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 device *hwmon_dev; 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 66 ticks = ticks >> 2; 67 /* 68 * from data sheet section 5.0 69 * Formula T = ( ticks / ( 2^14 - 2 ) ) * 165 -40 70 */ 71 return (DIV_ROUND_CLOSEST(ticks * 1650, 16382) - 400) * 100; 72 } 73 74 /** 75 * hih6130_rh_ticks_to_per_cent_mille() - convert raw humidity ticks to 76 * one-thousandths of a percent relative humidity 77 * @ticks: humidity ticks value received from sensor 78 */ 79 static inline int hih6130_rh_ticks_to_per_cent_mille(int ticks) 80 { 81 82 ticks &= ~0xC000; /* clear status bits */ 83 /* 84 * from data sheet section 4.0 85 * Formula RH = ( ticks / ( 2^14 -2 ) ) * 100 86 */ 87 return DIV_ROUND_CLOSEST(ticks * 1000, 16382) * 100; 88 } 89 90 /** 91 * hih6130_update_measurements() - get updated measurements from device 92 * @client: I2C client device 93 * 94 * Returns 0 on success, else negative errno. 95 */ 96 static int hih6130_update_measurements(struct i2c_client *client) 97 { 98 int ret = 0; 99 int t; 100 struct hih6130 *hih6130 = i2c_get_clientdata(client); 101 unsigned char tmp[4]; 102 struct i2c_msg msgs[1] = { 103 { 104 .addr = client->addr, 105 .flags = I2C_M_RD, 106 .len = 4, 107 .buf = tmp, 108 } 109 }; 110 111 mutex_lock(&hih6130->lock); 112 113 /* 114 * While the measurement can be completed in ~40ms the sensor takes 115 * much longer to react to a change in external conditions. How quickly 116 * it reacts depends on airflow and other factors outwith our control. 117 * The datasheet specifies maximum 'Response time' for humidity at 8s 118 * and temperature at 30s under specified conditions. 119 * We therefore choose to only read the sensor at most once per second. 120 * This trades off pointless activity polling the sensor much faster 121 * than it can react against better response times in conditions more 122 * favourable than specified in the datasheet. 123 */ 124 if (time_after(jiffies, hih6130->last_update + HZ) || !hih6130->valid) { 125 126 /* 127 * Write to slave address to request a measurement. 128 * According with the datasheet it should be with no data, but 129 * for systems with I2C bus drivers that do not allow zero 130 * length packets we write one dummy byte to allow sensor 131 * measurements on them. 132 */ 133 tmp[0] = 0; 134 ret = i2c_master_send(client, tmp, hih6130->write_length); 135 if (ret < 0) 136 goto out; 137 138 /* measurement cycle time is ~36.65msec */ 139 msleep(40); 140 141 ret = i2c_transfer(client->adapter, msgs, 1); 142 if (ret < 0) 143 goto out; 144 145 if ((tmp[0] & 0xC0) != 0) { 146 dev_err(&client->dev, "Error while reading measurement result\n"); 147 ret = -EIO; 148 goto out; 149 } 150 151 t = (tmp[0] << 8) + tmp[1]; 152 hih6130->humidity = hih6130_rh_ticks_to_per_cent_mille(t); 153 154 t = (tmp[2] << 8) + tmp[3]; 155 hih6130->temperature = hih6130_temp_ticks_to_millicelsius(t); 156 157 hih6130->last_update = jiffies; 158 hih6130->valid = true; 159 } 160 out: 161 mutex_unlock(&hih6130->lock); 162 163 return ret >= 0 ? 0 : ret; 164 } 165 166 /** 167 * hih6130_show_temperature() - show temperature measurement value in sysfs 168 * @dev: device 169 * @attr: device attribute 170 * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to 171 * 172 * Will be called on read access to temp1_input sysfs attribute. 173 * Returns number of bytes written into buffer, negative errno on error. 174 */ 175 static ssize_t hih6130_show_temperature(struct device *dev, 176 struct device_attribute *attr, 177 char *buf) 178 { 179 struct i2c_client *client = to_i2c_client(dev); 180 struct hih6130 *hih6130 = i2c_get_clientdata(client); 181 int ret = hih6130_update_measurements(client); 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 i2c_client *client = to_i2c_client(dev); 200 struct hih6130 *hih6130 = i2c_get_clientdata(client); 201 int ret = hih6130_update_measurements(client); 202 if (ret < 0) 203 return ret; 204 return sprintf(buf, "%d\n", hih6130->humidity); 205 } 206 207 /* sysfs attributes */ 208 static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, hih6130_show_temperature, 209 NULL, 0); 210 static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO, hih6130_show_humidity, 211 NULL, 0); 212 213 static struct attribute *hih6130_attributes[] = { 214 &sensor_dev_attr_temp1_input.dev_attr.attr, 215 &sensor_dev_attr_humidity1_input.dev_attr.attr, 216 NULL 217 }; 218 219 static const struct attribute_group hih6130_attr_group = { 220 .attrs = hih6130_attributes, 221 }; 222 223 /** 224 * hih6130_probe() - probe device 225 * @client: I2C client device 226 * @id: device ID 227 * 228 * Called by the I2C core when an entry in the ID table matches a 229 * device's name. 230 * Returns 0 on success. 231 */ 232 static int hih6130_probe(struct i2c_client *client, 233 const struct i2c_device_id *id) 234 { 235 struct hih6130 *hih6130; 236 int err; 237 238 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) { 239 dev_err(&client->dev, "adapter does not support true I2C\n"); 240 return -ENODEV; 241 } 242 243 hih6130 = devm_kzalloc(&client->dev, sizeof(*hih6130), GFP_KERNEL); 244 if (!hih6130) 245 return -ENOMEM; 246 247 i2c_set_clientdata(client, hih6130); 248 249 mutex_init(&hih6130->lock); 250 251 err = sysfs_create_group(&client->dev.kobj, &hih6130_attr_group); 252 if (err) { 253 dev_dbg(&client->dev, "could not create sysfs files\n"); 254 return err; 255 } 256 257 hih6130->hwmon_dev = hwmon_device_register(&client->dev); 258 if (IS_ERR(hih6130->hwmon_dev)) { 259 dev_dbg(&client->dev, "unable to register hwmon device\n"); 260 err = PTR_ERR(hih6130->hwmon_dev); 261 goto fail_remove_sysfs; 262 } 263 264 if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_QUICK)) 265 hih6130->write_length = 1; 266 267 return 0; 268 269 fail_remove_sysfs: 270 sysfs_remove_group(&client->dev.kobj, &hih6130_attr_group); 271 return err; 272 } 273 274 /** 275 * hih6130_remove() - remove device 276 * @client: I2C client device 277 */ 278 static int hih6130_remove(struct i2c_client *client) 279 { 280 struct hih6130 *hih6130 = i2c_get_clientdata(client); 281 282 hwmon_device_unregister(hih6130->hwmon_dev); 283 sysfs_remove_group(&client->dev.kobj, &hih6130_attr_group); 284 285 return 0; 286 } 287 288 /* Device ID table */ 289 static const struct i2c_device_id hih6130_id[] = { 290 { "hih6130", 0 }, 291 { } 292 }; 293 MODULE_DEVICE_TABLE(i2c, hih6130_id); 294 295 static struct i2c_driver hih6130_driver = { 296 .driver.name = "hih6130", 297 .probe = hih6130_probe, 298 .remove = hih6130_remove, 299 .id_table = hih6130_id, 300 }; 301 302 module_i2c_driver(hih6130_driver); 303 304 MODULE_AUTHOR("Iain Paton <ipaton0@gmail.com>"); 305 MODULE_DESCRIPTION("Honeywell HIH-6130 humidity and temperature sensor driver"); 306 MODULE_LICENSE("GPL"); 307