Messages in this thread | | | Date | Mon, 22 Sep 2014 10:40:09 -0500 | From | David Barksdale <> | Subject | Re: [PATCH v2] IIO: add si7020 driver |
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On 09/21/2014 07:27 AM, Hartmut Knaack wrote: > David Barksdale schrieb, Am 18.09.2014 22:01: >> 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> >> > Hi, > I'm not really convinced of the concept of treating all measurements as 16 bit data, since the datasheet states a maximum resolution of 14 bits for temperature and 12 bits for humidity. It also states, that the 2 LSBs contain an identifier rather than measured data. So, the least to do would be to mask out everything, which is not measured data (which should also include the 2 MSBs of humidity channel). Even better would be to also apply a shift and treat the data with the real resolution (especially for scale, as it would represent the sensitivity of the sensor a bit better). > Besides that, I think it would be a good idea to initialize the sensor during probe (for example set resolution to maximum), since you can never be sure, in which state the sensor has been before. > Also, find some small style issues inline.
The math done by iio_convert_raw_to_processed_unlocked loses accuracy in my case because I need the offset to be fractional. It assumes offset is an integer so I have to round the true offset to the nearest integer. If I provide IIO_CHAN_INFO_PROCESSED then I can do the math correctly. Would it be kosher to provide only IIO_CHAN_INFO_RAW and IIO_CHAN_INFO_PROCESSED?
>> -- >> 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. >> >> --- >> drivers/iio/humidity/Kconfig | 10 +++ >> drivers/iio/humidity/Makefile | 1 + >> drivers/iio/humidity/si7020.c | 142 ++++++++++++++++++++++++++++++++++++++++++ >> 3 files changed, 153 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..cabdb7d >> --- /dev/null >> +++ b/drivers/iio/humidity/si7020.c >> @@ -0,0 +1,142 @@ >> +/* >> + * 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/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, >> +}; >> + >> +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; >> + *val = ret; >> + 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; >> + return IIO_VAL_FRACTIONAL; >> + case IIO_CHAN_INFO_OFFSET: >> + if (chan->type == IIO_TEMP) >> + *val = -17473; /* = -46.85 * 65536 / 175.72 */ >> + else >> + *val = -3146; /* = -6 * 65536 / 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 *dev; > Better name it indio_dev. >> + struct i2c_client **data; >> + >> + if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA)) >> + return -ENODEV; >> + >> + dev = devm_iio_device_alloc(&client->dev, sizeof(*client)); >> + if (!dev) >> + return -ENOMEM; >> + >> + data = iio_priv(dev); >> + *data = client; >> + i2c_set_clientdata(client, dev); >> + >> + dev->dev.parent = &client->dev; >> + dev->name = dev_name(&client->dev); >> + dev->modes = INDIO_DIRECT_MODE; >> + dev->info = &si7020_info; >> + dev->channels = si7020_channels; >> + dev->num_channels = ARRAY_SIZE(si7020_channels); >> + >> + return devm_iio_device_register(&client->dev, 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 " > Trailing whitespace in string. >> + "Relative Humidity and Temperature Sensors"); >> +MODULE_AUTHOR("David Barksdale <dbarksdale@uplogix.com>"); >> +MODULE_LICENSE("GPL"); >> + >> >
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