xref: /openbmc/linux/drivers/hwmon/max6650.c (revision b34e08d5)
1 /*
2  * max6650.c - Part of lm_sensors, Linux kernel modules for hardware
3  *             monitoring.
4  *
5  * (C) 2007 by Hans J. Koch <hjk@hansjkoch.de>
6  *
7  * based on code written by John Morris <john.morris@spirentcom.com>
8  * Copyright (c) 2003 Spirent Communications
9  * and Claus Gindhart <claus.gindhart@kontron.com>
10  *
11  * This module has only been tested with the MAX6650 chip. It should
12  * also work with the MAX6651. It does not distinguish max6650 and max6651
13  * chips.
14  *
15  * The datasheet was last seen at:
16  *
17  *        http://pdfserv.maxim-ic.com/en/ds/MAX6650-MAX6651.pdf
18  *
19  * This program is free software; you can redistribute it and/or modify
20  * it under the terms of the GNU General Public License as published by
21  * the Free Software Foundation; either version 2 of the License, or
22  * (at your option) any later version.
23  *
24  * This program is distributed in the hope that it will be useful,
25  * but WITHOUT ANY WARRANTY; without even the implied warranty of
26  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
27  * GNU General Public License for more details.
28  *
29  * You should have received a copy of the GNU General Public License
30  * along with this program; if not, write to the Free Software
31  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
32  */
33 
34 #include <linux/module.h>
35 #include <linux/init.h>
36 #include <linux/slab.h>
37 #include <linux/jiffies.h>
38 #include <linux/i2c.h>
39 #include <linux/hwmon.h>
40 #include <linux/hwmon-sysfs.h>
41 #include <linux/err.h>
42 
43 /*
44  * Insmod parameters
45  */
46 
47 /* fan_voltage: 5=5V fan, 12=12V fan, 0=don't change */
48 static int fan_voltage;
49 /* prescaler: Possible values are 1, 2, 4, 8, 16 or 0 for don't change */
50 static int prescaler;
51 /* clock: The clock frequency of the chip the driver should assume */
52 static int clock = 254000;
53 
54 module_param(fan_voltage, int, S_IRUGO);
55 module_param(prescaler, int, S_IRUGO);
56 module_param(clock, int, S_IRUGO);
57 
58 /*
59  * MAX 6650/6651 registers
60  */
61 
62 #define MAX6650_REG_SPEED	0x00
63 #define MAX6650_REG_CONFIG	0x02
64 #define MAX6650_REG_GPIO_DEF	0x04
65 #define MAX6650_REG_DAC		0x06
66 #define MAX6650_REG_ALARM_EN	0x08
67 #define MAX6650_REG_ALARM	0x0A
68 #define MAX6650_REG_TACH0	0x0C
69 #define MAX6650_REG_TACH1	0x0E
70 #define MAX6650_REG_TACH2	0x10
71 #define MAX6650_REG_TACH3	0x12
72 #define MAX6650_REG_GPIO_STAT	0x14
73 #define MAX6650_REG_COUNT	0x16
74 
75 /*
76  * Config register bits
77  */
78 
79 #define MAX6650_CFG_V12			0x08
80 #define MAX6650_CFG_PRESCALER_MASK	0x07
81 #define MAX6650_CFG_PRESCALER_2		0x01
82 #define MAX6650_CFG_PRESCALER_4		0x02
83 #define MAX6650_CFG_PRESCALER_8		0x03
84 #define MAX6650_CFG_PRESCALER_16	0x04
85 #define MAX6650_CFG_MODE_MASK		0x30
86 #define MAX6650_CFG_MODE_ON		0x00
87 #define MAX6650_CFG_MODE_OFF		0x10
88 #define MAX6650_CFG_MODE_CLOSED_LOOP	0x20
89 #define MAX6650_CFG_MODE_OPEN_LOOP	0x30
90 #define MAX6650_COUNT_MASK		0x03
91 
92 /*
93  * Alarm status register bits
94  */
95 
96 #define MAX6650_ALRM_MAX	0x01
97 #define MAX6650_ALRM_MIN	0x02
98 #define MAX6650_ALRM_TACH	0x04
99 #define MAX6650_ALRM_GPIO1	0x08
100 #define MAX6650_ALRM_GPIO2	0x10
101 
102 /* Minimum and maximum values of the FAN-RPM */
103 #define FAN_RPM_MIN 240
104 #define FAN_RPM_MAX 30000
105 
106 #define DIV_FROM_REG(reg) (1 << (reg & 7))
107 
108 /*
109  * Client data (each client gets its own)
110  */
111 
112 struct max6650_data {
113 	struct i2c_client *client;
114 	const struct attribute_group *groups[3];
115 	struct mutex update_lock;
116 	int nr_fans;
117 	char valid; /* zero until following fields are valid */
118 	unsigned long last_updated; /* in jiffies */
119 
120 	/* register values */
121 	u8 speed;
122 	u8 config;
123 	u8 tach[4];
124 	u8 count;
125 	u8 dac;
126 	u8 alarm;
127 };
128 
129 static const u8 tach_reg[] = {
130 	MAX6650_REG_TACH0,
131 	MAX6650_REG_TACH1,
132 	MAX6650_REG_TACH2,
133 	MAX6650_REG_TACH3,
134 };
135 
136 static struct max6650_data *max6650_update_device(struct device *dev)
137 {
138 	struct max6650_data *data = dev_get_drvdata(dev);
139 	struct i2c_client *client = data->client;
140 	int i;
141 
142 	mutex_lock(&data->update_lock);
143 
144 	if (time_after(jiffies, data->last_updated + HZ) || !data->valid) {
145 		data->speed = i2c_smbus_read_byte_data(client,
146 						       MAX6650_REG_SPEED);
147 		data->config = i2c_smbus_read_byte_data(client,
148 							MAX6650_REG_CONFIG);
149 		for (i = 0; i < data->nr_fans; i++) {
150 			data->tach[i] = i2c_smbus_read_byte_data(client,
151 								 tach_reg[i]);
152 		}
153 		data->count = i2c_smbus_read_byte_data(client,
154 							MAX6650_REG_COUNT);
155 		data->dac = i2c_smbus_read_byte_data(client, MAX6650_REG_DAC);
156 
157 		/*
158 		 * Alarms are cleared on read in case the condition that
159 		 * caused the alarm is removed. Keep the value latched here
160 		 * for providing the register through different alarm files.
161 		 */
162 		data->alarm |= i2c_smbus_read_byte_data(client,
163 							MAX6650_REG_ALARM);
164 
165 		data->last_updated = jiffies;
166 		data->valid = 1;
167 	}
168 
169 	mutex_unlock(&data->update_lock);
170 
171 	return data;
172 }
173 
174 static ssize_t get_fan(struct device *dev, struct device_attribute *devattr,
175 		       char *buf)
176 {
177 	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
178 	struct max6650_data *data = max6650_update_device(dev);
179 	int rpm;
180 
181 	/*
182 	 * Calculation details:
183 	 *
184 	 * Each tachometer counts over an interval given by the "count"
185 	 * register (0.25, 0.5, 1 or 2 seconds). This module assumes
186 	 * that the fans produce two pulses per revolution (this seems
187 	 * to be the most common).
188 	 */
189 
190 	rpm = ((data->tach[attr->index] * 120) / DIV_FROM_REG(data->count));
191 	return sprintf(buf, "%d\n", rpm);
192 }
193 
194 /*
195  * Set the fan speed to the specified RPM (or read back the RPM setting).
196  * This works in closed loop mode only. Use pwm1 for open loop speed setting.
197  *
198  * The MAX6650/1 will automatically control fan speed when in closed loop
199  * mode.
200  *
201  * Assumptions:
202  *
203  * 1) The MAX6650/1 internal 254kHz clock frequency is set correctly. Use
204  *    the clock module parameter if you need to fine tune this.
205  *
206  * 2) The prescaler (low three bits of the config register) has already
207  *    been set to an appropriate value. Use the prescaler module parameter
208  *    if your BIOS doesn't initialize the chip properly.
209  *
210  * The relevant equations are given on pages 21 and 22 of the datasheet.
211  *
212  * From the datasheet, the relevant equation when in regulation is:
213  *
214  *    [fCLK / (128 x (KTACH + 1))] = 2 x FanSpeed / KSCALE
215  *
216  * where:
217  *
218  *    fCLK is the oscillator frequency (either the 254kHz internal
219  *         oscillator or the externally applied clock)
220  *
221  *    KTACH is the value in the speed register
222  *
223  *    FanSpeed is the speed of the fan in rps
224  *
225  *    KSCALE is the prescaler value (1, 2, 4, 8, or 16)
226  *
227  * When reading, we need to solve for FanSpeed. When writing, we need to
228  * solve for KTACH.
229  *
230  * Note: this tachometer is completely separate from the tachometers
231  * used to measure the fan speeds. Only one fan's speed (fan1) is
232  * controlled.
233  */
234 
235 static ssize_t get_target(struct device *dev, struct device_attribute *devattr,
236 			 char *buf)
237 {
238 	struct max6650_data *data = max6650_update_device(dev);
239 	int kscale, ktach, rpm;
240 
241 	/*
242 	 * Use the datasheet equation:
243 	 *
244 	 *    FanSpeed = KSCALE x fCLK / [256 x (KTACH + 1)]
245 	 *
246 	 * then multiply by 60 to give rpm.
247 	 */
248 
249 	kscale = DIV_FROM_REG(data->config);
250 	ktach = data->speed;
251 	rpm = 60 * kscale * clock / (256 * (ktach + 1));
252 	return sprintf(buf, "%d\n", rpm);
253 }
254 
255 static ssize_t set_target(struct device *dev, struct device_attribute *devattr,
256 			 const char *buf, size_t count)
257 {
258 	struct max6650_data *data = dev_get_drvdata(dev);
259 	struct i2c_client *client = data->client;
260 	int kscale, ktach;
261 	unsigned long rpm;
262 	int err;
263 
264 	err = kstrtoul(buf, 10, &rpm);
265 	if (err)
266 		return err;
267 
268 	rpm = clamp_val(rpm, FAN_RPM_MIN, FAN_RPM_MAX);
269 
270 	/*
271 	 * Divide the required speed by 60 to get from rpm to rps, then
272 	 * use the datasheet equation:
273 	 *
274 	 *     KTACH = [(fCLK x KSCALE) / (256 x FanSpeed)] - 1
275 	 */
276 
277 	mutex_lock(&data->update_lock);
278 
279 	kscale = DIV_FROM_REG(data->config);
280 	ktach = ((clock * kscale) / (256 * rpm / 60)) - 1;
281 	if (ktach < 0)
282 		ktach = 0;
283 	if (ktach > 255)
284 		ktach = 255;
285 	data->speed = ktach;
286 
287 	i2c_smbus_write_byte_data(client, MAX6650_REG_SPEED, data->speed);
288 
289 	mutex_unlock(&data->update_lock);
290 
291 	return count;
292 }
293 
294 /*
295  * Get/set the fan speed in open loop mode using pwm1 sysfs file.
296  * Speed is given as a relative value from 0 to 255, where 255 is maximum
297  * speed. Note that this is done by writing directly to the chip's DAC,
298  * it won't change the closed loop speed set by fan1_target.
299  * Also note that due to rounding errors it is possible that you don't read
300  * back exactly the value you have set.
301  */
302 
303 static ssize_t get_pwm(struct device *dev, struct device_attribute *devattr,
304 		       char *buf)
305 {
306 	int pwm;
307 	struct max6650_data *data = max6650_update_device(dev);
308 
309 	/*
310 	 * Useful range for dac is 0-180 for 12V fans and 0-76 for 5V fans.
311 	 * Lower DAC values mean higher speeds.
312 	 */
313 	if (data->config & MAX6650_CFG_V12)
314 		pwm = 255 - (255 * (int)data->dac)/180;
315 	else
316 		pwm = 255 - (255 * (int)data->dac)/76;
317 
318 	if (pwm < 0)
319 		pwm = 0;
320 
321 	return sprintf(buf, "%d\n", pwm);
322 }
323 
324 static ssize_t set_pwm(struct device *dev, struct device_attribute *devattr,
325 			const char *buf, size_t count)
326 {
327 	struct max6650_data *data = dev_get_drvdata(dev);
328 	struct i2c_client *client = data->client;
329 	unsigned long pwm;
330 	int err;
331 
332 	err = kstrtoul(buf, 10, &pwm);
333 	if (err)
334 		return err;
335 
336 	pwm = clamp_val(pwm, 0, 255);
337 
338 	mutex_lock(&data->update_lock);
339 
340 	if (data->config & MAX6650_CFG_V12)
341 		data->dac = 180 - (180 * pwm)/255;
342 	else
343 		data->dac = 76 - (76 * pwm)/255;
344 
345 	i2c_smbus_write_byte_data(client, MAX6650_REG_DAC, data->dac);
346 
347 	mutex_unlock(&data->update_lock);
348 
349 	return count;
350 }
351 
352 /*
353  * Get/Set controller mode:
354  * Possible values:
355  * 0 = Fan always on
356  * 1 = Open loop, Voltage is set according to speed, not regulated.
357  * 2 = Closed loop, RPM for all fans regulated by fan1 tachometer
358  */
359 
360 static ssize_t get_enable(struct device *dev, struct device_attribute *devattr,
361 			  char *buf)
362 {
363 	struct max6650_data *data = max6650_update_device(dev);
364 	int mode = (data->config & MAX6650_CFG_MODE_MASK) >> 4;
365 	int sysfs_modes[4] = {0, 1, 2, 1};
366 
367 	return sprintf(buf, "%d\n", sysfs_modes[mode]);
368 }
369 
370 static ssize_t set_enable(struct device *dev, struct device_attribute *devattr,
371 			  const char *buf, size_t count)
372 {
373 	struct max6650_data *data = dev_get_drvdata(dev);
374 	struct i2c_client *client = data->client;
375 	int max6650_modes[3] = {0, 3, 2};
376 	unsigned long mode;
377 	int err;
378 
379 	err = kstrtoul(buf, 10, &mode);
380 	if (err)
381 		return err;
382 
383 	if (mode > 2)
384 		return -EINVAL;
385 
386 	mutex_lock(&data->update_lock);
387 
388 	data->config = i2c_smbus_read_byte_data(client, MAX6650_REG_CONFIG);
389 	data->config = (data->config & ~MAX6650_CFG_MODE_MASK)
390 		       | (max6650_modes[mode] << 4);
391 
392 	i2c_smbus_write_byte_data(client, MAX6650_REG_CONFIG, data->config);
393 
394 	mutex_unlock(&data->update_lock);
395 
396 	return count;
397 }
398 
399 /*
400  * Read/write functions for fan1_div sysfs file. The MAX6650 has no such
401  * divider. We handle this by converting between divider and counttime:
402  *
403  * (counttime == k) <==> (divider == 2^k), k = 0, 1, 2, or 3
404  *
405  * Lower values of k allow to connect a faster fan without the risk of
406  * counter overflow. The price is lower resolution. You can also set counttime
407  * using the module parameter. Note that the module parameter "prescaler" also
408  * influences the behaviour. Unfortunately, there's no sysfs attribute
409  * defined for that. See the data sheet for details.
410  */
411 
412 static ssize_t get_div(struct device *dev, struct device_attribute *devattr,
413 		       char *buf)
414 {
415 	struct max6650_data *data = max6650_update_device(dev);
416 
417 	return sprintf(buf, "%d\n", DIV_FROM_REG(data->count));
418 }
419 
420 static ssize_t set_div(struct device *dev, struct device_attribute *devattr,
421 		       const char *buf, size_t count)
422 {
423 	struct max6650_data *data = dev_get_drvdata(dev);
424 	struct i2c_client *client = data->client;
425 	unsigned long div;
426 	int err;
427 
428 	err = kstrtoul(buf, 10, &div);
429 	if (err)
430 		return err;
431 
432 	mutex_lock(&data->update_lock);
433 	switch (div) {
434 	case 1:
435 		data->count = 0;
436 		break;
437 	case 2:
438 		data->count = 1;
439 		break;
440 	case 4:
441 		data->count = 2;
442 		break;
443 	case 8:
444 		data->count = 3;
445 		break;
446 	default:
447 		mutex_unlock(&data->update_lock);
448 		return -EINVAL;
449 	}
450 
451 	i2c_smbus_write_byte_data(client, MAX6650_REG_COUNT, data->count);
452 	mutex_unlock(&data->update_lock);
453 
454 	return count;
455 }
456 
457 /*
458  * Get alarm stati:
459  * Possible values:
460  * 0 = no alarm
461  * 1 = alarm
462  */
463 
464 static ssize_t get_alarm(struct device *dev, struct device_attribute *devattr,
465 			 char *buf)
466 {
467 	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
468 	struct max6650_data *data = max6650_update_device(dev);
469 	struct i2c_client *client = data->client;
470 	int alarm = 0;
471 
472 	if (data->alarm & attr->index) {
473 		mutex_lock(&data->update_lock);
474 		alarm = 1;
475 		data->alarm &= ~attr->index;
476 		data->alarm |= i2c_smbus_read_byte_data(client,
477 							MAX6650_REG_ALARM);
478 		mutex_unlock(&data->update_lock);
479 	}
480 
481 	return sprintf(buf, "%d\n", alarm);
482 }
483 
484 static SENSOR_DEVICE_ATTR(fan1_input, S_IRUGO, get_fan, NULL, 0);
485 static SENSOR_DEVICE_ATTR(fan2_input, S_IRUGO, get_fan, NULL, 1);
486 static SENSOR_DEVICE_ATTR(fan3_input, S_IRUGO, get_fan, NULL, 2);
487 static SENSOR_DEVICE_ATTR(fan4_input, S_IRUGO, get_fan, NULL, 3);
488 static DEVICE_ATTR(fan1_target, S_IWUSR | S_IRUGO, get_target, set_target);
489 static DEVICE_ATTR(fan1_div, S_IWUSR | S_IRUGO, get_div, set_div);
490 static DEVICE_ATTR(pwm1_enable, S_IWUSR | S_IRUGO, get_enable, set_enable);
491 static DEVICE_ATTR(pwm1, S_IWUSR | S_IRUGO, get_pwm, set_pwm);
492 static SENSOR_DEVICE_ATTR(fan1_max_alarm, S_IRUGO, get_alarm, NULL,
493 			  MAX6650_ALRM_MAX);
494 static SENSOR_DEVICE_ATTR(fan1_min_alarm, S_IRUGO, get_alarm, NULL,
495 			  MAX6650_ALRM_MIN);
496 static SENSOR_DEVICE_ATTR(fan1_fault, S_IRUGO, get_alarm, NULL,
497 			  MAX6650_ALRM_TACH);
498 static SENSOR_DEVICE_ATTR(gpio1_alarm, S_IRUGO, get_alarm, NULL,
499 			  MAX6650_ALRM_GPIO1);
500 static SENSOR_DEVICE_ATTR(gpio2_alarm, S_IRUGO, get_alarm, NULL,
501 			  MAX6650_ALRM_GPIO2);
502 
503 static umode_t max6650_attrs_visible(struct kobject *kobj, struct attribute *a,
504 				    int n)
505 {
506 	struct device *dev = container_of(kobj, struct device, kobj);
507 	struct max6650_data *data = dev_get_drvdata(dev);
508 	struct i2c_client *client = data->client;
509 	u8 alarm_en = i2c_smbus_read_byte_data(client, MAX6650_REG_ALARM_EN);
510 	struct device_attribute *devattr;
511 
512 	/*
513 	 * Hide the alarms that have not been enabled by the firmware
514 	 */
515 
516 	devattr = container_of(a, struct device_attribute, attr);
517 	if (devattr == &sensor_dev_attr_fan1_max_alarm.dev_attr
518 	 || devattr == &sensor_dev_attr_fan1_min_alarm.dev_attr
519 	 || devattr == &sensor_dev_attr_fan1_fault.dev_attr
520 	 || devattr == &sensor_dev_attr_gpio1_alarm.dev_attr
521 	 || devattr == &sensor_dev_attr_gpio2_alarm.dev_attr) {
522 		if (!(alarm_en & to_sensor_dev_attr(devattr)->index))
523 			return 0;
524 	}
525 
526 	return a->mode;
527 }
528 
529 static struct attribute *max6650_attrs[] = {
530 	&sensor_dev_attr_fan1_input.dev_attr.attr,
531 	&dev_attr_fan1_target.attr,
532 	&dev_attr_fan1_div.attr,
533 	&dev_attr_pwm1_enable.attr,
534 	&dev_attr_pwm1.attr,
535 	&sensor_dev_attr_fan1_max_alarm.dev_attr.attr,
536 	&sensor_dev_attr_fan1_min_alarm.dev_attr.attr,
537 	&sensor_dev_attr_fan1_fault.dev_attr.attr,
538 	&sensor_dev_attr_gpio1_alarm.dev_attr.attr,
539 	&sensor_dev_attr_gpio2_alarm.dev_attr.attr,
540 	NULL
541 };
542 
543 static const struct attribute_group max6650_group = {
544 	.attrs = max6650_attrs,
545 	.is_visible = max6650_attrs_visible,
546 };
547 
548 static struct attribute *max6651_attrs[] = {
549 	&sensor_dev_attr_fan2_input.dev_attr.attr,
550 	&sensor_dev_attr_fan3_input.dev_attr.attr,
551 	&sensor_dev_attr_fan4_input.dev_attr.attr,
552 	NULL
553 };
554 
555 static const struct attribute_group max6651_group = {
556 	.attrs = max6651_attrs,
557 };
558 
559 /*
560  * Real code
561  */
562 
563 static int max6650_init_client(struct max6650_data *data,
564 			       struct i2c_client *client)
565 {
566 	struct device *dev = &client->dev;
567 	int config;
568 	int err = -EIO;
569 
570 	config = i2c_smbus_read_byte_data(client, MAX6650_REG_CONFIG);
571 
572 	if (config < 0) {
573 		dev_err(dev, "Error reading config, aborting.\n");
574 		return err;
575 	}
576 
577 	switch (fan_voltage) {
578 	case 0:
579 		break;
580 	case 5:
581 		config &= ~MAX6650_CFG_V12;
582 		break;
583 	case 12:
584 		config |= MAX6650_CFG_V12;
585 		break;
586 	default:
587 		dev_err(dev, "illegal value for fan_voltage (%d)\n",
588 			fan_voltage);
589 	}
590 
591 	dev_info(dev, "Fan voltage is set to %dV.\n",
592 		 (config & MAX6650_CFG_V12) ? 12 : 5);
593 
594 	switch (prescaler) {
595 	case 0:
596 		break;
597 	case 1:
598 		config &= ~MAX6650_CFG_PRESCALER_MASK;
599 		break;
600 	case 2:
601 		config = (config & ~MAX6650_CFG_PRESCALER_MASK)
602 			 | MAX6650_CFG_PRESCALER_2;
603 		break;
604 	case  4:
605 		config = (config & ~MAX6650_CFG_PRESCALER_MASK)
606 			 | MAX6650_CFG_PRESCALER_4;
607 		break;
608 	case  8:
609 		config = (config & ~MAX6650_CFG_PRESCALER_MASK)
610 			 | MAX6650_CFG_PRESCALER_8;
611 		break;
612 	case 16:
613 		config = (config & ~MAX6650_CFG_PRESCALER_MASK)
614 			 | MAX6650_CFG_PRESCALER_16;
615 		break;
616 	default:
617 		dev_err(dev, "illegal value for prescaler (%d)\n", prescaler);
618 	}
619 
620 	dev_info(dev, "Prescaler is set to %d.\n",
621 		 1 << (config & MAX6650_CFG_PRESCALER_MASK));
622 
623 	/*
624 	 * If mode is set to "full off", we change it to "open loop" and
625 	 * set DAC to 255, which has the same effect. We do this because
626 	 * there's no "full off" mode defined in hwmon specifications.
627 	 */
628 
629 	if ((config & MAX6650_CFG_MODE_MASK) == MAX6650_CFG_MODE_OFF) {
630 		dev_dbg(dev, "Change mode to open loop, full off.\n");
631 		config = (config & ~MAX6650_CFG_MODE_MASK)
632 			 | MAX6650_CFG_MODE_OPEN_LOOP;
633 		if (i2c_smbus_write_byte_data(client, MAX6650_REG_DAC, 255)) {
634 			dev_err(dev, "DAC write error, aborting.\n");
635 			return err;
636 		}
637 	}
638 
639 	if (i2c_smbus_write_byte_data(client, MAX6650_REG_CONFIG, config)) {
640 		dev_err(dev, "Config write error, aborting.\n");
641 		return err;
642 	}
643 
644 	data->config = config;
645 	data->count = i2c_smbus_read_byte_data(client, MAX6650_REG_COUNT);
646 
647 	return 0;
648 }
649 
650 static int max6650_probe(struct i2c_client *client,
651 			 const struct i2c_device_id *id)
652 {
653 	struct device *dev = &client->dev;
654 	struct max6650_data *data;
655 	struct device *hwmon_dev;
656 	int err;
657 
658 	data = devm_kzalloc(dev, sizeof(struct max6650_data), GFP_KERNEL);
659 	if (!data)
660 		return -ENOMEM;
661 
662 	data->client = client;
663 	mutex_init(&data->update_lock);
664 	data->nr_fans = id->driver_data;
665 
666 	/*
667 	 * Initialize the max6650 chip
668 	 */
669 	err = max6650_init_client(data, client);
670 	if (err)
671 		return err;
672 
673 	data->groups[0] = &max6650_group;
674 	/* 3 additional fan inputs for the MAX6651 */
675 	if (data->nr_fans == 4)
676 		data->groups[1] = &max6651_group;
677 
678 	hwmon_dev = devm_hwmon_device_register_with_groups(dev,
679 							   client->name, data,
680 							   data->groups);
681 	return PTR_ERR_OR_ZERO(hwmon_dev);
682 }
683 
684 static const struct i2c_device_id max6650_id[] = {
685 	{ "max6650", 1 },
686 	{ "max6651", 4 },
687 	{ }
688 };
689 MODULE_DEVICE_TABLE(i2c, max6650_id);
690 
691 static struct i2c_driver max6650_driver = {
692 	.driver = {
693 		.name	= "max6650",
694 	},
695 	.probe		= max6650_probe,
696 	.id_table	= max6650_id,
697 };
698 
699 module_i2c_driver(max6650_driver);
700 
701 MODULE_AUTHOR("Hans J. Koch");
702 MODULE_DESCRIPTION("MAX6650 sensor driver");
703 MODULE_LICENSE("GPL");
704