summaryrefslogtreecommitdiffstats
path: root/fs/sysfs/file.c
blob: 62f4fb37789e0f5b634c44b7adc782d1c04c67fd (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
/*
 * fs/sysfs/file.c - sysfs regular (text) file implementation
 *
 * Copyright (c) 2001-3 Patrick Mochel
 * Copyright (c) 2007 SUSE Linux Products GmbH
 * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
 *
 * This file is released under the GPLv2.
 *
 * Please see Documentation/filesystems/sysfs.txt for more information.
 */

#include <linux/module.h>
#include <linux/kobject.h>
#include <linux/kallsyms.h>
#include <linux/slab.h>
#include <linux/fsnotify.h>
#include <linux/namei.h>
#include <linux/poll.h>
#include <linux/list.h>
#include <linux/mutex.h>
#include <linux/limits.h>
#include <asm/uaccess.h>

#include "sysfs.h"

/*
 * There's one sysfs_buffer for each open file and one
 * sysfs_open_dirent for each sysfs_dirent with one or more open
 * files.
 *
 * filp->private_data points to sysfs_buffer and
 * sysfs_dirent->s_attr.open points to sysfs_open_dirent.  s_attr.open
 * is protected by sysfs_open_dirent_lock.
 */
static DEFINE_SPINLOCK(sysfs_open_dirent_lock);

struct sysfs_open_dirent {
	atomic_t		refcnt;
	atomic_t		event;
	wait_queue_head_t	poll;
	struct list_head	buffers; /* goes through sysfs_buffer.list */
};

struct sysfs_buffer {
	size_t			count;
	loff_t			pos;
	char			* page;
	const struct sysfs_ops	* ops;
	struct mutex		mutex;
	int			needs_read_fill;
	int			event;
	struct list_head	list;
};

/**
 *	fill_read_buffer - allocate and fill buffer from object.
 *	@dentry:	dentry pointer.
 *	@buffer:	data buffer for file.
 *
 *	Allocate @buffer->page, if it hasn't been already, then call the
 *	kobject's show() method to fill the buffer with this attribute's 
 *	data. 
 *	This is called only once, on the file's first read unless an error
 *	is returned.
 */
static int fill_read_buffer(struct dentry * dentry, struct sysfs_buffer * buffer)
{
	struct sysfs_dirent *attr_sd = dentry->d_fsdata;
	struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
	const struct sysfs_ops * ops = buffer->ops;
	int ret = 0;
	ssize_t count;

	if (!buffer->page)
		buffer->page = (char *) get_zeroed_page(GFP_KERNEL);
	if (!buffer->page)
		return -ENOMEM;

	/* need attr_sd for attr and ops, its parent for kobj */
	if (!sysfs_get_active(attr_sd))
		return -ENODEV;

	buffer->event = atomic_read(&attr_sd->s_attr.open->event);
	count = ops->show(kobj, attr_sd->s_attr.attr, buffer->page);

	sysfs_put_active(attr_sd);

	/*
	 * The code works fine with PAGE_SIZE return but it's likely to
	 * indicate truncated result or overflow in normal use cases.
	 */
	if (count >= (ssize_t)PAGE_SIZE) {
		print_symbol("fill_read_buffer: %s returned bad count\n",
			(unsigned long)ops->show);
		/* Try to struggle along */
		count = PAGE_SIZE - 1;
	}
	if (count >= 0) {
		buffer->needs_read_fill = 0;
		buffer->count = count;
	} else {
		ret = count;
	}
	return ret;
}

/**
 *	sysfs_read_file - read an attribute. 
 *	@file:	file pointer.
 *	@buf:	buffer to fill.
 *	@count:	number of bytes to read.
 *	@ppos:	starting offset in file.
 *
 *	Userspace wants to read an attribute file. The attribute descriptor
 *	is in the file's ->d_fsdata. The target object is in the directory's
 *	->d_fsdata.
 *
 *	We call fill_read_buffer() to allocate and fill the buffer from the
 *	object's show() method exactly once (if the read is happening from
 *	the beginning of the file). That should fill the entire buffer with
 *	all the data the object has to offer for that attribute.
 *	We then call flush_read_buffer() to copy the buffer to userspace
 *	in the increments specified.
 */

static ssize_t
sysfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
	struct sysfs_buffer * buffer = file->private_data;
	ssize_t retval = 0;

	mutex_lock(&buffer->mutex);
	if (buffer->needs_read_fill || *ppos == 0) {
		retval = fill_read_buffer(file->f_path.dentry,buffer);
		if (retval)
			goto out;
	}
	pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n",
		 __func__, count, *ppos, buffer->page);
	retval = simple_read_from_buffer(buf, count, ppos, buffer->page,
					 buffer->count);
out:
	mutex_unlock(&buffer->mutex);
	return retval;
}

/**
 *	fill_write_buffer - copy buffer from userspace.
 *	@buffer:	data buffer for file.
 *	@buf:		data from user.
 *	@count:		number of bytes in @userbuf.
 *
 *	Allocate @buffer->page if it hasn't been already, then
 *	copy the user-supplied buffer into it.
 */

static int 
fill_write_buffer(struct sysfs_buffer * buffer, const char __user * buf, size_t count)
{
	int error;

	if (!buffer->page)
		buffer->page = (char *)get_zeroed_page(GFP_KERNEL);
	if (!buffer->page)
		return -ENOMEM;

	if (count >= PAGE_SIZE)
		count = PAGE_SIZE - 1;
	error = copy_from_user(buffer->page,buf,count);
	buffer->needs_read_fill = 1;
	/* if buf is assumed to contain a string, terminate it by \0,
	   so e.g. sscanf() can scan the string easily */
	buffer->page[count] = 0;
	return error ? -EFAULT : count;
}


/**
 *	flush_write_buffer - push buffer to kobject.
 *	@dentry:	dentry to the attribute
 *	@buffer:	data buffer for file.
 *	@count:		number of bytes
 *
 *	Get the correct pointers for the kobject and the attribute we're
 *	dealing with, then call the store() method for the attribute, 
 *	passing the buffer that we acquired in fill_write_buffer().
 */

static int
flush_write_buffer(struct dentry * dentry, struct sysfs_buffer * buffer, size_t count)
{
	struct sysfs_dirent *attr_sd = dentry->d_fsdata;
	struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
	const struct sysfs_ops * ops = buffer->ops;
	int rc;

	/* need attr_sd for attr and ops, its parent for kobj */
	if (!sysfs_get_active(attr_sd))
		return -ENODEV;

	rc = ops->store(kobj, attr_sd->s_attr.attr, buffer->page, count);

	sysfs_put_active(attr_sd);

	return rc;
}


/**
 *	sysfs_write_file - write an attribute.
 *	@file:	file pointer
 *	@buf:	data to write
 *	@count:	number of bytes
 *	@ppos:	starting offset
 *
 *	Similar to sysfs_read_file(), though working in the opposite direction.
 *	We allocate and fill the data from the user in fill_write_buffer(),
 *	then push it to the kobject in flush_write_buffer().
 *	There is no easy way for us to know if userspace is only doing a partial
 *	write, so we don't support them. We expect the entire buffer to come
 *	on the first write. 
 *	Hint: if you're writing a value, first read the file, modify only the
 *	the value you're changing, then write entire buffer back. 
 */

static ssize_t
sysfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
{
	struct sysfs_buffer * buffer = file->private_data;
	ssize_t len;

	mutex_lock(&buffer->mutex);
	len = fill_write_buffer(buffer, buf, count);
	if (len > 0)
		len = flush_write_buffer(file->f_path.dentry, buffer, len);
	if (len > 0)
		*ppos += len;
	mutex_unlock(&buffer->mutex);
	return len;
}

/**
 *	sysfs_get_open_dirent - get or create sysfs_open_dirent
 *	@sd: target sysfs_dirent
 *	@buffer: sysfs_buffer for this instance of open
 *
 *	If @sd->s_attr.open exists, increment its reference count;
 *	otherwise, create one.  @buffer is chained to the buffers
 *	list.
 *
 *	LOCKING:
 *	Kernel thread context (may sleep).
 *
 *	RETURNS:
 *	0 on success, -errno on failure.
 */
static int sysfs_get_open_dirent(struct sysfs_dirent *sd,
				 struct sysfs_buffer *buffer)
{
	struct sysfs_open_dirent *od, *new_od = NULL;

 retry:
	spin_lock_irq(&sysfs_open_dirent_lock);

	if (!sd->s_attr.open && new_od) {
		sd->s_attr.open = new_od;
		new_od = NULL;
	}

	od = sd->s_attr.open;
	if (od) {
		atomic_inc(&od->refcnt);
		list_add_tail(&buffer->list, &od->buffers);
	}

	spin_unlock_irq(&sysfs_open_dirent_lock);

	if (od) {
		kfree(new_od);
		return 0;
	}

	/* not there, initialize a new one and retry */
	new_od = kmalloc(sizeof(*new_od), GFP_KERNEL);
	if (!new_od)
		return -ENOMEM;

	atomic_set(&new_od->refcnt, 0);
	atomic_set(&new_od->event, 1);
	init_waitqueue_head(&new_od->poll);
	INIT_LIST_HEAD(&new_od->buffers);
	goto retry;
}

/**
 *	sysfs_put_open_dirent - put sysfs_open_dirent
 *	@sd: target sysfs_dirent
 *	@buffer: associated sysfs_buffer
 *
 *	Put @sd->s_attr.open and unlink @buffer from the buffers list.
 *	If reference count reaches zero, disassociate and free it.
 *
 *	LOCKING:
 *	None.
 */
static void sysfs_put_open_dirent(struct sysfs_dirent *sd,
				  struct sysfs_buffer *buffer)
{
	struct sysfs_open_dirent *od = sd->s_attr.open;
	unsigned long flags;

	spin_lock_irqsave(&sysfs_open_dirent_lock, flags);

	list_del(&buffer->list);
	if (atomic_dec_and_test(&od->refcnt))
		sd->s_attr.open = NULL;
	else
		od = NULL;

	spin_unlock_irqrestore(&sysfs_open_dirent_lock, flags);

	kfree(od);
}

static int sysfs_open_file(struct inode *inode, struct file *file)
{
	struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
	struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
	struct sysfs_buffer *buffer;
	const struct sysfs_ops *ops;
	int error = -EACCES;

	/* need attr_sd for attr and ops, its parent for kobj */
	if (!sysfs_get_active(attr_sd))
		return -ENODEV;

	/* every kobject with an attribute needs a ktype assigned */
	if (kobj->ktype && kobj->ktype->sysfs_ops)
		ops = kobj->ktype->sysfs_ops;
	else {
		WARN(1, KERN_ERR "missing sysfs attribute operations for "
		       "kobject: %s\n", kobject_name(kobj));
		goto err_out;
	}

	/* File needs write support.
	 * The inode's perms must say it's ok, 
	 * and we must have a store method.
	 */
	if (file->f_mode & FMODE_WRITE) {
		if (!(inode->i_mode & S_IWUGO) || !ops->store)
			goto err_out;
	}

	/* File needs read support.
	 * The inode's perms must say it's ok, and we there
	 * must be a show method for it.
	 */
	if (file->f_mode & FMODE_READ) {
		if (!(inode->i_mode & S_IRUGO) || !ops->show)
			goto err_out;
	}

	/* No error? Great, allocate a buffer for the file, and store it
	 * it in file->private_data for easy access.
	 */
	error = -ENOMEM;
	buffer = kzalloc(sizeof(struct sysfs_buffer), GFP_KERNEL);
	if (!buffer)
		goto err_out;

	mutex_init(&buffer->mutex);
	buffer->needs_read_fill = 1;
	buffer->ops = ops;
	file->private_data = buffer;

	/* make sure we have open dirent struct */
	error = sysfs_get_open_dirent(attr_sd, buffer);
	if (error)
		goto err_free;

	/* open succeeded, put active references */
	sysfs_put_active(attr_sd);
	return 0;

 err_free:
	kfree(buffer);
 err_out:
	sysfs_put_active(attr_sd);
	return error;
}

static int sysfs_release(struct inode *inode, struct file *filp)
{
	struct sysfs_dirent *sd = filp->f_path.dentry->d_fsdata;
	struct sysfs_buffer *buffer = filp->private_data;

	sysfs_put_open_dirent(sd, buffer);

	if (buffer->page)
		free_page((unsigned long)buffer->page);
	kfree(buffer);

	return 0;
}

/* Sysfs attribute files are pollable.  The idea is that you read
 * the content and then you use 'poll' or 'select' to wait for
 * the content to change.  When the content changes (assuming the
 * manager for the kobject supports notification), poll will
 * return POLLERR|POLLPRI, and select will return the fd whether
 * it is waiting for read, write, or exceptions.
 * Once poll/select indicates that the value has changed, you
 * need to close and re-open the file, or seek to 0 and read again.
 * Reminder: this only works for attributes which actively support
 * it, and it is not possible to test an attribute from userspace
 * to see if it supports poll (Neither 'poll' nor 'select' return
 * an appropriate error code).  When in doubt, set a suitable timeout value.
 */
static unsigned int sysfs_poll(struct file *filp, poll_table *wait)
{
	struct sysfs_buffer * buffer = filp->private_data;
	struct sysfs_dirent *attr_sd = filp->f_path.dentry->d_fsdata;
	struct sysfs_open_dirent *od = attr_sd->s_attr.open;

	/* need parent for the kobj, grab both */
	if (!sysfs_get_active(attr_sd))
		goto trigger;

	poll_wait(filp, &od->poll, wait);

	sysfs_put_active(attr_sd);

	if (buffer->event != atomic_read(&od->event))
		goto trigger;

	return DEFAULT_POLLMASK;

 trigger:
	buffer->needs_read_fill = 1;
	return DEFAULT_POLLMASK|POLLERR|POLLPRI;
}

void sysfs_notify_dirent(struct sysfs_dirent *sd)
{
	struct sysfs_open_dirent *od;
	unsigned long flags;

	spin_lock_irqsave(&sysfs_open_dirent_lock, flags);

	od = sd->s_attr.open;
	if (od) {
		atomic_inc(&od->event);
		wake_up_interruptible(&od->poll);
	}

	spin_unlock_irqrestore(&sysfs_open_dirent_lock, flags);
}
EXPORT_SYMBOL_GPL(sysfs_notify_dirent);

void sysfs_notify(struct kobject *k, const char *dir, const char *attr)
{
	struct sysfs_dirent *sd = k->sd;

	mutex_lock(&sysfs_mutex);

	if (sd && dir)
		sd = sysfs_find_dirent(sd, NULL, dir);
	if (sd && attr)
		sd = sysfs_find_dirent(sd, NULL, attr);
	if (sd)
		sysfs_notify_dirent(sd);

	mutex_unlock(&sysfs_mutex);
}
EXPORT_SYMBOL_GPL(sysfs_notify);

const struct file_operations sysfs_file_operations = {
	.read		= sysfs_read_file,
	.write		= sysfs_write_file,
	.llseek		= generic_file_llseek,
	.open		= sysfs_open_file,
	.release	= sysfs_release,
	.poll		= sysfs_poll,
};

int sysfs_attr_ns(struct kobject *kobj, const struct attribute *attr,
		  const void **pns)
{
	struct sysfs_dirent *dir_sd = kobj->sd;
	const struct sysfs_ops *ops;
	const void *ns = NULL;
	int err;

	err = 0;
	if (!sysfs_ns_type(dir_sd))
		goto out;

	err = -EINVAL;
	if (!kobj->ktype)
		goto out;
	ops = kobj->ktype->sysfs_ops;
	if (!ops)
		goto out;
	if (!ops->namespace)
		goto out;

	err = 0;
	ns = ops->namespace(kobj, attr);
out:
	if (err) {
		WARN(1, KERN_ERR "missing sysfs namespace attribute operation for "
		     "kobject: %s\n", kobject_name(kobj));
	}
	*pns = ns;
	return err;
}

int sysfs_add_file_mode(struct sysfs_dirent *dir_sd,
			const struct attribute *attr, int type, umode_t amode)
{
	umode_t mode = (amode & S_IALLUGO) | S_IFREG;
	struct sysfs_addrm_cxt acxt;
	struct sysfs_dirent *sd;
	const void *ns;
	int rc;

	rc = sysfs_attr_ns(dir_sd->s_dir.kobj, attr, &ns);
	if (rc)
		return rc;

	sd = sysfs_new_dirent(attr->name, mode, type);
	if (!sd)
		return -ENOMEM;

	sd->s_ns = ns;
	sd->s_attr.attr = (void *)attr;
	sysfs_dirent_init_lockdep(sd);

	sysfs_addrm_start(&acxt, dir_sd);
	rc = sysfs_add_one(&acxt, sd);
	sysfs_addrm_finish(&acxt);

	if (rc)
		sysfs_put(sd);

	return rc;
}


int sysfs_add_file(struct sysfs_dirent *dir_sd, const struct attribute *attr,
		   int type)
{
	return sysfs_add_file_mode(dir_sd, attr, type, attr->mode);
}


/**
 *	sysfs_create_file - create an attribute file for an object.
 *	@kobj:	object we're creating for. 
 *	@attr:	attribute descriptor.
 */

int sysfs_create_file(struct kobject * kobj, const struct attribute * attr)
{
	BUG_ON(!kobj || !kobj->sd || !attr);

	return sysfs_add_file(kobj->sd, attr, SYSFS_KOBJ_ATTR);

}

int sysfs_create_files(struct kobject *kobj, const struct attribute **ptr)
{
	int err = 0;
	int i;

	for (i = 0; ptr[i] && !err; i++)
		err = sysfs_create_file(kobj, ptr[i]);
	if (err)
		while (--i >= 0)
			sysfs_remove_file(kobj, ptr[i]);
	return err;
}

/**
 * sysfs_add_file_to_group - add an attribute file to a pre-existing group.
 * @kobj: object we're acting for.
 * @attr: attribute descriptor.
 * @group: group name.
 */
int sysfs_add_file_to_group(struct kobject *kobj,
		const struct attribute *attr, const char *group)
{
	struct sysfs_dirent *dir_sd;
	int error;

	if (group)
		dir_sd = sysfs_get_dirent(kobj->sd, NULL, group);
	else
		dir_sd = sysfs_get(kobj->sd);

	if (!dir_sd)
		return -ENOENT;

	error = sysfs_add_file(dir_sd, attr, SYSFS_KOBJ_ATTR);
	sysfs_put(dir_sd);

	return error;
}
EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);

/**
 * sysfs_chmod_file - update the modified mode value on an object attribute.
 * @kobj: object we're acting for.
 * @attr: attribute descriptor.
 * @mode: file permissions.
 *
 */
int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
		     umode_t mode)
{
	struct sysfs_dirent *sd;
	struct iattr newattrs;
	const void *ns;
	int rc;

	rc = sysfs_attr_ns(kobj, attr, &ns);
	if (rc)
		return rc;

	mutex_lock(&sysfs_mutex);

	rc = -ENOENT;
	sd = sysfs_find_dirent(kobj->sd, ns, attr->name);
	if (!sd)
		goto out;

	newattrs.ia_mode = (mode & S_IALLUGO) | (sd->s_mode & ~S_IALLUGO);
	newattrs.ia_valid = ATTR_MODE;
	rc = sysfs_sd_setattr(sd, &newattrs);

 out:
	mutex_unlock(&sysfs_mutex);
	return rc;
}
EXPORT_SYMBOL_GPL(sysfs_chmod_file);


/**
 *	sysfs_remove_file - remove an object attribute.
 *	@kobj:	object we're acting for.
 *	@attr:	attribute descriptor.
 *
 *	Hash the attribute name and kill the victim.
 */

void sysfs_remove_file(struct kobject * kobj, const struct attribute * attr)
{
	const void *ns;

	if (sysfs_attr_ns(kobj, attr, &ns))
		return;

	sysfs_hash_and_remove(kobj->sd, ns, attr->name);
}

void sysfs_remove_files(struct kobject * kobj, const struct attribute **ptr)
{
	int i;
	for (i = 0; ptr[i]; i++)
		sysfs_remove_file(kobj, ptr[i]);
}

/**
 * sysfs_remove_file_from_group - remove an attribute file from a group.
 * @kobj: object we're acting for.
 * @attr: attribute descriptor.
 * @group: group name.
 */
void sysfs_remove_file_from_group(struct kobject *kobj,
		const struct attribute *attr, const char *group)
{
	struct sysfs_dirent *dir_sd;

	if (group)
		dir_sd = sysfs_get_dirent(kobj->sd, NULL, group);
	else
		dir_sd = sysfs_get(kobj->sd);
	if (dir_sd) {
		sysfs_hash_and_remove(dir_sd, NULL, attr->name);
		sysfs_put(dir_sd);
	}
}
EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);

struct sysfs_schedule_callback_struct {
	struct list_head	workq_list;
	struct kobject		*kobj;
	void			(*func)(void *);
	void			*data;
	struct module		*owner;
	struct work_struct	work;
};

static struct workqueue_struct *sysfs_workqueue;
static DEFINE_MUTEX(sysfs_workq_mutex);
static LIST_HEAD(sysfs_workq);
static void sysfs_schedule_callback_work(struct work_struct *work)
{
	struct sysfs_schedule_callback_struct *ss = container_of(work,
			struct sysfs_schedule_callback_struct, work);

	(ss->func)(ss->data);
	kobject_put(ss->kobj);
	module_put(ss->owner);
	mutex_lock(&sysfs_workq_mutex);
	list_del(&ss->workq_list);
	mutex_unlock(&sysfs_workq_mutex);
	kfree(ss);
}

/**
 * sysfs_schedule_callback - helper to schedule a callback for a kobject
 * @kobj: object we're acting for.
 * @func: callback function to invoke later.
 * @data: argument to pass to @func.
 * @owner: module owning the callback code
 *
 * sysfs attribute methods must not unregister themselves or their parent
 * kobject (which would amount to the same thing).  Attempts to do so will
 * deadlock, since unregistration is mutually exclusive with driver
 * callbacks.
 *
 * Instead methods can call this routine, which will attempt to allocate
 * and schedule a workqueue request to call back @func with @data as its
 * argument in the workqueue's process context.  @kobj will be pinned
 * until @func returns.
 *
 * Returns 0 if the request was submitted, -ENOMEM if storage could not
 * be allocated, -ENODEV if a reference to @owner isn't available,
 * -EAGAIN if a callback has already been scheduled for @kobj.
 */
int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
		void *data, struct module *owner)
{
	struct sysfs_schedule_callback_struct *ss, *tmp;

	if (!try_module_get(owner))
		return -ENODEV;

	mutex_lock(&sysfs_workq_mutex);
	list_for_each_entry_safe(ss, tmp, &sysfs_workq, workq_list)
		if (ss->kobj == kobj) {
			module_put(owner);
			mutex_unlock(&sysfs_workq_mutex);
			return -EAGAIN;
		}
	mutex_unlock(&sysfs_workq_mutex);

	if (sysfs_workqueue == NULL) {
		sysfs_workqueue = create_singlethread_workqueue("sysfsd");
		if (sysfs_workqueue == NULL) {
			module_put(owner);
			return -ENOMEM;
		}
	}

	ss = kmalloc(sizeof(*ss), GFP_KERNEL);
	if (!ss) {
		module_put(owner);
		return -ENOMEM;
	}
	kobject_get(kobj);
	ss->kobj = kobj;
	ss->func = func;
	ss->data = data;
	ss->owner = owner;
	INIT_WORK(&ss->work, sysfs_schedule_callback_work);
	INIT_LIST_HEAD(&ss->workq_list);
	mutex_lock(&sysfs_workq_mutex);
	list_add_tail(&ss->workq_list, &sysfs_workq);
	mutex_unlock(&sysfs_workq_mutex);
	queue_work(sysfs_workqueue, &ss->work);
	return 0;
}
EXPORT_SYMBOL_GPL(sysfs_schedule_callback);


EXPORT_SYMBOL_GPL(sysfs_create_file);
EXPORT_SYMBOL_GPL(sysfs_remove_file);
EXPORT_SYMBOL_GPL(sysfs_remove_files);
EXPORT_SYMBOL_GPL(sysfs_create_files);