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Date:	Thu, 18 Sep 2014 19:43:23 +0200 (CEST)
From:	Peter Meerwald <pmeerw@...erw.net>
To:	David Barksdale <dbarksdale@...ogix.com>
cc:	Jonathan Cameron <jic23@...nel.org>, linux-kernel@...r.kernel.org,
	linux-iio@...r.kernel.org
Subject: Re: [PATCH] IIO: add si701x driver


> This patch adds support to the Industrial IO subsystem
> for the Silicon Labs Si701x/2x Relative Humidity and
> Temperature Sensors.

the name si701x is problematic; the si7015 for example is supported by 
the si7005 driver

how about calling the driver si7020 and stating that it also supports 
si7013, si7021 -- the x notation in driver names always leads to touble...

the additional features of the si7013 are not supported by the driver
 
> 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@...ogix.com>
> 
> ---
>  drivers/iio/humidity/Kconfig  |  10 +++
>  drivers/iio/humidity/Makefile |   1 +
>  drivers/iio/humidity/si701x.c | 159 ++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 170 insertions(+)
> 
> diff --git a/drivers/iio/humidity/Kconfig b/drivers/iio/humidity/Kconfig
> index e116bd8..ba0ef61 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 SI701X
> +	tristate "Si701x/2x Relative Humidity and Temperature Sensors"
> +	depends on I2C
> +	help
> +	  Say yes here to build support for the Silicon Labs Si701x/2x Relative
> +	  Humidity and Temperature Sensors.
> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called si701x.
> +
>  endmenu
> diff --git a/drivers/iio/humidity/Makefile b/drivers/iio/humidity/Makefile
> index e3f3d94..d2e9645 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_SI701X) += si701x.o
> diff --git a/drivers/iio/humidity/si701x.c b/drivers/iio/humidity/si701x.c
> new file mode 100644
> index 0000000..1a2ee22
> --- /dev/null
> +++ b/drivers/iio/humidity/si701x.c
> @@ -0,0 +1,159 @@
> +/*
> + * si701x.c - Silicon Labs Si701x/2x Relative Humidity and Temperature Sensors
> + * Copyright (c) 2013,2014  Uplogix, Inc.
> + * David Barksdale <dbarksdale@...ogix.com>
> + *
> + * 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 Si701x/2x 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/i2c.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/sysfs.h>
> +
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +
> +enum {
> +	/* Measure Relative Humidity, Hold Master Mode */
> +	SI701XCMD_RH_HOLD	= 0xE5,
> +	/* Measure Temperature, Hold Master Mode */
> +	SI701XCMD_TEMP_HOLD	= 0xE3,
> +};
> +
> +struct si701x_data {
> +	struct i2c_client *client;
> +	struct mutex lock;
> +};
> +
> +static int si701x_read_raw(struct iio_dev *indio_dev,
> +			   struct iio_chan_spec const *chan, int *val,
> +			   int *val2, long mask)
> +{
> +	struct si701x_data *data = iio_priv(indio_dev);
> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		mutex_lock(&data->lock);

is the locking needed? what is protected?

> +		ret = i2c_smbus_read_word_data(data->client,
> +					       chan->type == IIO_TEMP ?
> +					       SI701XCMD_TEMP_HOLD :
> +					       SI701XCMD_RH_HOLD);
> +		mutex_unlock(&data->lock);
> +		if (ret < 0)
> +			return ret;
> +		*val = ret;
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_SCALE:
> +		if (chan->type == IIO_TEMP) {
> +			*val = 175.72 * 1000;

floating-point constants in kernel space makes me nervous

> +			*val2 = 65536;

could set val2 once after the if

> +		} else {
> +			*val = 125 * 1000;
> +			*val2 = 65536;
> +		}
> +		return IIO_VAL_FRACTIONAL;
> +	case IIO_CHAN_INFO_OFFSET:
> +		if (chan->type == IIO_TEMP)
> +			*val = -46.85 * 65536 / 175.72;
> +		else
> +			*val = -6 * 65536 / 125;
> +		return IIO_VAL_INT;
> +	default:
> +		break;
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static const struct iio_chan_spec si701x_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 si701x_info = {
> +	.read_raw = si701x_read_raw,
> +	.driver_module = THIS_MODULE,
> +};
> +
> +static int si701x_probe(struct i2c_client *client,
> +			const struct i2c_device_id *id)
> +{
> +	struct iio_dev *dev;
> +	struct si701x_data *data;
> +
> +	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA))
> +		return -ENODEV;
> +
> +	dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
> +	if (!dev)
> +		return -ENOMEM;
> +
> +	data = iio_priv(dev);
> +	i2c_set_clientdata(client, dev);
> +	data->client = client;
> +	mutex_init(&data->lock);
> +
> +	dev->dev.parent = &client->dev;
> +	dev->name = dev_name(&client->dev);
> +	dev->modes = INDIO_DIRECT_MODE;
> +	dev->info = &si701x_info;
> +	dev->channels = si701x_channels;
> +	dev->num_channels = ARRAY_SIZE(si701x_channels);
> +
> +	return devm_iio_device_register(&client->dev, dev);
> +}
> +
> +static const unsigned short si701x_address_list[] = {
> +	0x40,

the alternate address is 0x41

> +	I2C_CLIENT_END
> +};
> +
> +static const struct i2c_device_id si701x_id[] = {
> +	{ "si701x", 0 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, si701x_id);
> +
> +static struct i2c_driver si701x_driver = {
> +	.class		= I2C_CLASS_HWMON,
> +	.driver.name	= "si701x",
> +	.probe		= si701x_probe,
> +	.address_list	= si701x_address_list,
> +	.id_table	= si701x_id,

address_list and I2C_CLASS_HWMON -- what for?

if doing auto-probing, I'd check the chip's ID

> +};
> +
> +module_i2c_driver(si701x_driver);
> +MODULE_DESCRIPTION("Silicon Labs Si701x/2x "
> +		   "Relative Humidity and Temperature Sensors");
> +MODULE_AUTHOR("David Barksdale <dbarksdale@...ogix.com>");
> +MODULE_LICENSE("GPL");
> +
> 

-- 

Peter Meerwald
+43-664-2444418 (mobile)
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