Kernel driver max6875
=====================

Supported chips:
  * Maxim MAX6874, MAX6875
    Prefix: 'max6875'
    Addresses scanned: 0x50, 0x52
    Datasheet:
        http://pdfserv.maxim-ic.com/en/ds/MAX6874-MAX6875.pdf

Author: Ben Gardner <bgardner@wabtec.com>


Module Parameters
-----------------

* allow_write int
  Set to non-zero to enable write permission:
  *0: Read only
   1: Read and write


Description
-----------

The Maxim MAX6875 is an EEPROM-programmable power-supply sequencer/supervisor.
It provides timed outputs that can be used as a watchdog, if properly wired.
It also provides 512 bytes of user EEPROM.

At reset, the MAX6875 reads the configuration EEPROM into its configuration
registers.  The chip then begins to operate according to the values in the
registers.

The Maxim MAX6874 is a similar, mostly compatible device, with more intputs
and outputs:

             vin     gpi    vout
MAX6874        6       4       8
MAX6875        4       3       5

MAX6874 chips can have four different addresses (as opposed to only two for
the MAX6875). The additional addresses (0x54 and 0x56) are not probed by
this driver by default, but the probe module parameter can be used if
needed.

See the datasheet for details on how to program the EEPROM.


Sysfs entries
-------------

eeprom_user   - 512 bytes of user-defined EEPROM space. Only writable if
                allow_write was set and register 0x43 is 0.

eeprom_config - 70 bytes of config EEPROM. Note that changes will not get
                loaded into register space until a power cycle or device reset.

reg_config    - 70 bytes of register space. Any changes take affect immediately.


General Remarks
---------------

A typical application will require that the EEPROMs be programmed once and
never altered afterwards.