/Documentation/watchdog/wdt.txt

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  1. Last Reviewed: 10/05/2007
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  3. 	WDT Watchdog Timer Interfaces For The Linux Operating System
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  4. 		Alan Cox <alan@lxorguk.ukuu.org.uk>
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  6. 	ICS	WDT501-P
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  7. 	ICS	WDT501-P (no fan tachometer)
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  8. 	ICS	WDT500-P
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  10. All the interfaces provide /dev/watchdog, which when open must be written
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  11. to within a timeout or the machine will reboot. Each write delays the reboot
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  12. time another timeout. In the case of the software watchdog the ability to
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  13. reboot will depend on the state of the machines and interrupts. The hardware
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  14. boards physically pull the machine down off their own onboard timers and
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  15. will reboot from almost anything.
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  17. A second temperature monitoring interface is available on the WDT501P cards
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  18. This provides /dev/temperature. This is the machine internal temperature in
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  19. degrees Fahrenheit. Each read returns a single byte giving the temperature.
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  21. The third interface logs kernel messages on additional alert events.
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  23. The wdt card cannot be safely probed for. Instead you need to pass
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  24. wdt=ioaddr,irq as a boot parameter - eg "wdt=0x240,11".
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  26. Features
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  27. --------
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  28. 		WDT501P		WDT500P
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  29. Reboot Timer	   X               X
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  30. External Reboot	   X	           X
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  31. I/O Port Monitor   o		   o
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  32. Temperature	   X		   o
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  33. Fan Speed          X		   o
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  34. Power Under	   X               o
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  35. Power Over         X               o
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  36. Overheat           X               o
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  38. The external event interfaces on the WDT boards are not currently supported.
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  39. Minor numbers are however allocated for it.
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  42. Example Watchdog Driver:  see Documentation/watchdog/src/watchdog-simple.c
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