| Alan Cox | 4d389dc | 2007-05-23 14:43:52 -0700 | [diff] [blame^] | 1 | Last Reviewed: 10/05/2007 |
| 2 | |
| 3 | WDT Watchdog Timer Interfaces For The Linux Operating System |
| 4 | Alan Cox <alan@lxorguk.ukuu.org.uk> |
| 5 | |
| 6 | ICS WDT501-P |
| 7 | ICS WDT501-P (no fan tachometer) |
| 8 | ICS WDT500-P |
| 9 | |
| 10 | All the interfaces provide /dev/watchdog, which when open must be written |
| 11 | to within a timeout or the machine will reboot. Each write delays the reboot |
| 12 | time another timeout. In the case of the software watchdog the ability to |
| 13 | reboot will depend on the state of the machines and interrupts. The hardware |
| 14 | boards physically pull the machine down off their own onboard timers and |
| 15 | will reboot from almost anything. |
| 16 | |
| 17 | A second temperature monitoring interface is available on the WDT501P cards |
| 18 | This provides /dev/temperature. This is the machine internal temperature in |
| 19 | degrees Fahrenheit. Each read returns a single byte giving the temperature. |
| 20 | |
| 21 | The third interface logs kernel messages on additional alert events. |
| 22 | |
| 23 | The wdt card cannot be safely probed for. Instead you need to pass |
| 24 | wdt=ioaddr,irq as a boot parameter - eg "wdt=0x240,11". |
| 25 | |
| 26 | Features |
| 27 | -------- |
| 28 | WDT501P WDT500P |
| 29 | Reboot Timer X X |
| 30 | External Reboot X X |
| 31 | I/O Port Monitor o o |
| 32 | Temperature X o |
| 33 | Fan Speed X o |
| 34 | Power Under X o |
| 35 | Power Over X o |
| 36 | Overheat X o |
| 37 | |
| 38 | The external event interfaces on the WDT boards are not currently supported. |
| 39 | Minor numbers are however allocated for it. |
| 40 | |
| 41 | |
| 42 | Example Watchdog Driver: see Documentation/watchdog/src/watchdog-simple.c |
| 43 | |