summaryrefslogtreecommitdiff
path: root/drivers/w1/slaves/w1_therm.c
blob: 3c350dfbcd0be40ef3c300e43117a2229aa6929b (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
/*
 *	w1_therm.c
 *
 * Copyright (c) 2004 Evgeniy Polyakov <zbr@ioremap.net>
 *
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the therms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

#include <asm/types.h>

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/sched.h>
#include <linux/device.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/delay.h>
#include <linux/hwmon.h>

#include <linux/w1.h>

#define W1_THERM_DS18S20	0x10
#define W1_THERM_DS1822		0x22
#define W1_THERM_DS18B20	0x28
#define W1_THERM_DS1825		0x3B
#define W1_THERM_DS28EA00	0x42

/* Allow the strong pullup to be disabled, but default to enabled.
 * If it was disabled a parasite powered device might not get the require
 * current to do a temperature conversion.  If it is enabled parasite powered
 * devices have a better chance of getting the current required.
 * In case the parasite power-detection is not working (seems to be the case
 * for some DS18S20) the strong pullup can also be forced, regardless of the
 * power state of the devices.
 *
 * Summary of options:
 * - strong_pullup = 0	Disable strong pullup completely
 * - strong_pullup = 1	Enable automatic strong pullup detection
 * - strong_pullup = 2	Force strong pullup
 */
static int w1_strong_pullup = 1;
module_param_named(strong_pullup, w1_strong_pullup, int, 0);

struct w1_therm_family_data {
	uint8_t rom[9];
	atomic_t refcnt;
};

struct therm_info {
	u8 rom[9];
	u8 crc;
	u8 verdict;
};

/* return the address of the refcnt in the family data */
#define THERM_REFCNT(family_data) \
	(&((struct w1_therm_family_data *)family_data)->refcnt)

static int w1_therm_add_slave(struct w1_slave *sl)
{
	sl->family_data = kzalloc(sizeof(struct w1_therm_family_data),
		GFP_KERNEL);
	if (!sl->family_data)
		return -ENOMEM;
	atomic_set(THERM_REFCNT(sl->family_data), 1);
	return 0;
}

static void w1_therm_remove_slave(struct w1_slave *sl)
{
	int refcnt = atomic_sub_return(1, THERM_REFCNT(sl->family_data));

	while (refcnt) {
		msleep(1000);
		refcnt = atomic_read(THERM_REFCNT(sl->family_data));
	}
	kfree(sl->family_data);
	sl->family_data = NULL;
}

static ssize_t w1_slave_show(struct device *device,
	struct device_attribute *attr, char *buf);

static ssize_t w1_slave_store(struct device *device,
	struct device_attribute *attr, const char *buf, size_t size);

static ssize_t w1_seq_show(struct device *device,
	struct device_attribute *attr, char *buf);

static DEVICE_ATTR_RW(w1_slave);
static DEVICE_ATTR_RO(w1_seq);

static struct attribute *w1_therm_attrs[] = {
	&dev_attr_w1_slave.attr,
	NULL,
};

static struct attribute *w1_ds28ea00_attrs[] = {
	&dev_attr_w1_slave.attr,
	&dev_attr_w1_seq.attr,
	NULL,
};

ATTRIBUTE_GROUPS(w1_therm);
ATTRIBUTE_GROUPS(w1_ds28ea00);

#if IS_REACHABLE(CONFIG_HWMON)
static int w1_read_temp(struct device *dev, u32 attr, int channel,
			long *val);

static umode_t w1_is_visible(const void *_data, enum hwmon_sensor_types type,
			     u32 attr, int channel)
{
	return attr == hwmon_temp_input ? 0444 : 0;
}

static int w1_read(struct device *dev, enum hwmon_sensor_types type,
		   u32 attr, int channel, long *val)
{
	switch (type) {
	case hwmon_temp:
		return w1_read_temp(dev, attr, channel, val);
	default:
		return -EOPNOTSUPP;
	}
}

static const u32 w1_temp_config[] = {
	HWMON_T_INPUT,
	0
};

static const struct hwmon_channel_info w1_temp = {
	.type = hwmon_temp,
	.config = w1_temp_config,
};

static const struct hwmon_channel_info *w1_info[] = {
	&w1_temp,
	NULL
};

static const struct hwmon_ops w1_hwmon_ops = {
	.is_visible = w1_is_visible,
	.read = w1_read,
};

static const struct hwmon_chip_info w1_chip_info = {
	.ops = &w1_hwmon_ops,
	.info = w1_info,
};
#define W1_CHIPINFO	(&w1_chip_info)
#else
#define W1_CHIPINFO	NULL
#endif

static struct w1_family_ops w1_therm_fops = {
	.add_slave	= w1_therm_add_slave,
	.remove_slave	= w1_therm_remove_slave,
	.groups		= w1_therm_groups,
	.chip_info	= W1_CHIPINFO,
};

static struct w1_family_ops w1_ds28ea00_fops = {
	.add_slave	= w1_therm_add_slave,
	.remove_slave	= w1_therm_remove_slave,
	.groups		= w1_ds28ea00_groups,
	.chip_info	= W1_CHIPINFO,
};

static struct w1_family w1_therm_family_DS18S20 = {
	.fid = W1_THERM_DS18S20,
	.fops = &w1_therm_fops,
};

static struct w1_family w1_therm_family_DS18B20 = {
	.fid = W1_THERM_DS18B20,
	.fops = &w1_therm_fops,
};

static struct w1_family w1_therm_family_DS1822 = {
	.fid = W1_THERM_DS1822,
	.fops = &w1_therm_fops,
};

static struct w1_family w1_therm_family_DS28EA00 = {
	.fid = W1_THERM_DS28EA00,
	.fops = &w1_ds28ea00_fops,
};

static struct w1_family w1_therm_family_DS1825 = {
	.fid = W1_THERM_DS1825,
	.fops = &w1_therm_fops,
};

struct w1_therm_family_converter {
	u8			broken;
	u16			reserved;
	struct w1_family	*f;
	int			(*convert)(u8 rom[9]);
	int			(*precision)(struct device *device, int val);
	int			(*eeprom)(struct device *device);
};

/* write configuration to eeprom */
static inline int w1_therm_eeprom(struct device *device);

/* Set precision for conversion */
static inline int w1_DS18B20_precision(struct device *device, int val);
static inline int w1_DS18S20_precision(struct device *device, int val);

/* The return value is millidegrees Centigrade. */
static inline int w1_DS18B20_convert_temp(u8 rom[9]);
static inline int w1_DS18S20_convert_temp(u8 rom[9]);

static struct w1_therm_family_converter w1_therm_families[] = {
	{
		.f		= &w1_therm_family_DS18S20,
		.convert	= w1_DS18S20_convert_temp,
		.precision	= w1_DS18S20_precision,
		.eeprom		= w1_therm_eeprom
	},
	{
		.f		= &w1_therm_family_DS1822,
		.convert	= w1_DS18B20_convert_temp,
		.precision	= w1_DS18S20_precision,
		.eeprom		= w1_therm_eeprom
	},
	{
		.f		= &w1_therm_family_DS18B20,
		.convert	= w1_DS18B20_convert_temp,
		.precision	= w1_DS18B20_precision,
		.eeprom		= w1_therm_eeprom
	},
	{
		.f		= &w1_therm_family_DS28EA00,
		.convert	= w1_DS18B20_convert_temp,
		.precision	= w1_DS18S20_precision,
		.eeprom		= w1_therm_eeprom
	},
	{
		.f		= &w1_therm_family_DS1825,
		.convert	= w1_DS18B20_convert_temp,
		.precision	= w1_DS18S20_precision,
		.eeprom		= w1_therm_eeprom
	}
};

static inline int w1_therm_eeprom(struct device *device)
{
	struct w1_slave *sl = dev_to_w1_slave(device);
	struct w1_master *dev = sl->master;
	u8 rom[9], external_power;
	int ret, max_trying = 10;
	u8 *family_data = sl->family_data;

	if (!sl->family_data) {
		ret = -ENODEV;
		goto error;
	}

	/* prevent the slave from going away in sleep */
	atomic_inc(THERM_REFCNT(family_data));

	ret = mutex_lock_interruptible(&dev->bus_mutex);
	if (ret != 0)
		goto dec_refcnt;

	memset(rom, 0, sizeof(rom));

	while (max_trying--) {
		if (!w1_reset_select_slave(sl)) {
			unsigned int tm = 10;
			unsigned long sleep_rem;

			/* check if in parasite mode */
			w1_write_8(dev, W1_READ_PSUPPLY);
			external_power = w1_read_8(dev);

			if (w1_reset_select_slave(sl))
				continue;

			/* 10ms strong pullup/delay after the copy command */
			if (w1_strong_pullup == 2 ||
			    (!external_power && w1_strong_pullup))
				w1_next_pullup(dev, tm);

			w1_write_8(dev, W1_COPY_SCRATCHPAD);

			if (external_power) {
				mutex_unlock(&dev->bus_mutex);

				sleep_rem = msleep_interruptible(tm);
				if (sleep_rem != 0) {
					ret = -EINTR;
					goto dec_refcnt;
				}

				ret = mutex_lock_interruptible(&dev->bus_mutex);
				if (ret != 0)
					goto dec_refcnt;
			} else if (!w1_strong_pullup) {
				sleep_rem = msleep_interruptible(tm);
				if (sleep_rem != 0) {
					ret = -EINTR;
					goto mt_unlock;
				}
			}

			break;
		}
	}

mt_unlock:
	mutex_unlock(&dev->bus_mutex);
dec_refcnt:
	atomic_dec(THERM_REFCNT(family_data));
error:
	return ret;
}

/* DS18S20 does not feature configuration register */
static inline int w1_DS18S20_precision(struct device *device, int val)
{
	return 0;
}

static inline int w1_DS18B20_precision(struct device *device, int val)
{
	struct w1_slave *sl = dev_to_w1_slave(device);
	struct w1_master *dev = sl->master;
	u8 rom[9], crc;
	int ret, max_trying = 10;
	u8 *family_data = sl->family_data;
	uint8_t precision_bits;
	uint8_t mask = 0x60;

	if (val > 12 || val < 9) {
		pr_warn("Unsupported precision\n");
		ret = -EINVAL;
		goto error;
	}

	if (!sl->family_data) {
		ret = -ENODEV;
		goto error;
	}

	/* prevent the slave from going away in sleep */
	atomic_inc(THERM_REFCNT(family_data));

	ret = mutex_lock_interruptible(&dev->bus_mutex);
	if (ret != 0)
		goto dec_refcnt;

	memset(rom, 0, sizeof(rom));

	/* translate precision to bitmask (see datasheet page 9) */
	switch (val) {
	case 9:
		precision_bits = 0x00;
		break;
	case 10:
		precision_bits = 0x20;
		break;
	case 11:
		precision_bits = 0x40;
		break;
	case 12:
	default:
		precision_bits = 0x60;
		break;
	}

	while (max_trying--) {
		crc = 0;

		if (!w1_reset_select_slave(sl)) {
			int count = 0;

			/* read values to only alter precision bits */
			w1_write_8(dev, W1_READ_SCRATCHPAD);
			count = w1_read_block(dev, rom, 9);
			if (count != 9)
				dev_warn(device, "w1_read_block() returned %u instead of 9.\n",	count);

			crc = w1_calc_crc8(rom, 8);
			if (rom[8] == crc) {
				rom[4] = (rom[4] & ~mask) | (precision_bits & mask);

				if (!w1_reset_select_slave(sl)) {
					w1_write_8(dev, W1_WRITE_SCRATCHPAD);
					w1_write_8(dev, rom[2]);
					w1_write_8(dev, rom[3]);
					w1_write_8(dev, rom[4]);

					break;
				}
			}
		}
	}

	mutex_unlock(&dev->bus_mutex);
dec_refcnt:
	atomic_dec(THERM_REFCNT(family_data));
error:
	return ret;
}

static inline int w1_DS18B20_convert_temp(u8 rom[9])
{
	s16 t = le16_to_cpup((__le16 *)rom);

	return t*1000/16;
}

static inline int w1_DS18S20_convert_temp(u8 rom[9])
{
	int t, h;

	if (!rom[7])
		return 0;

	if (rom[1] == 0)
		t = ((s32)rom[0] >> 1)*1000;
	else
		t = 1000*(-1*(s32)(0x100-rom[0]) >> 1);

	t -= 250;
	h = 1000*((s32)rom[7] - (s32)rom[6]);
	h /= (s32)rom[7];
	t += h;

	return t;
}

static inline int w1_convert_temp(u8 rom[9], u8 fid)
{
	int i;

	for (i = 0; i < ARRAY_SIZE(w1_therm_families); ++i)
		if (w1_therm_families[i].f->fid == fid)
			return w1_therm_families[i].convert(rom);

	return 0;
}

static ssize_t w1_slave_store(struct device *device,
			      struct device_attribute *attr, const char *buf,
			      size_t size)
{
	int val, ret;
	struct w1_slave *sl = dev_to_w1_slave(device);
	int i;

	ret = kstrtoint(buf, 0, &val);
	if (ret)
		return ret;

	for (i = 0; i < ARRAY_SIZE(w1_therm_families); ++i) {
		if (w1_therm_families[i].f->fid == sl->family->fid) {
			/* zero value indicates to write current configuration to eeprom */
			if (val == 0)
				ret = w1_therm_families[i].eeprom(device);
			else
				ret = w1_therm_families[i].precision(device, val);
			break;
		}
	}
	return ret ? : size;
}

static ssize_t read_therm(struct device *device,
			  struct w1_slave *sl, struct therm_info *info)
{
	struct w1_master *dev = sl->master;
	u8 external_power;
	int ret, max_trying = 10;
	u8 *family_data = sl->family_data;

	if (!family_data) {
		ret = -ENODEV;
		goto error;
	}

	/* prevent the slave from going away in sleep */
	atomic_inc(THERM_REFCNT(family_data));

	ret = mutex_lock_interruptible(&dev->bus_mutex);
	if (ret != 0)
		goto dec_refcnt;

	memset(info->rom, 0, sizeof(info->rom));

	while (max_trying--) {

		info->verdict = 0;
		info->crc = 0;

		if (!w1_reset_select_slave(sl)) {
			int count = 0;
			unsigned int tm = 750;
			unsigned long sleep_rem;

			w1_write_8(dev, W1_READ_PSUPPLY);
			external_power = w1_read_8(dev);

			if (w1_reset_select_slave(sl))
				continue;

			/* 750ms strong pullup (or delay) after the convert */
			if (w1_strong_pullup == 2 ||
					(!external_power && w1_strong_pullup))
				w1_next_pullup(dev, tm);

			w1_write_8(dev, W1_CONVERT_TEMP);

			if (external_power) {
				mutex_unlock(&dev->bus_mutex);

				sleep_rem = msleep_interruptible(tm);
				if (sleep_rem != 0) {
					ret = -EINTR;
					goto dec_refcnt;
				}

				ret = mutex_lock_interruptible(&dev->bus_mutex);
				if (ret != 0)
					goto dec_refcnt;
			} else if (!w1_strong_pullup) {
				sleep_rem = msleep_interruptible(tm);
				if (sleep_rem != 0) {
					ret = -EINTR;
					goto mt_unlock;
				}
			}

			if (!w1_reset_select_slave(sl)) {

				w1_write_8(dev, W1_READ_SCRATCHPAD);
				count = w1_read_block(dev, info->rom, 9);
				if (count != 9) {
					dev_warn(device, "w1_read_block() "
						"returned %u instead of 9.\n",
						count);
				}

				info->crc = w1_calc_crc8(info->rom, 8);

				if (info->rom[8] == info->crc)
					info->verdict = 1;
			}
		}

		if (info->verdict)
			break;
	}

mt_unlock:
	mutex_unlock(&dev->bus_mutex);
dec_refcnt:
	atomic_dec(THERM_REFCNT(family_data));
error:
	return ret;
}

static ssize_t w1_slave_show(struct device *device,
			     struct device_attribute *attr, char *buf)
{
	struct w1_slave *sl = dev_to_w1_slave(device);
	struct therm_info info;
	u8 *family_data = sl->family_data;
	int ret, i;
	ssize_t c = PAGE_SIZE;
	u8 fid = sl->family->fid;

	ret = read_therm(device, sl, &info);
	if (ret)
		return ret;

	for (i = 0; i < 9; ++i)
		c -= snprintf(buf + PAGE_SIZE - c, c, "%02x ", info.rom[i]);
	c -= snprintf(buf + PAGE_SIZE - c, c, ": crc=%02x %s\n",
		      info.crc, (info.verdict) ? "YES" : "NO");
	if (info.verdict)
		memcpy(family_data, info.rom, sizeof(info.rom));
	else
		dev_warn(device, "Read failed CRC check\n");

	for (i = 0; i < 9; ++i)
		c -= snprintf(buf + PAGE_SIZE - c, c, "%02x ",
			      ((u8 *)family_data)[i]);

	c -= snprintf(buf + PAGE_SIZE - c, c, "t=%d\n",
			w1_convert_temp(info.rom, fid));
	ret = PAGE_SIZE - c;
	return ret;
}

#if IS_REACHABLE(CONFIG_HWMON)
static int w1_read_temp(struct device *device, u32 attr, int channel,
			long *val)
{
	struct w1_slave *sl = dev_get_drvdata(device);
	struct therm_info info;
	u8 fid = sl->family->fid;
	int ret;

	switch (attr) {
	case hwmon_temp_input:
		ret = read_therm(device, sl, &info);
		if (ret)
			return ret;

		if (!info.verdict) {
			ret = -EIO;
			return ret;
		}

		*val = w1_convert_temp(info.rom, fid);
		ret = 0;
		break;
	default:
		ret = -EOPNOTSUPP;
		break;
	}

	return ret;
}
#endif

#define W1_42_CHAIN	0x99
#define W1_42_CHAIN_OFF	0x3C
#define W1_42_CHAIN_OFF_INV	0xC3
#define W1_42_CHAIN_ON	0x5A
#define W1_42_CHAIN_ON_INV	0xA5
#define W1_42_CHAIN_DONE 0x96
#define W1_42_CHAIN_DONE_INV 0x69
#define W1_42_COND_READ	0x0F
#define W1_42_SUCCESS_CONFIRM_BYTE 0xAA
#define W1_42_FINISHED_BYTE 0xFF
static ssize_t w1_seq_show(struct device *device,
	struct device_attribute *attr, char *buf)
{
	struct w1_slave *sl = dev_to_w1_slave(device);
	ssize_t c = PAGE_SIZE;
	int rv;
	int i;
	u8 ack;
	u64 rn;
	struct w1_reg_num *reg_num;
	int seq = 0;

	mutex_lock(&sl->master->bus_mutex);
	/* Place all devices in CHAIN state */
	if (w1_reset_bus(sl->master))
		goto error;
	w1_write_8(sl->master, W1_SKIP_ROM);
	w1_write_8(sl->master, W1_42_CHAIN);
	w1_write_8(sl->master, W1_42_CHAIN_ON);
	w1_write_8(sl->master, W1_42_CHAIN_ON_INV);
	msleep(sl->master->pullup_duration);

	/* check for acknowledgment */
	ack = w1_read_8(sl->master);
	if (ack != W1_42_SUCCESS_CONFIRM_BYTE)
		goto error;

	/* In case the bus fails to send 0xFF, limit*/
	for (i = 0; i <= 64; i++) {
		if (w1_reset_bus(sl->master))
			goto error;

		w1_write_8(sl->master, W1_42_COND_READ);
		rv = w1_read_block(sl->master, (u8 *)&rn, 8);
		reg_num = (struct w1_reg_num *) &rn;
		if (reg_num->family == W1_42_FINISHED_BYTE)
			break;
		if (sl->reg_num.id == reg_num->id)
			seq = i;

		w1_write_8(sl->master, W1_42_CHAIN);
		w1_write_8(sl->master, W1_42_CHAIN_DONE);
		w1_write_8(sl->master, W1_42_CHAIN_DONE_INV);
		w1_read_block(sl->master, &ack, sizeof(ack));

		/* check for acknowledgment */
		ack = w1_read_8(sl->master);
		if (ack != W1_42_SUCCESS_CONFIRM_BYTE)
			goto error;

	}

	/* Exit from CHAIN state */
	if (w1_reset_bus(sl->master))
		goto error;
	w1_write_8(sl->master, W1_SKIP_ROM);
	w1_write_8(sl->master, W1_42_CHAIN);
	w1_write_8(sl->master, W1_42_CHAIN_OFF);
	w1_write_8(sl->master, W1_42_CHAIN_OFF_INV);

	/* check for acknowledgment */
	ack = w1_read_8(sl->master);
	if (ack != W1_42_SUCCESS_CONFIRM_BYTE)
		goto error;
	mutex_unlock(&sl->master->bus_mutex);

	c -= snprintf(buf + PAGE_SIZE - c, c, "%d\n", seq);
	return PAGE_SIZE - c;
error:
	mutex_unlock(&sl->master->bus_mutex);
	return -EIO;
}

static int __init w1_therm_init(void)
{
	int err, i;

	for (i = 0; i < ARRAY_SIZE(w1_therm_families); ++i) {
		err = w1_register_family(w1_therm_families[i].f);
		if (err)
			w1_therm_families[i].broken = 1;
	}

	return 0;
}

static void __exit w1_therm_fini(void)
{
	int i;

	for (i = 0; i < ARRAY_SIZE(w1_therm_families); ++i)
		if (!w1_therm_families[i].broken)
			w1_unregister_family(w1_therm_families[i].f);
}

module_init(w1_therm_init);
module_exit(w1_therm_fini);

MODULE_AUTHOR("Evgeniy Polyakov <zbr@ioremap.net>");
MODULE_DESCRIPTION("Driver for 1-wire Dallas network protocol, temperature family.");
MODULE_LICENSE("GPL");
MODULE_ALIAS("w1-family-" __stringify(W1_THERM_DS18S20));
MODULE_ALIAS("w1-family-" __stringify(W1_THERM_DS1822));
MODULE_ALIAS("w1-family-" __stringify(W1_THERM_DS18B20));
MODULE_ALIAS("w1-family-" __stringify(W1_THERM_DS1825));
MODULE_ALIAS("w1-family-" __stringify(W1_THERM_DS28EA00));