Last Reviewed: 10/05/2007
  
  	WDT Watchdog Timer Interfaces For The Linux Operating System
  		Alan Cox <alan@lxorguk.ukuu.org.uk>
  
  	ICS	WDT501-P
  	ICS	WDT501-P (no fan tachometer)
  	ICS	WDT500-P
  
  All the interfaces provide /dev/watchdog, which when open must be written
  to within a timeout or the machine will reboot. Each write delays the reboot
  time another timeout. In the case of the software watchdog the ability to
  reboot will depend on the state of the machines and interrupts. The hardware
  boards physically pull the machine down off their own onboard timers and
  will reboot from almost anything.
  
  A second temperature monitoring interface is available on the WDT501P cards
  This provides /dev/temperature. This is the machine internal temperature in
  degrees Fahrenheit. Each read returns a single byte giving the temperature.
  
  The third interface logs kernel messages on additional alert events.
  
  The wdt card cannot be safely probed for. Instead you need to pass
  wdt=ioaddr,irq as a boot parameter - eg "wdt=0x240,11".
  
  Features
  --------
  		WDT501P		WDT500P
  Reboot Timer	   X               X
  External Reboot	   X	           X
  I/O Port Monitor   o		   o
  Temperature	   X		   o
  Fan Speed          X		   o
  Power Under	   X               o
  Power Over         X               o
  Overheat           X               o
  
  The external event interfaces on the WDT boards are not currently supported.
  Minor numbers are however allocated for it.
  
  
  Example Watchdog Driver:  see Documentation/watchdog/src/watchdog-simple.c