xref: /linux/drivers/w1/slaves/w1_therm.c (revision fd639726bf15fca8ee1a00dce8e0096d0ad9bd18)
1 /*
2  *	w1_therm.c
3  *
4  * Copyright (c) 2004 Evgeniy Polyakov <zbr@ioremap.net>
5  *
6  *
7  * This program is free software; you can redistribute it and/or modify
8  * it under the therms of the GNU General Public License as published by
9  * the Free Software Foundation; either version 2 of the License, or
10  * (at your option) any later version.
11  *
12  * This program is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15  * GNU General Public License for more details.
16  *
17  * You should have received a copy of the GNU General Public License
18  * along with this program; if not, write to the Free Software
19  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
20  */
21 
22 #include <asm/types.h>
23 
24 #include <linux/kernel.h>
25 #include <linux/module.h>
26 #include <linux/moduleparam.h>
27 #include <linux/sched.h>
28 #include <linux/device.h>
29 #include <linux/types.h>
30 #include <linux/slab.h>
31 #include <linux/delay.h>
32 #include <linux/hwmon.h>
33 
34 #include <linux/w1.h>
35 
36 #define W1_THERM_DS18S20	0x10
37 #define W1_THERM_DS1822		0x22
38 #define W1_THERM_DS18B20	0x28
39 #define W1_THERM_DS1825		0x3B
40 #define W1_THERM_DS28EA00	0x42
41 
42 /* Allow the strong pullup to be disabled, but default to enabled.
43  * If it was disabled a parasite powered device might not get the require
44  * current to do a temperature conversion.  If it is enabled parasite powered
45  * devices have a better chance of getting the current required.
46  * In case the parasite power-detection is not working (seems to be the case
47  * for some DS18S20) the strong pullup can also be forced, regardless of the
48  * power state of the devices.
49  *
50  * Summary of options:
51  * - strong_pullup = 0	Disable strong pullup completely
52  * - strong_pullup = 1	Enable automatic strong pullup detection
53  * - strong_pullup = 2	Force strong pullup
54  */
55 static int w1_strong_pullup = 1;
56 module_param_named(strong_pullup, w1_strong_pullup, int, 0);
57 
58 struct w1_therm_family_data {
59 	uint8_t rom[9];
60 	atomic_t refcnt;
61 };
62 
63 struct therm_info {
64 	u8 rom[9];
65 	u8 crc;
66 	u8 verdict;
67 };
68 
69 /* return the address of the refcnt in the family data */
70 #define THERM_REFCNT(family_data) \
71 	(&((struct w1_therm_family_data *)family_data)->refcnt)
72 
73 static int w1_therm_add_slave(struct w1_slave *sl)
74 {
75 	sl->family_data = kzalloc(sizeof(struct w1_therm_family_data),
76 		GFP_KERNEL);
77 	if (!sl->family_data)
78 		return -ENOMEM;
79 	atomic_set(THERM_REFCNT(sl->family_data), 1);
80 	return 0;
81 }
82 
83 static void w1_therm_remove_slave(struct w1_slave *sl)
84 {
85 	int refcnt = atomic_sub_return(1, THERM_REFCNT(sl->family_data));
86 
87 	while (refcnt) {
88 		msleep(1000);
89 		refcnt = atomic_read(THERM_REFCNT(sl->family_data));
90 	}
91 	kfree(sl->family_data);
92 	sl->family_data = NULL;
93 }
94 
95 static ssize_t w1_slave_show(struct device *device,
96 	struct device_attribute *attr, char *buf);
97 
98 static ssize_t w1_slave_store(struct device *device,
99 	struct device_attribute *attr, const char *buf, size_t size);
100 
101 static ssize_t w1_seq_show(struct device *device,
102 	struct device_attribute *attr, char *buf);
103 
104 static DEVICE_ATTR_RW(w1_slave);
105 static DEVICE_ATTR_RO(w1_seq);
106 
107 static struct attribute *w1_therm_attrs[] = {
108 	&dev_attr_w1_slave.attr,
109 	NULL,
110 };
111 
112 static struct attribute *w1_ds28ea00_attrs[] = {
113 	&dev_attr_w1_slave.attr,
114 	&dev_attr_w1_seq.attr,
115 	NULL,
116 };
117 
118 ATTRIBUTE_GROUPS(w1_therm);
119 ATTRIBUTE_GROUPS(w1_ds28ea00);
120 
121 #if IS_REACHABLE(CONFIG_HWMON)
122 static int w1_read_temp(struct device *dev, u32 attr, int channel,
123 			long *val);
124 
125 static umode_t w1_is_visible(const void *_data, enum hwmon_sensor_types type,
126 			     u32 attr, int channel)
127 {
128 	return attr == hwmon_temp_input ? 0444 : 0;
129 }
130 
131 static int w1_read(struct device *dev, enum hwmon_sensor_types type,
132 		   u32 attr, int channel, long *val)
133 {
134 	switch (type) {
135 	case hwmon_temp:
136 		return w1_read_temp(dev, attr, channel, val);
137 	default:
138 		return -EOPNOTSUPP;
139 	}
140 }
141 
142 static const u32 w1_temp_config[] = {
143 	HWMON_T_INPUT,
144 	0
145 };
146 
147 static const struct hwmon_channel_info w1_temp = {
148 	.type = hwmon_temp,
149 	.config = w1_temp_config,
150 };
151 
152 static const struct hwmon_channel_info *w1_info[] = {
153 	&w1_temp,
154 	NULL
155 };
156 
157 static const struct hwmon_ops w1_hwmon_ops = {
158 	.is_visible = w1_is_visible,
159 	.read = w1_read,
160 };
161 
162 static const struct hwmon_chip_info w1_chip_info = {
163 	.ops = &w1_hwmon_ops,
164 	.info = w1_info,
165 };
166 #define W1_CHIPINFO	(&w1_chip_info)
167 #else
168 #define W1_CHIPINFO	NULL
169 #endif
170 
171 static struct w1_family_ops w1_therm_fops = {
172 	.add_slave	= w1_therm_add_slave,
173 	.remove_slave	= w1_therm_remove_slave,
174 	.groups		= w1_therm_groups,
175 	.chip_info	= W1_CHIPINFO,
176 };
177 
178 static struct w1_family_ops w1_ds28ea00_fops = {
179 	.add_slave	= w1_therm_add_slave,
180 	.remove_slave	= w1_therm_remove_slave,
181 	.groups		= w1_ds28ea00_groups,
182 	.chip_info	= W1_CHIPINFO,
183 };
184 
185 static struct w1_family w1_therm_family_DS18S20 = {
186 	.fid = W1_THERM_DS18S20,
187 	.fops = &w1_therm_fops,
188 };
189 
190 static struct w1_family w1_therm_family_DS18B20 = {
191 	.fid = W1_THERM_DS18B20,
192 	.fops = &w1_therm_fops,
193 };
194 
195 static struct w1_family w1_therm_family_DS1822 = {
196 	.fid = W1_THERM_DS1822,
197 	.fops = &w1_therm_fops,
198 };
199 
200 static struct w1_family w1_therm_family_DS28EA00 = {
201 	.fid = W1_THERM_DS28EA00,
202 	.fops = &w1_ds28ea00_fops,
203 };
204 
205 static struct w1_family w1_therm_family_DS1825 = {
206 	.fid = W1_THERM_DS1825,
207 	.fops = &w1_therm_fops,
208 };
209 
210 struct w1_therm_family_converter {
211 	u8			broken;
212 	u16			reserved;
213 	struct w1_family	*f;
214 	int			(*convert)(u8 rom[9]);
215 	int			(*precision)(struct device *device, int val);
216 	int			(*eeprom)(struct device *device);
217 };
218 
219 /* write configuration to eeprom */
220 static inline int w1_therm_eeprom(struct device *device);
221 
222 /* Set precision for conversion */
223 static inline int w1_DS18B20_precision(struct device *device, int val);
224 static inline int w1_DS18S20_precision(struct device *device, int val);
225 
226 /* The return value is millidegrees Centigrade. */
227 static inline int w1_DS18B20_convert_temp(u8 rom[9]);
228 static inline int w1_DS18S20_convert_temp(u8 rom[9]);
229 
230 static struct w1_therm_family_converter w1_therm_families[] = {
231 	{
232 		.f		= &w1_therm_family_DS18S20,
233 		.convert	= w1_DS18S20_convert_temp,
234 		.precision	= w1_DS18S20_precision,
235 		.eeprom		= w1_therm_eeprom
236 	},
237 	{
238 		.f		= &w1_therm_family_DS1822,
239 		.convert	= w1_DS18B20_convert_temp,
240 		.precision	= w1_DS18S20_precision,
241 		.eeprom		= w1_therm_eeprom
242 	},
243 	{
244 		.f		= &w1_therm_family_DS18B20,
245 		.convert	= w1_DS18B20_convert_temp,
246 		.precision	= w1_DS18B20_precision,
247 		.eeprom		= w1_therm_eeprom
248 	},
249 	{
250 		.f		= &w1_therm_family_DS28EA00,
251 		.convert	= w1_DS18B20_convert_temp,
252 		.precision	= w1_DS18S20_precision,
253 		.eeprom		= w1_therm_eeprom
254 	},
255 	{
256 		.f		= &w1_therm_family_DS1825,
257 		.convert	= w1_DS18B20_convert_temp,
258 		.precision	= w1_DS18S20_precision,
259 		.eeprom		= w1_therm_eeprom
260 	}
261 };
262 
263 static inline int w1_therm_eeprom(struct device *device)
264 {
265 	struct w1_slave *sl = dev_to_w1_slave(device);
266 	struct w1_master *dev = sl->master;
267 	u8 rom[9], external_power;
268 	int ret, max_trying = 10;
269 	u8 *family_data = sl->family_data;
270 
271 	if (!sl->family_data) {
272 		ret = -ENODEV;
273 		goto error;
274 	}
275 
276 	/* prevent the slave from going away in sleep */
277 	atomic_inc(THERM_REFCNT(family_data));
278 
279 	ret = mutex_lock_interruptible(&dev->bus_mutex);
280 	if (ret != 0)
281 		goto dec_refcnt;
282 
283 	memset(rom, 0, sizeof(rom));
284 
285 	while (max_trying--) {
286 		if (!w1_reset_select_slave(sl)) {
287 			unsigned int tm = 10;
288 			unsigned long sleep_rem;
289 
290 			/* check if in parasite mode */
291 			w1_write_8(dev, W1_READ_PSUPPLY);
292 			external_power = w1_read_8(dev);
293 
294 			if (w1_reset_select_slave(sl))
295 				continue;
296 
297 			/* 10ms strong pullup/delay after the copy command */
298 			if (w1_strong_pullup == 2 ||
299 			    (!external_power && w1_strong_pullup))
300 				w1_next_pullup(dev, tm);
301 
302 			w1_write_8(dev, W1_COPY_SCRATCHPAD);
303 
304 			if (external_power) {
305 				mutex_unlock(&dev->bus_mutex);
306 
307 				sleep_rem = msleep_interruptible(tm);
308 				if (sleep_rem != 0) {
309 					ret = -EINTR;
310 					goto dec_refcnt;
311 				}
312 
313 				ret = mutex_lock_interruptible(&dev->bus_mutex);
314 				if (ret != 0)
315 					goto dec_refcnt;
316 			} else if (!w1_strong_pullup) {
317 				sleep_rem = msleep_interruptible(tm);
318 				if (sleep_rem != 0) {
319 					ret = -EINTR;
320 					goto mt_unlock;
321 				}
322 			}
323 
324 			break;
325 		}
326 	}
327 
328 mt_unlock:
329 	mutex_unlock(&dev->bus_mutex);
330 dec_refcnt:
331 	atomic_dec(THERM_REFCNT(family_data));
332 error:
333 	return ret;
334 }
335 
336 /* DS18S20 does not feature configuration register */
337 static inline int w1_DS18S20_precision(struct device *device, int val)
338 {
339 	return 0;
340 }
341 
342 static inline int w1_DS18B20_precision(struct device *device, int val)
343 {
344 	struct w1_slave *sl = dev_to_w1_slave(device);
345 	struct w1_master *dev = sl->master;
346 	u8 rom[9], crc;
347 	int ret, max_trying = 10;
348 	u8 *family_data = sl->family_data;
349 	uint8_t precision_bits;
350 	uint8_t mask = 0x60;
351 
352 	if (val > 12 || val < 9) {
353 		pr_warn("Unsupported precision\n");
354 		ret = -EINVAL;
355 		goto error;
356 	}
357 
358 	if (!sl->family_data) {
359 		ret = -ENODEV;
360 		goto error;
361 	}
362 
363 	/* prevent the slave from going away in sleep */
364 	atomic_inc(THERM_REFCNT(family_data));
365 
366 	ret = mutex_lock_interruptible(&dev->bus_mutex);
367 	if (ret != 0)
368 		goto dec_refcnt;
369 
370 	memset(rom, 0, sizeof(rom));
371 
372 	/* translate precision to bitmask (see datasheet page 9) */
373 	switch (val) {
374 	case 9:
375 		precision_bits = 0x00;
376 		break;
377 	case 10:
378 		precision_bits = 0x20;
379 		break;
380 	case 11:
381 		precision_bits = 0x40;
382 		break;
383 	case 12:
384 	default:
385 		precision_bits = 0x60;
386 		break;
387 	}
388 
389 	while (max_trying--) {
390 		crc = 0;
391 
392 		if (!w1_reset_select_slave(sl)) {
393 			int count = 0;
394 
395 			/* read values to only alter precision bits */
396 			w1_write_8(dev, W1_READ_SCRATCHPAD);
397 			count = w1_read_block(dev, rom, 9);
398 			if (count != 9)
399 				dev_warn(device, "w1_read_block() returned %u instead of 9.\n",	count);
400 
401 			crc = w1_calc_crc8(rom, 8);
402 			if (rom[8] == crc) {
403 				rom[4] = (rom[4] & ~mask) | (precision_bits & mask);
404 
405 				if (!w1_reset_select_slave(sl)) {
406 					w1_write_8(dev, W1_WRITE_SCRATCHPAD);
407 					w1_write_8(dev, rom[2]);
408 					w1_write_8(dev, rom[3]);
409 					w1_write_8(dev, rom[4]);
410 
411 					break;
412 				}
413 			}
414 		}
415 	}
416 
417 	mutex_unlock(&dev->bus_mutex);
418 dec_refcnt:
419 	atomic_dec(THERM_REFCNT(family_data));
420 error:
421 	return ret;
422 }
423 
424 static inline int w1_DS18B20_convert_temp(u8 rom[9])
425 {
426 	s16 t = le16_to_cpup((__le16 *)rom);
427 
428 	return t*1000/16;
429 }
430 
431 static inline int w1_DS18S20_convert_temp(u8 rom[9])
432 {
433 	int t, h;
434 
435 	if (!rom[7])
436 		return 0;
437 
438 	if (rom[1] == 0)
439 		t = ((s32)rom[0] >> 1)*1000;
440 	else
441 		t = 1000*(-1*(s32)(0x100-rom[0]) >> 1);
442 
443 	t -= 250;
444 	h = 1000*((s32)rom[7] - (s32)rom[6]);
445 	h /= (s32)rom[7];
446 	t += h;
447 
448 	return t;
449 }
450 
451 static inline int w1_convert_temp(u8 rom[9], u8 fid)
452 {
453 	int i;
454 
455 	for (i = 0; i < ARRAY_SIZE(w1_therm_families); ++i)
456 		if (w1_therm_families[i].f->fid == fid)
457 			return w1_therm_families[i].convert(rom);
458 
459 	return 0;
460 }
461 
462 static ssize_t w1_slave_store(struct device *device,
463 			      struct device_attribute *attr, const char *buf,
464 			      size_t size)
465 {
466 	int val, ret;
467 	struct w1_slave *sl = dev_to_w1_slave(device);
468 	int i;
469 
470 	ret = kstrtoint(buf, 0, &val);
471 	if (ret)
472 		return ret;
473 
474 	for (i = 0; i < ARRAY_SIZE(w1_therm_families); ++i) {
475 		if (w1_therm_families[i].f->fid == sl->family->fid) {
476 			/* zero value indicates to write current configuration to eeprom */
477 			if (val == 0)
478 				ret = w1_therm_families[i].eeprom(device);
479 			else
480 				ret = w1_therm_families[i].precision(device, val);
481 			break;
482 		}
483 	}
484 	return ret ? : size;
485 }
486 
487 static ssize_t read_therm(struct device *device,
488 			  struct w1_slave *sl, struct therm_info *info)
489 {
490 	struct w1_master *dev = sl->master;
491 	u8 external_power;
492 	int ret, max_trying = 10;
493 	u8 *family_data = sl->family_data;
494 
495 	if (!family_data) {
496 		ret = -ENODEV;
497 		goto error;
498 	}
499 
500 	/* prevent the slave from going away in sleep */
501 	atomic_inc(THERM_REFCNT(family_data));
502 
503 	ret = mutex_lock_interruptible(&dev->bus_mutex);
504 	if (ret != 0)
505 		goto dec_refcnt;
506 
507 	memset(info->rom, 0, sizeof(info->rom));
508 
509 	while (max_trying--) {
510 
511 		info->verdict = 0;
512 		info->crc = 0;
513 
514 		if (!w1_reset_select_slave(sl)) {
515 			int count = 0;
516 			unsigned int tm = 750;
517 			unsigned long sleep_rem;
518 
519 			w1_write_8(dev, W1_READ_PSUPPLY);
520 			external_power = w1_read_8(dev);
521 
522 			if (w1_reset_select_slave(sl))
523 				continue;
524 
525 			/* 750ms strong pullup (or delay) after the convert */
526 			if (w1_strong_pullup == 2 ||
527 					(!external_power && w1_strong_pullup))
528 				w1_next_pullup(dev, tm);
529 
530 			w1_write_8(dev, W1_CONVERT_TEMP);
531 
532 			if (external_power) {
533 				mutex_unlock(&dev->bus_mutex);
534 
535 				sleep_rem = msleep_interruptible(tm);
536 				if (sleep_rem != 0) {
537 					ret = -EINTR;
538 					goto dec_refcnt;
539 				}
540 
541 				ret = mutex_lock_interruptible(&dev->bus_mutex);
542 				if (ret != 0)
543 					goto dec_refcnt;
544 			} else if (!w1_strong_pullup) {
545 				sleep_rem = msleep_interruptible(tm);
546 				if (sleep_rem != 0) {
547 					ret = -EINTR;
548 					goto mt_unlock;
549 				}
550 			}
551 
552 			if (!w1_reset_select_slave(sl)) {
553 
554 				w1_write_8(dev, W1_READ_SCRATCHPAD);
555 				count = w1_read_block(dev, info->rom, 9);
556 				if (count != 9) {
557 					dev_warn(device, "w1_read_block() "
558 						"returned %u instead of 9.\n",
559 						count);
560 				}
561 
562 				info->crc = w1_calc_crc8(info->rom, 8);
563 
564 				if (info->rom[8] == info->crc)
565 					info->verdict = 1;
566 			}
567 		}
568 
569 		if (info->verdict)
570 			break;
571 	}
572 
573 mt_unlock:
574 	mutex_unlock(&dev->bus_mutex);
575 dec_refcnt:
576 	atomic_dec(THERM_REFCNT(family_data));
577 error:
578 	return ret;
579 }
580 
581 static ssize_t w1_slave_show(struct device *device,
582 			     struct device_attribute *attr, char *buf)
583 {
584 	struct w1_slave *sl = dev_to_w1_slave(device);
585 	struct therm_info info;
586 	u8 *family_data = sl->family_data;
587 	int ret, i;
588 	ssize_t c = PAGE_SIZE;
589 	u8 fid = sl->family->fid;
590 
591 	ret = read_therm(device, sl, &info);
592 	if (ret)
593 		return ret;
594 
595 	for (i = 0; i < 9; ++i)
596 		c -= snprintf(buf + PAGE_SIZE - c, c, "%02x ", info.rom[i]);
597 	c -= snprintf(buf + PAGE_SIZE - c, c, ": crc=%02x %s\n",
598 		      info.crc, (info.verdict) ? "YES" : "NO");
599 	if (info.verdict)
600 		memcpy(family_data, info.rom, sizeof(info.rom));
601 	else
602 		dev_warn(device, "Read failed CRC check\n");
603 
604 	for (i = 0; i < 9; ++i)
605 		c -= snprintf(buf + PAGE_SIZE - c, c, "%02x ",
606 			      ((u8 *)family_data)[i]);
607 
608 	c -= snprintf(buf + PAGE_SIZE - c, c, "t=%d\n",
609 			w1_convert_temp(info.rom, fid));
610 	ret = PAGE_SIZE - c;
611 	return ret;
612 }
613 
614 #if IS_REACHABLE(CONFIG_HWMON)
615 static int w1_read_temp(struct device *device, u32 attr, int channel,
616 			long *val)
617 {
618 	struct w1_slave *sl = dev_get_drvdata(device);
619 	struct therm_info info;
620 	u8 fid = sl->family->fid;
621 	int ret;
622 
623 	switch (attr) {
624 	case hwmon_temp_input:
625 		ret = read_therm(device, sl, &info);
626 		if (ret)
627 			return ret;
628 
629 		if (!info.verdict) {
630 			ret = -EIO;
631 			return ret;
632 		}
633 
634 		*val = w1_convert_temp(info.rom, fid);
635 		ret = 0;
636 		break;
637 	default:
638 		ret = -EOPNOTSUPP;
639 		break;
640 	}
641 
642 	return ret;
643 }
644 #endif
645 
646 #define W1_42_CHAIN	0x99
647 #define W1_42_CHAIN_OFF	0x3C
648 #define W1_42_CHAIN_OFF_INV	0xC3
649 #define W1_42_CHAIN_ON	0x5A
650 #define W1_42_CHAIN_ON_INV	0xA5
651 #define W1_42_CHAIN_DONE 0x96
652 #define W1_42_CHAIN_DONE_INV 0x69
653 #define W1_42_COND_READ	0x0F
654 #define W1_42_SUCCESS_CONFIRM_BYTE 0xAA
655 #define W1_42_FINISHED_BYTE 0xFF
656 static ssize_t w1_seq_show(struct device *device,
657 	struct device_attribute *attr, char *buf)
658 {
659 	struct w1_slave *sl = dev_to_w1_slave(device);
660 	ssize_t c = PAGE_SIZE;
661 	int rv;
662 	int i;
663 	u8 ack;
664 	u64 rn;
665 	struct w1_reg_num *reg_num;
666 	int seq = 0;
667 
668 	mutex_lock(&sl->master->bus_mutex);
669 	/* Place all devices in CHAIN state */
670 	if (w1_reset_bus(sl->master))
671 		goto error;
672 	w1_write_8(sl->master, W1_SKIP_ROM);
673 	w1_write_8(sl->master, W1_42_CHAIN);
674 	w1_write_8(sl->master, W1_42_CHAIN_ON);
675 	w1_write_8(sl->master, W1_42_CHAIN_ON_INV);
676 	msleep(sl->master->pullup_duration);
677 
678 	/* check for acknowledgment */
679 	ack = w1_read_8(sl->master);
680 	if (ack != W1_42_SUCCESS_CONFIRM_BYTE)
681 		goto error;
682 
683 	/* In case the bus fails to send 0xFF, limit*/
684 	for (i = 0; i <= 64; i++) {
685 		if (w1_reset_bus(sl->master))
686 			goto error;
687 
688 		w1_write_8(sl->master, W1_42_COND_READ);
689 		rv = w1_read_block(sl->master, (u8 *)&rn, 8);
690 		reg_num = (struct w1_reg_num *) &rn;
691 		if (reg_num->family == W1_42_FINISHED_BYTE)
692 			break;
693 		if (sl->reg_num.id == reg_num->id)
694 			seq = i;
695 
696 		w1_write_8(sl->master, W1_42_CHAIN);
697 		w1_write_8(sl->master, W1_42_CHAIN_DONE);
698 		w1_write_8(sl->master, W1_42_CHAIN_DONE_INV);
699 		w1_read_block(sl->master, &ack, sizeof(ack));
700 
701 		/* check for acknowledgment */
702 		ack = w1_read_8(sl->master);
703 		if (ack != W1_42_SUCCESS_CONFIRM_BYTE)
704 			goto error;
705 
706 	}
707 
708 	/* Exit from CHAIN state */
709 	if (w1_reset_bus(sl->master))
710 		goto error;
711 	w1_write_8(sl->master, W1_SKIP_ROM);
712 	w1_write_8(sl->master, W1_42_CHAIN);
713 	w1_write_8(sl->master, W1_42_CHAIN_OFF);
714 	w1_write_8(sl->master, W1_42_CHAIN_OFF_INV);
715 
716 	/* check for acknowledgment */
717 	ack = w1_read_8(sl->master);
718 	if (ack != W1_42_SUCCESS_CONFIRM_BYTE)
719 		goto error;
720 	mutex_unlock(&sl->master->bus_mutex);
721 
722 	c -= snprintf(buf + PAGE_SIZE - c, c, "%d\n", seq);
723 	return PAGE_SIZE - c;
724 error:
725 	mutex_unlock(&sl->master->bus_mutex);
726 	return -EIO;
727 }
728 
729 static int __init w1_therm_init(void)
730 {
731 	int err, i;
732 
733 	for (i = 0; i < ARRAY_SIZE(w1_therm_families); ++i) {
734 		err = w1_register_family(w1_therm_families[i].f);
735 		if (err)
736 			w1_therm_families[i].broken = 1;
737 	}
738 
739 	return 0;
740 }
741 
742 static void __exit w1_therm_fini(void)
743 {
744 	int i;
745 
746 	for (i = 0; i < ARRAY_SIZE(w1_therm_families); ++i)
747 		if (!w1_therm_families[i].broken)
748 			w1_unregister_family(w1_therm_families[i].f);
749 }
750 
751 module_init(w1_therm_init);
752 module_exit(w1_therm_fini);
753 
754 MODULE_AUTHOR("Evgeniy Polyakov <zbr@ioremap.net>");
755 MODULE_DESCRIPTION("Driver for 1-wire Dallas network protocol, temperature family.");
756 MODULE_LICENSE("GPL");
757 MODULE_ALIAS("w1-family-" __stringify(W1_THERM_DS18S20));
758 MODULE_ALIAS("w1-family-" __stringify(W1_THERM_DS1822));
759 MODULE_ALIAS("w1-family-" __stringify(W1_THERM_DS18B20));
760 MODULE_ALIAS("w1-family-" __stringify(W1_THERM_DS1825));
761 MODULE_ALIAS("w1-family-" __stringify(W1_THERM_DS28EA00));
762