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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 | * | |
8e1d6fe9 | 19 | * Data sheet available at http://www.sensirion.com/file/datasheet_sht21 |
430400b8 UF |
20 | */ |
21 | ||
22 | #include <linux/module.h> | |
23 | #include <linux/init.h> | |
24 | #include <linux/slab.h> | |
25 | #include <linux/i2c.h> | |
26 | #include <linux/hwmon.h> | |
27 | #include <linux/hwmon-sysfs.h> | |
28 | #include <linux/err.h> | |
29 | #include <linux/mutex.h> | |
30 | #include <linux/device.h> | |
dcd8f392 | 31 | #include <linux/jiffies.h> |
430400b8 UF |
32 | |
33 | /* I2C command bytes */ | |
34 | #define SHT21_TRIG_T_MEASUREMENT_HM 0xe3 | |
35 | #define SHT21_TRIG_RH_MEASUREMENT_HM 0xe5 | |
53e678d7 PB |
36 | #define SHT21_READ_SNB_CMD1 0xFA |
37 | #define SHT21_READ_SNB_CMD2 0x0F | |
38 | #define SHT21_READ_SNAC_CMD1 0xFC | |
39 | #define SHT21_READ_SNAC_CMD2 0xC9 | |
430400b8 UF |
40 | |
41 | /** | |
42 | * struct sht21 - SHT21 device specific data | |
679f50b8 | 43 | * @client: I2C client device |
430400b8 | 44 | * @lock: mutex to protect measurement values |
430400b8 UF |
45 | * @last_update: time of last update (jiffies) |
46 | * @temperature: cached temperature measurement value | |
47 | * @humidity: cached humidity measurement value | |
53e678d7 PB |
48 | * @valid: only 0 before first measurement is taken |
49 | * @eic: cached electronic identification code text | |
430400b8 UF |
50 | */ |
51 | struct sht21 { | |
b8d56898 | 52 | struct i2c_client *client; |
430400b8 | 53 | struct mutex lock; |
430400b8 UF |
54 | unsigned long last_update; |
55 | int temperature; | |
56 | int humidity; | |
53e678d7 PB |
57 | char valid; |
58 | char eic[18]; | |
430400b8 UF |
59 | }; |
60 | ||
61 | /** | |
62 | * sht21_temp_ticks_to_millicelsius() - convert raw temperature ticks to | |
63 | * milli celsius | |
64 | * @ticks: temperature ticks value received from sensor | |
65 | */ | |
66 | static inline int sht21_temp_ticks_to_millicelsius(int ticks) | |
67 | { | |
68 | ticks &= ~0x0003; /* clear status bits */ | |
69 | /* | |
70 | * Formula T = -46.85 + 175.72 * ST / 2^16 from data sheet 6.2, | |
71 | * optimized for integer fixed point (3 digits) arithmetic | |
72 | */ | |
73 | return ((21965 * ticks) >> 13) - 46850; | |
74 | } | |
75 | ||
76 | /** | |
77 | * sht21_rh_ticks_to_per_cent_mille() - convert raw humidity ticks to | |
78 | * one-thousandths of a percent relative humidity | |
79 | * @ticks: humidity ticks value received from sensor | |
80 | */ | |
81 | static inline int sht21_rh_ticks_to_per_cent_mille(int ticks) | |
82 | { | |
83 | ticks &= ~0x0003; /* clear status bits */ | |
84 | /* | |
85 | * Formula RH = -6 + 125 * SRH / 2^16 from data sheet 6.1, | |
86 | * optimized for integer fixed point (3 digits) arithmetic | |
87 | */ | |
88 | return ((15625 * ticks) >> 13) - 6000; | |
89 | } | |
90 | ||
430400b8 UF |
91 | /** |
92 | * sht21_update_measurements() - get updated measurements from device | |
b8d56898 | 93 | * @dev: device |
430400b8 UF |
94 | * |
95 | * Returns 0 on success, else negative errno. | |
96 | */ | |
b8d56898 | 97 | static int sht21_update_measurements(struct device *dev) |
430400b8 UF |
98 | { |
99 | int ret = 0; | |
b8d56898 AL |
100 | struct sht21 *sht21 = dev_get_drvdata(dev); |
101 | struct i2c_client *client = sht21->client; | |
430400b8 UF |
102 | |
103 | mutex_lock(&sht21->lock); | |
104 | /* | |
105 | * Data sheet 2.4: | |
106 | * SHT2x should not be active for more than 10% of the time - e.g. | |
107 | * maximum two measurements per second at 12bit accuracy shall be made. | |
108 | */ | |
109 | if (time_after(jiffies, sht21->last_update + HZ / 2) || !sht21->valid) { | |
90f4102c JD |
110 | ret = i2c_smbus_read_word_swapped(client, |
111 | SHT21_TRIG_T_MEASUREMENT_HM); | |
430400b8 UF |
112 | if (ret < 0) |
113 | goto out; | |
114 | sht21->temperature = sht21_temp_ticks_to_millicelsius(ret); | |
90f4102c JD |
115 | ret = i2c_smbus_read_word_swapped(client, |
116 | SHT21_TRIG_RH_MEASUREMENT_HM); | |
430400b8 UF |
117 | if (ret < 0) |
118 | goto out; | |
119 | sht21->humidity = sht21_rh_ticks_to_per_cent_mille(ret); | |
120 | sht21->last_update = jiffies; | |
121 | sht21->valid = 1; | |
122 | } | |
123 | out: | |
124 | mutex_unlock(&sht21->lock); | |
125 | ||
126 | return ret >= 0 ? 0 : ret; | |
127 | } | |
128 | ||
129 | /** | |
130 | * sht21_show_temperature() - show temperature measurement value in sysfs | |
131 | * @dev: device | |
132 | * @attr: device attribute | |
133 | * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to | |
134 | * | |
135 | * Will be called on read access to temp1_input sysfs attribute. | |
136 | * Returns number of bytes written into buffer, negative errno on error. | |
137 | */ | |
5512eb06 GR |
138 | static ssize_t sht21_temperature_show(struct device *dev, |
139 | struct device_attribute *attr, | |
140 | char *buf) | |
430400b8 | 141 | { |
b8d56898 AL |
142 | struct sht21 *sht21 = dev_get_drvdata(dev); |
143 | int ret; | |
144 | ||
145 | ret = sht21_update_measurements(dev); | |
430400b8 UF |
146 | if (ret < 0) |
147 | return ret; | |
148 | return sprintf(buf, "%d\n", sht21->temperature); | |
149 | } | |
150 | ||
151 | /** | |
152 | * sht21_show_humidity() - show humidity measurement value in sysfs | |
153 | * @dev: device | |
154 | * @attr: device attribute | |
155 | * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to | |
156 | * | |
157 | * Will be called on read access to humidity1_input sysfs attribute. | |
158 | * Returns number of bytes written into buffer, negative errno on error. | |
159 | */ | |
5512eb06 GR |
160 | static ssize_t sht21_humidity_show(struct device *dev, |
161 | struct device_attribute *attr, char *buf) | |
430400b8 | 162 | { |
b8d56898 AL |
163 | struct sht21 *sht21 = dev_get_drvdata(dev); |
164 | int ret; | |
165 | ||
166 | ret = sht21_update_measurements(dev); | |
430400b8 UF |
167 | if (ret < 0) |
168 | return ret; | |
169 | return sprintf(buf, "%d\n", sht21->humidity); | |
170 | } | |
171 | ||
53e678d7 PB |
172 | static ssize_t eic_read(struct sht21 *sht21) |
173 | { | |
174 | struct i2c_client *client = sht21->client; | |
175 | u8 tx[2]; | |
176 | u8 rx[8]; | |
177 | u8 eic[8]; | |
178 | struct i2c_msg msgs[2] = { | |
179 | { | |
180 | .addr = client->addr, | |
181 | .flags = 0, | |
182 | .len = 2, | |
183 | .buf = tx, | |
184 | }, | |
185 | { | |
186 | .addr = client->addr, | |
187 | .flags = I2C_M_RD, | |
188 | .len = 8, | |
189 | .buf = rx, | |
190 | }, | |
191 | }; | |
192 | int ret; | |
193 | ||
194 | tx[0] = SHT21_READ_SNB_CMD1; | |
195 | tx[1] = SHT21_READ_SNB_CMD2; | |
196 | ret = i2c_transfer(client->adapter, msgs, 2); | |
197 | if (ret < 0) | |
198 | goto out; | |
199 | eic[2] = rx[0]; | |
200 | eic[3] = rx[2]; | |
201 | eic[4] = rx[4]; | |
202 | eic[5] = rx[6]; | |
203 | ||
204 | tx[0] = SHT21_READ_SNAC_CMD1; | |
205 | tx[1] = SHT21_READ_SNAC_CMD2; | |
206 | msgs[1].len = 6; | |
207 | ret = i2c_transfer(client->adapter, msgs, 2); | |
208 | if (ret < 0) | |
209 | goto out; | |
210 | eic[0] = rx[3]; | |
211 | eic[1] = rx[4]; | |
212 | eic[6] = rx[0]; | |
213 | eic[7] = rx[1]; | |
214 | ||
215 | ret = snprintf(sht21->eic, sizeof(sht21->eic), | |
216 | "%02x%02x%02x%02x%02x%02x%02x%02x\n", | |
217 | eic[0], eic[1], eic[2], eic[3], | |
218 | eic[4], eic[5], eic[6], eic[7]); | |
219 | out: | |
220 | if (ret < 0) | |
221 | sht21->eic[0] = 0; | |
222 | ||
223 | return ret; | |
224 | } | |
225 | ||
226 | /** | |
227 | * eic_show() - show Electronic Identification Code in sysfs | |
228 | * @dev: device | |
229 | * @attr: device attribute | |
230 | * @buf: sysfs buffer (PAGE_SIZE) where EIC is written | |
231 | * | |
232 | * Will be called on read access to eic sysfs attribute. | |
233 | * Returns number of bytes written into buffer, negative errno on error. | |
234 | */ | |
235 | static ssize_t eic_show(struct device *dev, | |
236 | struct device_attribute *attr, | |
237 | char *buf) | |
238 | { | |
239 | struct sht21 *sht21 = dev_get_drvdata(dev); | |
240 | int ret; | |
241 | ||
242 | ret = sizeof(sht21->eic) - 1; | |
243 | mutex_lock(&sht21->lock); | |
244 | if (!sht21->eic[0]) | |
245 | ret = eic_read(sht21); | |
246 | if (ret > 0) | |
247 | memcpy(buf, sht21->eic, ret); | |
248 | mutex_unlock(&sht21->lock); | |
249 | return ret; | |
250 | } | |
251 | ||
430400b8 | 252 | /* sysfs attributes */ |
5512eb06 GR |
253 | static SENSOR_DEVICE_ATTR_RO(temp1_input, sht21_temperature, 0); |
254 | static SENSOR_DEVICE_ATTR_RO(humidity1_input, sht21_humidity, 0); | |
53e678d7 | 255 | static DEVICE_ATTR_RO(eic); |
430400b8 | 256 | |
b8d56898 | 257 | static struct attribute *sht21_attrs[] = { |
430400b8 UF |
258 | &sensor_dev_attr_temp1_input.dev_attr.attr, |
259 | &sensor_dev_attr_humidity1_input.dev_attr.attr, | |
53e678d7 | 260 | &dev_attr_eic.attr, |
430400b8 UF |
261 | NULL |
262 | }; | |
263 | ||
b8d56898 | 264 | ATTRIBUTE_GROUPS(sht21); |
430400b8 | 265 | |
6c931ae1 | 266 | static int sht21_probe(struct i2c_client *client, |
430400b8 UF |
267 | const struct i2c_device_id *id) |
268 | { | |
b8d56898 AL |
269 | struct device *dev = &client->dev; |
270 | struct device *hwmon_dev; | |
430400b8 | 271 | struct sht21 *sht21; |
430400b8 UF |
272 | |
273 | if (!i2c_check_functionality(client->adapter, | |
274 | I2C_FUNC_SMBUS_WORD_DATA)) { | |
275 | dev_err(&client->dev, | |
276 | "adapter does not support SMBus word transactions\n"); | |
277 | return -ENODEV; | |
278 | } | |
279 | ||
b8d56898 | 280 | sht21 = devm_kzalloc(dev, sizeof(*sht21), GFP_KERNEL); |
a844af19 | 281 | if (!sht21) |
430400b8 | 282 | return -ENOMEM; |
a844af19 | 283 | |
b8d56898 | 284 | sht21->client = client; |
430400b8 UF |
285 | |
286 | mutex_init(&sht21->lock); | |
287 | ||
b8d56898 AL |
288 | hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name, |
289 | sht21, sht21_groups); | |
290 | return PTR_ERR_OR_ZERO(hwmon_dev); | |
430400b8 UF |
291 | } |
292 | ||
293 | /* Device ID table */ | |
294 | static const struct i2c_device_id sht21_id[] = { | |
295 | { "sht21", 0 }, | |
296 | { } | |
297 | }; | |
298 | MODULE_DEVICE_TABLE(i2c, sht21_id); | |
299 | ||
300 | static struct i2c_driver sht21_driver = { | |
301 | .driver.name = "sht21", | |
302 | .probe = sht21_probe, | |
430400b8 UF |
303 | .id_table = sht21_id, |
304 | }; | |
305 | ||
f0967eea | 306 | module_i2c_driver(sht21_driver); |
430400b8 UF |
307 | |
308 | MODULE_AUTHOR("Urs Fleisch <urs.fleisch@sensirion.com>"); | |
309 | MODULE_DESCRIPTION("Sensirion SHT21 humidity and temperature sensor driver"); | |
310 | MODULE_LICENSE("GPL"); |