system
 */
static void serio_destroy_port(struct serio *serio)
{
	struct serio *child;

	while ((child = serio_get_pending_child(serio)) != NULL) {
		serio_remove_pending_events(child);
		put_device(&child->dev);
	}

	if (serio->stop)
		serio->stop(serio);

	if (serio->parent) {
		serio_pause_rx(serio->parent);
		list_del_init(&serio->child_node);
		serio_continue_rx(serio->parent);
		serio->parent = NULL;
	}

	if (device_is_registered(&serio->dev))
		device_del(&serio->dev);

	list_del_init(&serio->node);
	serio_remove_pending_events(serio);
	put_device(&serio->dev);
}

/*
 * Reconnect serio port (re-initialize attached device).
 * If reconnect fails (old device is no longer attached or
 * there was no device to begin with) we do full rescan in
 * hope of finding a driver for the port.
 */
static int serio_reconnect_port(struct serio *serio)
{
	int error = serio_reconnect_driver(serio);

	if (error) {
		serio_disconnect_port(serio);
		serio_find_driver(serio);
	}

	return error;
}

/*
 * Reconnect serio port and all its children (re-initialize attached
 * devices).
 */
static void serio_reconnect_subtree(struct serio *root)
{
	struct serio *s = root;
	int error;

	do {
		error = serio_reconnect_port(s);
		if (!error) {
			/*
			 * Reconnect was successful, move on to do the
			 * first child.
			 */
			if (!list_empty(&s->children)) {
				s = list_first_entry(&s->children,
						     struct serio, child_node);
				continue;
			}
		}

		/*
		 * Either it was a leaf node or reconnect failed and it
		 * became a leaf node. Continue reconnecting starting with
		 * the next sibling of the parent node.
		 */
		while (s != root) {
			struct serio *parent = s->parent;

			if (!list_is_last(&s->child_node, &parent->children)) {
				s = list_entry(s->child_node.next,
					       struct serio, child_node);
				break;
			}

			s = parent;
		}
	} while (s != root);
}

/*
 * serio_disconnect_port() unbinds a port from its driver. As a side effect
 * all children ports are unbound and destroyed.
 */
static void serio_disconnect_port(struct serio *serio)
{
	struct serio *s = serio;

	/*
	 * Children ports should be disconnected and destroyed
	 * first; we travel the tree in depth-first order.
	 */
	while (!list_empty(&serio->children)) {

		/* Locate a leaf */
		while (!list_empty(&s->children))
			s = list_first_entry(&s->children,
					     struct serio, child_node);

		/*
		 * Prune this leaf node unless it is the one we
		 * started with.
		 */
		if (s != serio) {
			struct serio *parent = s->parent;

			device_release_driver(&s->dev);
			serio_destroy_port(s);

			s = parent;
		}
	}

	/*
	 * OK, no children left, now disconnect this port.
	 */
	device_release_driver(&serio->dev);
}

void serio_rescan(struct serio *serio)
{
	serio_queue_event(serio, NULL, SERIO_RESCAN_PORT);
}
EXPORT_SYMBOL(serio_rescan);

void serio_reconnect(struct serio *serio)
{
	serio_queue_event(serio, NULL, SERIO_RECONNECT_SUBTREE);
}
EXPORT_SYMBOL(serio_reconnect);

/*
 * Submits register request to kseriod for subsequent execution.
 * Note that port registration is always asynchronous.
 */
void __serio_register_port(struct serio *serio, struct module *owner)
{
	serio_init_port(serio);
	serio_queue_event(serio, owner, SERIO_REGISTER_PORT);
}
EXPORT_SYMBOL(__serio_register_port);

/*
 * Synchronously unregisters serio port.
 */
void serio_unregister_port(struct serio *serio)
{
	mutex_lock(&serio_mutex);
	serio_disconnect_port(serio);
	serio_destroy_port(serio);
	mutex_unlock(&serio_mutex);
}
EXPORT_SYMBOL(serio_unregister_port);

/*
 * Safely unregisters children ports if they are present.
 */
void serio_unregister_child_port(struct serio *serio)
{
	struct serio *s, *next;

	mutex_lock(&serio_mutex);
	list_for_each_entry_safe(s, next, &serio->children, child_node) {
		serio_disconnect_port(s);
		serio_destroy_port(s);
	}
	mutex_unlock(&serio_mutex);
}
EXPORT_SYMBOL(serio_unregister_child_port);


/*
 * Serio driver operations
 */

static ssize_t description_show(struct device_driver *drv, char *buf)
{
	struct serio_driver *driver = to_serio_driver(drv);
	return sprintf(buf, "%s\n", driver->description ? driver->description : "(none)");
}
static DRIVER_ATTR_RO(description);

static ssize_t bind_mode_show(struct device_driver *drv, char *buf)
{
	struct serio_driver *serio_drv = to_serio_driver(drv);
	return sprintf(buf, "%s\n", serio_drv->manual_bind ? "manual" : "auto");
}

static ssize_t bind_mode_store(struct device_driver *drv, const char *buf, size_t count)
{
	struct serio_driver *serio_drv = to_serio_driver(drv);
	int retval;

	retval = count;
	if (!strncmp(buf, "manual", count)) {
		serio_drv->manual_bind = true;
	} else if (!strncmp(buf, "auto", count)) {
		serio_drv->manual_bind = false;
	} else {
		retval = -EINVAL;
	}

	return retval;
}
static DRIVER_ATTR_RW(bind_mode);

static struct attribute *serio_driver_attrs[] = {
	&driver_attr_description.attr,
	&driver_attr_bind_mode.attr,
	NULL,
};
ATTRIBUTE_GROUPS(serio_driver);

static int serio_driver_probe(struct device *dev)
{
	struct serio *serio = to_serio_port(dev);
	struct serio_driver *drv = to_serio_driver(dev->driver);

	return serio_connect_driver(serio, drv);
}

static int serio_driver_remove(struct device *dev)
{
	struct serio *serio = to_serio_port(dev);

	serio_disconnect_driver(serio);
	return 0;
}

static void serio_cleanup(struct serio *serio)
{
	mutex_lock(&serio->drv_mutex);
	if (serio->drv && serio->drv->cleanup)
		serio->drv->cleanup(serio);
	mutex_unlock(&serio->drv_mutex);
}

static void serio_shutdown(struct device *dev)
{
	struct serio *serio = to_serio_port(dev);

	serio_cleanup(serio);
}

static void serio_attach_driver(struct serio_driver *drv)
{
	int error;

	error = driver_attach(&drv->driver);
	if (error)
		pr_warning("driver_attach() failed for %s with error %d\n",
			   drv->driver.name, error);
}

int __serio_register_driver(struct serio_driver *drv, struct module *owner, const char *mod_name)
{
	bool manual_bind = drv->manual_bind;
	int error;

	drv->driver.bus = &serio_bus;
	drv->driver.owner = owner;
	drv->driver.mod_name = mod_name;

	/*
	 * Temporarily disable automatic binding because probing
	 * takes long time and we are better off doing it in kseriod
	 */
	drv->manual_bind = true;

	error = driver_register(&drv->driver);
	if (error) {
		pr_err("driver_register() failed for %s, error: %d\n",
			drv->driver.name, error);
		return error;
	}

	/*
	 * Restore original bind mode and let kseriod bind the
	 * driver to free ports
	 */
	if (!manual_bind) {
		drv->manual_bind = false;
		error = serio_queue_event(drv, NULL, SERIO_ATTACH_DRIVER);
		if (error) {
			driver_unregister(&drv->driver);
			return error;
		}
	}

	return 0;
}
EXPORT_SYMBOL(__serio_register_driver);

void serio_unregister_driver(struct serio_driver *drv)
{
	struct serio *serio;

	mutex_lock(&serio_mutex);

	drv->manual_bind = true;	/* so serio_find_driver ignores it */
	serio_remove_pending_events(drv);

start_over:
	list_for_each_entry(serio, &serio_list, node) {
		if (serio->drv == drv) {
			serio_disconnect_port(serio);
			serio_find_driver(serio);
			/* we could've deleted some ports, restart */
			goto start_over;
		}
	}

	driver_unregister(&drv->driver);
	mutex_unlock(&serio_mutex);
}
EXPORT_SYMBOL(serio_unregister_driver);

static void serio_set_drv(struct serio *serio, struct serio_driver *drv)
{
	serio_pause_rx(serio);
	serio->drv = drv;
	serio_continue_rx(serio);
}

static int serio_bus_match(struct device *dev, struct device_driver *drv)
{
	struct serio *serio = to_serio_port(dev);
	struct serio_driver *serio_drv = to_serio_driver(drv);

	if (serio->manual_bind || serio_drv->manual_bind)
		return 0;

	return serio_match_port(serio_drv->id_table, serio);
}

#define SERIO_ADD_UEVENT_VAR(fmt, val...)				\
	do {								\
		int err = add_uevent_var(env, fmt, val);		\
		if (err)						\
			return err;					\
	} while (0)

static int serio_uevent(struct device *dev, struct kobj_uevent_env *env)
{
	struct serio *serio;

	if (!dev)
		return -ENODEV;

	serio = to_serio_port(dev);

	SERIO_ADD_UEVENT_VAR("SERIO_TYPE=%02x", serio->id.type);
	SERIO_ADD_UEVENT_VAR("SERIO_PROTO=%02x", serio->id.proto);
	SERIO_ADD_UEVENT_VAR("SERIO_ID=%02x", serio->id.id);
	SERIO_ADD_UEVENT_VAR("SERIO_EXTRA=%02x", serio->id.extra);

	SERIO_ADD_UEVENT_VAR("MODALIAS=serio:ty%02Xpr%02Xid%02Xex%02X",
				serio->id.type, serio->id.proto, serio->id.id, serio->id.extra);

	if (serio->firmware_id[0])
		SERIO_ADD_UEVENT_VAR("SERIO_FIRMWARE_ID=%s",
				     serio->firmware_id);

	return 0;
}
#undef SERIO_ADD_UEVENT_VAR

#ifdef CONFIG_PM
static int serio_suspend(struct device *dev)
{
	struct serio *serio = to_serio_port(dev);

	serio_cleanup(serio);

	return 0;
}

static int serio_resume(struct device *dev)
{
	struct serio *serio = to_serio_port(dev);

	/*
	 * Driver reconnect can take a while, so better let kseriod
	 * deal with it.
	 */
	serio_queue_event(serio, NULL, SERIO_RECONNECT_PORT);

	return 0;
}

static const struct dev_pm_ops serio_pm_ops = {
	.suspend	= serio_suspend,
	.resume		= serio_resume,
	.poweroff	= serio_suspend,
	.restore	= serio_resume,
};
#endif /* CONFIG_PM */

/* called from serio_driver->connect/disconnect methods under serio_mutex */
int serio_open(struct serio *serio, struct serio_driver *drv)
{
	serio_set_drv(serio, drv);

	if (serio->open && serio->open(serio)) {
		serio_set_drv(serio, NULL);
		return -1;
	}
	return 0;
}
EXPORT_SYMBOL(serio_open);

/* called from serio_driver->connect/disconnect methods under serio_mutex */
void serio_close(struct serio *serio)
{
	if (serio->close)
		serio->close(serio);

	serio_set_drv(serio, NULL);
}
EXPORT_SYMBOL(serio_close);

irqreturn_t serio_interrupt(struct serio *serio,
		unsigned char data, unsigned int dfl)
{
	unsigned long flags;
	irqreturn_t ret = IRQ_NONE;

	spin_lock_irqsave(&serio->lock, flags);

        if (likely(serio->drv)) {
                ret = serio->drv->interrupt(serio, data, dfl);
	} else if (!dfl && device_is_registered(&serio->dev)) {
		serio_rescan(serio);
		ret = IRQ_HANDLED;
	}

	spin_unlock_irqrestore(&serio->lock, flags);

	return ret;
}
EXPORT_SYMBOL(serio_interrupt);

struct bus_type serio_bus = {
	.name		= "serio",
	.drv_groups	= serio_driver_groups,
	.match		= serio_bus_match,
	.uevent		= serio_uevent,
	.probe		= serio_driver_probe,
	.remove		= serio_driver_remove,
	.shutdown	= serio_shutdown,
#ifdef CONFIG_PM
	.pm		= &serio_pm_ops,
#endif
};
EXPORT_SYMBOL(serio_bus);

static int __init serio_init(void)
{
	int error;

	error = bus_register(&serio_bus);
	if (error) {
		pr_err("Failed to register serio bus, error: %d\n", error);
		return error;
	}

	return 0;
}

static void __exit serio_exit(void)
{
	bus_unregister(&serio_bus);

	/*
	 * There should not be any outstanding events but work may
	 * still be scheduled so simply cancel it.
	 */
	cancel_work_sync(&serio_event_work);
}

subsys_initcall(serio_init);
module_exit(serio_exit);