1 /* Honeywell HIH-6130/HIH-6131 humidity and temperature sensor driver 2 * 3 * Copyright (C) 2012 Iain Paton <ipaton0@gmail.com> 4 * 5 * heavily based on the sht21 driver 6 * Copyright (C) 2010 Urs Fleisch <urs.fleisch@sensirion.com> 7 * 8 * This program is free software; you can redistribute it and/or modify 9 * it under the terms of the GNU General Public License as published by 10 * the Free Software Foundation; either version 2 of the License, or 11 * (at your option) any later version. 12 * 13 * This program is distributed in the hope that it will be useful, 14 * but WITHOUT ANY WARRANTY; without even the implied warranty of 15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 16 * GNU General Public License for more details. 17 * 18 * You should have received a copy of the GNU General Public License 19 * along with this program; if not, write to the Free Software 20 * Foundation, Inc., 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA 21 * 22 * Data sheets available (2012-06-22) at 23 * http://sensing.honeywell.com/index.php?ci_id=3106&la_id=1&defId=44872 24 */ 25 26 #include <linux/module.h> 27 #include <linux/init.h> 28 #include <linux/slab.h> 29 #include <linux/i2c.h> 30 #include <linux/hwmon.h> 31 #include <linux/hwmon-sysfs.h> 32 #include <linux/err.h> 33 #include <linux/mutex.h> 34 #include <linux/device.h> 35 #include <linux/delay.h> 36 #include <linux/jiffies.h> 37 38 /** 39 * struct hih6130 - HIH-6130 device specific data 40 * @hwmon_dev: device registered with hwmon 41 * @lock: mutex to protect measurement values 42 * @valid: only false before first measurement is taken 43 * @last_update: time of last update (jiffies) 44 * @temperature: cached temperature measurement value 45 * @humidity: cached humidity measurement value 46 * @write_length: length for I2C measurement request 47 */ 48 struct hih6130 { 49 struct i2c_client *client; 50 struct mutex lock; 51 bool valid; 52 unsigned long last_update; 53 int temperature; 54 int humidity; 55 size_t write_length; 56 }; 57 58 /** 59 * hih6130_temp_ticks_to_millicelsius() - convert raw temperature ticks to 60 * milli celsius 61 * @ticks: temperature ticks value received from sensor 62 */ 63 static inline int hih6130_temp_ticks_to_millicelsius(int ticks) 64 { 65 ticks = ticks >> 2; 66 /* 67 * from data sheet section 5.0 68 * Formula T = ( ticks / ( 2^14 - 2 ) ) * 165 -40 69 */ 70 return (DIV_ROUND_CLOSEST(ticks * 1650, 16382) - 400) * 100; 71 } 72 73 /** 74 * hih6130_rh_ticks_to_per_cent_mille() - convert raw humidity ticks to 75 * one-thousandths of a percent relative humidity 76 * @ticks: humidity ticks value received from sensor 77 */ 78 static inline int hih6130_rh_ticks_to_per_cent_mille(int ticks) 79 { 80 ticks &= ~0xC000; /* clear status bits */ 81 /* 82 * from data sheet section 4.0 83 * Formula RH = ( ticks / ( 2^14 -2 ) ) * 100 84 */ 85 return DIV_ROUND_CLOSEST(ticks * 1000, 16382) * 100; 86 } 87 88 /** 89 * hih6130_update_measurements() - get updated measurements from device 90 * @dev: device 91 * 92 * Returns 0 on success, else negative errno. 93 */ 94 static int hih6130_update_measurements(struct device *dev) 95 { 96 struct hih6130 *hih6130 = dev_get_drvdata(dev); 97 struct i2c_client *client = hih6130->client; 98 int ret = 0; 99 int t; 100 unsigned char tmp[4]; 101 struct i2c_msg msgs[1] = { 102 { 103 .addr = client->addr, 104 .flags = I2C_M_RD, 105 .len = 4, 106 .buf = tmp, 107 } 108 }; 109 110 mutex_lock(&hih6130->lock); 111 112 /* 113 * While the measurement can be completed in ~40ms the sensor takes 114 * much longer to react to a change in external conditions. How quickly 115 * it reacts depends on airflow and other factors outwith our control. 116 * The datasheet specifies maximum 'Response time' for humidity at 8s 117 * and temperature at 30s under specified conditions. 118 * We therefore choose to only read the sensor at most once per second. 119 * This trades off pointless activity polling the sensor much faster 120 * than it can react against better response times in conditions more 121 * favourable than specified in the datasheet. 122 */ 123 if (time_after(jiffies, hih6130->last_update + HZ) || !hih6130->valid) { 124 125 /* 126 * Write to slave address to request a measurement. 127 * According with the datasheet it should be with no data, but 128 * for systems with I2C bus drivers that do not allow zero 129 * length packets we write one dummy byte to allow sensor 130 * measurements on them. 131 */ 132 tmp[0] = 0; 133 ret = i2c_master_send(client, tmp, hih6130->write_length); 134 if (ret < 0) 135 goto out; 136 137 /* measurement cycle time is ~36.65msec */ 138 msleep(40); 139 140 ret = i2c_transfer(client->adapter, msgs, 1); 141 if (ret < 0) 142 goto out; 143 144 if ((tmp[0] & 0xC0) != 0) { 145 dev_err(&client->dev, "Error while reading measurement result\n"); 146 ret = -EIO; 147 goto out; 148 } 149 150 t = (tmp[0] << 8) + tmp[1]; 151 hih6130->humidity = hih6130_rh_ticks_to_per_cent_mille(t); 152 153 t = (tmp[2] << 8) + tmp[3]; 154 hih6130->temperature = hih6130_temp_ticks_to_millicelsius(t); 155 156 hih6130->last_update = jiffies; 157 hih6130->valid = true; 158 } 159 out: 160 mutex_unlock(&hih6130->lock); 161 162 return ret >= 0 ? 0 : ret; 163 } 164 165 /** 166 * hih6130_show_temperature() - show temperature measurement value in sysfs 167 * @dev: device 168 * @attr: device attribute 169 * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to 170 * 171 * Will be called on read access to temp1_input sysfs attribute. 172 * Returns number of bytes written into buffer, negative errno on error. 173 */ 174 static ssize_t hih6130_show_temperature(struct device *dev, 175 struct device_attribute *attr, 176 char *buf) 177 { 178 struct hih6130 *hih6130 = dev_get_drvdata(dev); 179 int ret; 180 181 ret = hih6130_update_measurements(dev); 182 if (ret < 0) 183 return ret; 184 return sprintf(buf, "%d\n", hih6130->temperature); 185 } 186 187 /** 188 * hih6130_show_humidity() - show humidity measurement value in sysfs 189 * @dev: device 190 * @attr: device attribute 191 * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to 192 * 193 * Will be called on read access to humidity1_input sysfs attribute. 194 * Returns number of bytes written into buffer, negative errno on error. 195 */ 196 static ssize_t hih6130_show_humidity(struct device *dev, 197 struct device_attribute *attr, char *buf) 198 { 199 struct hih6130 *hih6130 = dev_get_drvdata(dev); 200 int ret; 201 202 ret = hih6130_update_measurements(dev); 203 if (ret < 0) 204 return ret; 205 return sprintf(buf, "%d\n", hih6130->humidity); 206 } 207 208 /* sysfs attributes */ 209 static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, hih6130_show_temperature, 210 NULL, 0); 211 static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO, hih6130_show_humidity, 212 NULL, 0); 213 214 static struct attribute *hih6130_attrs[] = { 215 &sensor_dev_attr_temp1_input.dev_attr.attr, 216 &sensor_dev_attr_humidity1_input.dev_attr.attr, 217 NULL 218 }; 219 220 ATTRIBUTE_GROUPS(hih6130); 221 222 static int hih6130_probe(struct i2c_client *client, 223 const struct i2c_device_id *id) 224 { 225 struct device *dev = &client->dev; 226 struct hih6130 *hih6130; 227 struct device *hwmon_dev; 228 229 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) { 230 dev_err(&client->dev, "adapter does not support true I2C\n"); 231 return -ENODEV; 232 } 233 234 hih6130 = devm_kzalloc(dev, sizeof(*hih6130), GFP_KERNEL); 235 if (!hih6130) 236 return -ENOMEM; 237 238 hih6130->client = client; 239 mutex_init(&hih6130->lock); 240 241 if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_QUICK)) 242 hih6130->write_length = 1; 243 244 hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name, 245 hih6130, 246 hih6130_groups); 247 return PTR_ERR_OR_ZERO(hwmon_dev); 248 } 249 250 /* Device ID table */ 251 static const struct i2c_device_id hih6130_id[] = { 252 { "hih6130", 0 }, 253 { } 254 }; 255 MODULE_DEVICE_TABLE(i2c, hih6130_id); 256 257 static struct i2c_driver hih6130_driver = { 258 .driver.name = "hih6130", 259 .probe = hih6130_probe, 260 .id_table = hih6130_id, 261 }; 262 263 module_i2c_driver(hih6130_driver); 264 265 MODULE_AUTHOR("Iain Paton <ipaton0@gmail.com>"); 266 MODULE_DESCRIPTION("Honeywell HIH-6130 humidity and temperature sensor driver"); 267 MODULE_LICENSE("GPL"); 268