David Barksdale schrieb, Am 22.09.2014 17:40: > > 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@xxxxxxxxxxx> >>> >> 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? It would be a bit more accurate using a fractional offset, but this error is just in the range of 10 m°C or 4 m%RH. Compared to the tolerances of the sensor for temperature (at least 500 m°C) or humidity (at least 3000 m%RH), this doesn't seem relevant. > >>> -- >>> 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@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/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@xxxxxxxxxxx>"); >>> +MODULE_LICENSE("GPL"); >>> + >>> >> > -- > To unsubscribe from this list: send the line "unsubscribe linux-iio" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
