1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
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>
32#include <linux/jiffies.h>
33
34
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
41
42
43
44
45
46
47
48
49
50
51
52struct 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];
60};
61
62
63
64
65
66
67static inline int sht21_temp_ticks_to_millicelsius(int ticks)
68{
69 ticks &= ~0x0003;
70
71
72
73
74 return ((21965 * ticks) >> 13) - 46850;
75}
76
77
78
79
80
81
82static inline int sht21_rh_ticks_to_per_cent_mille(int ticks)
83{
84 ticks &= ~0x0003;
85
86
87
88
89 return ((15625 * ticks) >> 13) - 6000;
90}
91
92
93
94
95
96
97
98static int sht21_update_measurements(struct device *dev)
99{
100 int ret = 0;
101 struct sht21 *sht21 = dev_get_drvdata(dev);
102 struct i2c_client *client = sht21->client;
103
104 mutex_lock(&sht21->lock);
105
106
107
108
109
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;
123 }
124out:
125 mutex_unlock(&sht21->lock);
126
127 return ret >= 0 ? 0 : ret;
128}
129
130
131
132
133
134
135
136
137
138
139static ssize_t sht21_show_temperature(struct device *dev,
140 struct device_attribute *attr,
141 char *buf)
142{
143 struct sht21 *sht21 = dev_get_drvdata(dev);
144 int ret;
145
146 ret = sht21_update_measurements(dev);
147 if (ret < 0)
148 return ret;
149 return sprintf(buf, "%d\n", sht21->temperature);
150}
151
152
153
154
155
156
157
158
159
160
161static ssize_t sht21_show_humidity(struct device *dev,
162 struct device_attribute *attr,
163 char *buf)
164{
165 struct sht21 *sht21 = dev_get_drvdata(dev);
166 int ret;
167
168 ret = sht21_update_measurements(dev);
169 if (ret < 0)
170 return ret;
171 return sprintf(buf, "%d\n", sht21->humidity);
172}
173
174static 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
230
231
232
233
234
235
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
254
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);
259static DEVICE_ATTR_RO(eic);
260
261static 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
266};
267
268ATTRIBUTE_GROUPS(sht21);
269
270static int sht21_probe(struct i2c_client *client,
271 const struct i2c_device_id *id)
272{
273 struct device *dev = &client->dev;
274 struct device *hwmon_dev;
275 struct sht21 *sht21;
276
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
284 sht21 = devm_kzalloc(dev, sizeof(*sht21), GFP_KERNEL);
285 if (!sht21)
286 return -ENOMEM;
287
288 sht21->client = client;
289
290 mutex_init(&sht21->lock);
291
292 hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
293 sht21, sht21_groups);
294 return PTR_ERR_OR_ZERO(hwmon_dev);
295}
296
297
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,
307 .id_table = sht21_id,
308};
309
310module_i2c_driver(sht21_driver);
311
312MODULE_AUTHOR("Urs Fleisch <urs.fleisch@sensirion.com>");
313MODULE_DESCRIPTION("Sensirion SHT21 humidity and temperature sensor driver");
314MODULE_LICENSE("GPL");
315