x86/mm/pat: Don't report PAT on CPUs that don't support it
[linux/fpc-iii.git] / drivers / hwmon / sht21.c
blob06706d288355b8e13a794579b06a13b72852b0bb
1 /* Sensirion SHT21 humidity and temperature sensor driver
3 * Copyright (C) 2010 Urs Fleisch <urs.fleisch@sensirion.com>
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.
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.
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
19 * Data sheet available (5/2010) at
20 * http://www.sensirion.com/en/pdf/product_information/Datasheet-humidity-sensor-SHT21.pdf
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>
32 #include <linux/jiffies.h>
34 /* I2C command bytes */
35 #define SHT21_TRIG_T_MEASUREMENT_HM 0xe3
36 #define SHT21_TRIG_RH_MEASUREMENT_HM 0xe5
37 #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
42 /**
43 * struct sht21 - SHT21 device specific data
44 * @hwmon_dev: device registered with hwmon
45 * @lock: mutex to protect measurement values
46 * @last_update: time of last update (jiffies)
47 * @temperature: cached temperature measurement value
48 * @humidity: cached humidity measurement value
49 * @valid: only 0 before first measurement is taken
50 * @eic: cached electronic identification code text
52 struct sht21 {
53 struct i2c_client *client;
54 struct mutex lock;
55 unsigned long last_update;
56 int temperature;
57 int humidity;
58 char valid;
59 char eic[18];
62 /**
63 * sht21_temp_ticks_to_millicelsius() - convert raw temperature ticks to
64 * milli celsius
65 * @ticks: temperature ticks value received from sensor
67 static inline int sht21_temp_ticks_to_millicelsius(int ticks)
69 ticks &= ~0x0003; /* clear status bits */
71 * Formula T = -46.85 + 175.72 * ST / 2^16 from data sheet 6.2,
72 * optimized for integer fixed point (3 digits) arithmetic
74 return ((21965 * ticks) >> 13) - 46850;
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
82 static inline int sht21_rh_ticks_to_per_cent_mille(int ticks)
84 ticks &= ~0x0003; /* clear status bits */
86 * Formula RH = -6 + 125 * SRH / 2^16 from data sheet 6.1,
87 * optimized for integer fixed point (3 digits) arithmetic
89 return ((15625 * ticks) >> 13) - 6000;
92 /**
93 * sht21_update_measurements() - get updated measurements from device
94 * @dev: device
96 * Returns 0 on success, else negative errno.
98 static int sht21_update_measurements(struct device *dev)
100 int ret = 0;
101 struct sht21 *sht21 = dev_get_drvdata(dev);
102 struct i2c_client *client = sht21->client;
104 mutex_lock(&sht21->lock);
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.
110 if (time_after(jiffies, sht21->last_update + HZ / 2) || !sht21->valid) {
111 ret = i2c_smbus_read_word_swapped(client,
112 SHT21_TRIG_T_MEASUREMENT_HM);
113 if (ret < 0)
114 goto out;
115 sht21->temperature = sht21_temp_ticks_to_millicelsius(ret);
116 ret = i2c_smbus_read_word_swapped(client,
117 SHT21_TRIG_RH_MEASUREMENT_HM);
118 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;
124 out:
125 mutex_unlock(&sht21->lock);
127 return ret >= 0 ? 0 : ret;
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
136 * Will be called on read access to temp1_input sysfs attribute.
137 * Returns number of bytes written into buffer, negative errno on error.
139 static ssize_t sht21_show_temperature(struct device *dev,
140 struct device_attribute *attr,
141 char *buf)
143 struct sht21 *sht21 = dev_get_drvdata(dev);
144 int ret;
146 ret = sht21_update_measurements(dev);
147 if (ret < 0)
148 return ret;
149 return sprintf(buf, "%d\n", sht21->temperature);
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
158 * Will be called on read access to humidity1_input sysfs attribute.
159 * Returns number of bytes written into buffer, negative errno on error.
161 static ssize_t sht21_show_humidity(struct device *dev,
162 struct device_attribute *attr,
163 char *buf)
165 struct sht21 *sht21 = dev_get_drvdata(dev);
166 int ret;
168 ret = sht21_update_measurements(dev);
169 if (ret < 0)
170 return ret;
171 return sprintf(buf, "%d\n", sht21->humidity);
174 static ssize_t eic_read(struct sht21 *sht21)
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] = {
182 .addr = client->addr,
183 .flags = 0,
184 .len = 2,
185 .buf = tx,
188 .addr = client->addr,
189 .flags = I2C_M_RD,
190 .len = 8,
191 .buf = rx,
194 int ret;
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];
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];
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]);
221 out:
222 if (ret < 0)
223 sht21->eic[0] = 0;
225 return ret;
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
234 * Will be called on read access to eic sysfs attribute.
235 * Returns number of bytes written into buffer, negative errno on error.
237 static ssize_t eic_show(struct device *dev,
238 struct device_attribute *attr,
239 char *buf)
241 struct sht21 *sht21 = dev_get_drvdata(dev);
242 int ret;
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;
254 /* sysfs attributes */
255 static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, sht21_show_temperature,
256 NULL, 0);
257 static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO, sht21_show_humidity,
258 NULL, 0);
259 static DEVICE_ATTR_RO(eic);
261 static struct attribute *sht21_attrs[] = {
262 &sensor_dev_attr_temp1_input.dev_attr.attr,
263 &sensor_dev_attr_humidity1_input.dev_attr.attr,
264 &dev_attr_eic.attr,
265 NULL
268 ATTRIBUTE_GROUPS(sht21);
270 static int sht21_probe(struct i2c_client *client,
271 const struct i2c_device_id *id)
273 struct device *dev = &client->dev;
274 struct device *hwmon_dev;
275 struct sht21 *sht21;
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;
284 sht21 = devm_kzalloc(dev, sizeof(*sht21), GFP_KERNEL);
285 if (!sht21)
286 return -ENOMEM;
288 sht21->client = client;
290 mutex_init(&sht21->lock);
292 hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
293 sht21, sht21_groups);
294 return PTR_ERR_OR_ZERO(hwmon_dev);
297 /* Device ID table */
298 static const struct i2c_device_id sht21_id[] = {
299 { "sht21", 0 },
302 MODULE_DEVICE_TABLE(i2c, sht21_id);
304 static struct i2c_driver sht21_driver = {
305 .driver.name = "sht21",
306 .probe = sht21_probe,
307 .id_table = sht21_id,
310 module_i2c_driver(sht21_driver);
312 MODULE_AUTHOR("Urs Fleisch <urs.fleisch@sensirion.com>");
313 MODULE_DESCRIPTION("Sensirion SHT21 humidity and temperature sensor driver");
314 MODULE_LICENSE("GPL");