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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 { | |
fa0efc40 | 34 | struct i2c_client *client; |
f060c658 WM |
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 | ||
fa0efc40 | 62 | static int htu21_update_measurements(struct device *dev) |
f060c658 | 63 | { |
fa0efc40 AL |
64 | struct htu21 *htu21 = dev_get_drvdata(dev); |
65 | struct i2c_client *client = htu21->client; | |
f060c658 | 66 | int ret = 0; |
f060c658 WM |
67 | |
68 | mutex_lock(&htu21->lock); | |
69 | ||
70 | if (time_after(jiffies, htu21->last_update + HZ / 2) || | |
71 | !htu21->valid) { | |
72 | ret = i2c_smbus_read_word_swapped(client, | |
73 | HTU21_T_MEASUREMENT_HM); | |
74 | if (ret < 0) | |
75 | goto out; | |
76 | htu21->temperature = htu21_temp_ticks_to_millicelsius(ret); | |
77 | ret = i2c_smbus_read_word_swapped(client, | |
78 | HTU21_RH_MEASUREMENT_HM); | |
79 | if (ret < 0) | |
80 | goto out; | |
81 | htu21->humidity = htu21_rh_ticks_to_per_cent_mille(ret); | |
82 | htu21->last_update = jiffies; | |
83 | htu21->valid = true; | |
84 | } | |
85 | out: | |
86 | mutex_unlock(&htu21->lock); | |
87 | ||
88 | return ret >= 0 ? 0 : ret; | |
89 | } | |
90 | ||
91 | static ssize_t htu21_show_temperature(struct device *dev, | |
92 | struct device_attribute *attr, char *buf) | |
93 | { | |
fa0efc40 AL |
94 | struct htu21 *htu21 = dev_get_drvdata(dev); |
95 | int ret; | |
96 | ||
97 | ret = htu21_update_measurements(dev); | |
f060c658 WM |
98 | if (ret < 0) |
99 | return ret; | |
100 | return sprintf(buf, "%d\n", htu21->temperature); | |
101 | } | |
102 | ||
103 | static ssize_t htu21_show_humidity(struct device *dev, | |
104 | struct device_attribute *attr, char *buf) | |
105 | { | |
fa0efc40 AL |
106 | struct htu21 *htu21 = dev_get_drvdata(dev); |
107 | int ret; | |
108 | ||
109 | ret = htu21_update_measurements(dev); | |
f060c658 WM |
110 | if (ret < 0) |
111 | return ret; | |
112 | return sprintf(buf, "%d\n", htu21->humidity); | |
113 | } | |
114 | ||
115 | static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, | |
116 | htu21_show_temperature, NULL, 0); | |
117 | static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO, | |
118 | htu21_show_humidity, NULL, 0); | |
119 | ||
fa0efc40 | 120 | static struct attribute *htu21_attrs[] = { |
f060c658 WM |
121 | &sensor_dev_attr_temp1_input.dev_attr.attr, |
122 | &sensor_dev_attr_humidity1_input.dev_attr.attr, | |
123 | NULL | |
124 | }; | |
125 | ||
fa0efc40 | 126 | ATTRIBUTE_GROUPS(htu21); |
f060c658 WM |
127 | |
128 | static int htu21_probe(struct i2c_client *client, | |
129 | const struct i2c_device_id *id) | |
130 | { | |
fa0efc40 | 131 | struct device *dev = &client->dev; |
f060c658 | 132 | struct htu21 *htu21; |
fa0efc40 | 133 | struct device *hwmon_dev; |
f060c658 WM |
134 | |
135 | if (!i2c_check_functionality(client->adapter, | |
136 | I2C_FUNC_SMBUS_READ_WORD_DATA)) { | |
137 | dev_err(&client->dev, | |
138 | "adapter does not support SMBus word transactions\n"); | |
139 | return -ENODEV; | |
140 | } | |
141 | ||
fa0efc40 | 142 | htu21 = devm_kzalloc(dev, sizeof(*htu21), GFP_KERNEL); |
f060c658 WM |
143 | if (!htu21) |
144 | return -ENOMEM; | |
145 | ||
fa0efc40 | 146 | htu21->client = client; |
f060c658 WM |
147 | mutex_init(&htu21->lock); |
148 | ||
fa0efc40 AL |
149 | hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name, |
150 | htu21, | |
151 | htu21_groups); | |
152 | return PTR_ERR_OR_ZERO(hwmon_dev); | |
f060c658 WM |
153 | } |
154 | ||
155 | static const struct i2c_device_id htu21_id[] = { | |
156 | { "htu21", 0 }, | |
157 | { } | |
158 | }; | |
159 | MODULE_DEVICE_TABLE(i2c, htu21_id); | |
160 | ||
161 | static struct i2c_driver htu21_driver = { | |
162 | .class = I2C_CLASS_HWMON, | |
163 | .driver = { | |
164 | .name = "htu21", | |
165 | }, | |
166 | .probe = htu21_probe, | |
f060c658 WM |
167 | .id_table = htu21_id, |
168 | }; | |
169 | ||
170 | module_i2c_driver(htu21_driver); | |
171 | ||
172 | MODULE_AUTHOR("William Markezana <william.markezana@meas-spec.com>"); | |
173 | MODULE_DESCRIPTION("MEAS HTU21D humidity and temperature sensor driver"); | |
174 | MODULE_LICENSE("GPL"); |