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    SubjectRe: [PATCH V4] hwmon: driver for Sensirion SHT21 humidity and temperature sensor
    On 01/06/11 07:43, Urs Fleisch wrote:
    > Thanks for the review, Jonathan and Guenter.
    >
    > Changes:
    > - removed user register related sysfs attributes, keeping only temp1_input and
    > humidity1_input
    > - cleaned up code flow when returning errors for better readability
    Short and clean. I do wonder if you want some of those users register
    bits available via platform data though. Perhaps that can be added in
    a later patch as and when someone needs them.
    >
    > Regards,
    > Urs
    >
    > Signed-off-by: Urs Fleisch <urs.fleisch@sensirion.com>
    Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
    > ---
    > 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 +1,300 @@
    > +/* 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 command bytes */
    > +#define SHT21_TRIG_T_MEASUREMENT_HM 0xe3
    > +#define SHT21_TRIG_RH_MEASUREMENT_HM 0xe5
    > +
    > +/**
    > + * struct sht21 - SHT21 device specific data
    > + * @hwmon_dev: device registered with hwmon
    > + * @lock: mutex to protect measurement values
    > + * @valid: only 0 before first measurement is taken
    > + * @last_update: time of last update (jiffies)
    > + * @temperature: cached temperature measurement value
    > + * @humidity: cached humidity measurement value
    > + */
    > +struct sht21 {
    > + struct device *hwmon_dev;
    > + struct mutex lock;
    > + char valid;
    > + unsigned long last_update;
    > + int temperature;
    > + int humidity;
    > +};
    > +
    > +/**
    > + * sht21_temp_ticks_to_millicelsius() - convert raw temperature ticks to
    > + * milli celsius
    > + * @ticks: temperature ticks value received from sensor
    > + */
    > +static inline 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 inline 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;
    > +}
    > +
    > +/**
    > + * sht21_read_word_data() - read word from register
    > + * @client: I2C client device
    > + * @reg: I2C command byte
    > + *
    > + * Returns value, negative errno on error.
    > + */
    > +static inline int sht21_read_word_data(struct i2c_client *client, u8 reg)
    > +{
    > + int ret = i2c_smbus_read_word_data(client, reg);
    > + if (ret < 0)
    > + return ret;
    > + /* SMBus specifies low byte first, but the SHT21 returns MSB
    > + * first, so we have to swab16 the values */
    > + return swab16(ret);
    > +}
    > +
    > +/**
    > + * sht21_update_measurements() - get updated measurements from device
    > + * @client: I2C client device
    > + *
    > + * Returns 0 on success, else negative errno.
    > + */
    > +static int sht21_update_measurements(struct i2c_client *client)
    > +{
    > + int ret = 0;
    > + 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) {
    > + ret = sht21_read_word_data(client, SHT21_TRIG_T_MEASUREMENT_HM);
    > + if (ret < 0)
    > + goto out;
    > + sht21->temperature = sht21_temp_ticks_to_millicelsius(ret);
    > + ret = sht21_read_word_data(client,
    > + SHT21_TRIG_RH_MEASUREMENT_HM);
    > + if (ret < 0)
    > + goto out;
    > + sht21->humidity = sht21_rh_ticks_to_per_cent_mille(ret);
    > + sht21->last_update = jiffies;
    > + sht21->valid = 1;
    > + }
    > +out:
    > + mutex_unlock(&sht21->lock);
    > +
    > + return ret >= 0 ? 0 : ret;
    > +}
    > +
    > +/**
    > + * sht21_show_temperature() - show temperature 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 temp1_input sysfs attribute.
    > + * Returns number of bytes written into buffer, negative errno on error.
    > + */
    > +static ssize_t sht21_show_temperature(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 ret = sht21_update_measurements(client);
    > + if (ret < 0)
    > + return ret;
    > + return sprintf(buf, "%d\n", sht21->temperature);
    > +}
    > +
    > +/**
    > + * sht21_show_humidity() - show humidity 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 humidity1_input sysfs attribute.
    > + * Returns number of bytes written into buffer, negative errno on error.
    > + */
    > +static ssize_t sht21_show_humidity(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 ret = sht21_update_measurements(client);
    > + if (ret < 0)
    > + return ret;
    > + return sprintf(buf, "%d\n", sht21->humidity);
    > +}
    > +
    > +/* sysfs attributes */
    > +static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, sht21_show_temperature,
    > + NULL, 0);
    > +static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO, sht21_show_humidity,
    > + NULL, 0);
    > +
    > +static struct attribute *sht21_attributes[] = {
    > + &sensor_dev_attr_temp1_input.dev_attr.attr,
    > + &sensor_dev_attr_humidity1_input.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 err;
    > +
    > + 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);
    > +
    > + mutex_init(&sht21->lock);
    > +
    > + err = sysfs_create_group(&client->dev.kobj, &sht21_attr_group);
    > + if (err) {
    > + dev_dbg(&client->dev, "could not create sysfs files\n");
    > + goto fail_free;
    > + }
    > + sht21->hwmon_dev = hwmon_device_register(&client->dev);
    > + if (IS_ERR(sht21->hwmon_dev)) {
    > + dev_dbg(&client->dev, "unable to register hwmon device\n");
    > + err = 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_free:
    > + kfree(sht21);
    > +
    > + return err;
    > +}
    > +
    > +/**
    > + * sht21_remove() - remove device
    > + * @client: I2C client device
    > + */
    > +static int __devexit sht21_remove(struct i2c_client *client)
    > +{
    > + struct sht21 *sht21 = i2c_get_clientdata(client);
    > +
    > + hwmon_device_unregister(sht21->hwmon_dev);
    > + sysfs_remove_group(&client->dev.kobj, &sht21_attr_group);
    > + 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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