summaryrefslogtreecommitdiff
path: root/drivers/i2c/i2c-dev.c
blob: a91201509bc169a387d5b94289e10946f7de329a (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
// SPDX-License-Identifier: GPL-2.0-or-later
/*
    i2c-dev.c - i2c-bus driver, char device interface

    Copyright (C) 1995-97 Simon G. Vogl
    Copyright (C) 1998-99 Frodo Looijaard <frodol@dds.nl>
    Copyright (C) 2003 Greg Kroah-Hartman <greg@kroah.com>

*/

/* Note that this is a complete rewrite of Simon Vogl's i2c-dev module.
   But I have used so much of his original code and ideas that it seems
   only fair to recognize him as co-author -- Frodo */

/* The I2C_RDWR ioctl code is written by Kolja Waschk <waschk@telos.de> */

#define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt

#include <linux/cdev.h>
#include <linux/compat.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/i2c-dev.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/notifier.h>
#include <linux/slab.h>
#include <linux/uaccess.h>

/*
 * An i2c_dev represents an i2c_adapter ... an I2C or SMBus master, not a
 * slave (i2c_client) with which messages will be exchanged.  It's coupled
 * with a character special file which is accessed by user mode drivers.
 *
 * The list of i2c_dev structures is parallel to the i2c_adapter lists
 * maintained by the driver model, and is updated using bus notifications.
 */
struct i2c_dev {
	struct list_head list;
	struct i2c_adapter *adap;
	struct device dev;
	struct cdev cdev;
};

#define I2C_MINORS	(MINORMASK + 1)
static LIST_HEAD(i2c_dev_list);
static DEFINE_SPINLOCK(i2c_dev_list_lock);

static struct i2c_dev *i2c_dev_get_by_minor(unsigned index)
{
	struct i2c_dev *i2c_dev;

	spin_lock(&i2c_dev_list_lock);
	list_for_each_entry(i2c_dev, &i2c_dev_list, list) {
		if (i2c_dev->adap->nr == index)
			goto found;
	}
	i2c_dev = NULL;
found:
	spin_unlock(&i2c_dev_list_lock);
	return i2c_dev;
}

static struct i2c_dev *get_free_i2c_dev(struct i2c_adapter *adap)
{
	struct i2c_dev *i2c_dev;

	if (adap->nr >= I2C_MINORS) {
		pr_err("Out of device minors (%d)\n", adap->nr);
		return ERR_PTR(-ENODEV);
	}

	i2c_dev = kzalloc(sizeof(*i2c_dev), GFP_KERNEL);
	if (!i2c_dev)
		return ERR_PTR(-ENOMEM);
	i2c_dev->adap = adap;

	spin_lock(&i2c_dev_list_lock);
	list_add_tail(&i2c_dev->list, &i2c_dev_list);
	spin_unlock(&i2c_dev_list_lock);
	return i2c_dev;
}

static void put_i2c_dev(struct i2c_dev *i2c_dev, bool del_cdev)
{
	spin_lock(&i2c_dev_list_lock);
	list_del(&i2c_dev->list);
	spin_unlock(&i2c_dev_list_lock);
	if (del_cdev)
		cdev_device_del(&i2c_dev->cdev, &i2c_dev->dev);
	put_device(&i2c_dev->dev);
}

static ssize_t name_show(struct device *dev,
			 struct device_attribute *attr, char *buf)
{
	struct i2c_dev *i2c_dev = i2c_dev_get_by_minor(MINOR(dev->devt));

	if (!i2c_dev)
		return -ENODEV;
	return sysfs_emit(buf, "%s\n", i2c_dev->adap->name);
}
static DEVICE_ATTR_RO(name);

static struct attribute *i2c_attrs[] = {
	&dev_attr_name.attr,
	NULL,
};
ATTRIBUTE_GROUPS(i2c);

/* ------------------------------------------------------------------------- */

/*
 * After opening an instance of this character special file, a file
 * descriptor starts out associated only with an i2c_adapter (and bus).
 *
 * Using the I2C_RDWR ioctl(), you can then *immediately* issue i2c_msg
 * traffic to any devices on the bus used by that adapter.  That's because
 * the i2c_msg vectors embed all the addressing information they need, and
 * are submitted directly to an i2c_adapter.  However, SMBus-only adapters
 * don't support that interface.
 *
 * To use read()/write() system calls on that file descriptor, or to use
 * SMBus interfaces (and work with SMBus-only hosts!), you must first issue
 * an I2C_SLAVE (or I2C_SLAVE_FORCE) ioctl.  That configures an anonymous
 * (never registered) i2c_client so it holds the addressing information
 * needed by those system calls and by this SMBus interface.
 */

static ssize_t i2cdev_read(struct file *file, char __user *buf, size_t count,
		loff_t *offset)
{
	char *tmp;
	int ret;

	struct i2c_client *client = file->private_data;

	if (count > 8192)
		count = 8192;

	tmp = kzalloc(count, GFP_KERNEL);
	if (tmp == NULL)
		return -ENOMEM;

	pr_debug("i2c-%d reading %zu bytes.\n", iminor(file_inode(file)), count);

	ret = i2c_master_recv(client, tmp, count);
	if (ret >= 0)
		if (copy_to_user(buf, tmp, ret))
			ret = -EFAULT;
	kfree(tmp);
	return ret;
}

static ssize_t i2cdev_write(struct file *file, const char __user *buf,
		size_t count, loff_t *offset)
{
	int ret;
	char *tmp;
	struct i2c_client *client = file->private_data;

	if (count > 8192)
		count = 8192;

	tmp = memdup_user(buf, count);
	if (IS_ERR(tmp))
		return PTR_ERR(tmp);

	pr_debug("i2c-%d writing %zu bytes.\n", iminor(file_inode(file)), count);

	ret = i2c_master_send(client, tmp, count);
	kfree(tmp);
	return ret;
}

static int i2cdev_check(struct device *dev, void *addrp)
{
	struct i2c_client *client = i2c_verify_client(dev);

	if (!client || client->addr != *(unsigned int *)addrp)
		return 0;

	return dev->driver ? -EBUSY : 0;
}

/* walk up mux tree */
static int i2cdev_check_mux_parents(struct i2c_adapter *adapter, int addr)
{
	struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);
	int result;

	result = device_for_each_child(&adapter->dev, &addr, i2cdev_check);
	if (!result && parent)
		result = i2cdev_check_mux_parents(parent, addr);

	return result;
}

/* recurse down mux tree */
static int i2cdev_check_mux_children(struct device *dev, void *addrp)
{
	int result;

	if (dev->type == &i2c_adapter_type)
		result = device_for_each_child(dev, addrp,
						i2cdev_check_mux_children);
	else
		result = i2cdev_check(dev, addrp);

	return result;
}

/* This address checking function differs from the one in i2c-core
   in that it considers an address with a registered device, but no
   driver bound to it, as NOT busy. */
static int i2cdev_check_addr(struct i2c_adapter *adapter, unsigned int addr)
{
	struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);
	int result = 0;

	if (parent)
		result = i2cdev_check_mux_parents(parent, addr);

	if (!result)
		result = device_for_each_child(&adapter->dev, &addr,
						i2cdev_check_mux_children);

	return result;
}

static noinline int i2cdev_ioctl_rdwr(struct i2c_client *client,
		unsigned nmsgs, struct i2c_msg *msgs)
{
	u8 __user **data_ptrs;
	int i, res;

	data_ptrs = kmalloc_array(nmsgs, sizeof(u8 __user *), GFP_KERNEL);
	if (data_ptrs == NULL) {
		kfree(msgs);
		return -ENOMEM;
	}

	res = 0;
	for (i = 0; i < nmsgs; i++) {
		/* Limit the size of the message to a sane amount */
		if (msgs[i].len > 8192) {
			res = -EINVAL;
			break;
		}

		data_ptrs[i] = (u8 __user *)msgs[i].buf;
		msgs[i].buf = memdup_user(data_ptrs[i], msgs[i].len);
		if (IS_ERR(msgs[i].buf)) {
			res = PTR_ERR(msgs[i].buf);
			break;
		}
		/* memdup_user allocates with GFP_KERNEL, so DMA is ok */
		msgs[i].flags |= I2C_M_DMA_SAFE;

		/*
		 * If the message length is received from the slave (similar
		 * to SMBus block read), we must ensure that the buffer will
		 * be large enough to cope with a message length of
		 * I2C_SMBUS_BLOCK_MAX as this is the maximum underlying bus
		 * drivers allow. The first byte in the buffer must be
		 * pre-filled with the number of extra bytes, which must be
		 * at least one to hold the message length, but can be
		 * greater (for example to account for a checksum byte at
		 * the end of the message.)
		 */
		if (msgs[i].flags & I2C_M_RECV_LEN) {
			if (!(msgs[i].flags & I2C_M_RD) ||
			    msgs[i].len < 1 || msgs[i].buf[0] < 1 ||
			    msgs[i].len < msgs[i].buf[0] +
					     I2C_SMBUS_BLOCK_MAX) {
				i++;
				res = -EINVAL;
				break;
			}

			msgs[i].len = msgs[i].buf[0];
		}
	}
	if (res < 0) {
		int j;
		for (j = 0; j < i; ++j)
			kfree(msgs[j].buf);
		kfree(data_ptrs);
		kfree(msgs);
		return res;
	}

	res = i2c_transfer(client->adapter, msgs, nmsgs);
	while (i-- > 0) {
		if (res >= 0 && (msgs[i].flags & I2C_M_RD)) {
			if (copy_to_user(data_ptrs[i], msgs[i].buf,
					 msgs[i].len))
				res = -EFAULT;
		}
		kfree(msgs[i].buf);
	}
	kfree(data_ptrs);
	kfree(msgs);
	return res;
}

static noinline int i2cdev_ioctl_smbus(struct i2c_client *client,
		u8 read_write, u8 command, u32 size,
		union i2c_smbus_data __user *data)
{
	union i2c_smbus_data temp = {};
	int datasize, res;

	if ((size != I2C_SMBUS_BYTE) &&
	    (size != I2C_SMBUS_QUICK) &&
	    (size != I2C_SMBUS_BYTE_DATA) &&
	    (size != I2C_SMBUS_WORD_DATA) &&
	    (size != I2C_SMBUS_PROC_CALL) &&
	    (size != I2C_SMBUS_BLOCK_DATA) &&
	    (size != I2C_SMBUS_I2C_BLOCK_BROKEN) &&
	    (size != I2C_SMBUS_I2C_BLOCK_DATA) &&
	    (size != I2C_SMBUS_BLOCK_PROC_CALL)) {
		dev_dbg(&client->adapter->dev,
			"size out of range (%x) in ioctl I2C_SMBUS.\n",
			size);
		return -EINVAL;
	}
	/* Note that I2C_SMBUS_READ and I2C_SMBUS_WRITE are 0 and 1,
	   so the check is valid if size==I2C_SMBUS_QUICK too. */
	if ((read_write != I2C_SMBUS_READ) &&
	    (read_write != I2C_SMBUS_WRITE)) {
		dev_dbg(&client->adapter->dev,
			"read_write out of range (%x) in ioctl I2C_SMBUS.\n",
			read_write);
		return -EINVAL;
	}

	/* Note that command values are always valid! */

	if ((size == I2C_SMBUS_QUICK) ||
	    ((size == I2C_SMBUS_BYTE) &&
	    (read_write == I2C_SMBUS_WRITE)))
		/* These are special: we do not use data */
		return i2c_smbus_xfer(client->adapter, client->addr,
				      client->flags, read_write,
				      command, size, NULL);

	if (data == NULL) {
		dev_dbg(&client->adapter->dev,
			"data is NULL pointer in ioctl I2C_SMBUS.\n");
		return -EINVAL;
	}

	if ((size == I2C_SMBUS_BYTE_DATA) ||
	    (size == I2C_SMBUS_BYTE))
		datasize = sizeof(data->byte);
	else if ((size == I2C_SMBUS_WORD_DATA) ||
		 (size == I2C_SMBUS_PROC_CALL))
		datasize = sizeof(data->word);
	else /* size == smbus block, i2c block, or block proc. call */
		datasize = sizeof(data->block);

	if ((size == I2C_SMBUS_PROC_CALL) ||
	    (size == I2C_SMBUS_BLOCK_PROC_CALL) ||
	    (size == I2C_SMBUS_I2C_BLOCK_DATA) ||
	    (read_write == I2C_SMBUS_WRITE)) {
		if (copy_from_user(&temp, data, datasize))
			return -EFAULT;
	}
	if (size == I2C_SMBUS_I2C_BLOCK_BROKEN) {
		/* Convert old I2C block commands to the new
		   convention. This preserves binary compatibility. */
		size = I2C_SMBUS_I2C_BLOCK_DATA;
		if (read_write == I2C_SMBUS_READ)
			temp.block[0] = I2C_SMBUS_BLOCK_MAX;
	}
	res = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
	      read_write, command, size, &temp);
	if (!res && ((size == I2C_SMBUS_PROC_CALL) ||
		     (size == I2C_SMBUS_BLOCK_PROC_CALL) ||
		     (read_write == I2C_SMBUS_READ))) {
		if (copy_to_user(data, &temp, datasize))
			return -EFAULT;
	}
	return res;
}

static long i2cdev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
	struct i2c_client *client = file->private_data;
	unsigned long funcs;

	dev_dbg(&client->adapter->dev, "ioctl, cmd=0x%02x, arg=0x%02lx\n",
		cmd, arg);

	switch (cmd) {
	case I2C_SLAVE:
	case I2C_SLAVE_FORCE:
		if ((arg > 0x3ff) ||
		    (((client->flags & I2C_M_TEN) == 0) && arg > 0x7f))
			return -EINVAL;
		if (cmd == I2C_SLAVE && i2cdev_check_addr(client->adapter, arg))
			return -EBUSY;
		/* REVISIT: address could become busy later */
		client->addr = arg;
		return 0;
	case I2C_TENBIT:
		if (arg)
			client->flags |= I2C_M_TEN;
		else
			client->flags &= ~I2C_M_TEN;
		return 0;
	case I2C_PEC:
		/*
		 * Setting the PEC flag here won't affect kernel drivers,
		 * which will be using the i2c_client node registered with
		 * the driver model core.  Likewise, when that client has
		 * the PEC flag already set, the i2c-dev driver won't see
		 * (or use) this setting.
		 */
		if (arg)
			client->flags |= I2C_CLIENT_PEC;
		else
			client->flags &= ~I2C_CLIENT_PEC;
		return 0;
	case I2C_FUNCS:
		funcs = i2c_get_functionality(client->adapter);
		return put_user(funcs, (unsigned long __user *)arg);

	case I2C_RDWR: {
		struct i2c_rdwr_ioctl_data rdwr_arg;
		struct i2c_msg *rdwr_pa;

		if (copy_from_user(&rdwr_arg,
				   (struct i2c_rdwr_ioctl_data __user *)arg,
				   sizeof(rdwr_arg)))
			return -EFAULT;

		if (!rdwr_arg.msgs || rdwr_arg.nmsgs == 0)
			return -EINVAL;

		/*
		 * Put an arbitrary limit on the number of messages that can
		 * be sent at once
		 */
		if (rdwr_arg.nmsgs > I2C_RDWR_IOCTL_MAX_MSGS)
			return -EINVAL;

		rdwr_pa = memdup_user(rdwr_arg.msgs,
				      rdwr_arg.nmsgs * sizeof(struct i2c_msg));
		if (IS_ERR(rdwr_pa))
			return PTR_ERR(rdwr_pa);

		return i2cdev_ioctl_rdwr(client, rdwr_arg.nmsgs, rdwr_pa);
	}

	case I2C_SMBUS: {
		struct i2c_smbus_ioctl_data data_arg;
		if (copy_from_user(&data_arg,
				   (struct i2c_smbus_ioctl_data __user *) arg,
				   sizeof(struct i2c_smbus_ioctl_data)))
			return -EFAULT;
		return i2cdev_ioctl_smbus(client, data_arg.read_write,
					  data_arg.command,
					  data_arg.size,
					  data_arg.data);
	}
	case I2C_RETRIES:
		if (arg > INT_MAX)
			return -EINVAL;

		client->adapter->retries = arg;
		break;
	case I2C_TIMEOUT:
		if (arg > INT_MAX)
			return -EINVAL;

		/* For historical reasons, user-space sets the timeout
		 * value in units of 10 ms.
		 */
		client->adapter->timeout = msecs_to_jiffies(arg * 10);
		break;
	default:
		/* NOTE:  returning a fault code here could cause trouble
		 * in buggy userspace code.  Some old kernel bugs returned
		 * zero in this case, and userspace code might accidentally
		 * have depended on that bug.
		 */
		return -ENOTTY;
	}
	return 0;
}

#ifdef CONFIG_COMPAT

struct i2c_smbus_ioctl_data32 {
	u8 read_write;
	u8 command;
	u32 size;
	compat_caddr_t data; /* union i2c_smbus_data *data */
};

struct i2c_msg32 {
	u16 addr;
	u16 flags;
	u16 len;
	compat_caddr_t buf;
};

struct i2c_rdwr_ioctl_data32 {
	compat_caddr_t msgs; /* struct i2c_msg __user *msgs */
	u32 nmsgs;
};

static long compat_i2cdev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
	struct i2c_client *client = file->private_data;
	unsigned long funcs;
	switch (cmd) {
	case I2C_FUNCS:
		funcs = i2c_get_functionality(client->adapter);
		return put_user(funcs, (compat_ulong_t __user *)arg);
	case I2C_RDWR: {
		struct i2c_rdwr_ioctl_data32 rdwr_arg;
		struct i2c_msg32 __user *p;
		struct i2c_msg *rdwr_pa;
		int i;

		if (copy_from_user(&rdwr_arg,
				   (struct i2c_rdwr_ioctl_data32 __user *)arg,
				   sizeof(rdwr_arg)))
			return -EFAULT;

		if (!rdwr_arg.msgs || rdwr_arg.nmsgs == 0)
			return -EINVAL;

		if (rdwr_arg.nmsgs > I2C_RDWR_IOCTL_MAX_MSGS)
			return -EINVAL;

		rdwr_pa = kmalloc_array(rdwr_arg.nmsgs, sizeof(struct i2c_msg),
				      GFP_KERNEL);
		if (!rdwr_pa)
			return -ENOMEM;

		p = compat_ptr(rdwr_arg.msgs);
		for (i = 0; i < rdwr_arg.nmsgs; i++) {
			struct i2c_msg32 umsg;
			if (copy_from_user(&umsg, p + i, sizeof(umsg))) {
				kfree(rdwr_pa);
				return -EFAULT;
			}
			rdwr_pa[i] = (struct i2c_msg) {
				.addr = umsg.addr,
				.flags = umsg.flags,
				.len = umsg.len,
				.buf = (__force __u8 *)compat_ptr(umsg.buf),
			};
		}

		return i2cdev_ioctl_rdwr(client, rdwr_arg.nmsgs, rdwr_pa);
	}
	case I2C_SMBUS: {
		struct i2c_smbus_ioctl_data32	data32;
		if (copy_from_user(&data32,
				   (void __user *) arg,
				   sizeof(data32)))
			return -EFAULT;
		return i2cdev_ioctl_smbus(client, data32.read_write,
					  data32.command,
					  data32.size,
					  compat_ptr(data32.data));
	}
	default:
		return i2cdev_ioctl(file, cmd, arg);
	}
}
#else
#define compat_i2cdev_ioctl NULL
#endif

static int i2cdev_open(struct inode *inode, struct file *file)
{
	unsigned int minor = iminor(inode);
	struct i2c_client *client;
	struct i2c_adapter *adap;

	adap = i2c_get_adapter(minor);
	if (!adap)
		return -ENODEV;

	/* This creates an anonymous i2c_client, which may later be
	 * pointed to some address using I2C_SLAVE or I2C_SLAVE_FORCE.
	 *
	 * This client is ** NEVER REGISTERED ** with the driver model
	 * or I2C core code!!  It just holds private copies of addressing
	 * information and maybe a PEC flag.
	 */
	client = kzalloc(sizeof(*client), GFP_KERNEL);
	if (!client) {
		i2c_put_adapter(adap);
		return -ENOMEM;
	}
	snprintf(client->name, I2C_NAME_SIZE, "i2c-dev %d", adap->nr);

	client->adapter = adap;
	file->private_data = client;

	return 0;
}

static int i2cdev_release(struct inode *inode, struct file *file)
{
	struct i2c_client *client = file->private_data;

	i2c_put_adapter(client->adapter);
	kfree(client);
	file->private_data = NULL;

	return 0;
}

static const struct file_operations i2cdev_fops = {
	.owner		= THIS_MODULE,
	.llseek		= no_llseek,
	.read		= i2cdev_read,
	.write		= i2cdev_write,
	.unlocked_ioctl	= i2cdev_ioctl,
	.compat_ioctl	= compat_i2cdev_ioctl,
	.open		= i2cdev_open,
	.release	= i2cdev_release,
};

/* ------------------------------------------------------------------------- */

static const struct class i2c_dev_class = {
	.name = "i2c-dev",
	.dev_groups = i2c_groups,
};

static void i2cdev_dev_release(struct device *dev)
{
	struct i2c_dev *i2c_dev;

	i2c_dev = container_of(dev, struct i2c_dev, dev);
	kfree(i2c_dev);
}

static int i2cdev_attach_adapter(struct device *dev)
{
	struct i2c_adapter *adap;
	struct i2c_dev *i2c_dev;
	int res;

	if (dev->type != &i2c_adapter_type)
		return NOTIFY_DONE;
	adap = to_i2c_adapter(dev);

	i2c_dev = get_free_i2c_dev(adap);
	if (IS_ERR(i2c_dev))
		return NOTIFY_DONE;

	cdev_init(&i2c_dev->cdev, &i2cdev_fops);
	i2c_dev->cdev.owner = THIS_MODULE;

	device_initialize(&i2c_dev->dev);
	i2c_dev->dev.devt = MKDEV(I2C_MAJOR, adap->nr);
	i2c_dev->dev.class = &i2c_dev_class;
	i2c_dev->dev.parent = &adap->dev;
	i2c_dev->dev.release = i2cdev_dev_release;

	res = dev_set_name(&i2c_dev->dev, "i2c-%d", adap->nr);
	if (res)
		goto err_put_i2c_dev;

	res = cdev_device_add(&i2c_dev->cdev, &i2c_dev->dev);
	if (res)
		goto err_put_i2c_dev;

	pr_debug("adapter [%s] registered as minor %d\n", adap->name, adap->nr);
	return NOTIFY_OK;

err_put_i2c_dev:
	put_i2c_dev(i2c_dev, false);
	return NOTIFY_DONE;
}

static int i2cdev_detach_adapter(struct device *dev)
{
	struct i2c_adapter *adap;
	struct i2c_dev *i2c_dev;

	if (dev->type != &i2c_adapter_type)
		return NOTIFY_DONE;
	adap = to_i2c_adapter(dev);

	i2c_dev = i2c_dev_get_by_minor(adap->nr);
	if (!i2c_dev) /* attach_adapter must have failed */
		return NOTIFY_DONE;

	put_i2c_dev(i2c_dev, true);

	pr_debug("adapter [%s] unregistered\n", adap->name);
	return NOTIFY_OK;
}

static int i2cdev_notifier_call(struct notifier_block *nb, unsigned long action,
			 void *data)
{
	struct device *dev = data;

	switch (action) {
	case BUS_NOTIFY_ADD_DEVICE:
		return i2cdev_attach_adapter(dev);
	case BUS_NOTIFY_DEL_DEVICE:
		return i2cdev_detach_adapter(dev);
	}

	return NOTIFY_DONE;
}

static struct notifier_block i2cdev_notifier = {
	.notifier_call = i2cdev_notifier_call,
};

/* ------------------------------------------------------------------------- */

static int __init i2c_dev_attach_adapter(struct device *dev, void *dummy)
{
	i2cdev_attach_adapter(dev);
	return 0;
}

static int __exit i2c_dev_detach_adapter(struct device *dev, void *dummy)
{
	i2cdev_detach_adapter(dev);
	return 0;
}

/*
 * module load/unload record keeping
 */

static int __init i2c_dev_init(void)
{
	int res;

	pr_info("i2c /dev entries driver\n");

	res = register_chrdev_region(MKDEV(I2C_MAJOR, 0), I2C_MINORS, "i2c");
	if (res)
		goto out;

	res = class_register(&i2c_dev_class);
	if (res)
		goto out_unreg_chrdev;

	/* Keep track of adapters which will be added or removed later */
	res = bus_register_notifier(&i2c_bus_type, &i2cdev_notifier);
	if (res)
		goto out_unreg_class;

	/* Bind to already existing adapters right away */
	i2c_for_each_dev(NULL, i2c_dev_attach_adapter);

	return 0;

out_unreg_class:
	class_unregister(&i2c_dev_class);
out_unreg_chrdev:
	unregister_chrdev_region(MKDEV(I2C_MAJOR, 0), I2C_MINORS);
out:
	pr_err("Driver Initialisation failed\n");
	return res;
}

static void __exit i2c_dev_exit(void)
{
	bus_unregister_notifier(&i2c_bus_type, &i2cdev_notifier);
	i2c_for_each_dev(NULL, i2c_dev_detach_adapter);
	class_unregister(&i2c_dev_class);
	unregister_chrdev_region(MKDEV(I2C_MAJOR, 0), I2C_MINORS);
}

MODULE_AUTHOR("Frodo Looijaard <frodol@dds.nl>");
MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
MODULE_DESCRIPTION("I2C /dev entries driver");
MODULE_LICENSE("GPL");

module_init(i2c_dev_init);
module_exit(i2c_dev_exit);