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f060c658 WM |
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 | ||
33 | struct 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 | ||
42 | static 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 | ||
52 | static 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 | ||
62 | static 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 | } | |
84 | out: | |
85 | mutex_unlock(&htu21->lock); | |
86 | ||
87 | return ret >= 0 ? 0 : ret; | |
88 | } | |
89 | ||
90 | static 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 | ||
101 | static 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 | ||
112 | static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, | |
113 | htu21_show_temperature, NULL, 0); | |
114 | static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO, | |
115 | htu21_show_humidity, NULL, 0); | |
116 | ||
117 | static 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 | ||
123 | static const struct attribute_group htu21_group = { | |
124 | .attrs = htu21_attributes, | |
125 | }; | |
126 | ||
127 | static 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 | ||
164 | error: | |
165 | sysfs_remove_group(&client->dev.kobj, &htu21_group); | |
166 | return err; | |
167 | } | |
168 | ||
169 | static 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 | ||
179 | static const struct i2c_device_id htu21_id[] = { | |
180 | { "htu21", 0 }, | |
181 | { } | |
182 | }; | |
183 | MODULE_DEVICE_TABLE(i2c, htu21_id); | |
184 | ||
185 | static 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 | ||
195 | module_i2c_driver(htu21_driver); | |
196 | ||
197 | MODULE_AUTHOR("William Markezana <william.markezana@meas-spec.com>"); | |
198 | MODULE_DESCRIPTION("MEAS HTU21D humidity and temperature sensor driver"); | |
199 | MODULE_LICENSE("GPL"); |