Kernel driver sht21
  ===================
  
  Supported chips:
    * Sensirion SHT21
      Prefix: 'sht21'
      Addresses scanned: none
      Datasheet: Publicly available at the Sensirion website
      http://www.sensirion.com/en/pdf/product_information/Datasheet-humidity-sensor-SHT21.pdf
  
    * Sensirion SHT25
      Prefix: 'sht21'
      Addresses scanned: none
      Datasheet: Publicly available at the Sensirion website
      http://www.sensirion.com/en/pdf/product_information/Datasheet-humidity-sensor-SHT25.pdf
  
  Author:
    Urs Fleisch <urs.fleisch@sensirion.com>
  
  Description
  -----------
  
  The SHT21 and SHT25 are humidity and temperature sensors in a DFN package of
  only 3 x 3 mm footprint and 1.1 mm height. The difference between the two
  devices is the higher level of precision of the SHT25 (1.8% relative humidity,
  0.2 degree Celsius) compared with the SHT21 (2.0% relative humidity,
  0.3 degree Celsius).
  
  The devices communicate with the I2C protocol. All sensors are set to the same
  I2C address 0x40, so an entry with I2C_BOARD_INFO("sht21", 0x40) can be used
  in the board setup code.
  
  sysfs-Interface
  ---------------
  
  temp1_input - temperature input
  humidity1_input - humidity input
  
  Notes
  -----
  
  The driver uses the default resolution settings of 12 bit for humidity and 14
  bit for temperature, which results in typical measurement times of 22 ms for
  humidity and 66 ms for temperature. To keep self heating below 0.1 degree
  Celsius, the device should not be active for more than 10% of the time,
  e.g. maximum two measurements per second at the given resolution.
  
  Different resolutions, the on-chip heater, using the CRC checksum and reading
  the serial number are not supported yet.