1============================================================ 2WDT Watchdog Timer Interfaces For The Linux Operating System 3============================================================ 4 5Last Reviewed: 10/05/2007 6 7Alan Cox <alan@lxorguk.ukuu.org.uk> 8 9 - ICS WDT501-P 10 - ICS WDT501-P (no fan tachometer) 11 - ICS WDT500-P 12 13All the interfaces provide /dev/watchdog, which when open must be written 14to within a timeout or the machine will reboot. Each write delays the reboot 15time another timeout. In the case of the software watchdog the ability to 16reboot will depend on the state of the machines and interrupts. The hardware 17boards physically pull the machine down off their own onboard timers and 18will reboot from almost anything. 19 20A second temperature monitoring interface is available on the WDT501P cards. 21This provides /dev/temperature. This is the machine internal temperature in 22degrees Fahrenheit. Each read returns a single byte giving the temperature. 23 24The third interface logs kernel messages on additional alert events. 25 26The ICS ISA-bus wdt card cannot be safely probed for. Instead you need to 27pass IO address and IRQ boot parameters. E.g.:: 28 29 wdt.io=0x240 wdt.irq=11 30 31Other "wdt" driver parameters are: 32 33 =========== ====================================================== 34 heartbeat Watchdog heartbeat in seconds (default 60) 35 nowayout Watchdog cannot be stopped once started (kernel 36 build parameter) 37 tachometer WDT501-P Fan Tachometer support (0=disable, default=0) 38 type WDT501-P Card type (500 or 501, default=500) 39 =========== ====================================================== 40 41Features 42-------- 43 44================ ======= ======= 45 WDT501P WDT500P 46================ ======= ======= 47Reboot Timer X X 48External Reboot X X 49I/O Port Monitor o o 50Temperature X o 51Fan Speed X o 52Power Under X o 53Power Over X o 54Overheat X o 55================ ======= ======= 56 57The external event interfaces on the WDT boards are not currently supported. 58Minor numbers are however allocated for it. 59 60 61Example Watchdog Driver: 62 63 see samples/watchdog/watchdog-simple.c 64