1 /* Honeywell HIH-6130/HIH-6131 humidity and temperature sensor driver
2 *
3 * Copyright (C) 2012 Iain Paton <ipaton0@gmail.com>
4 *
5 * heavily based on the sht21 driver
6 * Copyright (C) 2010 Urs Fleisch <urs.fleisch@sensirion.com>
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
12 *
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
17 *
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA
21 *
22 * Data sheets available (2012-06-22) at
23 * http://sensing.honeywell.com/index.php?ci_id=3106&la_id=1&defId=44872
24 */
25
26 #include <linux/module.h>
27 #include <linux/init.h>
28 #include <linux/slab.h>
29 #include <linux/i2c.h>
30 #include <linux/hwmon.h>
31 #include <linux/hwmon-sysfs.h>
32 #include <linux/err.h>
33 #include <linux/mutex.h>
34 #include <linux/device.h>
35 #include <linux/delay.h>
36 #include <linux/jiffies.h>
37
38 /**
39 * struct hih6130 - HIH-6130 device specific data
40 * @hwmon_dev: device registered with hwmon
41 * @lock: mutex to protect measurement values
42 * @valid: only false before first measurement is taken
43 * @last_update: time of last update (jiffies)
44 * @temperature: cached temperature measurement value
45 * @humidity: cached humidity measurement value
46 * @write_length: length for I2C measurement request
47 */
48 struct hih6130 {
49 struct i2c_client *client;
50 struct mutex lock;
51 bool valid;
52 unsigned long last_update;
53 int temperature;
54 int humidity;
55 size_t write_length;
56 };
57
58 /**
59 * hih6130_temp_ticks_to_millicelsius() - convert raw temperature ticks to
60 * milli celsius
61 * @ticks: temperature ticks value received from sensor
62 */
hih6130_temp_ticks_to_millicelsius(int ticks)63 static inline int hih6130_temp_ticks_to_millicelsius(int ticks)
64 {
65 ticks = ticks >> 2;
66 /*
67 * from data sheet section 5.0
68 * Formula T = ( ticks / ( 2^14 - 2 ) ) * 165 -40
69 */
70 return (DIV_ROUND_CLOSEST(ticks * 1650, 16382) - 400) * 100;
71 }
72
73 /**
74 * hih6130_rh_ticks_to_per_cent_mille() - convert raw humidity ticks to
75 * one-thousandths of a percent relative humidity
76 * @ticks: humidity ticks value received from sensor
77 */
hih6130_rh_ticks_to_per_cent_mille(int ticks)78 static inline int hih6130_rh_ticks_to_per_cent_mille(int ticks)
79 {
80 ticks &= ~0xC000; /* clear status bits */
81 /*
82 * from data sheet section 4.0
83 * Formula RH = ( ticks / ( 2^14 -2 ) ) * 100
84 */
85 return DIV_ROUND_CLOSEST(ticks * 1000, 16382) * 100;
86 }
87
88 /**
89 * hih6130_update_measurements() - get updated measurements from device
90 * @dev: device
91 *
92 * Returns 0 on success, else negative errno.
93 */
hih6130_update_measurements(struct device * dev)94 static int hih6130_update_measurements(struct device *dev)
95 {
96 struct hih6130 *hih6130 = dev_get_drvdata(dev);
97 struct i2c_client *client = hih6130->client;
98 int ret = 0;
99 int t;
100 unsigned char tmp[4];
101 struct i2c_msg msgs[1] = {
102 {
103 .addr = client->addr,
104 .flags = I2C_M_RD,
105 .len = 4,
106 .buf = tmp,
107 }
108 };
109
110 mutex_lock(&hih6130->lock);
111
112 /*
113 * While the measurement can be completed in ~40ms the sensor takes
114 * much longer to react to a change in external conditions. How quickly
115 * it reacts depends on airflow and other factors outwith our control.
116 * The datasheet specifies maximum 'Response time' for humidity at 8s
117 * and temperature at 30s under specified conditions.
118 * We therefore choose to only read the sensor at most once per second.
119 * This trades off pointless activity polling the sensor much faster
120 * than it can react against better response times in conditions more
121 * favourable than specified in the datasheet.
122 */
123 if (time_after(jiffies, hih6130->last_update + HZ) || !hih6130->valid) {
124
125 /*
126 * Write to slave address to request a measurement.
127 * According with the datasheet it should be with no data, but
128 * for systems with I2C bus drivers that do not allow zero
129 * length packets we write one dummy byte to allow sensor
130 * measurements on them.
131 */
132 tmp[0] = 0;
133 ret = i2c_master_send(client, tmp, hih6130->write_length);
134 if (ret < 0)
135 goto out;
136
137 /* measurement cycle time is ~36.65msec */
138 msleep(40);
139
140 ret = i2c_transfer(client->adapter, msgs, 1);
141 if (ret < 0)
142 goto out;
143
144 if ((tmp[0] & 0xC0) != 0) {
145 dev_err(&client->dev, "Error while reading measurement result\n");
146 ret = -EIO;
147 goto out;
148 }
149
150 t = (tmp[0] << 8) + tmp[1];
151 hih6130->humidity = hih6130_rh_ticks_to_per_cent_mille(t);
152
153 t = (tmp[2] << 8) + tmp[3];
154 hih6130->temperature = hih6130_temp_ticks_to_millicelsius(t);
155
156 hih6130->last_update = jiffies;
157 hih6130->valid = true;
158 }
159 out:
160 mutex_unlock(&hih6130->lock);
161
162 return ret >= 0 ? 0 : ret;
163 }
164
165 /**
166 * hih6130_show_temperature() - show temperature measurement value in sysfs
167 * @dev: device
168 * @attr: device attribute
169 * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to
170 *
171 * Will be called on read access to temp1_input sysfs attribute.
172 * Returns number of bytes written into buffer, negative errno on error.
173 */
hih6130_show_temperature(struct device * dev,struct device_attribute * attr,char * buf)174 static ssize_t hih6130_show_temperature(struct device *dev,
175 struct device_attribute *attr,
176 char *buf)
177 {
178 struct hih6130 *hih6130 = dev_get_drvdata(dev);
179 int ret;
180
181 ret = hih6130_update_measurements(dev);
182 if (ret < 0)
183 return ret;
184 return sprintf(buf, "%d\n", hih6130->temperature);
185 }
186
187 /**
188 * hih6130_show_humidity() - show humidity measurement value in sysfs
189 * @dev: device
190 * @attr: device attribute
191 * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to
192 *
193 * Will be called on read access to humidity1_input sysfs attribute.
194 * Returns number of bytes written into buffer, negative errno on error.
195 */
hih6130_show_humidity(struct device * dev,struct device_attribute * attr,char * buf)196 static ssize_t hih6130_show_humidity(struct device *dev,
197 struct device_attribute *attr, char *buf)
198 {
199 struct hih6130 *hih6130 = dev_get_drvdata(dev);
200 int ret;
201
202 ret = hih6130_update_measurements(dev);
203 if (ret < 0)
204 return ret;
205 return sprintf(buf, "%d\n", hih6130->humidity);
206 }
207
208 /* sysfs attributes */
209 static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, hih6130_show_temperature,
210 NULL, 0);
211 static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO, hih6130_show_humidity,
212 NULL, 0);
213
214 static struct attribute *hih6130_attrs[] = {
215 &sensor_dev_attr_temp1_input.dev_attr.attr,
216 &sensor_dev_attr_humidity1_input.dev_attr.attr,
217 NULL
218 };
219
220 ATTRIBUTE_GROUPS(hih6130);
221
hih6130_probe(struct i2c_client * client,const struct i2c_device_id * id)222 static int hih6130_probe(struct i2c_client *client,
223 const struct i2c_device_id *id)
224 {
225 struct device *dev = &client->dev;
226 struct hih6130 *hih6130;
227 struct device *hwmon_dev;
228
229 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
230 dev_err(&client->dev, "adapter does not support true I2C\n");
231 return -ENODEV;
232 }
233
234 hih6130 = devm_kzalloc(dev, sizeof(*hih6130), GFP_KERNEL);
235 if (!hih6130)
236 return -ENOMEM;
237
238 hih6130->client = client;
239 mutex_init(&hih6130->lock);
240
241 if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_QUICK))
242 hih6130->write_length = 1;
243
244 hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
245 hih6130,
246 hih6130_groups);
247 return PTR_ERR_OR_ZERO(hwmon_dev);
248 }
249
250 /* Device ID table */
251 static const struct i2c_device_id hih6130_id[] = {
252 { "hih6130", 0 },
253 { }
254 };
255 MODULE_DEVICE_TABLE(i2c, hih6130_id);
256
257 static struct i2c_driver hih6130_driver = {
258 .driver.name = "hih6130",
259 .probe = hih6130_probe,
260 .id_table = hih6130_id,
261 };
262
263 module_i2c_driver(hih6130_driver);
264
265 MODULE_AUTHOR("Iain Paton <ipaton0@gmail.com>");
266 MODULE_DESCRIPTION("Honeywell HIH-6130 humidity and temperature sensor driver");
267 MODULE_LICENSE("GPL");
268