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430400b8 UF |
1 | /* 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> | |
dcd8f392 | 32 | #include <linux/jiffies.h> |
430400b8 UF |
33 | |
34 | /* I2C command bytes */ | |
35 | #define SHT21_TRIG_T_MEASUREMENT_HM 0xe3 | |
36 | #define SHT21_TRIG_RH_MEASUREMENT_HM 0xe5 | |
37 | ||
38 | /** | |
39 | * struct sht21 - SHT21 device specific data | |
40 | * @hwmon_dev: device registered with hwmon | |
41 | * @lock: mutex to protect measurement values | |
42 | * @valid: only 0 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 | */ | |
47 | struct sht21 { | |
48 | struct device *hwmon_dev; | |
49 | struct mutex lock; | |
50 | char valid; | |
51 | unsigned long last_update; | |
52 | int temperature; | |
53 | int humidity; | |
54 | }; | |
55 | ||
56 | /** | |
57 | * sht21_temp_ticks_to_millicelsius() - convert raw temperature ticks to | |
58 | * milli celsius | |
59 | * @ticks: temperature ticks value received from sensor | |
60 | */ | |
61 | static inline int sht21_temp_ticks_to_millicelsius(int ticks) | |
62 | { | |
63 | ticks &= ~0x0003; /* clear status bits */ | |
64 | /* | |
65 | * Formula T = -46.85 + 175.72 * ST / 2^16 from data sheet 6.2, | |
66 | * optimized for integer fixed point (3 digits) arithmetic | |
67 | */ | |
68 | return ((21965 * ticks) >> 13) - 46850; | |
69 | } | |
70 | ||
71 | /** | |
72 | * sht21_rh_ticks_to_per_cent_mille() - convert raw humidity ticks to | |
73 | * one-thousandths of a percent relative humidity | |
74 | * @ticks: humidity ticks value received from sensor | |
75 | */ | |
76 | static inline int sht21_rh_ticks_to_per_cent_mille(int ticks) | |
77 | { | |
78 | ticks &= ~0x0003; /* clear status bits */ | |
79 | /* | |
80 | * Formula RH = -6 + 125 * SRH / 2^16 from data sheet 6.1, | |
81 | * optimized for integer fixed point (3 digits) arithmetic | |
82 | */ | |
83 | return ((15625 * ticks) >> 13) - 6000; | |
84 | } | |
85 | ||
430400b8 UF |
86 | /** |
87 | * sht21_update_measurements() - get updated measurements from device | |
88 | * @client: I2C client device | |
89 | * | |
90 | * Returns 0 on success, else negative errno. | |
91 | */ | |
92 | static int sht21_update_measurements(struct i2c_client *client) | |
93 | { | |
94 | int ret = 0; | |
95 | struct sht21 *sht21 = i2c_get_clientdata(client); | |
96 | ||
97 | mutex_lock(&sht21->lock); | |
98 | /* | |
99 | * Data sheet 2.4: | |
100 | * SHT2x should not be active for more than 10% of the time - e.g. | |
101 | * maximum two measurements per second at 12bit accuracy shall be made. | |
102 | */ | |
103 | if (time_after(jiffies, sht21->last_update + HZ / 2) || !sht21->valid) { | |
90f4102c JD |
104 | ret = i2c_smbus_read_word_swapped(client, |
105 | SHT21_TRIG_T_MEASUREMENT_HM); | |
430400b8 UF |
106 | if (ret < 0) |
107 | goto out; | |
108 | sht21->temperature = sht21_temp_ticks_to_millicelsius(ret); | |
90f4102c JD |
109 | ret = i2c_smbus_read_word_swapped(client, |
110 | SHT21_TRIG_RH_MEASUREMENT_HM); | |
430400b8 UF |
111 | if (ret < 0) |
112 | goto out; | |
113 | sht21->humidity = sht21_rh_ticks_to_per_cent_mille(ret); | |
114 | sht21->last_update = jiffies; | |
115 | sht21->valid = 1; | |
116 | } | |
117 | out: | |
118 | mutex_unlock(&sht21->lock); | |
119 | ||
120 | return ret >= 0 ? 0 : ret; | |
121 | } | |
122 | ||
123 | /** | |
124 | * sht21_show_temperature() - show temperature measurement value in sysfs | |
125 | * @dev: device | |
126 | * @attr: device attribute | |
127 | * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to | |
128 | * | |
129 | * Will be called on read access to temp1_input sysfs attribute. | |
130 | * Returns number of bytes written into buffer, negative errno on error. | |
131 | */ | |
132 | static ssize_t sht21_show_temperature(struct device *dev, | |
133 | struct device_attribute *attr, | |
134 | char *buf) | |
135 | { | |
136 | struct i2c_client *client = to_i2c_client(dev); | |
137 | struct sht21 *sht21 = i2c_get_clientdata(client); | |
138 | int ret = sht21_update_measurements(client); | |
139 | if (ret < 0) | |
140 | return ret; | |
141 | return sprintf(buf, "%d\n", sht21->temperature); | |
142 | } | |
143 | ||
144 | /** | |
145 | * sht21_show_humidity() - show humidity measurement value in sysfs | |
146 | * @dev: device | |
147 | * @attr: device attribute | |
148 | * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to | |
149 | * | |
150 | * Will be called on read access to humidity1_input sysfs attribute. | |
151 | * Returns number of bytes written into buffer, negative errno on error. | |
152 | */ | |
153 | static ssize_t sht21_show_humidity(struct device *dev, | |
154 | struct device_attribute *attr, | |
155 | char *buf) | |
156 | { | |
157 | struct i2c_client *client = to_i2c_client(dev); | |
158 | struct sht21 *sht21 = i2c_get_clientdata(client); | |
159 | int ret = sht21_update_measurements(client); | |
160 | if (ret < 0) | |
161 | return ret; | |
162 | return sprintf(buf, "%d\n", sht21->humidity); | |
163 | } | |
164 | ||
165 | /* sysfs attributes */ | |
166 | static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, sht21_show_temperature, | |
167 | NULL, 0); | |
168 | static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO, sht21_show_humidity, | |
169 | NULL, 0); | |
170 | ||
171 | static struct attribute *sht21_attributes[] = { | |
172 | &sensor_dev_attr_temp1_input.dev_attr.attr, | |
173 | &sensor_dev_attr_humidity1_input.dev_attr.attr, | |
174 | NULL | |
175 | }; | |
176 | ||
177 | static const struct attribute_group sht21_attr_group = { | |
178 | .attrs = sht21_attributes, | |
179 | }; | |
180 | ||
181 | /** | |
182 | * sht21_probe() - probe device | |
183 | * @client: I2C client device | |
184 | * @id: device ID | |
185 | * | |
186 | * Called by the I2C core when an entry in the ID table matches a | |
187 | * device's name. | |
188 | * Returns 0 on success. | |
189 | */ | |
6c931ae1 | 190 | static int sht21_probe(struct i2c_client *client, |
430400b8 UF |
191 | const struct i2c_device_id *id) |
192 | { | |
193 | struct sht21 *sht21; | |
194 | int err; | |
195 | ||
196 | if (!i2c_check_functionality(client->adapter, | |
197 | I2C_FUNC_SMBUS_WORD_DATA)) { | |
198 | dev_err(&client->dev, | |
199 | "adapter does not support SMBus word transactions\n"); | |
200 | return -ENODEV; | |
201 | } | |
202 | ||
a844af19 GR |
203 | sht21 = devm_kzalloc(&client->dev, sizeof(*sht21), GFP_KERNEL); |
204 | if (!sht21) | |
430400b8 | 205 | return -ENOMEM; |
a844af19 | 206 | |
430400b8 UF |
207 | i2c_set_clientdata(client, sht21); |
208 | ||
209 | mutex_init(&sht21->lock); | |
210 | ||
211 | err = sysfs_create_group(&client->dev.kobj, &sht21_attr_group); | |
212 | if (err) { | |
213 | dev_dbg(&client->dev, "could not create sysfs files\n"); | |
a844af19 | 214 | return err; |
430400b8 UF |
215 | } |
216 | sht21->hwmon_dev = hwmon_device_register(&client->dev); | |
217 | if (IS_ERR(sht21->hwmon_dev)) { | |
218 | dev_dbg(&client->dev, "unable to register hwmon device\n"); | |
219 | err = PTR_ERR(sht21->hwmon_dev); | |
220 | goto fail_remove_sysfs; | |
221 | } | |
222 | ||
223 | dev_info(&client->dev, "initialized\n"); | |
224 | ||
225 | return 0; | |
226 | ||
227 | fail_remove_sysfs: | |
228 | sysfs_remove_group(&client->dev.kobj, &sht21_attr_group); | |
430400b8 UF |
229 | return err; |
230 | } | |
231 | ||
232 | /** | |
233 | * sht21_remove() - remove device | |
234 | * @client: I2C client device | |
235 | */ | |
281dfd0b | 236 | static int sht21_remove(struct i2c_client *client) |
430400b8 UF |
237 | { |
238 | struct sht21 *sht21 = i2c_get_clientdata(client); | |
239 | ||
240 | hwmon_device_unregister(sht21->hwmon_dev); | |
241 | sysfs_remove_group(&client->dev.kobj, &sht21_attr_group); | |
430400b8 UF |
242 | |
243 | return 0; | |
244 | } | |
245 | ||
246 | /* Device ID table */ | |
247 | static const struct i2c_device_id sht21_id[] = { | |
248 | { "sht21", 0 }, | |
249 | { } | |
250 | }; | |
251 | MODULE_DEVICE_TABLE(i2c, sht21_id); | |
252 | ||
253 | static struct i2c_driver sht21_driver = { | |
254 | .driver.name = "sht21", | |
255 | .probe = sht21_probe, | |
9e5e9b7a | 256 | .remove = sht21_remove, |
430400b8 UF |
257 | .id_table = sht21_id, |
258 | }; | |
259 | ||
f0967eea | 260 | module_i2c_driver(sht21_driver); |
430400b8 UF |
261 | |
262 | MODULE_AUTHOR("Urs Fleisch <urs.fleisch@sensirion.com>"); | |
263 | MODULE_DESCRIPTION("Sensirion SHT21 humidity and temperature sensor driver"); | |
264 | MODULE_LICENSE("GPL"); |