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  * @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");