Re: [PATCH v3] IIO: add si7020 driver

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On Wed, Sep 24, 2014 at 6:02 PM, David Barksdale <dbarksdale@xxxxxxxxxxx> 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>
>
> --
> 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.
>
> ---
>  drivers/iio/humidity/Kconfig  |  10 +++
>  drivers/iio/humidity/Makefile |   1 +
>  drivers/iio/humidity/si7020.c | 165 ++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 176 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..4aacb55
> --- /dev/null
> +++ b/drivers/iio/humidity/si7020.c
> @@ -0,0 +1,165 @@
> +/*
> + * 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>
> +
> +enum {
> +       /* Measure Relative Humidity, Hold Master Mode */
> +       SI7020CMD_RH_HOLD       = 0xE5,
> +       /* Measure Temperature, Hold Master Mode */
> +       SI7020CMD_TEMP_HOLD     = 0xE3,
> +       /* Software Reset */
> +       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);

Nit: checkpatch.pl says:

WARNING: msleep < 20ms can sleep for up to 20ms; see
Documentation/timers/timers-howto.txt
#155: FILE: drivers/iio/humidity/si7020.c:129:
+ msleep(15);

Sorry for spotting this so late in the review. I don't now if this is
a real problem.

thanks,
Daniel.
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