tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1/*
2 * Measurement Specialties HTU21D humidity and temperature sensor driver
3 *
4 * Copyright (C) 2013 William Markezana <william.markezana@meas-spec.com>
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
15 *
16 */
17
18#include <linux/module.h>
19#include <linux/init.h>
20#include <linux/slab.h>
21#include <linux/i2c.h>
22#include <linux/hwmon.h>
23#include <linux/hwmon-sysfs.h>
24#include <linux/err.h>
25#include <linux/mutex.h>
26#include <linux/device.h>
27#include <linux/jiffies.h>
28
29/* HTU21 Commands */
30#define HTU21_T_MEASUREMENT_HM 0xE3
31#define HTU21_RH_MEASUREMENT_HM 0xE5
32
33struct htu21 {
34 struct device *hwmon_dev;
35 struct mutex lock;
36 bool valid;
37 unsigned long last_update;
38 int temperature;
39 int humidity;
40};
41
42static inline int htu21_temp_ticks_to_millicelsius(int ticks)
43{
44 ticks &= ~0x0003; /* clear status bits */
45 /*
46 * Formula T = -46.85 + 175.72 * ST / 2^16 from datasheet p14,
47 * optimized for integer fixed point (3 digits) arithmetic
48 */
49 return ((21965 * ticks) >> 13) - 46850;
50}
51
52static inline int htu21_rh_ticks_to_per_cent_mille(int ticks)
53{
54 ticks &= ~0x0003; /* clear status bits */
55 /*
56 * Formula RH = -6 + 125 * SRH / 2^16 from datasheet p14,
57 * optimized for integer fixed point (3 digits) arithmetic
58 */
59 return ((15625 * ticks) >> 13) - 6000;
60}
61
62static int htu21_update_measurements(struct i2c_client *client)
63{
64 int ret = 0;
65 struct htu21 *htu21 = i2c_get_clientdata(client);
66
67 mutex_lock(&htu21->lock);
68
69 if (time_after(jiffies, htu21->last_update + HZ / 2) ||
70 !htu21->valid) {
71 ret = i2c_smbus_read_word_swapped(client,
72 HTU21_T_MEASUREMENT_HM);
73 if (ret < 0)
74 goto out;
75 htu21->temperature = htu21_temp_ticks_to_millicelsius(ret);
76 ret = i2c_smbus_read_word_swapped(client,
77 HTU21_RH_MEASUREMENT_HM);
78 if (ret < 0)
79 goto out;
80 htu21->humidity = htu21_rh_ticks_to_per_cent_mille(ret);
81 htu21->last_update = jiffies;
82 htu21->valid = true;
83 }
84out:
85 mutex_unlock(&htu21->lock);
86
87 return ret >= 0 ? 0 : ret;
88}
89
90static ssize_t htu21_show_temperature(struct device *dev,
91 struct device_attribute *attr, char *buf)
92{
93 struct i2c_client *client = to_i2c_client(dev);
94 struct htu21 *htu21 = i2c_get_clientdata(client);
95 int ret = htu21_update_measurements(client);
96 if (ret < 0)
97 return ret;
98 return sprintf(buf, "%d\n", htu21->temperature);
99}
100
101static ssize_t htu21_show_humidity(struct device *dev,
102 struct device_attribute *attr, char *buf)
103{
104 struct i2c_client *client = to_i2c_client(dev);
105 struct htu21 *htu21 = i2c_get_clientdata(client);
106 int ret = htu21_update_measurements(client);
107 if (ret < 0)
108 return ret;
109 return sprintf(buf, "%d\n", htu21->humidity);
110}
111
112static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO,
113 htu21_show_temperature, NULL, 0);
114static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO,
115 htu21_show_humidity, NULL, 0);
116
117static struct attribute *htu21_attributes[] = {
118 &sensor_dev_attr_temp1_input.dev_attr.attr,
119 &sensor_dev_attr_humidity1_input.dev_attr.attr,
120 NULL
121};
122
123static const struct attribute_group htu21_group = {
124 .attrs = htu21_attributes,
125};
126
127static int htu21_probe(struct i2c_client *client,
128 const struct i2c_device_id *id)
129{
130 struct htu21 *htu21;
131 int err;
132
133 if (!i2c_check_functionality(client->adapter,
134 I2C_FUNC_SMBUS_READ_WORD_DATA)) {
135 dev_err(&client->dev,
136 "adapter does not support SMBus word transactions\n");
137 return -ENODEV;
138 }
139
140 htu21 = devm_kzalloc(&client->dev, sizeof(*htu21), GFP_KERNEL);
141 if (!htu21)
142 return -ENOMEM;
143
144 i2c_set_clientdata(client, htu21);
145
146 mutex_init(&htu21->lock);
147
148 err = sysfs_create_group(&client->dev.kobj, &htu21_group);
149 if (err) {
150 dev_dbg(&client->dev, "could not create sysfs files\n");
151 return err;
152 }
153 htu21->hwmon_dev = hwmon_device_register(&client->dev);
154 if (IS_ERR(htu21->hwmon_dev)) {
155 dev_dbg(&client->dev, "unable to register hwmon device\n");
156 err = PTR_ERR(htu21->hwmon_dev);
157 goto error;
158 }
159
160 dev_info(&client->dev, "initialized\n");
161
162 return 0;
163
164error:
165 sysfs_remove_group(&client->dev.kobj, &htu21_group);
166 return err;
167}
168
169static int htu21_remove(struct i2c_client *client)
170{
171 struct htu21 *htu21 = i2c_get_clientdata(client);
172
173 hwmon_device_unregister(htu21->hwmon_dev);
174 sysfs_remove_group(&client->dev.kobj, &htu21_group);
175
176 return 0;
177}
178
179static const struct i2c_device_id htu21_id[] = {
180 { "htu21", 0 },
181 { }
182};
183MODULE_DEVICE_TABLE(i2c, htu21_id);
184
185static struct i2c_driver htu21_driver = {
186 .class = I2C_CLASS_HWMON,
187 .driver = {
188 .name = "htu21",
189 },
190 .probe = htu21_probe,
191 .remove = htu21_remove,
192 .id_table = htu21_id,
193};
194
195module_i2c_driver(htu21_driver);
196
197MODULE_AUTHOR("William Markezana <william.markezana@meas-spec.com>");
198MODULE_DESCRIPTION("MEAS HTU21D humidity and temperature sensor driver");
199MODULE_LICENSE("GPL");