Re: [PATCH v3] iio: humidity: add HDC100x support

[Jonathan Cameron <jic23@kernel.org>]

On 02/09/15 04:58, Matt Ranostay wrote:
> Add support for the HDC100x temperature and humidity sensors
> including the resistive heater element.
> 
> Signed-off-by: Matt Ranostay <mranostay@gmail.com>
Just a couple of corners of program flow that I think could be cleaned
up slightly (I'd have probably let it go as is, but we are very early
in the cycle, so might as well aim for perfection!)

Jonathan
> ---
>  .../ABI/testing/sysfs-bus-iio-humidity-hdc100x     |   9 +
>  drivers/iio/humidity/Kconfig                       |  10 +
>  drivers/iio/humidity/Makefile                      |   1 +
>  drivers/iio/humidity/hdc100x.c                     | 317 +++++++++++++++++++++
>  4 files changed, 337 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-humidity-hdc100x
>  create mode 100644 drivers/iio/humidity/hdc100x.c
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-iio-humidity-hdc100x b/Documentation/ABI/testing/sysfs-bus-iio-humidity-hdc100x
> new file mode 100644
> index 0000000..b72bb62
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-bus-iio-humidity-hdc100x
> @@ -0,0 +1,9 @@
> +What:		/sys/bus/iio/devices/iio:deviceX/out_current_heater_raw
> +What:		/sys/bus/iio/devices/iio:deviceX/out_current_heater_raw_available
> +KernelVersion:	4.3
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Controls the heater device within the humidity sensor to get
> +		rid of excess condensation.
> +
> +		Valid control values are 0 = OFF, and 1 = ON.
> diff --git a/drivers/iio/humidity/Kconfig b/drivers/iio/humidity/Kconfig
> index 688c0d1..353ee9a 100644
> --- a/drivers/iio/humidity/Kconfig
> +++ b/drivers/iio/humidity/Kconfig
> @@ -12,6 +12,16 @@ config DHT11
>  	  Other sensors should work as well as long as they speak the
>  	  same protocol.
>  
> +config HDC100X
> +	tristate "TI HDC100x relative humidity and temperature sensor"
> +	depends on I2C
> +	help
> +	 Say yes here to build support for the TI HDC100x series of
> +	 relative humidity and temperature sensors.
> +
> +	 To compile this driver as a module, choose M here: the module
> +	 will be called hdc100x.
> +
>  config SI7005
>  	tristate "SI7005 relative humidity and temperature sensor"
>  	depends on I2C
> diff --git a/drivers/iio/humidity/Makefile b/drivers/iio/humidity/Makefile
> index 86e2d26..3e62c0a 100644
> --- a/drivers/iio/humidity/Makefile
> +++ b/drivers/iio/humidity/Makefile
> @@ -3,5 +3,6 @@
>  #
>  
>  obj-$(CONFIG_DHT11) += dht11.o
> +obj-$(CONFIG_HDC100X) += hdc100x.o
>  obj-$(CONFIG_SI7005) += si7005.o
>  obj-$(CONFIG_SI7020) += si7020.o
> diff --git a/drivers/iio/humidity/hdc100x.c b/drivers/iio/humidity/hdc100x.c
> new file mode 100644
> index 0000000..591bd92
> --- /dev/null
> +++ b/drivers/iio/humidity/hdc100x.c
> @@ -0,0 +1,317 @@
> +/*
> + * hdc100x.c - Support for the TI HDC100x temperature + humidity sensors
> + *
> + * Copyright (C) 2015 Matt Ranostay <mranostay@gmail.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.
> + *
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/i2c.h>
> +
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +
> +#define HDC100X_REG_TEMP			0x00
> +#define HDC100X_REG_HUMIDITY			0x01
> +
> +#define HDC100X_REG_CONFIG			0x02
> +#define HDC100X_REG_CONFIG_HEATER_EN		BIT(13)
> +
> +struct hdc100x_data {
> +	struct i2c_client *client;
> +	struct mutex lock;
> +	u16 config;
> +
> +	/* integration time of the sensor */
> +	int adc_int_us[2];
> +};
> +
> +/* integration time in us */
> +static const int hdc100x_int_time[][3] = {
> +	{ 6350, 3650, 0 },	/* IIO_TEMP channel*/
> +	{ 6500, 3850, 2500 },	/* IIO_HUMIDITYRELATIVE channel */
> +};
> +
> +/* HDC100X_REG_CONFIG shift and mask values */
> +static const struct {
> +	int shift;
> +	int mask;
> +} hdc100x_resolution_shift[2] = {
> +	{ /* IIO_TEMP channel */
> +		.shift = 10,
> +		.mask = 1
> +	},
> +	{ /* IIO_HUMIDITYRELATIVE channel */
> +		.shift = 8,
> +		.mask = 2,
> +	},
> +};
> +
> +static IIO_CONST_ATTR(temp_integration_time_available,
> +		"0.00365 0.00635");
> +
> +static IIO_CONST_ATTR(humidityrelative_integration_time_available,
> +		"0.0025 0.00385 0.0065");
> +
> +static IIO_CONST_ATTR(out_current_heater_raw_available,
> +		"0 1");
> +
> +static struct attribute *hdc100x_attributes[] = {
> +	&iio_const_attr_temp_integration_time_available.dev_attr.attr,
> +	&iio_const_attr_humidityrelative_integration_time_available.dev_attr.attr,
> +	&iio_const_attr_out_current_heater_raw_available.dev_attr.attr,
> +	NULL
> +};
> +
> +static struct attribute_group hdc100x_attribute_group = {
> +	.attrs = hdc100x_attributes,
> +};
> +
> +static const struct iio_chan_spec hdc100x_channels[] = {
> +	{
> +		.type = IIO_TEMP,
> +		.address = HDC100X_REG_TEMP,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
> +			BIT(IIO_CHAN_INFO_SCALE) |
> +			BIT(IIO_CHAN_INFO_INT_TIME) |
> +			BIT(IIO_CHAN_INFO_OFFSET),
> +	},
> +	{
> +		.type = IIO_HUMIDITYRELATIVE,
> +		.address = HDC100X_REG_HUMIDITY,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
> +			BIT(IIO_CHAN_INFO_SCALE) |
> +			BIT(IIO_CHAN_INFO_INT_TIME)
> +	},
> +	{
> +		.type = IIO_CURRENT,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
> +		.extend_name = "heater",
> +		.output = 1,
> +	},
> +};
> +
> +static int hdc100x_update_config(struct hdc100x_data *data, int mask, int val)
> +{
> +	int tmp = (~mask & data->config) | val;
> +	int ret;
> +
> +	ret = i2c_smbus_write_word_swapped(data->client,
> +						HDC100X_REG_CONFIG, tmp);
> +	if (!ret)
> +		data->config = tmp;
> +
> +	return ret;
> +}
> +
> +static int hdc100x_set_it_time(struct hdc100x_data *data, int chan, int val2)
> +{
> +	int shift = hdc100x_resolution_shift[chan].shift;
> +	int ret = -EINVAL;
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(hdc100x_int_time[chan]); i++) {
> +		if (val2 && val2 == hdc100x_int_time[chan][i]) {
> +			ret = hdc100x_update_config(data,
> +				hdc100x_resolution_shift[chan].mask << shift,
> +				i << shift);
> +			if (!ret)
> +				data->adc_int_us[chan] = val2;
> +			break;
> +		}
> +	}
> +
> +	return ret;
> +}
> +
> +static int hdc100x_get_measurement(struct hdc100x_data *data,
> +				   struct iio_chan_spec const *chan)
> +{
> +	struct i2c_client *client = data->client;
> +	int delay = data->adc_int_us[chan->address];
> +	int ret;
> +	int val;
> +
> +	/* start measurement */
> +	ret = i2c_smbus_write_byte(client, chan->address);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "cannot start measurement");
> +		return ret;
> +	}
> +
> +	/* wait for integration time to pass */
> +	usleep_range(delay, delay + 1000);
> +
> +	ret = i2c_smbus_read_byte(client);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "cannot read high byte measurement");
> +		return ret;
> +	}
> +	val = ret << 6;
> +
> +	ret = i2c_smbus_read_byte(client);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "cannot read low byte measurement");
> +		return ret;
> +	}
> +	val |= ret >> 2;
If you can't use a read word here I'd like docs to say why (presumably
starts / stops are wrong for what the device expects?)
> +
> +	return val;
> +}
> +
> +static int hdc100x_get_heater_status(struct hdc100x_data *data)
> +{
> +	return !!(data->config & HDC100X_REG_CONFIG_HEATER_EN);
> +}
> +
> +static int hdc100x_read_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan, int *val,
> +			    int *val2, long mask)
> +{
> +	struct hdc100x_data *data = iio_priv(indio_dev);
> +	int ret = -EINVAL;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		mutex_lock(&data->lock);
> +		if (chan->type == IIO_CURRENT) {
> +			*val = hdc100x_get_heater_status(data);
> +			ret = IIO_VAL_INT;
> +		} else {
> +			ret = hdc100x_get_measurement(data, chan);
> +			if (ret >= 0) {
> +				*val = ret;
> +				ret = IIO_VAL_INT;
> +			}
> +		}
> +		mutex_unlock(&data->lock);r
I'd return ret here to have consistency across different parts of
this function.

> +		break;
> +	case IIO_CHAN_INFO_INT_TIME:
> +		*val = 0;
> +		*val2 = data->adc_int_us[chan->address];
> +		return IIO_VAL_INT_PLUS_MICRO;
> +	case IIO_CHAN_INFO_SCALE:
> +		if (chan->type == IIO_TEMP) {
> +			*val = 165;
> +			*val2 = 65536 >> 2;
return directly in both these cases.
> +			ret = IIO_VAL_FRACTIONAL;
> +		} else {
> +			*val = 0;
> +			*val2 = 10000;
> +			ret = IIO_VAL_INT_PLUS_MICRO;
> +		}
> +		break;
> +	case IIO_CHAN_INFO_OFFSET:
> +		*val = -40;
> +		return IIO_VAL_INT;
> +	default:
return -EINVAL; and you can loose the outer parts of this function.
> +		break;
> +	}
> +
> +	return ret;
> +}
> +
> +static int hdc100x_write_raw(struct iio_dev *indio_dev,
> +			     struct iio_chan_spec const *chan,
> +			     int val, int val2, long mask)
> +{
> +	struct hdc100x_data *data = iio_priv(indio_dev);
> +	int ret = -EINVAL;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_INT_TIME:
> +		if (val != 0)
> +			return -EINVAL;
> +
> +		mutex_lock(&data->lock);
> +		ret = hdc100x_set_it_time(data, chan->address, val2);
> +		mutex_unlock(&data->lock);
> +		break;
> +	case IIO_CHAN_INFO_RAW:
> +		if (chan->type == IIO_CURRENT) {
> +			if (val2 != 0)
> +				return -EINVAL;
> +
> +			mutex_lock(&data->lock);
> +			ret = hdc100x_update_config(data,
> +					HDC100X_REG_CONFIG_HEATER_EN,
> +					val ? HDC100X_REG_CONFIG_HEATER_EN : 0);
> +			mutex_unlock(&data->lock);
> +		}
This return ret is different from the other case for no particular
reason.  If it makes sense to return here, it makes sense there
as well.

I think I'd martinally prefer if you inverted the logic to
check if the channel isn't IIO_CURRENT and return -EINVAL directly
if it isn't.  Drops a level of indentation.  You could the use a default:
statement returning -EINVAL to drop the return below and seeing of a
default value for ret above.  Makes for slightly longer but
simpler code.

> +		return ret;
> +	}
> +
> +	return ret;
> +}
> +
> +static const struct iio_info hdc100x_info = {
> +	.read_raw = hdc100x_read_raw,
> +	.write_raw = hdc100x_write_raw,
> +	.attrs = &hdc100x_attribute_group,
> +	.driver_module = THIS_MODULE,
> +};
> +
> +static int hdc100x_probe(struct i2c_client *client,
> +			 const struct i2c_device_id *id)
> +{
> +	struct iio_dev *indio_dev;
> +	struct hdc100x_data *data;
> +
> +	if (!i2c_check_functionality(client->adapter,
> +				I2C_FUNC_SMBUS_WORD_DATA | I2C_FUNC_SMBUS_BYTE))
> +		return -ENODEV;
> +
> +	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	data = iio_priv(indio_dev);
> +	i2c_set_clientdata(client, indio_dev);
> +	data->client = client;
> +	mutex_init(&data->lock);
> +
> +	indio_dev->dev.parent = &client->dev;
> +	indio_dev->name = dev_name(&client->dev);
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->info = &hdc100x_info;
> +
> +	indio_dev->channels = hdc100x_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(hdc100x_channels);
> +
> +	/* be sure we are in a known state */
> +	hdc100x_set_it_time(data, 0, hdc100x_int_time[0][0]);
> +	hdc100x_set_it_time(data, 1, hdc100x_int_time[1][0]);
> +
> +	return devm_iio_device_register(&client->dev, indio_dev);
> +}
> +
> +static const struct i2c_device_id hdc100x_id[] = {
> +	{ "hdc100x", 0 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, hdc100x_id);
> +
> +static struct i2c_driver hdc100x_driver = {
> +	.driver = {
> +		.name	= "hdc100x",
> +	},
> +	.probe = hdc100x_probe,
> +	.id_table = hdc100x_id,
> +};
> +module_i2c_driver(hdc100x_driver);
> +
> +MODULE_AUTHOR("Matt Ranostay <mranostay@gmail.com>");
> +MODULE_DESCRIPTION("TI HDC100x humidity and temperature sensor driver");
> +MODULE_LICENSE("GPL");
>