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 37 /** 38 * struct hih6130 - HIH-6130 device specific data 39 * @hwmon_dev: device registered with hwmon 40 * @lock: mutex to protect measurement values 41 * @valid: only false before first measurement is taken 42 * @last_update: time of last update (jiffies) 43 * @temperature: cached temperature measurement value 44 * @humidity: cached humidity measurement value 45 */ 46 struct hih6130 { 47 struct device *hwmon_dev; 48 struct mutex lock; 49 bool valid; 50 unsigned long last_update; 51 int temperature; 52 int humidity; 53 }; 54 55 /** 56 * hih6130_temp_ticks_to_millicelsius() - convert raw temperature ticks to 57 * milli celsius 58 * @ticks: temperature ticks value received from sensor 59 */ 60 static inline int hih6130_temp_ticks_to_millicelsius(int ticks) 61 { 62 63 ticks = ticks >> 2; 64 /* 65 * from data sheet section 5.0 66 * Formula T = ( ticks / ( 2^14 - 2 ) ) * 165 -40 67 */ 68 return (DIV_ROUND_CLOSEST(ticks * 1650, 16382) - 400) * 100; 69 } 70 71 /** 72 * hih6130_rh_ticks_to_per_cent_mille() - convert raw humidity ticks to 73 * one-thousandths of a percent relative humidity 74 * @ticks: humidity ticks value received from sensor 75 */ 76 static inline int hih6130_rh_ticks_to_per_cent_mille(int ticks) 77 { 78 79 ticks &= ~0xC000; /* clear status bits */ 80 /* 81 * from data sheet section 4.0 82 * Formula RH = ( ticks / ( 2^14 -2 ) ) * 100 83 */ 84 return DIV_ROUND_CLOSEST(ticks * 1000, 16382) * 100; 85 } 86 87 /** 88 * hih6130_update_measurements() - get updated measurements from device 89 * @client: I2C client device 90 * 91 * Returns 0 on success, else negative errno. 92 */ 93 static int hih6130_update_measurements(struct i2c_client *client) 94 { 95 int ret = 0; 96 int t; 97 struct hih6130 *hih6130 = i2c_get_clientdata(client); 98 unsigned char tmp[4]; 99 struct i2c_msg msgs[1] = { 100 { 101 .addr = client->addr, 102 .flags = I2C_M_RD, 103 .len = 4, 104 .buf = tmp, 105 } 106 }; 107 108 mutex_lock(&hih6130->lock); 109 110 /* 111 * While the measurement can be completed in ~40ms the sensor takes 112 * much longer to react to a change in external conditions. How quickly 113 * it reacts depends on airflow and other factors outwith our control. 114 * The datasheet specifies maximum 'Response time' for humidity at 8s 115 * and temperature at 30s under specified conditions. 116 * We therefore choose to only read the sensor at most once per second. 117 * This trades off pointless activity polling the sensor much faster 118 * than it can react against better response times in conditions more 119 * favourable than specified in the datasheet. 120 */ 121 if (time_after(jiffies, hih6130->last_update + HZ) || !hih6130->valid) { 122 123 /* write to slave address, no data, to request a measurement */ 124 ret = i2c_master_send(client, tmp, 0); 125 if (ret < 0) 126 goto out; 127 128 /* measurement cycle time is ~36.65msec */ 129 msleep(40); 130 131 ret = i2c_transfer(client->adapter, msgs, 1); 132 if (ret < 0) 133 goto out; 134 135 if ((tmp[0] & 0xC0) != 0) { 136 dev_err(&client->dev, "Error while reading measurement result\n"); 137 ret = -EIO; 138 goto out; 139 } 140 141 t = (tmp[0] << 8) + tmp[1]; 142 hih6130->humidity = hih6130_rh_ticks_to_per_cent_mille(t); 143 144 t = (tmp[2] << 8) + tmp[3]; 145 hih6130->temperature = hih6130_temp_ticks_to_millicelsius(t); 146 147 hih6130->last_update = jiffies; 148 hih6130->valid = true; 149 } 150 out: 151 mutex_unlock(&hih6130->lock); 152 153 return ret >= 0 ? 0 : ret; 154 } 155 156 /** 157 * hih6130_show_temperature() - show temperature measurement value in sysfs 158 * @dev: device 159 * @attr: device attribute 160 * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to 161 * 162 * Will be called on read access to temp1_input sysfs attribute. 163 * Returns number of bytes written into buffer, negative errno on error. 164 */ 165 static ssize_t hih6130_show_temperature(struct device *dev, 166 struct device_attribute *attr, 167 char *buf) 168 { 169 struct i2c_client *client = to_i2c_client(dev); 170 struct hih6130 *hih6130 = i2c_get_clientdata(client); 171 int ret = hih6130_update_measurements(client); 172 if (ret < 0) 173 return ret; 174 return sprintf(buf, "%d\n", hih6130->temperature); 175 } 176 177 /** 178 * hih6130_show_humidity() - show humidity measurement value in sysfs 179 * @dev: device 180 * @attr: device attribute 181 * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to 182 * 183 * Will be called on read access to humidity1_input sysfs attribute. 184 * Returns number of bytes written into buffer, negative errno on error. 185 */ 186 static ssize_t hih6130_show_humidity(struct device *dev, 187 struct device_attribute *attr, char *buf) 188 { 189 struct i2c_client *client = to_i2c_client(dev); 190 struct hih6130 *hih6130 = i2c_get_clientdata(client); 191 int ret = hih6130_update_measurements(client); 192 if (ret < 0) 193 return ret; 194 return sprintf(buf, "%d\n", hih6130->humidity); 195 } 196 197 /* sysfs attributes */ 198 static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, hih6130_show_temperature, 199 NULL, 0); 200 static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO, hih6130_show_humidity, 201 NULL, 0); 202 203 static struct attribute *hih6130_attributes[] = { 204 &sensor_dev_attr_temp1_input.dev_attr.attr, 205 &sensor_dev_attr_humidity1_input.dev_attr.attr, 206 NULL 207 }; 208 209 static const struct attribute_group hih6130_attr_group = { 210 .attrs = hih6130_attributes, 211 }; 212 213 /** 214 * hih6130_probe() - probe device 215 * @client: I2C client device 216 * @id: device ID 217 * 218 * Called by the I2C core when an entry in the ID table matches a 219 * device's name. 220 * Returns 0 on success. 221 */ 222 static int __devinit hih6130_probe(struct i2c_client *client, 223 const struct i2c_device_id *id) 224 { 225 struct hih6130 *hih6130; 226 int err; 227 228 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) { 229 dev_err(&client->dev, "adapter does not support true I2C\n"); 230 return -ENODEV; 231 } 232 233 hih6130 = devm_kzalloc(&client->dev, sizeof(*hih6130), GFP_KERNEL); 234 if (!hih6130) 235 return -ENOMEM; 236 237 i2c_set_clientdata(client, hih6130); 238 239 mutex_init(&hih6130->lock); 240 241 err = sysfs_create_group(&client->dev.kobj, &hih6130_attr_group); 242 if (err) { 243 dev_dbg(&client->dev, "could not create sysfs files\n"); 244 return err; 245 } 246 247 hih6130->hwmon_dev = hwmon_device_register(&client->dev); 248 if (IS_ERR(hih6130->hwmon_dev)) { 249 dev_dbg(&client->dev, "unable to register hwmon device\n"); 250 err = PTR_ERR(hih6130->hwmon_dev); 251 goto fail_remove_sysfs; 252 } 253 254 return 0; 255 256 fail_remove_sysfs: 257 sysfs_remove_group(&client->dev.kobj, &hih6130_attr_group); 258 return err; 259 } 260 261 /** 262 * hih6130_remove() - remove device 263 * @client: I2C client device 264 */ 265 static int __devexit hih6130_remove(struct i2c_client *client) 266 { 267 struct hih6130 *hih6130 = i2c_get_clientdata(client); 268 269 hwmon_device_unregister(hih6130->hwmon_dev); 270 sysfs_remove_group(&client->dev.kobj, &hih6130_attr_group); 271 272 return 0; 273 } 274 275 /* Device ID table */ 276 static const struct i2c_device_id hih6130_id[] = { 277 { "hih6130", 0 }, 278 { } 279 }; 280 MODULE_DEVICE_TABLE(i2c, hih6130_id); 281 282 static struct i2c_driver hih6130_driver = { 283 .driver.name = "hih6130", 284 .probe = hih6130_probe, 285 .remove = __devexit_p(hih6130_remove), 286 .id_table = hih6130_id, 287 }; 288 289 module_i2c_driver(hih6130_driver); 290 291 MODULE_AUTHOR("Iain Paton <ipaton0@gmail.com>"); 292 MODULE_DESCRIPTION("Honeywell HIH-6130 humidity and temperature sensor driver"); 293 MODULE_LICENSE("GPL"); 294