drivers/hwmon/hih6130.c

   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  * @client: pointer to I2C client device
  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");