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    AD525x Digital Potentiometers
  ---------------------------------
  
  The ad525x_dpot driver exports a simple sysfs interface.  This allows you to
  work with the immediate resistance settings as well as update the saved startup
  settings.  Access to the factory programmed tolerance is also provided, but
  interpretation of this settings is required by the end application according to
  the specific part in use.
  
  ---------
    Files
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  Each dpot device will have a set of eeprom, rdac, and tolerance files.  How
  many depends on the actual part you have, as will the range of allowed values.
  
  The eeprom files are used to program the startup value of the device.
  
  The rdac files are used to program the immediate value of the device.
  
  The tolerance files are the read-only factory programmed tolerance settings
  and may vary greatly on a part-by-part basis.  For exact interpretation of
  this field, please consult the datasheet for your part.  This is presented
  as a hex file for easier parsing.
  
  -----------
    Example
  -----------
  
  Locate the device in your sysfs tree.  This is probably easiest by going into
  the common i2c directory and locating the device by the i2c slave address.
  
  	# ls /sys/bus/i2c/devices/
  	0-0022  0-0027  0-002f
  
  So assuming the device in question is on the first i2c bus and has the slave
  address of 0x2f, we descend (unrelated sysfs entries have been trimmed).
  
  	# ls /sys/bus/i2c/devices/0-002f/
  	eeprom0 rdac0 tolerance0
  
  You can use simple reads/writes to access these files:
  
  	# cd /sys/bus/i2c/devices/0-002f/
  
  	# cat eeprom0
  	0
  	# echo 10 > eeprom0
  	# cat eeprom0
  	10
  
  	# cat rdac0
  	5
  	# echo 3 > rdac0
  	# cat rdac0
  	3