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
  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");