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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 */
48struct hih6130 {
49 struct device *hwmon_dev;
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 */
63static inline int hih6130_temp_ticks_to_millicelsius(int ticks)
64{
65
66 ticks = ticks >> 2;
67 /*
68 * from data sheet section 5.0
69 * Formula T = ( ticks / ( 2^14 - 2 ) ) * 165 -40
70 */
71 return (DIV_ROUND_CLOSEST(ticks * 1650, 16382) - 400) * 100;
72}
73
74/**
75 * hih6130_rh_ticks_to_per_cent_mille() - convert raw humidity ticks to
76 * one-thousandths of a percent relative humidity
77 * @ticks: humidity ticks value received from sensor
78 */
79static inline int hih6130_rh_ticks_to_per_cent_mille(int ticks)
80{
81
82 ticks &= ~0xC000; /* clear status bits */
83 /*
84 * from data sheet section 4.0
85 * Formula RH = ( ticks / ( 2^14 -2 ) ) * 100
86 */
87 return DIV_ROUND_CLOSEST(ticks * 1000, 16382) * 100;
88}
89
90/**
91 * hih6130_update_measurements() - get updated measurements from device
92 * @client: I2C client device
93 *
94 * Returns 0 on success, else negative errno.
95 */
96static int hih6130_update_measurements(struct i2c_client *client)
97{
98 int ret = 0;
99 int t;
100 struct hih6130 *hih6130 = i2c_get_clientdata(client);
101 unsigned char tmp[4];
102 struct i2c_msg msgs[1] = {
103 {
104 .addr = client->addr,
105 .flags = I2C_M_RD,
106 .len = 4,
107 .buf = tmp,
108 }
109 };
110
111 mutex_lock(&hih6130->lock);
112
113 /*
114 * While the measurement can be completed in ~40ms the sensor takes
115 * much longer to react to a change in external conditions. How quickly
116 * it reacts depends on airflow and other factors outwith our control.
117 * The datasheet specifies maximum 'Response time' for humidity at 8s
118 * and temperature at 30s under specified conditions.
119 * We therefore choose to only read the sensor at most once per second.
120 * This trades off pointless activity polling the sensor much faster
121 * than it can react against better response times in conditions more
122 * favourable than specified in the datasheet.
123 */
124 if (time_after(jiffies, hih6130->last_update + HZ) || !hih6130->valid) {
125
126 /*
127 * Write to slave address to request a measurement.
128 * According with the datasheet it should be with no data, but
129 * for systems with I2C bus drivers that do not allow zero
130 * length packets we write one dummy byte to allow sensor
131 * measurements on them.
132 */
133 tmp[0] = 0;
134 ret = i2c_master_send(client, tmp, hih6130->write_length);
135 if (ret < 0)
136 goto out;
137
138 /* measurement cycle time is ~36.65msec */
139 msleep(40);
140
141 ret = i2c_transfer(client->adapter, msgs, 1);
142 if (ret < 0)
143 goto out;
144
145 if ((tmp[0] & 0xC0) != 0) {
146 dev_err(&client->dev, "Error while reading measurement result\n");
147 ret = -EIO;
148 goto out;
149 }
150
151 t = (tmp[0] << 8) + tmp[1];
152 hih6130->humidity = hih6130_rh_ticks_to_per_cent_mille(t);
153
154 t = (tmp[2] << 8) + tmp[3];
155 hih6130->temperature = hih6130_temp_ticks_to_millicelsius(t);
156
157 hih6130->last_update = jiffies;
158 hih6130->valid = true;
159 }
160out:
161 mutex_unlock(&hih6130->lock);
162
163 return ret >= 0 ? 0 : ret;
164}
165
166/**
167 * hih6130_show_temperature() - show temperature measurement value in sysfs
168 * @dev: device
169 * @attr: device attribute
170 * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to
171 *
172 * Will be called on read access to temp1_input sysfs attribute.
173 * Returns number of bytes written into buffer, negative errno on error.
174 */
175static ssize_t hih6130_show_temperature(struct device *dev,
176 struct device_attribute *attr,
177 char *buf)
178{
179 struct i2c_client *client = to_i2c_client(dev);
180 struct hih6130 *hih6130 = i2c_get_clientdata(client);
181 int ret = hih6130_update_measurements(client);
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 */
196static ssize_t hih6130_show_humidity(struct device *dev,
197 struct device_attribute *attr, char *buf)
198{
199 struct i2c_client *client = to_i2c_client(dev);
200 struct hih6130 *hih6130 = i2c_get_clientdata(client);
201 int ret = hih6130_update_measurements(client);
202 if (ret < 0)
203 return ret;
204 return sprintf(buf, "%d\n", hih6130->humidity);
205}
206
207/* sysfs attributes */
208static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, hih6130_show_temperature,
209 NULL, 0);
210static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO, hih6130_show_humidity,
211 NULL, 0);
212
213static struct attribute *hih6130_attributes[] = {
214 &sensor_dev_attr_temp1_input.dev_attr.attr,
215 &sensor_dev_attr_humidity1_input.dev_attr.attr,
216 NULL
217};
218
219static const struct attribute_group hih6130_attr_group = {
220 .attrs = hih6130_attributes,
221};
222
223/**
224 * hih6130_probe() - probe device
225 * @client: I2C client device
226 * @id: device ID
227 *
228 * Called by the I2C core when an entry in the ID table matches a
229 * device's name.
230 * Returns 0 on success.
231 */
232static int hih6130_probe(struct i2c_client *client,
233 const struct i2c_device_id *id)
234{
235 struct hih6130 *hih6130;
236 int err;
237
238 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
239 dev_err(&client->dev, "adapter does not support true I2C\n");
240 return -ENODEV;
241 }
242
243 hih6130 = devm_kzalloc(&client->dev, sizeof(*hih6130), GFP_KERNEL);
244 if (!hih6130)
245 return -ENOMEM;
246
247 i2c_set_clientdata(client, hih6130);
248
249 mutex_init(&hih6130->lock);
250
251 err = sysfs_create_group(&client->dev.kobj, &hih6130_attr_group);
252 if (err) {
253 dev_dbg(&client->dev, "could not create sysfs files\n");
254 return err;
255 }
256
257 hih6130->hwmon_dev = hwmon_device_register(&client->dev);
258 if (IS_ERR(hih6130->hwmon_dev)) {
259 dev_dbg(&client->dev, "unable to register hwmon device\n");
260 err = PTR_ERR(hih6130->hwmon_dev);
261 goto fail_remove_sysfs;
262 }
263
264 if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_QUICK))
265 hih6130->write_length = 1;
266
267 return 0;
268
269fail_remove_sysfs:
270 sysfs_remove_group(&client->dev.kobj, &hih6130_attr_group);
271 return err;
272}
273
274/**
275 * hih6130_remove() - remove device
276 * @client: I2C client device
277 */
278static int hih6130_remove(struct i2c_client *client)
279{
280 struct hih6130 *hih6130 = i2c_get_clientdata(client);
281
282 hwmon_device_unregister(hih6130->hwmon_dev);
283 sysfs_remove_group(&client->dev.kobj, &hih6130_attr_group);
284
285 return 0;
286}
287
288/* Device ID table */
289static const struct i2c_device_id hih6130_id[] = {
290 { "hih6130", 0 },
291 { }
292};
293MODULE_DEVICE_TABLE(i2c, hih6130_id);
294
295static struct i2c_driver hih6130_driver = {
296 .driver.name = "hih6130",
297 .probe = hih6130_probe,
298 .remove = hih6130_remove,
299 .id_table = hih6130_id,
300};
301
302module_i2c_driver(hih6130_driver);
303
304MODULE_AUTHOR("Iain Paton <ipaton0@gmail.com>");
305MODULE_DESCRIPTION("Honeywell HIH-6130 humidity and temperature sensor driver");
306MODULE_LICENSE("GPL");