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 writtento within a timeout or the machine will reboot. Each write delays the reboottime another timeout. In the case of the software watchdog the ability toreboot will depend on the state of the machines and interrupts. The hardwareboards physically pull the machine down off their own onboard timers andwill 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 indegrees 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 topass 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 (kernelbuild parameter)
tachometer	WDT501-P Fan Tachometer support (0=disable, default=0)
type	WDT501-P Card type (500 or 501, default=500)