aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/base/core.c
blob: b224bb43ff638f812694efe1e4c8eaa5bbd47967 (plain)
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
/*
 * drivers/base/core.c - core driver model code (device registration, etc)
 *
 * Copyright (c) 2002-3 Patrick Mochel
 * Copyright (c) 2002-3 Open Source Development Labs
 * Copyright (c) 2006 Greg Kroah-Hartman <gregkh@suse.de>
 * Copyright (c) 2006 Novell, Inc.
 *
 * This file is released under the GPLv2
 *
 */

#include <linux/device.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/kdev_t.h>

#include <asm/semaphore.h>

#include "base.h"
#include "power/power.h"

int (*platform_notify)(struct device * dev) = NULL;
int (*platform_notify_remove)(struct device * dev) = NULL;

/*
 * sysfs bindings for devices.
 */

/**
 * dev_driver_string - Return a device's driver name, if at all possible
 * @dev: struct device to get the name of
 *
 * Will return the device's driver's name if it is bound to a device.  If
 * the device is not bound to a device, it will return the name of the bus
 * it is attached to.  If it is not attached to a bus either, an empty
 * string will be returned.
 */
const char *dev_driver_string(struct device *dev)
{
	return dev->driver ? dev->driver->name :
			(dev->bus ? dev->bus->name : "");
}
EXPORT_SYMBOL_GPL(dev_driver_string);

#define to_dev(obj) container_of(obj, struct device, kobj)
#define to_dev_attr(_attr) container_of(_attr, struct device_attribute, attr)

static ssize_t
dev_attr_show(struct kobject * kobj, struct attribute * attr, char * buf)
{
	struct device_attribute * dev_attr = to_dev_attr(attr);
	struct device * dev = to_dev(kobj);
	ssize_t ret = -EIO;

	if (dev_attr->show)
		ret = dev_attr->show(dev, dev_attr, buf);
	return ret;
}

static ssize_t
dev_attr_store(struct kobject * kobj, struct attribute * attr,
	       const char * buf, size_t count)
{
	struct device_attribute * dev_attr = to_dev_attr(attr);
	struct device * dev = to_dev(kobj);
	ssize_t ret = -EIO;

	if (dev_attr->store)
		ret = dev_attr->store(dev, dev_attr, buf, count);
	return ret;
}

static struct sysfs_ops dev_sysfs_ops = {
	.show	= dev_attr_show,
	.store	= dev_attr_store,
};


/**
 *	device_release - free device structure.
 *	@kobj:	device's kobject.
 *
 *	This is called once the reference count for the object
 *	reaches 0. We forward the call to the device's release
 *	method, which should handle actually freeing the structure.
 */
static void device_release(struct kobject * kobj)
{
	struct device * dev = to_dev(kobj);

	if (dev->release)
		dev->release(dev);
	else if (dev->class && dev->class->dev_release)
		dev->class->dev_release(dev);
	else {
		printk(KERN_ERR "Device '%s' does not have a release() function, "
			"it is broken and must be fixed.\n",
			dev->bus_id);
		WARN_ON(1);
	}
}

static struct kobj_type ktype_device = {
	.release	= device_release,
	.sysfs_ops	= &dev_sysfs_ops,
};


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

	if (ktype == &ktype_device) {
		struct device *dev = to_dev(kobj);
		if (dev->bus)
			return 1;
		if (dev->class)
			return 1;
	}
	return 0;
}

static const char *dev_uevent_name(struct kset *kset, struct kobject *kobj)
{
	struct device *dev = to_dev(kobj);

	if (dev->bus)
		return dev->bus->name;
	if (dev->class)
		return dev->class->name;
	return NULL;
}

static int dev_uevent(struct kset *kset, struct kobject *kobj, char **envp,
			int num_envp, char *buffer, int buffer_size)
{
	struct device *dev = to_dev(kobj);
	int i = 0;
	int length = 0;
	int retval = 0;

	/* add the major/minor if present */
	if (MAJOR(dev->devt)) {
		add_uevent_var(envp, num_envp, &i,
			       buffer, buffer_size, &length,
			       "MAJOR=%u", MAJOR(dev->devt));
		add_uevent_var(envp, num_envp, &i,
			       buffer, buffer_size, &length,
			       "MINOR=%u", MINOR(dev->devt));
	}

	/* add bus name (same as SUBSYSTEM, deprecated) */
	if (dev->bus)
		add_uevent_var(envp, num_envp, &i,
			       buffer, buffer_size, &length,
			       "PHYSDEVBUS=%s", dev->bus->name);

	/* add driver name (PHYSDEV* values are deprecated)*/
	if (dev->driver) {
		add_uevent_var(envp, num_envp, &i,
			       buffer, buffer_size, &length,
			       "DRIVER=%s", dev->driver->name);
		add_uevent_var(envp, num_envp, &i,
			       buffer, buffer_size, &length,
			       "PHYSDEVDRIVER=%s", dev->driver->name);
	}

	/* terminate, set to next free slot, shrink available space */
	envp[i] = NULL;
	envp = &envp[i];
	num_envp -= i;
	buffer = &buffer[length];
	buffer_size -= length;

	if (dev->bus && dev->bus->uevent) {
		/* have the bus specific function add its stuff */
		retval = dev->bus->uevent(dev, envp, num_envp, buffer, buffer_size);
			if (retval) {
			pr_debug ("%s - uevent() returned %d\n",
				  __FUNCTION__, retval);
		}
	}

	if (dev->class && dev->class->dev_uevent) {
		/* have the class specific function add its stuff */
		retval = dev->class->dev_uevent(dev, envp, num_envp, buffer, buffer_size);
			if (retval) {
				pr_debug("%s - dev_uevent() returned %d\n",
					 __FUNCTION__, retval);
		}
	}

	return retval;
}

static struct kset_uevent_ops device_uevent_ops = {
	.filter =	dev_uevent_filter,
	.name =		dev_uevent_name,
	.uevent =	dev_uevent,
};

static ssize_t store_uevent(struct device *dev, struct device_attribute *attr,
			    const char *buf, size_t count)
{
	kobject_uevent(&dev->kobj, KOBJ_ADD);
	return count;
}

static int device_add_groups(struct device *dev)
{
	int i;
	int error = 0;

	if (dev->groups) {
		for (i = 0; dev->groups[i]; i++) {
			error = sysfs_create_group(&dev->kobj, dev->groups[i]);
			if (error) {
				while (--i >= 0)
					sysfs_remove_group(&dev->kobj, dev->groups[i]);
				goto out;
			}
		}
	}
out:
	return error;
}

static void device_remove_groups(struct device *dev)
{
	int i;
	if (dev->groups) {
		for (i = 0; dev->groups[i]; i++) {
			sysfs_remove_group(&dev->kobj, dev->groups[i]);
		}
	}
}

static int device_add_attrs(struct device *dev)
{
	struct class *class = dev->class;
	int error = 0;
	int i;

	if (!class)
		return 0;

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

static void device_remove_attrs(struct device *dev)
{
	struct class *class = dev->class;
	int i;

	if (!class)
		return;

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


static ssize_t show_dev(struct device *dev, struct device_attribute *attr,
			char *buf)
{
	return print_dev_t(buf, dev->devt);
}

/*
 *	devices_subsys - structure to be registered with kobject core.
 */

decl_subsys(devices, &ktype_device, &device_uevent_ops);


/**
 *	device_create_file - create sysfs attribute file for device.
 *	@dev:	device.
 *	@attr:	device attribute descriptor.
 */

int device_create_file(struct device * dev, struct device_attribute * attr)
{
	int error = 0;
	if (get_device(dev)) {
		error = sysfs_create_file(&dev->kobj, &attr->attr);
		put_device(dev);
	}
	return error;
}

/**
 *	device_remove_file - remove sysfs attribute file.
 *	@dev:	device.
 *	@attr:	device attribute descriptor.
 */

void device_remove_file(struct device * dev, struct device_attribute * attr)
{
	if (get_device(dev)) {
		sysfs_remove_file(&dev->kobj, &attr->attr);
		put_device(dev);
	}
}

/**
 * device_create_bin_file - create sysfs binary attribute file for device.
 * @dev: device.
 * @attr: device binary attribute descriptor.
 */
int device_create_bin_file(struct device *dev, struct bin_attribute *attr)
{
	int error = -EINVAL;
	if (dev)
		error = sysfs_create_bin_file(&dev->kobj, attr);
	return error;
}
EXPORT_SYMBOL_GPL(device_create_bin_file);

/**
 * device_remove_bin_file - remove sysfs binary attribute file
 * @dev: device.
 * @attr: device binary attribute descriptor.
 */
void device_remove_bin_file(struct device *dev, struct bin_attribute *attr)
{
	if (dev)
		sysfs_remove_bin_file(&dev->kobj, attr);
}
EXPORT_SYMBOL_GPL(device_remove_bin_file);

static void klist_children_get(struct klist_node *n)
{
	struct device *dev = container_of(n, struct device, knode_parent);

	get_device(dev);
}

static void klist_children_put(struct klist_node *n)
{
	struct device *dev = container_of(n, struct device, knode_parent);

	put_device(dev);
}


/**
 *	device_initialize - init device structure.
 *	@dev:	device.
 *
 *	This prepares the device for use by other layers,
 *	including adding it to the device hierarchy.
 *	It is the first half of device_register(), if called by
 *	that, though it can also be called separately, so one
 *	may use @dev's fields (e.g. the refcount).
 */

void device_initialize(struct device *dev)
{
	kobj_set_kset_s(dev, devices_subsys);
	kobject_init(&dev->kobj);
	klist_init(&dev->klist_children, klist_children_get,
		   klist_children_put);
	INIT_LIST_HEAD(&dev->dma_pools);
	INIT_LIST_HEAD(&dev->node);
	init_MUTEX(&dev->sem);
	device_init_wakeup(dev, 0);
}

/**
 *	device_add - add device to device hierarchy.
 *	@dev:	device.
 *
 *	This is part 2 of device_register(), though may be called
 *	separately _iff_ device_initialize() has been called separately.
 *
 *	This adds it to the kobject hierarchy via kobject_add(), adds it
 *	to the global and sibling lists for the device, then
 *	adds it to the other relevant subsystems of the driver model.
 */
int device_add(struct device *dev)
{
	struct device *parent = NULL;
	char *class_name = NULL;
	struct class_interface *class_intf;
	int error = -EINVAL;

	dev = get_device(dev);
	if (!dev || !strlen(dev->bus_id))
		goto Error;

	/* if this is a class device, and has no parent, create one */
	if ((dev->class) && (dev->parent == NULL)) {
		error = virtual_device_parent(dev);
		if (error)
			goto Error;
	}

	parent = get_device(dev->parent);

	pr_debug("DEV: registering device: ID = '%s'\n", dev->bus_id);

	/* first, register with generic layer. */
	kobject_set_name(&dev->kobj, "%s", dev->bus_id);
	if (parent)
		dev->kobj.parent = &parent->kobj;

	if ((error = kobject_add(&dev->kobj)))
		goto Error;

	/* notify platform of device entry */
	if (platform_notify)
		platform_notify(dev);

	dev->uevent_attr.attr.name = "uevent";
	dev->uevent_attr.attr.mode = S_IWUSR;
	if (dev->driver)
		dev->uevent_attr.attr.owner = dev->driver->owner;
	dev->uevent_attr.store = store_uevent;
	device_create_file(dev, &dev->uevent_attr);

	if (MAJOR(dev->devt)) {
		struct device_attribute *attr;
		attr = kzalloc(sizeof(*attr), GFP_KERNEL);
		if (!attr) {
			error = -ENOMEM;
			goto PMError;
		}
		attr->attr.name = "dev";
		attr->attr.mode = S_IRUGO;
		if (dev->driver)
			attr->attr.owner = dev->driver->owner;
		attr->show = show_dev;
		error = device_create_file(dev, attr);
		if (error) {
			kfree(attr);
			goto attrError;
		}

		dev->devt_attr = attr;
	}

	if (dev->class) {
		sysfs_create_link(&dev->kobj, &dev->class->subsys.kset.kobj,
				  "subsystem");
		sysfs_create_link(&dev->class->subsys.kset.kobj, &dev->kobj,
				  dev->bus_id);
		if (parent) {
			sysfs_create_link(&dev->kobj, &dev->parent->kobj, "device");
			class_name = make_class_name(dev->class->name, &dev->kobj);
			sysfs_create_link(&dev->parent->kobj, &dev->kobj, class_name);
		}
	}

	if ((error = device_add_attrs(dev)))
		goto AttrsError;
	if ((error = device_add_groups(dev)))
		goto GroupError;
	if ((error = device_pm_add(dev)))
		goto PMError;
	if ((error = bus_add_device(dev)))
		goto BusError;
	kobject_uevent(&dev->kobj, KOBJ_ADD);
	bus_attach_device(dev);
	if (parent)
		klist_add_tail(&dev->knode_parent, &parent->klist_children);

	if (dev->class) {
		down(&dev->class->sem);
		/* tie the class to the device */
		list_add_tail(&dev->node, &dev->class->devices);

		/* notify any interfaces that the device is here */
		list_for_each_entry(class_intf, &dev->class->interfaces, node)
			if (class_intf->add_dev)
				class_intf->add_dev(dev, class_intf);
		up(&dev->class->sem);
	}
 Done:
 	kfree(class_name);
	put_device(dev);
	return error;
 BusError:
	device_pm_remove(dev);
 PMError:
	device_remove_groups(dev);
 GroupError:
 	device_remove_attrs(dev);
 AttrsError:
	if (dev->devt_attr) {
		device_remove_file(dev, dev->devt_attr);
		kfree(dev->devt_attr);
	}
 attrError:
	kobject_uevent(&dev->kobj, KOBJ_REMOVE);
	kobject_del(&dev->kobj);
 Error:
	if (parent)
		put_device(parent);
	goto Done;
}


/**
 *	device_register - register a device with the system.
 *	@dev:	pointer to the device structure
 *
 *	This happens in two clean steps - initialize the device
 *	and add it to the system. The two steps can be called
 *	separately, but this is the easiest and most common.
 *	I.e. you should only call the two helpers separately if
 *	have a clearly defined need to use and refcount the device
 *	before it is added to the hierarchy.
 */

int device_register(struct device *dev)
{
	device_initialize(dev);
	return device_add(dev);
}


/**
 *	get_device - increment reference count for device.
 *	@dev:	device.
 *
 *	This simply forwards the call to kobject_get(), though
 *	we do take care to provide for the case that we get a NULL
 *	pointer passed in.
 */

struct device * get_device(struct device * dev)
{
	return dev ? to_dev(kobject_get(&dev->kobj)) : NULL;
}


/**
 *	put_device - decrement reference count.
 *	@dev:	device in question.
 */
void put_device(struct device * dev)
{
	if (dev)
		kobject_put(&dev->kobj);
}


/**
 *	device_del - delete device from system.
 *	@dev:	device.
 *
 *	This is the first part of the device unregistration
 *	sequence. This removes the device from the lists we control
 *	from here, has it removed from the other driver model
 *	subsystems it was added to in device_add(), and removes it
 *	from the kobject hierarchy.
 *
 *	NOTE: this should be called manually _iff_ device_add() was
 *	also called manually.
 */

void device_del(struct device * dev)
{
	struct device * parent = dev->parent;
	char *class_name = NULL;
	struct class_interface *class_intf;

	if (parent)
		klist_del(&dev->knode_parent);
	if (dev->devt_attr)
		device_remove_file(dev, dev->devt_attr);
	if (dev->class) {
		sysfs_remove_link(&dev->kobj, "subsystem");
		sysfs_remove_link(&dev->class->subsys.kset.kobj, dev->bus_id);
		class_name = make_class_name(dev->class->name, &dev->kobj);
		if (parent) {
			sysfs_remove_link(&dev->kobj, "device");
			sysfs_remove_link(&dev->parent->kobj, class_name);
		}
		kfree(class_name);
		down(&dev->class->sem);
		/* notify any interfaces that the device is now gone */
		list_for_each_entry(class_intf, &dev->class->interfaces, node)
			if (class_intf->remove_dev)
				class_intf->remove_dev(dev, class_intf);
		/* remove the device from the class list */
		list_del_init(&dev->node);
		up(&dev->class->sem);
	}
	device_remove_file(dev, &dev->uevent_attr);
	device_remove_groups(dev);
	device_remove_attrs(dev);

	/* Notify the platform of the removal, in case they
	 * need to do anything...
	 */
	if (platform_notify_remove)
		platform_notify_remove(dev);
	bus_remove_device(dev);
	device_pm_remove(dev);
	kobject_uevent(&dev->kobj, KOBJ_REMOVE);
	kobject_del(&dev->kobj);
	if (parent)
		put_device(parent);
}

/**
 *	device_unregister - unregister device from system.
 *	@dev:	device going away.
 *
 *	We do this in two parts, like we do device_register(). First,
 *	we remove it from all the subsystems with device_del(), then
 *	we decrement the reference count via put_device(). If that
 *	is the final reference count, the device will be cleaned up
 *	via device_release() above. Otherwise, the structure will
 *	stick around until the final reference to the device is dropped.
 */
void device_unregister(struct device * dev)
{
	pr_debug("DEV: Unregistering device. ID = '%s'\n", dev->bus_id);
	device_del(dev);
	put_device(dev);
}


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

/**
 *	device_for_each_child - device child iterator.
 *	@parent: parent struct device.
 *	@data:	data for the callback.
 *	@fn:	function to be called for each device.
 *
 *	Iterate over @parent's child devices, and call @fn for each,
 *	passing it @data.
 *
 *	We check the return of @fn each time. If it returns anything
 *	other than 0, we break out and return that value.
 */
int device_for_each_child(struct device * parent, void * data,
		     int (*fn)(struct device *, void *))
{
	struct klist_iter i;
	struct device * child;
	int error = 0;

	klist_iter_init(&parent->klist_children, &i);
	while ((child = next_device(&i)) && !error)
		error = fn(child, data);
	klist_iter_exit(&i);
	return error;
}

int __init devices_init(void)
{
	return subsystem_register(&devices_subsys);
}

EXPORT_SYMBOL_GPL(device_for_each_child);

EXPORT_SYMBOL_GPL(device_initialize);
EXPORT_SYMBOL_GPL(device_add);
EXPORT_SYMBOL_GPL(device_register);

EXPORT_SYMBOL_GPL(device_del);
EXPORT_SYMBOL_GPL(device_unregister);
EXPORT_SYMBOL_GPL(get_device);
EXPORT_SYMBOL_GPL(put_device);

EXPORT_SYMBOL_GPL(device_create_file);
EXPORT_SYMBOL_GPL(device_remove_file);


static void device_create_release(struct device *dev)
{
	pr_debug("%s called for %s\n", __FUNCTION__, dev->bus_id);
	kfree(dev);
}

/**
 * device_create - creates a device and registers it with sysfs
 * @class: pointer to the struct class that this device should be registered to
 * @parent: pointer to the parent struct device of this new device, if any
 * @devt: the dev_t for the char device to be added
 * @fmt: string for the device's name
 *
 * This function can be used by char device classes.  A struct device
 * will be created in sysfs, registered to the specified class.
 *
 * A "dev" file will be created, showing the dev_t for the device, if
 * the dev_t is not 0,0.
 * If a pointer to a parent struct device is passed in, the newly created
 * struct device will be a child of that device in sysfs.
 * The pointer to the struct device will be returned from the call.
 * Any further sysfs files that might be required can be created using this
 * pointer.
 *
 * Note: the struct class passed to this function must have previously
 * been created with a call to class_create().
 */
struct device *device_create(struct class *class, struct device *parent,
			     dev_t devt, const char *fmt, ...)
{
	va_list args;
	struct device *dev = NULL;
	int retval = -ENODEV;

	if (class == NULL || IS_ERR(class))
		goto error;

	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
	if (!dev) {
		retval = -ENOMEM;
		goto error;
	}

	dev->devt = devt;
	dev->class = class;
	dev->parent = parent;
	dev->release = device_create_release;

	va_start(args, fmt);
	vsnprintf(dev->bus_id, BUS_ID_SIZE, fmt, args);
	va_end(args);
	retval = device_register(dev);
	if (retval)
		goto error;

	return dev;

error:
	kfree(dev);
	return ERR_PTR(retval);
}
EXPORT_SYMBOL_GPL(device_create);

/**
 * device_destroy - removes a device that was created with device_create()
 * @class: pointer to the struct class that this device was registered with
 * @devt: the dev_t of the device that was previously registered
 *
 * This call unregisters and cleans up a device that was created with a
 * call to device_create().
 */
void device_destroy(struct class *class, dev_t devt)
{
	struct device *dev = NULL;
	struct device *dev_tmp;

	down(&class->sem);
	list_for_each_entry(dev_tmp, &class->devices, node) {
		if (dev_tmp->devt == devt) {
			dev = dev_tmp;
			break;
		}
	}
	up(&class->sem);

	if (dev)
		device_unregister(dev);
}
EXPORT_SYMBOL_GPL(device_destroy);

/**
 * device_rename - renames a device
 * @dev: the pointer to the struct device to be renamed
 * @new_name: the new name of the device
 */
int device_rename(struct device *dev, char *new_name)
{
	char *old_class_name = NULL;
	char *new_class_name = NULL;
	char *old_symlink_name = NULL;
	int error;

	dev = get_device(dev);
	if (!dev)
		return -EINVAL;

	pr_debug("DEVICE: renaming '%s' to '%s'\n", dev->bus_id, new_name);

	if ((dev->class) && (dev->parent))
		old_class_name = make_class_name(dev->class->name, &dev->kobj);

	if (dev->class) {
		old_symlink_name = kmalloc(BUS_ID_SIZE, GFP_KERNEL);
		if (!old_symlink_name)
			return -ENOMEM;
		strlcpy(old_symlink_name, dev->bus_id, BUS_ID_SIZE);
	}

	strlcpy(dev->bus_id, new_name, BUS_ID_SIZE);

	error = kobject_rename(&dev->kobj, new_name);

	if (old_class_name) {
		new_class_name = make_class_name(dev->class->name, &dev->kobj);
		if (new_class_name) {
			sysfs_create_link(&dev->parent->kobj, &dev->kobj,
					  new_class_name);
			sysfs_remove_link(&dev->parent->kobj, old_class_name);
		}
	}
	if (dev->class) {
		sysfs_remove_link(&dev->class->subsys.kset.kobj,
				  old_symlink_name);
		sysfs_create_link(&dev->class->subsys.kset.kobj, &dev->kobj,
				  dev->bus_id);
	}
	put_device(dev);

	kfree(old_class_name);
	kfree(new_class_name);
	kfree(old_symlink_name);

	return error;
}