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Urs Fleisch430400b2011-01-07 07:15:39 +00001/* Sensirion SHT21 humidity and temperature sensor driver
2 *
3 * Copyright (C) 2010 Urs Fleisch <urs.fleisch@sensirion.com>
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA
18 *
19 * Data sheet available (5/2010) at
20 * http://www.sensirion.com/en/pdf/product_information/Datasheet-humidity-sensor-SHT21.pdf
21 */
22
23#include <linux/module.h>
24#include <linux/init.h>
25#include <linux/slab.h>
26#include <linux/i2c.h>
27#include <linux/hwmon.h>
28#include <linux/hwmon-sysfs.h>
29#include <linux/err.h>
30#include <linux/mutex.h>
31#include <linux/device.h>
Jean Delvaredcd8f392012-10-10 15:25:56 +020032#include <linux/jiffies.h>
Urs Fleisch430400b2011-01-07 07:15:39 +000033
34/* I2C command bytes */
35#define SHT21_TRIG_T_MEASUREMENT_HM 0xe3
36#define SHT21_TRIG_RH_MEASUREMENT_HM 0xe5
Peter A. Bigot53e678d2016-12-24 07:22:44 -060037#define SHT21_READ_SNB_CMD1 0xFA
38#define SHT21_READ_SNB_CMD2 0x0F
39#define SHT21_READ_SNAC_CMD1 0xFC
40#define SHT21_READ_SNAC_CMD2 0xC9
Urs Fleisch430400b2011-01-07 07:15:39 +000041
42/**
43 * struct sht21 - SHT21 device specific data
44 * @hwmon_dev: device registered with hwmon
45 * @lock: mutex to protect measurement values
Urs Fleisch430400b2011-01-07 07:15:39 +000046 * @last_update: time of last update (jiffies)
47 * @temperature: cached temperature measurement value
48 * @humidity: cached humidity measurement value
Peter A. Bigot53e678d2016-12-24 07:22:44 -060049 * @valid: only 0 before first measurement is taken
50 * @eic: cached electronic identification code text
Urs Fleisch430400b2011-01-07 07:15:39 +000051 */
52struct sht21 {
Axel Linb8d56892014-07-11 10:44:48 +080053 struct i2c_client *client;
Urs Fleisch430400b2011-01-07 07:15:39 +000054 struct mutex lock;
Urs Fleisch430400b2011-01-07 07:15:39 +000055 unsigned long last_update;
56 int temperature;
57 int humidity;
Peter A. Bigot53e678d2016-12-24 07:22:44 -060058 char valid;
59 char eic[18];
Urs Fleisch430400b2011-01-07 07:15:39 +000060};
61
62/**
63 * sht21_temp_ticks_to_millicelsius() - convert raw temperature ticks to
64 * milli celsius
65 * @ticks: temperature ticks value received from sensor
66 */
67static inline int sht21_temp_ticks_to_millicelsius(int ticks)
68{
69 ticks &= ~0x0003; /* clear status bits */
70 /*
71 * Formula T = -46.85 + 175.72 * ST / 2^16 from data sheet 6.2,
72 * optimized for integer fixed point (3 digits) arithmetic
73 */
74 return ((21965 * ticks) >> 13) - 46850;
75}
76
77/**
78 * sht21_rh_ticks_to_per_cent_mille() - convert raw humidity ticks to
79 * one-thousandths of a percent relative humidity
80 * @ticks: humidity ticks value received from sensor
81 */
82static inline int sht21_rh_ticks_to_per_cent_mille(int ticks)
83{
84 ticks &= ~0x0003; /* clear status bits */
85 /*
86 * Formula RH = -6 + 125 * SRH / 2^16 from data sheet 6.1,
87 * optimized for integer fixed point (3 digits) arithmetic
88 */
89 return ((15625 * ticks) >> 13) - 6000;
90}
91
92/**
Urs Fleisch430400b2011-01-07 07:15:39 +000093 * sht21_update_measurements() - get updated measurements from device
Axel Linb8d56892014-07-11 10:44:48 +080094 * @dev: device
Urs Fleisch430400b2011-01-07 07:15:39 +000095 *
96 * Returns 0 on success, else negative errno.
97 */
Axel Linb8d56892014-07-11 10:44:48 +080098static int sht21_update_measurements(struct device *dev)
Urs Fleisch430400b2011-01-07 07:15:39 +000099{
100 int ret = 0;
Axel Linb8d56892014-07-11 10:44:48 +0800101 struct sht21 *sht21 = dev_get_drvdata(dev);
102 struct i2c_client *client = sht21->client;
Urs Fleisch430400b2011-01-07 07:15:39 +0000103
104 mutex_lock(&sht21->lock);
105 /*
106 * Data sheet 2.4:
107 * SHT2x should not be active for more than 10% of the time - e.g.
108 * maximum two measurements per second at 12bit accuracy shall be made.
109 */
110 if (time_after(jiffies, sht21->last_update + HZ / 2) || !sht21->valid) {
Jean Delvare90f41022011-11-04 12:00:47 +0100111 ret = i2c_smbus_read_word_swapped(client,
112 SHT21_TRIG_T_MEASUREMENT_HM);
Urs Fleisch430400b2011-01-07 07:15:39 +0000113 if (ret < 0)
114 goto out;
115 sht21->temperature = sht21_temp_ticks_to_millicelsius(ret);
Jean Delvare90f41022011-11-04 12:00:47 +0100116 ret = i2c_smbus_read_word_swapped(client,
117 SHT21_TRIG_RH_MEASUREMENT_HM);
Urs Fleisch430400b2011-01-07 07:15:39 +0000118 if (ret < 0)
119 goto out;
120 sht21->humidity = sht21_rh_ticks_to_per_cent_mille(ret);
121 sht21->last_update = jiffies;
122 sht21->valid = 1;
123 }
124out:
125 mutex_unlock(&sht21->lock);
126
127 return ret >= 0 ? 0 : ret;
128}
129
130/**
131 * sht21_show_temperature() - show temperature measurement value in sysfs
132 * @dev: device
133 * @attr: device attribute
134 * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to
135 *
136 * Will be called on read access to temp1_input sysfs attribute.
137 * Returns number of bytes written into buffer, negative errno on error.
138 */
139static ssize_t sht21_show_temperature(struct device *dev,
140 struct device_attribute *attr,
141 char *buf)
142{
Axel Linb8d56892014-07-11 10:44:48 +0800143 struct sht21 *sht21 = dev_get_drvdata(dev);
144 int ret;
145
146 ret = sht21_update_measurements(dev);
Urs Fleisch430400b2011-01-07 07:15:39 +0000147 if (ret < 0)
148 return ret;
149 return sprintf(buf, "%d\n", sht21->temperature);
150}
151
152/**
153 * sht21_show_humidity() - show humidity measurement value in sysfs
154 * @dev: device
155 * @attr: device attribute
156 * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to
157 *
158 * Will be called on read access to humidity1_input sysfs attribute.
159 * Returns number of bytes written into buffer, negative errno on error.
160 */
161static ssize_t sht21_show_humidity(struct device *dev,
162 struct device_attribute *attr,
163 char *buf)
164{
Axel Linb8d56892014-07-11 10:44:48 +0800165 struct sht21 *sht21 = dev_get_drvdata(dev);
166 int ret;
167
168 ret = sht21_update_measurements(dev);
Urs Fleisch430400b2011-01-07 07:15:39 +0000169 if (ret < 0)
170 return ret;
171 return sprintf(buf, "%d\n", sht21->humidity);
172}
173
Peter A. Bigot53e678d2016-12-24 07:22:44 -0600174static ssize_t eic_read(struct sht21 *sht21)
175{
176 struct i2c_client *client = sht21->client;
177 u8 tx[2];
178 u8 rx[8];
179 u8 eic[8];
180 struct i2c_msg msgs[2] = {
181 {
182 .addr = client->addr,
183 .flags = 0,
184 .len = 2,
185 .buf = tx,
186 },
187 {
188 .addr = client->addr,
189 .flags = I2C_M_RD,
190 .len = 8,
191 .buf = rx,
192 },
193 };
194 int ret;
195
196 tx[0] = SHT21_READ_SNB_CMD1;
197 tx[1] = SHT21_READ_SNB_CMD2;
198 ret = i2c_transfer(client->adapter, msgs, 2);
199 if (ret < 0)
200 goto out;
201 eic[2] = rx[0];
202 eic[3] = rx[2];
203 eic[4] = rx[4];
204 eic[5] = rx[6];
205
206 tx[0] = SHT21_READ_SNAC_CMD1;
207 tx[1] = SHT21_READ_SNAC_CMD2;
208 msgs[1].len = 6;
209 ret = i2c_transfer(client->adapter, msgs, 2);
210 if (ret < 0)
211 goto out;
212 eic[0] = rx[3];
213 eic[1] = rx[4];
214 eic[6] = rx[0];
215 eic[7] = rx[1];
216
217 ret = snprintf(sht21->eic, sizeof(sht21->eic),
218 "%02x%02x%02x%02x%02x%02x%02x%02x\n",
219 eic[0], eic[1], eic[2], eic[3],
220 eic[4], eic[5], eic[6], eic[7]);
221out:
222 if (ret < 0)
223 sht21->eic[0] = 0;
224
225 return ret;
226}
227
228/**
229 * eic_show() - show Electronic Identification Code in sysfs
230 * @dev: device
231 * @attr: device attribute
232 * @buf: sysfs buffer (PAGE_SIZE) where EIC is written
233 *
234 * Will be called on read access to eic sysfs attribute.
235 * Returns number of bytes written into buffer, negative errno on error.
236 */
237static ssize_t eic_show(struct device *dev,
238 struct device_attribute *attr,
239 char *buf)
240{
241 struct sht21 *sht21 = dev_get_drvdata(dev);
242 int ret;
243
244 ret = sizeof(sht21->eic) - 1;
245 mutex_lock(&sht21->lock);
246 if (!sht21->eic[0])
247 ret = eic_read(sht21);
248 if (ret > 0)
249 memcpy(buf, sht21->eic, ret);
250 mutex_unlock(&sht21->lock);
251 return ret;
252}
253
Urs Fleisch430400b2011-01-07 07:15:39 +0000254/* sysfs attributes */
255static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, sht21_show_temperature,
256 NULL, 0);
257static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO, sht21_show_humidity,
258 NULL, 0);
Peter A. Bigot53e678d2016-12-24 07:22:44 -0600259static DEVICE_ATTR_RO(eic);
Urs Fleisch430400b2011-01-07 07:15:39 +0000260
Axel Linb8d56892014-07-11 10:44:48 +0800261static struct attribute *sht21_attrs[] = {
Urs Fleisch430400b2011-01-07 07:15:39 +0000262 &sensor_dev_attr_temp1_input.dev_attr.attr,
263 &sensor_dev_attr_humidity1_input.dev_attr.attr,
Peter A. Bigot53e678d2016-12-24 07:22:44 -0600264 &dev_attr_eic.attr,
Urs Fleisch430400b2011-01-07 07:15:39 +0000265 NULL
266};
267
Axel Linb8d56892014-07-11 10:44:48 +0800268ATTRIBUTE_GROUPS(sht21);
Urs Fleisch430400b2011-01-07 07:15:39 +0000269
Bill Pemberton6c931ae2012-11-19 13:22:35 -0500270static int sht21_probe(struct i2c_client *client,
Urs Fleisch430400b2011-01-07 07:15:39 +0000271 const struct i2c_device_id *id)
272{
Axel Linb8d56892014-07-11 10:44:48 +0800273 struct device *dev = &client->dev;
274 struct device *hwmon_dev;
Urs Fleisch430400b2011-01-07 07:15:39 +0000275 struct sht21 *sht21;
Urs Fleisch430400b2011-01-07 07:15:39 +0000276
277 if (!i2c_check_functionality(client->adapter,
278 I2C_FUNC_SMBUS_WORD_DATA)) {
279 dev_err(&client->dev,
280 "adapter does not support SMBus word transactions\n");
281 return -ENODEV;
282 }
283
Axel Linb8d56892014-07-11 10:44:48 +0800284 sht21 = devm_kzalloc(dev, sizeof(*sht21), GFP_KERNEL);
Guenter Roecka844af12012-06-02 11:20:22 -0700285 if (!sht21)
Urs Fleisch430400b2011-01-07 07:15:39 +0000286 return -ENOMEM;
Guenter Roecka844af12012-06-02 11:20:22 -0700287
Axel Linb8d56892014-07-11 10:44:48 +0800288 sht21->client = client;
Urs Fleisch430400b2011-01-07 07:15:39 +0000289
290 mutex_init(&sht21->lock);
291
Axel Linb8d56892014-07-11 10:44:48 +0800292 hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
293 sht21, sht21_groups);
294 return PTR_ERR_OR_ZERO(hwmon_dev);
Urs Fleisch430400b2011-01-07 07:15:39 +0000295}
296
297/* Device ID table */
298static const struct i2c_device_id sht21_id[] = {
299 { "sht21", 0 },
300 { }
301};
302MODULE_DEVICE_TABLE(i2c, sht21_id);
303
304static struct i2c_driver sht21_driver = {
305 .driver.name = "sht21",
306 .probe = sht21_probe,
Urs Fleisch430400b2011-01-07 07:15:39 +0000307 .id_table = sht21_id,
308};
309
Axel Linf0967ee2012-01-20 15:38:18 +0800310module_i2c_driver(sht21_driver);
Urs Fleisch430400b2011-01-07 07:15:39 +0000311
312MODULE_AUTHOR("Urs Fleisch <urs.fleisch@sensirion.com>");
313MODULE_DESCRIPTION("Sensirion SHT21 humidity and temperature sensor driver");
314MODULE_LICENSE("GPL");