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  */
  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");