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Iain Paton27f8b132012-06-27 08:55:11 +00001/* 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>
Jean Delvaredcd8f392012-10-10 15:25:56 +020036#include <linux/jiffies.h>
Iain Paton27f8b132012-06-27 08:55:11 +000037
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 */
47struct hih6130 {
48 struct device *hwmon_dev;
49 struct mutex lock;
50 bool valid;
51 unsigned long last_update;
52 int temperature;
53 int humidity;
54};
55
56/**
57 * hih6130_temp_ticks_to_millicelsius() - convert raw temperature ticks to
58 * milli celsius
59 * @ticks: temperature ticks value received from sensor
60 */
61static inline int hih6130_temp_ticks_to_millicelsius(int ticks)
62{
63
64 ticks = ticks >> 2;
65 /*
66 * from data sheet section 5.0
67 * Formula T = ( ticks / ( 2^14 - 2 ) ) * 165 -40
68 */
69 return (DIV_ROUND_CLOSEST(ticks * 1650, 16382) - 400) * 100;
70}
71
72/**
73 * hih6130_rh_ticks_to_per_cent_mille() - convert raw humidity ticks to
74 * one-thousandths of a percent relative humidity
75 * @ticks: humidity ticks value received from sensor
76 */
77static inline int hih6130_rh_ticks_to_per_cent_mille(int ticks)
78{
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 * @client: I2C client device
91 *
92 * Returns 0 on success, else negative errno.
93 */
94static int hih6130_update_measurements(struct i2c_client *client)
95{
96 int ret = 0;
97 int t;
98 struct hih6130 *hih6130 = i2c_get_clientdata(client);
99 unsigned char tmp[4];
100 struct i2c_msg msgs[1] = {
101 {
102 .addr = client->addr,
103 .flags = I2C_M_RD,
104 .len = 4,
105 .buf = tmp,
106 }
107 };
108
109 mutex_lock(&hih6130->lock);
110
111 /*
112 * While the measurement can be completed in ~40ms the sensor takes
113 * much longer to react to a change in external conditions. How quickly
114 * it reacts depends on airflow and other factors outwith our control.
115 * The datasheet specifies maximum 'Response time' for humidity at 8s
116 * and temperature at 30s under specified conditions.
117 * We therefore choose to only read the sensor at most once per second.
118 * This trades off pointless activity polling the sensor much faster
119 * than it can react against better response times in conditions more
120 * favourable than specified in the datasheet.
121 */
122 if (time_after(jiffies, hih6130->last_update + HZ) || !hih6130->valid) {
123
124 /* write to slave address, no data, to request a measurement */
125 ret = i2c_master_send(client, tmp, 0);
126 if (ret < 0)
127 goto out;
128
129 /* measurement cycle time is ~36.65msec */
130 msleep(40);
131
132 ret = i2c_transfer(client->adapter, msgs, 1);
133 if (ret < 0)
134 goto out;
135
136 if ((tmp[0] & 0xC0) != 0) {
137 dev_err(&client->dev, "Error while reading measurement result\n");
138 ret = -EIO;
139 goto out;
140 }
141
142 t = (tmp[0] << 8) + tmp[1];
143 hih6130->humidity = hih6130_rh_ticks_to_per_cent_mille(t);
144
145 t = (tmp[2] << 8) + tmp[3];
146 hih6130->temperature = hih6130_temp_ticks_to_millicelsius(t);
147
148 hih6130->last_update = jiffies;
149 hih6130->valid = true;
150 }
151out:
152 mutex_unlock(&hih6130->lock);
153
154 return ret >= 0 ? 0 : ret;
155}
156
157/**
158 * hih6130_show_temperature() - show temperature measurement value in sysfs
159 * @dev: device
160 * @attr: device attribute
161 * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to
162 *
163 * Will be called on read access to temp1_input sysfs attribute.
164 * Returns number of bytes written into buffer, negative errno on error.
165 */
166static ssize_t hih6130_show_temperature(struct device *dev,
167 struct device_attribute *attr,
168 char *buf)
169{
170 struct i2c_client *client = to_i2c_client(dev);
171 struct hih6130 *hih6130 = i2c_get_clientdata(client);
172 int ret = hih6130_update_measurements(client);
173 if (ret < 0)
174 return ret;
175 return sprintf(buf, "%d\n", hih6130->temperature);
176}
177
178/**
179 * hih6130_show_humidity() - show humidity measurement value in sysfs
180 * @dev: device
181 * @attr: device attribute
182 * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to
183 *
184 * Will be called on read access to humidity1_input sysfs attribute.
185 * Returns number of bytes written into buffer, negative errno on error.
186 */
187static ssize_t hih6130_show_humidity(struct device *dev,
188 struct device_attribute *attr, char *buf)
189{
190 struct i2c_client *client = to_i2c_client(dev);
191 struct hih6130 *hih6130 = i2c_get_clientdata(client);
192 int ret = hih6130_update_measurements(client);
193 if (ret < 0)
194 return ret;
195 return sprintf(buf, "%d\n", hih6130->humidity);
196}
197
198/* sysfs attributes */
199static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, hih6130_show_temperature,
200 NULL, 0);
201static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO, hih6130_show_humidity,
202 NULL, 0);
203
204static struct attribute *hih6130_attributes[] = {
205 &sensor_dev_attr_temp1_input.dev_attr.attr,
206 &sensor_dev_attr_humidity1_input.dev_attr.attr,
207 NULL
208};
209
210static const struct attribute_group hih6130_attr_group = {
211 .attrs = hih6130_attributes,
212};
213
214/**
215 * hih6130_probe() - probe device
216 * @client: I2C client device
217 * @id: device ID
218 *
219 * Called by the I2C core when an entry in the ID table matches a
220 * device's name.
221 * Returns 0 on success.
222 */
Bill Pemberton6c931ae2012-11-19 13:22:35 -0500223static int hih6130_probe(struct i2c_client *client,
Iain Paton27f8b132012-06-27 08:55:11 +0000224 const struct i2c_device_id *id)
225{
226 struct hih6130 *hih6130;
227 int err;
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(&client->dev, sizeof(*hih6130), GFP_KERNEL);
235 if (!hih6130)
236 return -ENOMEM;
237
238 i2c_set_clientdata(client, hih6130);
239
240 mutex_init(&hih6130->lock);
241
242 err = sysfs_create_group(&client->dev.kobj, &hih6130_attr_group);
243 if (err) {
244 dev_dbg(&client->dev, "could not create sysfs files\n");
245 return err;
246 }
247
248 hih6130->hwmon_dev = hwmon_device_register(&client->dev);
249 if (IS_ERR(hih6130->hwmon_dev)) {
250 dev_dbg(&client->dev, "unable to register hwmon device\n");
251 err = PTR_ERR(hih6130->hwmon_dev);
252 goto fail_remove_sysfs;
253 }
254
255 return 0;
256
257fail_remove_sysfs:
258 sysfs_remove_group(&client->dev.kobj, &hih6130_attr_group);
259 return err;
260}
261
262/**
263 * hih6130_remove() - remove device
264 * @client: I2C client device
265 */
Bill Pemberton281dfd02012-11-19 13:25:51 -0500266static int hih6130_remove(struct i2c_client *client)
Iain Paton27f8b132012-06-27 08:55:11 +0000267{
268 struct hih6130 *hih6130 = i2c_get_clientdata(client);
269
270 hwmon_device_unregister(hih6130->hwmon_dev);
271 sysfs_remove_group(&client->dev.kobj, &hih6130_attr_group);
272
273 return 0;
274}
275
276/* Device ID table */
277static const struct i2c_device_id hih6130_id[] = {
278 { "hih6130", 0 },
279 { }
280};
281MODULE_DEVICE_TABLE(i2c, hih6130_id);
282
283static struct i2c_driver hih6130_driver = {
284 .driver.name = "hih6130",
285 .probe = hih6130_probe,
Bill Pemberton9e5e9b72012-11-19 13:21:20 -0500286 .remove = hih6130_remove,
Iain Paton27f8b132012-06-27 08:55:11 +0000287 .id_table = hih6130_id,
288};
289
290module_i2c_driver(hih6130_driver);
291
292MODULE_AUTHOR("Iain Paton <ipaton0@gmail.com>");
293MODULE_DESCRIPTION("Honeywell HIH-6130 humidity and temperature sensor driver");
294MODULE_LICENSE("GPL");