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diff --git a/Documentation/watchdog/wdt.rst b/Documentation/watchdog/wdt.rst new file mode 100644 index 000000000000..d97b0361535b --- /dev/null +++ b/Documentation/watchdog/wdt.rst @@ -0,0 +1,63 @@ +============================================================ +WDT Watchdog Timer Interfaces For The Linux Operating System +============================================================ + +Last Reviewed: 10/05/2007 + +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 ICS ISA-bus wdt card cannot be safely probed for. Instead you need to +pass IO address and IRQ boot parameters. E.g.:: + + wdt.io=0x240 wdt.irq=11 + +Other "wdt" driver parameters are: + + =========== ====================================================== + heartbeat Watchdog heartbeat in seconds (default 60) + nowayout Watchdog cannot be stopped once started (kernel + build parameter) + tachometer WDT501-P Fan Tachometer support (0=disable, default=0) + type WDT501-P Card type (500 or 501, default=500) + =========== ====================================================== + +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 samples/watchdog/watchdog-simple.c |