linux-stable/Documentation/hwmon/sht15
Linus Walleij 186731145f hwmon: (sht15) Root out platform data
After finding out there are active users of this sensor I noticed:

- It has a single PXA27x board file using the platform data
- The platform data is only used to carry two GPIO pins, all other
  fields are unused
- The driver does not use GPIO descriptors but the legacy GPIO
  API

I saw we can swiftly fix this by:

- Killing off the platform data entirely
- Define a GPIO descriptor lookup table in the board file
- Use the standard devm_gpiod_get() to grab the GPIO descriptors
  from either the device tree or the board file table.

This compiles, but needs testing.

Cc: arm@kernel.org
Cc: Marco Franchi <marco.franchi@nxp.com>
Cc: Davide Hug <d@videhug.ch>
Cc: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Marco Franchi <marco.franchi@nxp.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
2017-10-29 18:36:03 -07:00

73 lines
2.2 KiB
Text

Kernel driver sht15
===================
Authors:
* Wouter Horre
* Jonathan Cameron
* Vivien Didelot <vivien.didelot@savoirfairelinux.com>
* Jerome Oufella <jerome.oufella@savoirfairelinux.com>
Supported chips:
* Sensirion SHT10
Prefix: 'sht10'
* Sensirion SHT11
Prefix: 'sht11'
* Sensirion SHT15
Prefix: 'sht15'
* Sensirion SHT71
Prefix: 'sht71'
* Sensirion SHT75
Prefix: 'sht75'
Datasheet: Publicly available at the Sensirion website
http://www.sensirion.ch/en/pdf/product_information/Datasheet-humidity-sensor-SHT1x.pdf
Description
-----------
The SHT10, SHT11, SHT15, SHT71, and SHT75 are humidity and temperature
sensors.
The devices communicate using two GPIO lines.
Supported resolutions for the measurements are 14 bits for temperature and 12
bits for humidity, or 12 bits for temperature and 8 bits for humidity.
The humidity calibration coefficients are programmed into an OTP memory on the
chip. These coefficients are used to internally calibrate the signals from the
sensors. Disabling the reload of those coefficients allows saving 10ms for each
measurement and decrease power consumption, while losing on precision.
Some options may be set via sysfs attributes.
Notes:
* The regulator supply name is set to "vcc".
* If a CRC validation fails, a soft reset command is sent, which resets
status register to its hardware default value, but the driver will try to
restore the previous device configuration.
Platform data
-------------
* checksum:
set it to true to enable CRC validation of the readings (default to false).
* no_otp_reload:
flag to indicate not to reload from OTP (default to false).
* low_resolution:
flag to indicate the temp/humidity resolution to use (default to false).
Sysfs interface
---------------
* temp1_input: temperature input
* humidity1_input: humidity input
* heater_enable: write 1 in this attribute to enable the on-chip heater,
0 to disable it. Be careful not to enable the heater
for too long.
* temp1_fault: if 1, this means that the voltage is low (below 2.47V) and
measurement may be invalid.
* humidity1_fault: same as temp1_fault.