Re: [PATCH v4] IIO: add si7020 driver

[Jonathan Cameron]

On 29/09/14 19:28, David Barksdale wrote:
> This patch adds support to the Industrial IO subsystem
> for the Silicon Labs Si7013/20/21 Relative Humidity and
> Temperature Sensors.
>
> Website: http://www.silabs.com/products/sensors/humidity-sensors/Pages/si7013-20-21.aspx
>
> These are i2c devices which measure relative humidity
> and temperature and all use the same protocol. The
> Si7013 has an additional input with programmable
> linearization which is not supported because that's
> complicated and I didn't need it.
>
> Signed-off-by: David Barksdale <dbarksdale@xxxxxxxxxxx>
Applied with some trivial whitespace and comment formatting fixups.
Applied to the togreg branch of iio.git - initially pushed out as
testing for the autobuilders to play with it.

Thanks,

Jonathan
>
> --
> Changes since v1:
> * Renamed to si7020 and replaced Si701x/2x with Si7013/20/21.
> * Removed unneeded mutex.
> * Pre-computed floating-point constant expressions.
> * Removed address_list and I2C_CLASS_HWMON.
>
> Changes since v2:
> * Return correct raw sensor values.
> * Rename dev variable to indio_dev.
> * Issue a software reset command during probe.
> * Un-broke string literal.
>
> Changes since v3:
> * enum changed to #define
>
> ---
>  drivers/iio/humidity/Kconfig  |  10 +++
>  drivers/iio/humidity/Makefile |   1 +
>  drivers/iio/humidity/si7020.c | 163 ++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 174 insertions(+)
>
> diff --git a/drivers/iio/humidity/Kconfig b/drivers/iio/humidity/Kconfig
> index e116bd8..4813b79 100644
> --- a/drivers/iio/humidity/Kconfig
> +++ b/drivers/iio/humidity/Kconfig
> @@ -22,4 +22,14 @@ config SI7005
>  	  To compile this driver as a module, choose M here: the module
>  	  will be called si7005.
>
> +config SI7020
> +	tristate "Si7013/20/21 Relative Humidity and Temperature Sensors"
> +	depends on I2C
> +	help
> +	  Say yes here to build support for the Silicon Labs Si7013/20/21
> +	  Relative Humidity and Temperature Sensors.
> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called si7020.
> +
>  endmenu
> diff --git a/drivers/iio/humidity/Makefile b/drivers/iio/humidity/Makefile
> index e3f3d94..86e2d26 100644
> --- a/drivers/iio/humidity/Makefile
> +++ b/drivers/iio/humidity/Makefile
> @@ -4,3 +4,4 @@
>
>  obj-$(CONFIG_DHT11) += dht11.o
>  obj-$(CONFIG_SI7005) += si7005.o
> +obj-$(CONFIG_SI7020) += si7020.o
> diff --git a/drivers/iio/humidity/si7020.c b/drivers/iio/humidity/si7020.c
> new file mode 100644
> index 0000000..db60ab7
> --- /dev/null
> +++ b/drivers/iio/humidity/si7020.c
> @@ -0,0 +1,163 @@
> +/*
> + * si7020.c - Silicon Labs Si7013/20/21 Relative Humidity and Temp Sensors
> + * Copyright (c) 2013,2014  Uplogix, Inc.
> + * David Barksdale <dbarksdale@xxxxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * 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.
> + */
> +
> +/*
> + * The Silicon Labs Si7013/20/21 Relative Humidity and Temperature Sensors
> + * are i2c devices which have an identical programming interface for
> + * measuring relative humidity and temperature. The Si7013 has an additional
> + * temperature input which this driver does not support.
> + *
> + * Data Sheets:
> + *   Si7013: http://www.silabs.com/Support%20Documents/TechnicalDocs/Si7013.pdf
> + *   Si7020: http://www.silabs.com/Support%20Documents/TechnicalDocs/Si7020.pdf
> + *   Si7021: http://www.silabs.com/Support%20Documents/TechnicalDocs/Si7021.pdf
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/i2c.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/sysfs.h>
> +
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +
> +/* Measure Relative Humidity, Hold Master Mode */
> +#define SI7020CMD_RH_HOLD	0xE5
> +/* Measure Temperature, Hold Master Mode */
> +#define SI7020CMD_TEMP_HOLD	0xE3
> +/* Software Reset */
> +#define SI7020CMD_RESET		0xFE
> +
> +static int si7020_read_raw(struct iio_dev *indio_dev,
> +			   struct iio_chan_spec const *chan, int *val,
> +			   int *val2, long mask)
> +{
> +	struct i2c_client **client = iio_priv(indio_dev);
> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		ret = i2c_smbus_read_word_data(*client,
> +					       chan->type == IIO_TEMP ?
> +					       SI7020CMD_TEMP_HOLD :
> +					       SI7020CMD_RH_HOLD);
> +		if (ret < 0)
> +			return ret;
> +		if (chan->type == IIO_TEMP)
> +			*val = ret >> 2;
> +		else
> +			*val = (ret & 0x3FFF) >> 2;
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_SCALE:
> +		if (chan->type == IIO_TEMP)
> +			*val = 175720; /* = 175.72 * 1000 */
> +		else
> +			*val = 125 * 1000;
> +		*val2 = 65536 >> 2;
> +		return IIO_VAL_FRACTIONAL;
> +	case IIO_CHAN_INFO_OFFSET:
> +		/* Since iio_convert_raw_to_processed_unlocked assumes offset
> +		 * is an integer we have to round these values and lose
> +		 * accuracy.
> +		 * Relative humidity will be 0.0032959% too high and
> +		 * temperature will be 0.00277344 degrees too high.
> +		 * This is no big deal because it's within the accuracy of the
> +		 * sensor.
> +		 */
> +		if (chan->type == IIO_TEMP)
> +			*val = -4368; /* = -46.85 * (65536 >> 2) / 175.72 */
> +		else
> +			*val = -786; /* = -6 * (65536 >> 2) / 125 */
> +		return IIO_VAL_INT;
> +	default:
> +		break;
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static const struct iio_chan_spec si7020_channels[] = {
> +	{
> +		.type = IIO_HUMIDITYRELATIVE,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
> +			BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET),
> +	},
> +	{
> +		.type = IIO_TEMP,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
> +			BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET),
> +	}
> +};
> +
> +static const struct iio_info si7020_info = {
> +	.read_raw = si7020_read_raw,
> +	.driver_module = THIS_MODULE,
> +};
> +
> +static int si7020_probe(struct i2c_client *client,
> +			const struct i2c_device_id *id)
> +{
> +	struct iio_dev *indio_dev;
> +	struct i2c_client **data;
> +	int ret;
> +
> +	if (!i2c_check_functionality(client->adapter,
> +				     I2C_FUNC_SMBUS_WRITE_BYTE |
> +				     I2C_FUNC_SMBUS_READ_WORD_DATA))
> +		return -ENODEV;
> +
> +	/* Reset device, loads default settings. */
> +	ret = i2c_smbus_write_byte(client, SI7020CMD_RESET);
> +	if (ret < 0)
> +		return ret;
> +	/* Wait the maximum power-up time after software reset. */
> +	msleep(15);
> +
> +	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*client));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	data = iio_priv(indio_dev);
> +	*data = client;
> +	i2c_set_clientdata(client, indio_dev);
> +
> +	indio_dev->dev.parent = &client->dev;
> +	indio_dev->name = dev_name(&client->dev);
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->info = &si7020_info;
> +	indio_dev->channels = si7020_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(si7020_channels);
> +
> +	return devm_iio_device_register(&client->dev, indio_dev);
> +}
> +
> +static const struct i2c_device_id si7020_id[] = {
> +	{ "si7020", 0 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, si7020_id);
> +
> +static struct i2c_driver si7020_driver = {
> +	.driver.name	= "si7020",
> +	.probe		= si7020_probe,
> +	.id_table	= si7020_id,
> +};
> +
> +module_i2c_driver(si7020_driver);
> +MODULE_DESCRIPTION("Silicon Labs Si7013/20/21 Relative Humidity and Temperature Sensors");
> +MODULE_AUTHOR("David Barksdale <dbarksdale@xxxxxxxxxxx>");
> +MODULE_LICENSE("GPL");
> +
>
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