Bootlin logo

Elixir Cross Referencer

  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
/*
 * bus.c - bus driver management
 *
 * Copyright (c) 2002-3 Patrick Mochel
 * Copyright (c) 2002-3 Open Source Development Labs
 * Copyright (c) 2007 Greg Kroah-Hartman <gregkh@suse.de>
 * Copyright (c) 2007 Novell Inc.
 *
 * This file is released under the GPLv2
 *
 */

#include <linux/device.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/string.h>
#include "base.h"
#include "power/power.h"

#define to_bus_attr(_attr) container_of(_attr, struct bus_attribute, attr)
#define to_bus(obj) container_of(obj, struct bus_type_private, subsys.kobj)

/*
 * sysfs bindings for drivers
 */

#define to_drv_attr(_attr) container_of(_attr, struct driver_attribute, attr)


static int __must_check bus_rescan_devices_helper(struct device *dev,
						void *data);

static struct bus_type *bus_get(struct bus_type *bus)
{
	if (bus) {
		kset_get(&bus->p->subsys);
		return bus;
	}
	return NULL;
}

static void bus_put(struct bus_type *bus)
{
	if (bus)
		kset_put(&bus->p->subsys);
}

static ssize_t drv_attr_show(struct kobject *kobj, struct attribute *attr,
			     char *buf)
{
	struct driver_attribute *drv_attr = to_drv_attr(attr);
	struct driver_private *drv_priv = to_driver(kobj);
	ssize_t ret = -EIO;

	if (drv_attr->show)
		ret = drv_attr->show(drv_priv->driver, buf);
	return ret;
}

static ssize_t drv_attr_store(struct kobject *kobj, struct attribute *attr,
			      const char *buf, size_t count)
{
	struct driver_attribute *drv_attr = to_drv_attr(attr);
	struct driver_private *drv_priv = to_driver(kobj);
	ssize_t ret = -EIO;

	if (drv_attr->store)
		ret = drv_attr->store(drv_priv->driver, buf, count);
	return ret;
}

static struct sysfs_ops driver_sysfs_ops = {
	.show	= drv_attr_show,
	.store	= drv_attr_store,
};

static void driver_release(struct kobject *kobj)
{
	struct driver_private *drv_priv = to_driver(kobj);

	pr_debug("driver: '%s': %s\n", kobject_name(kobj), __func__);
	kfree(drv_priv);
}

static struct kobj_type driver_ktype = {
	.sysfs_ops	= &driver_sysfs_ops,
	.release	= driver_release,
};

/*
 * sysfs bindings for buses
 */
static ssize_t bus_attr_show(struct kobject *kobj, struct attribute *attr,
			     char *buf)
{
	struct bus_attribute *bus_attr = to_bus_attr(attr);
	struct bus_type_private *bus_priv = to_bus(kobj);
	ssize_t ret = 0;

	if (bus_attr->show)
		ret = bus_attr->show(bus_priv->bus, buf);
	return ret;
}

static ssize_t bus_attr_store(struct kobject *kobj, struct attribute *attr,
			      const char *buf, size_t count)
{
	struct bus_attribute *bus_attr = to_bus_attr(attr);
	struct bus_type_private *bus_priv = to_bus(kobj);
	ssize_t ret = 0;

	if (bus_attr->store)
		ret = bus_attr->store(bus_priv->bus, buf, count);
	return ret;
}

static struct sysfs_ops bus_sysfs_ops = {
	.show	= bus_attr_show,
	.store	= bus_attr_store,
};

int bus_create_file(struct bus_type *bus, struct bus_attribute *attr)
{
	int error;
	if (bus_get(bus)) {
		error = sysfs_create_file(&bus->p->subsys.kobj, &attr->attr);
		bus_put(bus);
	} else
		error = -EINVAL;
	return error;
}
EXPORT_SYMBOL_GPL(bus_create_file);

void bus_remove_file(struct bus_type *bus, struct bus_attribute *attr)
{
	if (bus_get(bus)) {
		sysfs_remove_file(&bus->p->subsys.kobj, &attr->attr);
		bus_put(bus);
	}
}
EXPORT_SYMBOL_GPL(bus_remove_file);

static struct kobj_type bus_ktype = {
	.sysfs_ops	= &bus_sysfs_ops,
};

static int bus_uevent_filter(struct kset *kset, struct kobject *kobj)
{
	struct kobj_type *ktype = get_ktype(kobj);

	if (ktype == &bus_ktype)
		return 1;
	return 0;
}

static struct kset_uevent_ops bus_uevent_ops = {
	.filter = bus_uevent_filter,
};

static struct kset *bus_kset;


#ifdef CONFIG_HOTPLUG
/* Manually detach a device from its associated driver. */
static ssize_t driver_unbind(struct device_driver *drv,
			     const char *buf, size_t count)
{
	struct bus_type *bus = bus_get(drv->bus);
	struct device *dev;
	int err = -ENODEV;

	dev = bus_find_device_by_name(bus, NULL, buf);
	if (dev && dev->driver == drv) {
		if (dev->parent)	/* Needed for USB */
			down(&dev->parent->sem);
		device_release_driver(dev);
		if (dev->parent)
			up(&dev->parent->sem);
		err = count;
	}
	put_device(dev);
	bus_put(bus);
	return err;
}
static DRIVER_ATTR(unbind, S_IWUSR, NULL, driver_unbind);

/*
 * Manually attach a device to a driver.
 * Note: the driver must want to bind to the device,
 * it is not possible to override the driver's id table.
 */
static ssize_t driver_bind(struct device_driver *drv,
			   const char *buf, size_t count)
{
	struct bus_type *bus = bus_get(drv->bus);
	struct device *dev;
	int err = -ENODEV;

	dev = bus_find_device_by_name(bus, NULL, buf);
	if (dev && dev->driver == NULL) {
		if (dev->parent)	/* Needed for USB */
			down(&dev->parent->sem);
		down(&dev->sem);
		err = driver_probe_device(drv, dev);
		up(&dev->sem);
		if (dev->parent)
			up(&dev->parent->sem);

		if (err > 0) {
			/* success */
			err = count;
		} else if (err == 0) {
			/* driver didn't accept device */
			err = -ENODEV;
		}
	}
	put_device(dev);
	bus_put(bus);
	return err;
}
static DRIVER_ATTR(bind, S_IWUSR, NULL, driver_bind);

static ssize_t show_drivers_autoprobe(struct bus_type *bus, char *buf)
{
	return sprintf(buf, "%d\n", bus->p->drivers_autoprobe);
}

static ssize_t store_drivers_autoprobe(struct bus_type *bus,
				       const char *buf, size_t count)
{
	if (buf[0] == '0')
		bus->p->drivers_autoprobe = 0;
	else
		bus->p->drivers_autoprobe = 1;
	return count;
}

static ssize_t store_drivers_probe(struct bus_type *bus,
				   const char *buf, size_t count)
{
	struct device *dev;

	dev = bus_find_device_by_name(bus, NULL, buf);
	if (!dev)
		return -ENODEV;
	if (bus_rescan_devices_helper(dev, NULL) != 0)
		return -EINVAL;
	return count;
}
#endif

static struct device *next_device(struct klist_iter *i)
{
	struct klist_node *n = klist_next(i);
	return n ? container_of(n, struct device, knode_bus) : NULL;
}

/**
 * bus_for_each_dev - device iterator.
 * @bus: bus type.
 * @start: device to start iterating from.
 * @data: data for the callback.
 * @fn: function to be called for each device.
 *
 * Iterate over @bus's list of devices, and call @fn for each,
 * passing it @data. If @start is not NULL, we use that device to
 * begin iterating from.
 *
 * We check the return of @fn each time. If it returns anything
 * other than 0, we break out and return that value.
 *
 * NOTE: The device that returns a non-zero value is not retained
 * in any way, nor is its refcount incremented. If the caller needs
 * to retain this data, it should do, and increment the reference
 * count in the supplied callback.
 */
int bus_for_each_dev(struct bus_type *bus, struct device *start,
		     void *data, int (*fn)(struct device *, void *))
{
	struct klist_iter i;
	struct device *dev;
	int error = 0;

	if (!bus)
		return -EINVAL;

	klist_iter_init_node(&bus->p->klist_devices, &i,
			     (start ? &start->knode_bus : NULL));
	while ((dev = next_device(&i)) && !error)
		error = fn(dev, data);
	klist_iter_exit(&i);
	return error;
}
EXPORT_SYMBOL_GPL(bus_for_each_dev);

/**
 * bus_find_device - device iterator for locating a particular device.
 * @bus: bus type
 * @start: Device to begin with
 * @data: Data to pass to match function
 * @match: Callback function to check device
 *
 * This is similar to the bus_for_each_dev() function above, but it
 * returns a reference to a device that is 'found' for later use, as
 * determined by the @match callback.
 *
 * The callback should return 0 if the device doesn't match and non-zero
 * if it does.  If the callback returns non-zero, this function will
 * return to the caller and not iterate over any more devices.
 */
struct device *bus_find_device(struct bus_type *bus,
			       struct device *start, void *data,
			       int (*match)(struct device *dev, void *data))
{
	struct klist_iter i;
	struct device *dev;

	if (!bus)
		return NULL;

	klist_iter_init_node(&bus->p->klist_devices, &i,
			     (start ? &start->knode_bus : NULL));
	while ((dev = next_device(&i)))
		if (match(dev, data) && get_device(dev))
			break;
	klist_iter_exit(&i);
	return dev;
}
EXPORT_SYMBOL_GPL(bus_find_device);

static int match_name(struct device *dev, void *data)
{
	const char *name = data;

	if (strcmp(name, dev->bus_id) == 0)
		return 1;
	return 0;
}

/**
 * bus_find_device_by_name - device iterator for locating a particular device of a specific name
 * @bus: bus type
 * @start: Device to begin with
 * @name: name of the device to match
 *
 * This is similar to the bus_find_device() function above, but it handles
 * searching by a name automatically, no need to write another strcmp matching
 * function.
 */
struct device *bus_find_device_by_name(struct bus_type *bus,
				       struct device *start, const char *name)
{
	return bus_find_device(bus, start, (void *)name, match_name);
}
EXPORT_SYMBOL_GPL(bus_find_device_by_name);

static struct device_driver *next_driver(struct klist_iter *i)
{
	struct klist_node *n = klist_next(i);
	struct driver_private *drv_priv;

	if (n) {
		drv_priv = container_of(n, struct driver_private, knode_bus);
		return drv_priv->driver;
	}
	return NULL;
}

/**
 * bus_for_each_drv - driver iterator
 * @bus: bus we're dealing with.
 * @start: driver to start iterating on.
 * @data: data to pass to the callback.
 * @fn: function to call for each driver.
 *
 * This is nearly identical to the device iterator above.
 * We iterate over each driver that belongs to @bus, and call
 * @fn for each. If @fn returns anything but 0, we break out
 * and return it. If @start is not NULL, we use it as the head
 * of the list.
 *
 * NOTE: we don't return the driver that returns a non-zero
 * value, nor do we leave the reference count incremented for that
 * driver. If the caller needs to know that info, it must set it
 * in the callback. It must also be sure to increment the refcount
 * so it doesn't disappear before returning to the caller.
 */
int bus_for_each_drv(struct bus_type *bus, struct device_driver *start,
		     void *data, int (*fn)(struct device_driver *, void *))
{
	struct klist_iter i;
	struct device_driver *drv;
	int error = 0;

	if (!bus)
		return -EINVAL;

	klist_iter_init_node(&bus->p->klist_drivers, &i,
			     start ? &start->p->knode_bus : NULL);
	while ((drv = next_driver(&i)) && !error)
		error = fn(drv, data);
	klist_iter_exit(&i);
	return error;
}
EXPORT_SYMBOL_GPL(bus_for_each_drv);

static int device_add_attrs(struct bus_type *bus, struct device *dev)
{
	int error = 0;
	int i;

	if (!bus->dev_attrs)
		return 0;

	for (i = 0; attr_name(bus->dev_attrs[i]); i++) {
		error = device_create_file(dev, &bus->dev_attrs[i]);
		if (error) {
			while (--i >= 0)
				device_remove_file(dev, &bus->dev_attrs[i]);
			break;
		}
	}
	return error;
}

static void device_remove_attrs(struct bus_type *bus, struct device *dev)
{
	int i;

	if (bus->dev_attrs) {
		for (i = 0; attr_name(bus->dev_attrs[i]); i++)
			device_remove_file(dev, &bus->dev_attrs[i]);
	}
}

#ifdef CONFIG_SYSFS_DEPRECATED
static int make_deprecated_bus_links(struct device *dev)
{
	return sysfs_create_link(&dev->kobj,
				 &dev->bus->p->subsys.kobj, "bus");
}

static void remove_deprecated_bus_links(struct device *dev)
{
	sysfs_remove_link(&dev->kobj, "bus");
}
#else
static inline int make_deprecated_bus_links(struct device *dev) { return 0; }
static inline void remove_deprecated_bus_links(struct device *dev) { }
#endif

/**
 * bus_add_device - add device to bus
 * @dev: device being added
 *
 * - Add the device to its bus's list of devices.
 * - Create link to device's bus.
 */
int bus_add_device(struct device *dev)
{
	struct bus_type *bus = bus_get(dev->bus);
	int error = 0;

	if (bus) {
		pr_debug("bus: '%s': add device %s\n", bus->name, dev->bus_id);
		error = device_add_attrs(bus, dev);
		if (error)
			goto out_put;
		error = sysfs_create_link(&bus->p->devices_kset->kobj,
						&dev->kobj, dev->bus_id);
		if (error)
			goto out_id;
		error = sysfs_create_link(&dev->kobj,
				&dev->bus->p->subsys.kobj, "subsystem");
		if (error)
			goto out_subsys;
		error = make_deprecated_bus_links(dev);
		if (error)
			goto out_deprecated;
	}
	return 0;

out_deprecated:
	sysfs_remove_link(&dev->kobj, "subsystem");
out_subsys:
	sysfs_remove_link(&bus->p->devices_kset->kobj, dev->bus_id);
out_id:
	device_remove_attrs(bus, dev);
out_put:
	bus_put(dev->bus);
	return error;
}

/**
 * bus_attach_device - add device to bus
 * @dev: device tried to attach to a driver
 *
 * - Add device to bus's list of devices.
 * - Try to attach to driver.
 */
void bus_attach_device(struct device *dev)
{
	struct bus_type *bus = dev->bus;
	int ret = 0;

	if (bus) {
		if (bus->p->drivers_autoprobe)
			ret = device_attach(dev);
		WARN_ON(ret < 0);
		if (ret >= 0)
			klist_add_tail(&dev->knode_bus, &bus->p->klist_devices);
	}
}

/**
 * bus_remove_device - remove device from bus
 * @dev: device to be removed
 *
 * - Remove symlink from bus's directory.
 * - Delete device from bus's list.
 * - Detach from its driver.
 * - Drop reference taken in bus_add_device().
 */
void bus_remove_device(struct device *dev)
{
	if (dev->bus) {
		sysfs_remove_link(&dev->kobj, "subsystem");
		remove_deprecated_bus_links(dev);
		sysfs_remove_link(&dev->bus->p->devices_kset->kobj,
				  dev->bus_id);
		device_remove_attrs(dev->bus, dev);
		if (klist_node_attached(&dev->knode_bus))
			klist_del(&dev->knode_bus);

		pr_debug("bus: '%s': remove device %s\n",
			 dev->bus->name, dev->bus_id);
		device_release_driver(dev);
		bus_put(dev->bus);
	}
}

static int driver_add_attrs(struct bus_type *bus, struct device_driver *drv)
{
	int error = 0;
	int i;

	if (bus->drv_attrs) {
		for (i = 0; attr_name(bus->drv_attrs[i]); i++) {
			error = driver_create_file(drv, &bus->drv_attrs[i]);
			if (error)
				goto err;
		}
	}
done:
	return error;
err:
	while (--i >= 0)
		driver_remove_file(drv, &bus->drv_attrs[i]);
	goto done;
}

static void driver_remove_attrs(struct bus_type *bus,
				struct device_driver *drv)
{
	int i;

	if (bus->drv_attrs) {
		for (i = 0; attr_name(bus->drv_attrs[i]); i++)
			driver_remove_file(drv, &bus->drv_attrs[i]);
	}
}

#ifdef CONFIG_HOTPLUG
/*
 * Thanks to drivers making their tables __devinit, we can't allow manual
 * bind and unbind from userspace unless CONFIG_HOTPLUG is enabled.
 */
static int __must_check add_bind_files(struct device_driver *drv)
{
	int ret;

	ret = driver_create_file(drv, &driver_attr_unbind);
	if (ret == 0) {
		ret = driver_create_file(drv, &driver_attr_bind);
		if (ret)
			driver_remove_file(drv, &driver_attr_unbind);
	}
	return ret;
}

static void remove_bind_files(struct device_driver *drv)
{
	driver_remove_file(drv, &driver_attr_bind);
	driver_remove_file(drv, &driver_attr_unbind);
}

static BUS_ATTR(drivers_probe, S_IWUSR, NULL, store_drivers_probe);
static BUS_ATTR(drivers_autoprobe, S_IWUSR | S_IRUGO,
		show_drivers_autoprobe, store_drivers_autoprobe);

static int add_probe_files(struct bus_type *bus)
{
	int retval;

	retval = bus_create_file(bus, &bus_attr_drivers_probe);
	if (retval)
		goto out;

	retval = bus_create_file(bus, &bus_attr_drivers_autoprobe);
	if (retval)
		bus_remove_file(bus, &bus_attr_drivers_probe);
out:
	return retval;
}

static void remove_probe_files(struct bus_type *bus)
{
	bus_remove_file(bus, &bus_attr_drivers_autoprobe);
	bus_remove_file(bus, &bus_attr_drivers_probe);
}
#else
static inline int add_bind_files(struct device_driver *drv) { return 0; }
static inline void remove_bind_files(struct device_driver *drv) {}
static inline int add_probe_files(struct bus_type *bus) { return 0; }
static inline void remove_probe_files(struct bus_type *bus) {}
#endif

static ssize_t driver_uevent_store(struct device_driver *drv,
				   const char *buf, size_t count)
{
	enum kobject_action action;

	if (kobject_action_type(buf, count, &action) == 0)
		kobject_uevent(&drv->p->kobj, action);
	return count;
}
static DRIVER_ATTR(uevent, S_IWUSR, NULL, driver_uevent_store);

/**
 * bus_add_driver - Add a driver to the bus.
 * @drv: driver.
 */
int bus_add_driver(struct device_driver *drv)
{
	struct bus_type *bus;
	struct driver_private *priv;
	int error = 0;

	bus = bus_get(drv->bus);
	if (!bus)
		return -EINVAL;

	pr_debug("bus: '%s': add driver %s\n", bus->name, drv->name);

	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
	if (!priv) {
		error = -ENOMEM;
		goto out_put_bus;
	}
	klist_init(&priv->klist_devices, NULL, NULL);
	priv->driver = drv;
	drv->p = priv;
	priv->kobj.kset = bus->p->drivers_kset;
	error = kobject_init_and_add(&priv->kobj, &driver_ktype, NULL,
				     "%s", drv->name);
	if (error)
		goto out_unregister;

	if (drv->bus->p->drivers_autoprobe) {
		error = driver_attach(drv);
		if (error)
			goto out_unregister;
	}
	klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers);
	module_add_driver(drv->owner, drv);

	error = driver_create_file(drv, &driver_attr_uevent);
	if (error) {
		printk(KERN_ERR "%s: uevent attr (%s) failed\n",
			__func__, drv->name);
	}
	error = driver_add_attrs(bus, drv);
	if (error) {
		/* How the hell do we get out of this pickle? Give up */
		printk(KERN_ERR "%s: driver_add_attrs(%s) failed\n",
			__func__, drv->name);
	}
	error = add_bind_files(drv);
	if (error) {
		/* Ditto */
		printk(KERN_ERR "%s: add_bind_files(%s) failed\n",
			__func__, drv->name);
	}

	kobject_uevent(&priv->kobj, KOBJ_ADD);
	return error;
out_unregister:
	kobject_put(&priv->kobj);
out_put_bus:
	bus_put(bus);
	return error;
}

/**
 * bus_remove_driver - delete driver from bus's knowledge.
 * @drv: driver.
 *
 * Detach the driver from the devices it controls, and remove
 * it from its bus's list of drivers. Finally, we drop the reference
 * to the bus we took in bus_add_driver().
 */
void bus_remove_driver(struct device_driver *drv)
{
	if (!drv->bus)
		return;

	remove_bind_files(drv);
	driver_remove_attrs(drv->bus, drv);
	driver_remove_file(drv, &driver_attr_uevent);
	klist_remove(&drv->p->knode_bus);
	pr_debug("bus: '%s': remove driver %s\n", drv->bus->name, drv->name);
	driver_detach(drv);
	module_remove_driver(drv);
	kobject_put(&drv->p->kobj);
	bus_put(drv->bus);
}

/* Helper for bus_rescan_devices's iter */
static int __must_check bus_rescan_devices_helper(struct device *dev,
						  void *data)
{
	int ret = 0;

	if (!dev->driver) {
		if (dev->parent)	/* Needed for USB */
			down(&dev->parent->sem);
		ret = device_attach(dev);
		if (dev->parent)
			up(&dev->parent->sem);
	}
	return ret < 0 ? ret : 0;
}

/**
 * bus_rescan_devices - rescan devices on the bus for possible drivers
 * @bus: the bus to scan.
 *
 * This function will look for devices on the bus with no driver
 * attached and rescan it against existing drivers to see if it matches
 * any by calling device_attach() for the unbound devices.
 */
int bus_rescan_devices(struct bus_type *bus)
{
	return bus_for_each_dev(bus, NULL, NULL, bus_rescan_devices_helper);
}
EXPORT_SYMBOL_GPL(bus_rescan_devices);

/**
 * device_reprobe - remove driver for a device and probe for a new driver
 * @dev: the device to reprobe
 *
 * This function detaches the attached driver (if any) for the given
 * device and restarts the driver probing process.  It is intended
 * to use if probing criteria changed during a devices lifetime and
 * driver attachment should change accordingly.
 */
int device_reprobe(struct device *dev)
{
	if (dev->driver) {
		if (dev->parent)        /* Needed for USB */
			down(&dev->parent->sem);
		device_release_driver(dev);
		if (dev->parent)
			up(&dev->parent->sem);
	}
	return bus_rescan_devices_helper(dev, NULL);
}
EXPORT_SYMBOL_GPL(device_reprobe);

/**
 * find_bus - locate bus by name.
 * @name: name of bus.
 *
 * Call kset_find_obj() to iterate over list of buses to
 * find a bus by name. Return bus if found.
 *
 * Note that kset_find_obj increments bus' reference count.
 */
#if 0
struct bus_type *find_bus(char *name)
{
	struct kobject *k = kset_find_obj(bus_kset, name);
	return k ? to_bus(k) : NULL;
}
#endif  /*  0  */


/**
 * bus_add_attrs - Add default attributes for this bus.
 * @bus: Bus that has just been registered.
 */

static int bus_add_attrs(struct bus_type *bus)
{
	int error = 0;
	int i;

	if (bus->bus_attrs) {
		for (i = 0; attr_name(bus->bus_attrs[i]); i++) {
			error = bus_create_file(bus, &bus->bus_attrs[i]);
			if (error)
				goto err;
		}
	}
done:
	return error;
err:
	while (--i >= 0)
		bus_remove_file(bus, &bus->bus_attrs[i]);
	goto done;
}

static void bus_remove_attrs(struct bus_type *bus)
{
	int i;

	if (bus->bus_attrs) {
		for (i = 0; attr_name(bus->bus_attrs[i]); i++)
			bus_remove_file(bus, &bus->bus_attrs[i]);
	}
}

static void klist_devices_get(struct klist_node *n)
{
	struct device *dev = container_of(n, struct device, knode_bus);

	get_device(dev);
}

static void klist_devices_put(struct klist_node *n)
{
	struct device *dev = container_of(n, struct device, knode_bus);

	put_device(dev);
}

static ssize_t bus_uevent_store(struct bus_type *bus,
				const char *buf, size_t count)
{
	enum kobject_action action;

	if (kobject_action_type(buf, count, &action) == 0)
		kobject_uevent(&bus->p->subsys.kobj, action);
	return count;
}
static BUS_ATTR(uevent, S_IWUSR, NULL, bus_uevent_store);

/**
 * bus_register - register a bus with the system.
 * @bus: bus.
 *
 * Once we have that, we registered the bus with the kobject
 * infrastructure, then register the children subsystems it has:
 * the devices and drivers that belong to the bus.
 */
int bus_register(struct bus_type *bus)
{
	int retval;
	struct bus_type_private *priv;

	priv = kzalloc(sizeof(struct bus_type_private), GFP_KERNEL);
	if (!priv)
		return -ENOMEM;

	priv->bus = bus;
	bus->p = priv;

	BLOCKING_INIT_NOTIFIER_HEAD(&priv->bus_notifier);

	retval = kobject_set_name(&priv->subsys.kobj, "%s", bus->name);
	if (retval)
		goto out;

	priv->subsys.kobj.kset = bus_kset;
	priv->subsys.kobj.ktype = &bus_ktype;
	priv->drivers_autoprobe = 1;

	retval = kset_register(&priv->subsys);
	if (retval)
		goto out;

	retval = bus_create_file(bus, &bus_attr_uevent);
	if (retval)
		goto bus_uevent_fail;

	priv->devices_kset = kset_create_and_add("devices", NULL,
						 &priv->subsys.kobj);
	if (!priv->devices_kset) {
		retval = -ENOMEM;
		goto bus_devices_fail;
	}

	priv->drivers_kset = kset_create_and_add("drivers", NULL,
						 &priv->subsys.kobj);
	if (!priv->drivers_kset) {
		retval = -ENOMEM;
		goto bus_drivers_fail;
	}

	klist_init(&priv->klist_devices, klist_devices_get, klist_devices_put);
	klist_init(&priv->klist_drivers, NULL, NULL);

	retval = add_probe_files(bus);
	if (retval)
		goto bus_probe_files_fail;

	retval = bus_add_attrs(bus);
	if (retval)
		goto bus_attrs_fail;

	pr_debug("bus: '%s': registered\n", bus->name);
	return 0;

bus_attrs_fail:
	remove_probe_files(bus);
bus_probe_files_fail:
	kset_unregister(bus->p->drivers_kset);
bus_drivers_fail:
	kset_unregister(bus->p->devices_kset);
bus_devices_fail:
	bus_remove_file(bus, &bus_attr_uevent);
bus_uevent_fail:
	kset_unregister(&bus->p->subsys);
	kfree(bus->p);
out:
	return retval;
}
EXPORT_SYMBOL_GPL(bus_register);

/**
 * bus_unregister - remove a bus from the system
 * @bus: bus.
 *
 * Unregister the child subsystems and the bus itself.
 * Finally, we call bus_put() to release the refcount
 */
void bus_unregister(struct bus_type *bus)
{
	pr_debug("bus: '%s': unregistering\n", bus->name);
	bus_remove_attrs(bus);
	remove_probe_files(bus);
	kset_unregister(bus->p->drivers_kset);
	kset_unregister(bus->p->devices_kset);
	bus_remove_file(bus, &bus_attr_uevent);
	kset_unregister(&bus->p->subsys);
	kfree(bus->p);
}
EXPORT_SYMBOL_GPL(bus_unregister);

int bus_register_notifier(struct bus_type *bus, struct notifier_block *nb)
{
	return blocking_notifier_chain_register(&bus->p->bus_notifier, nb);
}
EXPORT_SYMBOL_GPL(bus_register_notifier);

int bus_unregister_notifier(struct bus_type *bus, struct notifier_block *nb)
{
	return blocking_notifier_chain_unregister(&bus->p->bus_notifier, nb);
}
EXPORT_SYMBOL_GPL(bus_unregister_notifier);

struct kset *bus_get_kset(struct bus_type *bus)
{
	return &bus->p->subsys;
}
EXPORT_SYMBOL_GPL(bus_get_kset);

struct klist *bus_get_device_klist(struct bus_type *bus)
{
	return &bus->p->klist_devices;
}
EXPORT_SYMBOL_GPL(bus_get_device_klist);

int __init buses_init(void)
{
	bus_kset = kset_create_and_add("bus", &bus_uevent_ops, NULL);
	if (!bus_kset)
		return -ENOMEM;
	return 0;
}