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 */ 47 struct hih6130 { 48 struct device *hwmon_dev; 49 struct mutex lock; 50 bool valid; 51 unsigned long last_update; 52 int temperature; 53 int humidity; 54 }; 55 56 /** 57 * hih6130_temp_ticks_to_millicelsius() - convert raw temperature ticks to 58 * milli celsius 59 * @ticks: temperature ticks value received from sensor 60 */ 61 static inline int hih6130_temp_ticks_to_millicelsius(int ticks) 62 { 63 64 ticks = ticks >> 2; 65 /* 66 * from data sheet section 5.0 67 * Formula T = ( ticks / ( 2^14 - 2 ) ) * 165 -40 68 */ 69 return (DIV_ROUND_CLOSEST(ticks * 1650, 16382) - 400) * 100; 70 } 71 72 /** 73 * hih6130_rh_ticks_to_per_cent_mille() - convert raw humidity ticks to 74 * one-thousandths of a percent relative humidity 75 * @ticks: humidity ticks value received from sensor 76 */ 77 static inline int hih6130_rh_ticks_to_per_cent_mille(int ticks) 78 { 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 * @client: I2C client device 91 * 92 * Returns 0 on success, else negative errno. 93 */ 94 static int hih6130_update_measurements(struct i2c_client *client) 95 { 96 int ret = 0; 97 int t; 98 struct hih6130 *hih6130 = i2c_get_clientdata(client); 99 unsigned char tmp[4]; 100 struct i2c_msg msgs[1] = { 101 { 102 .addr = client->addr, 103 .flags = I2C_M_RD, 104 .len = 4, 105 .buf = tmp, 106 } 107 }; 108 109 mutex_lock(&hih6130->lock); 110 111 /* 112 * While the measurement can be completed in ~40ms the sensor takes 113 * much longer to react to a change in external conditions. How quickly 114 * it reacts depends on airflow and other factors outwith our control. 115 * The datasheet specifies maximum 'Response time' for humidity at 8s 116 * and temperature at 30s under specified conditions. 117 * We therefore choose to only read the sensor at most once per second. 118 * This trades off pointless activity polling the sensor much faster 119 * than it can react against better response times in conditions more 120 * favourable than specified in the datasheet. 121 */ 122 if (time_after(jiffies, hih6130->last_update + HZ) || !hih6130->valid) { 123 124 /* write to slave address, no data, to request a measurement */ 125 ret = i2c_master_send(client, tmp, 0); 126 if (ret < 0) 127 goto out; 128 129 /* measurement cycle time is ~36.65msec */ 130 msleep(40); 131 132 ret = i2c_transfer(client->adapter, msgs, 1); 133 if (ret < 0) 134 goto out; 135 136 if ((tmp[0] & 0xC0) != 0) { 137 dev_err(&client->dev, "Error while reading measurement result\n"); 138 ret = -EIO; 139 goto out; 140 } 141 142 t = (tmp[0] << 8) + tmp[1]; 143 hih6130->humidity = hih6130_rh_ticks_to_per_cent_mille(t); 144 145 t = (tmp[2] << 8) + tmp[3]; 146 hih6130->temperature = hih6130_temp_ticks_to_millicelsius(t); 147 148 hih6130->last_update = jiffies; 149 hih6130->valid = true; 150 } 151 out: 152 mutex_unlock(&hih6130->lock); 153 154 return ret >= 0 ? 0 : ret; 155 } 156 157 /** 158 * hih6130_show_temperature() - show temperature measurement value in sysfs 159 * @dev: device 160 * @attr: device attribute 161 * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to 162 * 163 * Will be called on read access to temp1_input sysfs attribute. 164 * Returns number of bytes written into buffer, negative errno on error. 165 */ 166 static ssize_t hih6130_show_temperature(struct device *dev, 167 struct device_attribute *attr, 168 char *buf) 169 { 170 struct i2c_client *client = to_i2c_client(dev); 171 struct hih6130 *hih6130 = i2c_get_clientdata(client); 172 int ret = hih6130_update_measurements(client); 173 if (ret < 0) 174 return ret; 175 return sprintf(buf, "%d\n", hih6130->temperature); 176 } 177 178 /** 179 * hih6130_show_humidity() - show humidity measurement value in sysfs 180 * @dev: device 181 * @attr: device attribute 182 * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to 183 * 184 * Will be called on read access to humidity1_input sysfs attribute. 185 * Returns number of bytes written into buffer, negative errno on error. 186 */ 187 static ssize_t hih6130_show_humidity(struct device *dev, 188 struct device_attribute *attr, char *buf) 189 { 190 struct i2c_client *client = to_i2c_client(dev); 191 struct hih6130 *hih6130 = i2c_get_clientdata(client); 192 int ret = hih6130_update_measurements(client); 193 if (ret < 0) 194 return ret; 195 return sprintf(buf, "%d\n", hih6130->humidity); 196 } 197 198 /* sysfs attributes */ 199 static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, hih6130_show_temperature, 200 NULL, 0); 201 static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO, hih6130_show_humidity, 202 NULL, 0); 203 204 static struct attribute *hih6130_attributes[] = { 205 &sensor_dev_attr_temp1_input.dev_attr.attr, 206 &sensor_dev_attr_humidity1_input.dev_attr.attr, 207 NULL 208 }; 209 210 static const struct attribute_group hih6130_attr_group = { 211 .attrs = hih6130_attributes, 212 }; 213 214 /** 215 * hih6130_probe() - probe device 216 * @client: I2C client device 217 * @id: device ID 218 * 219 * Called by the I2C core when an entry in the ID table matches a 220 * device's name. 221 * Returns 0 on success. 222 */ 223 static int hih6130_probe(struct i2c_client *client, 224 const struct i2c_device_id *id) 225 { 226 struct hih6130 *hih6130; 227 int err; 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(&client->dev, sizeof(*hih6130), GFP_KERNEL); 235 if (!hih6130) 236 return -ENOMEM; 237 238 i2c_set_clientdata(client, hih6130); 239 240 mutex_init(&hih6130->lock); 241 242 err = sysfs_create_group(&client->dev.kobj, &hih6130_attr_group); 243 if (err) { 244 dev_dbg(&client->dev, "could not create sysfs files\n"); 245 return err; 246 } 247 248 hih6130->hwmon_dev = hwmon_device_register(&client->dev); 249 if (IS_ERR(hih6130->hwmon_dev)) { 250 dev_dbg(&client->dev, "unable to register hwmon device\n"); 251 err = PTR_ERR(hih6130->hwmon_dev); 252 goto fail_remove_sysfs; 253 } 254 255 return 0; 256 257 fail_remove_sysfs: 258 sysfs_remove_group(&client->dev.kobj, &hih6130_attr_group); 259 return err; 260 } 261 262 /** 263 * hih6130_remove() - remove device 264 * @client: I2C client device 265 */ 266 static int hih6130_remove(struct i2c_client *client) 267 { 268 struct hih6130 *hih6130 = i2c_get_clientdata(client); 269 270 hwmon_device_unregister(hih6130->hwmon_dev); 271 sysfs_remove_group(&client->dev.kobj, &hih6130_attr_group); 272 273 return 0; 274 } 275 276 /* Device ID table */ 277 static const struct i2c_device_id hih6130_id[] = { 278 { "hih6130", 0 }, 279 { } 280 }; 281 MODULE_DEVICE_TABLE(i2c, hih6130_id); 282 283 static struct i2c_driver hih6130_driver = { 284 .driver.name = "hih6130", 285 .probe = hih6130_probe, 286 .remove = hih6130_remove, 287 .id_table = hih6130_id, 288 }; 289 290 module_i2c_driver(hih6130_driver); 291 292 MODULE_AUTHOR("Iain Paton <ipaton0@gmail.com>"); 293 MODULE_DESCRIPTION("Honeywell HIH-6130 humidity and temperature sensor driver"); 294 MODULE_LICENSE("GPL"); 295