summaryrefslogtreecommitdiff
path: root/drivers/hwmon/hih6130.c
blob: 018df6074f7b21b1c3cfab2688d403d45c9a2d9c (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
// SPDX-License-Identifier: GPL-2.0-or-later
/* Honeywell HIH-6130/HIH-6131 humidity and temperature sensor driver
 *
 * Copyright (C) 2012 Iain Paton <ipaton0@gmail.com>
 *
 * heavily based on the sht21 driver
 * Copyright (C) 2010 Urs Fleisch <urs.fleisch@sensirion.com>
 *
 * Data sheets available (2012-06-22) at
 * http://sensing.honeywell.com/index.php?ci_id=3106&la_id=1&defId=44872
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>
#include <linux/err.h>
#include <linux/mutex.h>
#include <linux/device.h>
#include <linux/delay.h>
#include <linux/jiffies.h>

/**
 * struct hih6130 - HIH-6130 device specific data
 * @client: pointer to I2C client device
 * @lock: mutex to protect measurement values
 * @valid: only false before first measurement is taken
 * @last_update: time of last update (jiffies)
 * @temperature: cached temperature measurement value
 * @humidity: cached humidity measurement value
 * @write_length: length for I2C measurement request
 */
struct hih6130 {
	struct i2c_client *client;
	struct mutex lock;
	bool valid;
	unsigned long last_update;
	int temperature;
	int humidity;
	size_t write_length;
};

/**
 * hih6130_temp_ticks_to_millicelsius() - convert raw temperature ticks to
 * milli celsius
 * @ticks: temperature ticks value received from sensor
 */
static inline int hih6130_temp_ticks_to_millicelsius(int ticks)
{
	ticks = ticks >> 2;
	/*
	 * from data sheet section 5.0
	 * Formula T = ( ticks / ( 2^14 - 2 ) ) * 165 -40
	 */
	return (DIV_ROUND_CLOSEST(ticks * 1650, 16382) - 400) * 100;
}

/**
 * hih6130_rh_ticks_to_per_cent_mille() - convert raw humidity ticks to
 * one-thousandths of a percent relative humidity
 * @ticks: humidity ticks value received from sensor
 */
static inline int hih6130_rh_ticks_to_per_cent_mille(int ticks)
{
	ticks &= ~0xC000; /* clear status bits */
	/*
	 * from data sheet section 4.0
	 * Formula RH = ( ticks / ( 2^14 -2 ) ) * 100
	 */
	return DIV_ROUND_CLOSEST(ticks * 1000, 16382) * 100;
}

/**
 * hih6130_update_measurements() - get updated measurements from device
 * @dev: device
 *
 * Returns 0 on success, else negative errno.
 */
static int hih6130_update_measurements(struct device *dev)
{
	struct hih6130 *hih6130 = dev_get_drvdata(dev);
	struct i2c_client *client = hih6130->client;
	int ret = 0;
	int t;
	unsigned char tmp[4];
	struct i2c_msg msgs[1] = {
		{
			.addr = client->addr,
			.flags = I2C_M_RD,
			.len = 4,
			.buf = tmp,
		}
	};

	mutex_lock(&hih6130->lock);

	/*
	 * While the measurement can be completed in ~40ms the sensor takes
	 * much longer to react to a change in external conditions. How quickly
	 * it reacts depends on airflow and other factors outwith our control.
	 * The datasheet specifies maximum 'Response time' for humidity at 8s
	 * and temperature at 30s under specified conditions.
	 * We therefore choose to only read the sensor at most once per second.
	 * This trades off pointless activity polling the sensor much faster
	 * than it can react against better response times in conditions more
	 * favourable than specified in the datasheet.
	 */
	if (time_after(jiffies, hih6130->last_update + HZ) || !hih6130->valid) {

		/*
		 * Write to slave address to request a measurement.
		 * According with the datasheet it should be with no data, but
		 * for systems with I2C bus drivers that do not allow zero
		 * length packets we write one dummy byte to allow sensor
		 * measurements on them.
		 */
		tmp[0] = 0;
		ret = i2c_master_send(client, tmp, hih6130->write_length);
		if (ret < 0)
			goto out;

		/* measurement cycle time is ~36.65msec */
		msleep(40);

		ret = i2c_transfer(client->adapter, msgs, 1);
		if (ret < 0)
			goto out;

		if ((tmp[0] & 0xC0) != 0) {
			dev_err(&client->dev, "Error while reading measurement result\n");
			ret = -EIO;
			goto out;
		}

		t = (tmp[0] << 8) + tmp[1];
		hih6130->humidity = hih6130_rh_ticks_to_per_cent_mille(t);

		t = (tmp[2] << 8) + tmp[3];
		hih6130->temperature = hih6130_temp_ticks_to_millicelsius(t);

		hih6130->last_update = jiffies;
		hih6130->valid = true;
	}
out:
	mutex_unlock(&hih6130->lock);

	return ret >= 0 ? 0 : ret;
}

/**
 * hih6130_show_temperature() - show temperature measurement value in sysfs
 * @dev: device
 * @attr: device attribute
 * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to
 *
 * Will be called on read access to temp1_input sysfs attribute.
 * Returns number of bytes written into buffer, negative errno on error.
 */
static ssize_t hih6130_temperature_show(struct device *dev,
					struct device_attribute *attr,
					char *buf)
{
	struct hih6130 *hih6130 = dev_get_drvdata(dev);
	int ret;

	ret = hih6130_update_measurements(dev);
	if (ret < 0)
		return ret;
	return sprintf(buf, "%d\n", hih6130->temperature);
}

/**
 * hih6130_show_humidity() - show humidity measurement value in sysfs
 * @dev: device
 * @attr: device attribute
 * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to
 *
 * Will be called on read access to humidity1_input sysfs attribute.
 * Returns number of bytes written into buffer, negative errno on error.
 */
static ssize_t hih6130_humidity_show(struct device *dev,
				     struct device_attribute *attr, char *buf)
{
	struct hih6130 *hih6130 = dev_get_drvdata(dev);
	int ret;

	ret = hih6130_update_measurements(dev);
	if (ret < 0)
		return ret;
	return sprintf(buf, "%d\n", hih6130->humidity);
}

/* sysfs attributes */
static SENSOR_DEVICE_ATTR_RO(temp1_input, hih6130_temperature, 0);
static SENSOR_DEVICE_ATTR_RO(humidity1_input, hih6130_humidity, 0);

static struct attribute *hih6130_attrs[] = {
	&sensor_dev_attr_temp1_input.dev_attr.attr,
	&sensor_dev_attr_humidity1_input.dev_attr.attr,
	NULL
};

ATTRIBUTE_GROUPS(hih6130);

static int hih6130_probe(struct i2c_client *client,
				   const struct i2c_device_id *id)
{
	struct device *dev = &client->dev;
	struct hih6130 *hih6130;
	struct device *hwmon_dev;

	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
		dev_err(&client->dev, "adapter does not support true I2C\n");
		return -ENODEV;
	}

	hih6130 = devm_kzalloc(dev, sizeof(*hih6130), GFP_KERNEL);
	if (!hih6130)
		return -ENOMEM;

	hih6130->client = client;
	mutex_init(&hih6130->lock);

	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_QUICK))
		hih6130->write_length = 1;

	hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
							   hih6130,
							   hih6130_groups);
	return PTR_ERR_OR_ZERO(hwmon_dev);
}

/* Device ID table */
static const struct i2c_device_id hih6130_id[] = {
	{ "hih6130", 0 },
	{ }
};
MODULE_DEVICE_TABLE(i2c, hih6130_id);

static const struct of_device_id __maybe_unused hih6130_of_match[] = {
	{ .compatible = "honeywell,hih6130", },
	{ }
};
MODULE_DEVICE_TABLE(of, hih6130_of_match);

static struct i2c_driver hih6130_driver = {
	.driver = {
		.name = "hih6130",
		.of_match_table = of_match_ptr(hih6130_of_match),
	},
	.probe       = hih6130_probe,
	.id_table    = hih6130_id,
};

module_i2c_driver(hih6130_driver);

MODULE_AUTHOR("Iain Paton <ipaton0@gmail.com>");
MODULE_DESCRIPTION("Honeywell HIH-6130 humidity and temperature sensor driver");
MODULE_LICENSE("GPL");