Re: [PATCH v3] IIO: add si7020 driver

[David Barksdale <dbarksdale@uplogix.com>]

On 09/24/2014 10:15 AM, Daniel Baluta wrote:
> On Wed, Sep 24, 2014 at 6:02 PM, David Barksdale <dbarksdale@uplogix.com> 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@uplogix.com>
>>
>> --
>> 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@uplogix.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 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.
>

I just added it a few minutes ago so you spotted it pretty quickly! It's 
not a problem because we should sleep for at least 15 ms.