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    Subject[PATCH] hwmon: driver for Sensirion SHT21 humidity and temperature sensor
    Hi,

    This is a driver for the new humidity and temperature sensors SHT21 and SHT25 from Sensirion.

    Regards,
    Urs


    diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
    index 95ccbe3..4a96429 100644
    --- a/drivers/hwmon/Kconfig
    +++ b/drivers/hwmon/Kconfig
    @@ -688,6 +688,16 @@ config SENSORS_SHT15
    This driver can also be built as a module. If so, the module
    will be called sht15.

    +config SENSORS_SHT21
    + tristate "Sensiron humidity and temperature sensors. SHT21 and compat."
    + depends on I2C
    + help
    + If you say yes here you get support for the Sensiron SHT21, SHT25
    + humidity and temperature sensors.
    +
    + This driver can also be built as a module. If so, the module
    + will be called sht21.
    +
    config SENSORS_S3C
    tristate "S3C24XX/S3C64XX Inbuilt ADC"
    depends on ARCH_S3C2410
    diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
    index 33c2ee1..7439653 100644
    --- a/drivers/hwmon/Makefile
    +++ b/drivers/hwmon/Makefile
    @@ -80,6 +80,7 @@ obj-$(CONFIG_SENSORS_PC87427) += pc87427.o
    obj-$(CONFIG_SENSORS_PCF8591) += pcf8591.o
    obj-$(CONFIG_SENSORS_S3C) += s3c-hwmon.o
    obj-$(CONFIG_SENSORS_SHT15) += sht15.o
    +obj-$(CONFIG_SENSORS_SHT21) += sht21.o
    obj-$(CONFIG_SENSORS_SIS5595) += sis5595.o
    obj-$(CONFIG_SENSORS_SMM665) += smm665.o
    obj-$(CONFIG_SENSORS_SMSC47B397)+= smsc47b397.o
    diff --git a/drivers/hwmon/sht21.c b/drivers/hwmon/sht21.c
    new file mode 100644
    index 0000000..7d3ec82
    --- /dev/null
    +++ b/drivers/hwmon/sht21.c
    @@ -0,0 +1,392 @@
    +/* Sensirion SHT21 humidity and temperature sensor driver
    + *
    + * Copyright (C) 2010 Urs Fleisch <urs.fleisch@sensirion.com>
    + *
    + * This program is free software; you can redistribute it and/or modify
    + * it under the terms of the GNU General Public License as published by
    + * the Free Software Foundation; either version 2 of the License, or
    + * (at your option) any later version.
    + *
    + * This program is distributed in the hope that it will be useful,
    + * but WITHOUT ANY WARRANTY; without even the implied warranty of
    + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    + * GNU General Public License for more details.
    + *
    + * You should have received a copy of the GNU General Public License
    + * along with this program; if not, write to the Free Software
    + * Foundation, Inc., 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA
    + *
    + * Data sheet available (5/2010) at
    + * http://www.sensirion.com/en/pdf/product_information/Datasheet-humidity-sensor-SHT21.pdf
    + */
    +
    +#include <linux/module.h>
    +#include <linux/init.h>
    +#include <linux/slab.h>
    +#include <linux/i2c.h>
    +#include <linux/hwmon.h>
    +#include <linux/hwmon-sysfs.h>
    +#include <linux/err.h>
    +#include <linux/mutex.h>
    +#include <linux/device.h>
    +
    +/* I2C commands bytes */
    +enum sht21_command {
    + SHT21_TRIG_T_MEASUREMENT_HM = 0xe3,
    + SHT21_TRIG_RH_MEASUREMENT_HM = 0xe5,
    + SHT21_TRIG_T_MEASUREMENT_POLL = 0xf3,
    + SHT21_TRIG_RH_MEASUREMENT_POLL = 0xf5,
    + SHT21_USER_REG_W = 0xe6,
    + SHT21_USER_REG_R = 0xe7,
    + SHT21_SOFT_RESET = 0xfe
    +};
    +
    +/* User register bit masks */
    +enum sht21_userreg {
    + SHT21_RES_12_14BIT = 0x00,
    + SHT21_RES_8_12BIT = 0x01,
    + SHT21_RES_10_13BIT = 0x80,
    + SHT21_RES_11_11BIT = 0x81,
    + SHT21_RES_MASK = 0x81,
    + SHT21_END_OF_BATTERY = 0x40,
    + SHT21_ENABLE_HEATER = 0x04,
    + SHT21_WRITABLE_MASK = 0x87
    +};
    +
    +/* Types of measurements */
    +enum sht21_measurement_index {
    + SHT21_TEMPERATURE,
    + SHT21_HUMIDITY,
    + SHT21_NUM_MEASUREMENTS
    +};
    +
    +/**
    + * struct sht21 - SHT21 device specific data
    + * @hwmon_dev: device registered with hwmon
    + * @lock: mutex to ensure only one I2C transfer in progress at a time
    + * @userreg_orig: original value of user register
    + * @valid: !=0 if measurements are valid
    + * @last_update: time of last update (jiffies)
    + * @measurements: cached measurement values, temperature and humidity
    + */
    +struct sht21 {
    + struct device *hwmon_dev;
    + struct mutex lock;
    + u8 userreg_orig;
    + char valid;
    + unsigned long last_update;
    + int measurements[SHT21_NUM_MEASUREMENTS];
    +};
    +
    +/* I2C command to be used for a specifc measurement */
    +static u8 sht21_measurement_commands[SHT21_NUM_MEASUREMENTS] = {
    + SHT21_TRIG_T_MEASUREMENT_HM,
    + SHT21_TRIG_RH_MEASUREMENT_HM
    +};
    +
    +/**
    + * sht21_temp_ticks_to_millicelsius() - convert raw temperature ticks to
    + * milli celsius
    + * @ticks: temperature ticks value received from sensor
    + */
    +static int sht21_temp_ticks_to_millicelsius(int ticks)
    +{
    + ticks &= ~0x0003; /* clear status bits */
    + /* Formula T = -46.85 + 175.72 * ST / 2^16 from data sheet 6.2,
    + optimized for integer fixed point (3 digits) arithmetic */
    + return ((21965 * ticks) >> 13) - 46850;
    +}
    +
    +/**
    + * sht21_rh_ticks_to_per_cent_mille() - convert raw humidity ticks to
    + * one-thousandths of a percent relative humidity
    + * @ticks: humidity ticks value received from sensor
    + */
    +static int sht21_rh_ticks_to_per_cent_mille(int ticks)
    +{
    + ticks &= ~0x0003; /* clear status bits */
    + /* Formula RH = -6 + 125 * SRH / 2^16 from data sheet 6.1,
    + optimized for integer fixed point (3 digits) arithmetic */
    + return ((15625 * ticks) >> 13) - 6000;
    +}
    +
    +typedef int (*convert_func)(int);
    +
    +/* Conversion function to be used for a specifc measurement */
    +static convert_func sht21_convert_raw_value[SHT21_NUM_MEASUREMENTS] = {
    + sht21_temp_ticks_to_millicelsius,
    + sht21_rh_ticks_to_per_cent_mille
    +};
    +
    +/**
    + * sht21_update_measurements() - get updated measurements from device
    + * @client: I2C client device
    + *
    + * Returns SHT21 client data containing measurements.
    + */
    +static struct sht21 *sht21_update_measurements(struct i2c_client *client)
    +{
    + struct sht21 *sht21 = i2c_get_clientdata(client);
    +
    + mutex_lock(&sht21->lock);
    + /* Data sheet 2.4:
    + * SHT2x should not be active for more than 10% of the time - e.g. maximum
    + * two measurements per second at 12bit accuracy shall be made. */
    + if (time_after(jiffies, sht21->last_update + HZ / 2) || !sht21->valid) {
    + int meas_idx;
    + for (meas_idx = 0; meas_idx < SHT21_NUM_MEASUREMENTS; ++meas_idx) {
    + int result = i2c_smbus_read_word_data(client,
    + sht21_measurement_commands[meas_idx]);
    + /* SMBus specifies low byte first, but the SHT21 returns MSB first,
    + * so we have to swab16 the values */
    + if (result >= 0)
    + sht21->measurements[meas_idx] =
    + sht21_convert_raw_value[meas_idx](swab16(result));
    + }
    + sht21->last_update = jiffies;
    + sht21->valid = 1;
    + }
    + mutex_unlock(&sht21->lock);
    +
    + return sht21;
    +}
    +
    +/**
    + * sht21_show_measurement() - show measurement value in sysfs
    + * @dev: device
    + * @attr: device attribute
    + * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to
    + *
    + * Will be called on read access to a measurement sysfs attribute.
    + * Returns number of bytes written into buffer.
    + */
    +static ssize_t sht21_show_measurement(struct device *dev,
    + struct device_attribute *attr,
    + char *buf)
    +{
    + struct sensor_device_attribute *sda = to_sensor_dev_attr(attr);
    + struct sht21 *sht21 = sht21_update_measurements(to_i2c_client(dev));
    +
    + return sprintf(buf, "%d\n", sht21->measurements[sda->index]);
    +}
    +
    +/**
    + * sht21_show_userreg() - show user register value in sysfs
    + * @dev: device
    + * @attr: device attribute
    + * @buf: sysfs buffer (PAGE_SIZE) where user register value is written to
    + *
    + * Will be called on read access to user_register sysfs attribute.
    + * Returns number of bytes written into buffer, -EIO on error.
    + */
    +static ssize_t sht21_show_userreg(struct device *dev,
    + struct device_attribute *attr,
    + char *buf)
    +{
    + struct i2c_client *client = to_i2c_client(dev);
    + struct sht21 *sht21 = i2c_get_clientdata(client);
    + int result;
    + mutex_lock(&sht21->lock);
    + result = i2c_smbus_read_byte_data(client, SHT21_USER_REG_R);
    + mutex_unlock(&sht21->lock);
    +
    + return result >= 0 ? sprintf(buf, "%d\n", result) : -EIO;
    +}
    +
    +/**
    + * sht21_store_userreg() - store sysfs value in user register
    + * @dev: device
    + * @attr: device attribute
    + * @buf: sysfs buffer containing value as string
    + * @count: number of characters in @buf
    + *
    + * Will be called on write access to user_register sysfs attribute.
    + * Returns @count, -EIO on error.
    + */
    +static ssize_t sht21_store_userreg(struct device *dev, struct device_attribute *attr,
    + const char *buf, size_t count)
    +{
    + struct i2c_client *client = to_i2c_client(dev);
    + struct sht21 *sht21 = i2c_get_clientdata(client);
    + int result;
    + char *endptr;
    + unsigned long value = simple_strtoul(buf, &endptr, 0);
    + if (endptr == buf || value > 0xff)
    + return -EINVAL;
    +
    + mutex_lock(&sht21->lock);
    + result = i2c_smbus_read_byte_data(client, SHT21_USER_REG_R);
    + if (result >= 0)
    + result = i2c_smbus_write_byte_data(client, SHT21_USER_REG_W,
    + (result & ~SHT21_WRITABLE_MASK) | (value & SHT21_WRITABLE_MASK));
    + mutex_unlock(&sht21->lock);
    +
    + return result >= 0 ? count : -EIO;
    +}
    +
    +/* sysfs attributes */
    +static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, sht21_show_measurement,
    + NULL, SHT21_TEMPERATURE);
    +static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO, sht21_show_measurement,
    + NULL, SHT21_HUMIDITY);
    +static SENSOR_DEVICE_ATTR(user_register, S_IRUGO | S_IWUSR, sht21_show_userreg,
    + sht21_store_userreg, 0);
    +
    +static struct attribute *sht21_attributes[] = {
    + &sensor_dev_attr_temp1_input.dev_attr.attr,
    + &sensor_dev_attr_humidity1_input.dev_attr.attr,
    + &sensor_dev_attr_user_register.dev_attr.attr,
    + NULL
    +};
    +
    +static const struct attribute_group sht21_attr_group = {
    + .attrs = sht21_attributes,
    +};
    +
    +/**
    + * sht21_probe() - probe device
    + * @client: I2C client device
    + * @id: device ID
    + *
    + * Called by the I2C core when an entry in the ID table matches a
    + * device's name.
    + * Returns 0 on success.
    + */
    +static int __devinit sht21_probe(struct i2c_client *client,
    + const struct i2c_device_id *id)
    +{
    + struct sht21 *sht21;
    + int status;
    + u8 userreg_changed;
    +
    + if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA)) {
    + dev_err(&client->dev, "adapter does not support SMBus word transactions\n");
    + return -ENODEV;
    + }
    +
    + sht21 = kzalloc(sizeof(*sht21), GFP_KERNEL);
    + if (!sht21) {
    + dev_dbg(&client->dev, "kzalloc failed\n");
    + return -ENOMEM;
    + }
    + i2c_set_clientdata(client, sht21);
    +
    + status = i2c_smbus_read_byte_data(client, SHT21_USER_REG_R);
    + if (status < 0) {
    + dev_err(&client->dev, "error reading user register\n");
    + goto fail_free;
    + }
    + sht21->userreg_orig = status;
    +
    + userreg_changed = status ^ SHT21_RES_MASK;
    + status = i2c_smbus_write_byte_data(client, SHT21_USER_REG_W, userreg_changed);
    + if (status < 0) {
    + dev_err(&client->dev, "error writing user register\n");
    + goto fail_restore_config;
    + }
    + status = i2c_smbus_read_byte_data(client, SHT21_USER_REG_R);
    + if (status < 0) {
    + dev_err(&client->dev, "error reading user register\n");
    + goto fail_restore_config;
    + }
    + if (status != userreg_changed) {
    + dev_err(&client->dev, "user register settings did not stick\n");
    + status = -ENODEV;
    + goto fail_restore_config;
    + }
    + status = i2c_smbus_write_byte_data(client, SHT21_USER_REG_W, sht21->userreg_orig);
    + if (status < 0) {
    + dev_err(&client->dev, "error restoring user register\n");
    + goto fail_restore_config;
    + }
    + sht21->last_update = jiffies - HZ;
    + mutex_init(&sht21->lock);
    +
    + status = sysfs_create_group(&client->dev.kobj, &sht21_attr_group);
    + if (status) {
    + dev_dbg(&client->dev, "could not create sysfs files\n");
    + goto fail_restore_config;
    + }
    + sht21->hwmon_dev = hwmon_device_register(&client->dev);
    + if (IS_ERR(sht21->hwmon_dev)) {
    + dev_dbg(&client->dev, "unable to register hwmon device\n");
    + status = PTR_ERR(sht21->hwmon_dev);
    + goto fail_remove_sysfs;
    + }
    +
    + dev_info(&client->dev, "initialized\n");
    +
    + return 0;
    +
    +fail_remove_sysfs:
    + sysfs_remove_group(&client->dev.kobj, &sht21_attr_group);
    +fail_restore_config:
    + i2c_smbus_write_byte_data(client, SHT21_USER_REG_W, sht21->userreg_orig);
    +fail_free:
    + kfree(sht21);
    +
    + return status;
    +}
    +
    +/**
    + * sht21_remove() - remove device
    + * @client: I2C client device
    + */
    +static int __devexit sht21_remove(struct i2c_client *client)
    +{
    + struct sht21 *sht21 = i2c_get_clientdata(client);
    + int status;
    +
    + hwmon_device_unregister(sht21->hwmon_dev);
    + sysfs_remove_group(&client->dev.kobj, &sht21_attr_group);
    +
    + status = i2c_smbus_read_byte_data(client, SHT21_USER_REG_R);
    + if (status >= 0 && status != sht21->userreg_orig) {
    + i2c_smbus_write_byte_data(client, SHT21_USER_REG_W, sht21->userreg_orig);
    + }
    +
    + kfree(sht21);
    +
    + return 0;
    +}
    +
    +/* Device ID table */
    +static const struct i2c_device_id sht21_id[] = {
    + { "sht21", 0 },
    + { }
    +};
    +MODULE_DEVICE_TABLE(i2c, sht21_id);
    +
    +static struct i2c_driver sht21_driver = {
    + .driver.name = "sht21",
    + .probe = sht21_probe,
    + .remove = __devexit_p(sht21_remove),
    + .id_table = sht21_id,
    +};
    +
    +/**
    + * sht21_init() - initialize driver
    + *
    + * Called when kernel is booted or module is inserted.
    + * Returns 0 on success.
    + */
    +static int __init sht21_init(void)
    +{
    + return i2c_add_driver(&sht21_driver);
    +}
    +module_init(sht21_init);
    +
    +/**
    + * sht21_init() - clean up driver
    + *
    + * Called when module is removed.
    + */
    +static void __exit sht21_exit(void)
    +{
    + i2c_del_driver(&sht21_driver);
    +}
    +module_exit(sht21_exit);
    +
    +MODULE_AUTHOR("Urs Fleisch <urs.fleisch@sensirion.com>");
    +MODULE_DESCRIPTION("Sensirion SHT21 humidity and temperature sensor driver");
    +MODULE_LICENSE("GPL");

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