| 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 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 Documentation/watchdog/src/watchdog-simple.c |
