linux/drivers/hwmon/hih6130.c
<<
>>
Prefs
   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 */
  46struct 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 */
  60static 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 */
  76static 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 */
  93static 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        }
 150out:
 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 */
 165static 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 */
 186static 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 */
 198static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, hih6130_show_temperature,
 199        NULL, 0);
 200static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO, hih6130_show_humidity,
 201        NULL, 0);
 202
 203static 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
 209static 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 */
 222static 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
 256fail_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 */
 265static 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 */
 276static const struct i2c_device_id hih6130_id[] = {
 277        { "hih6130", 0 },
 278        { }
 279};
 280MODULE_DEVICE_TABLE(i2c, hih6130_id);
 281
 282static 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
 289module_i2c_driver(hih6130_driver);
 290
 291MODULE_AUTHOR("Iain Paton <ipaton0@gmail.com>");
 292MODULE_DESCRIPTION("Honeywell HIH-6130 humidity and temperature sensor driver");
 293MODULE_LICENSE("GPL");
 294
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.