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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 | ||
4724ba57 | 17 | A second temperature monitoring interface is available on the WDT501P cards. |
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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 | ||
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23 | The ICS ISA-bus wdt card cannot be safely probed for. Instead you need to |
24 | pass IO address and IRQ boot parameters. E.g.: | |
25 | wdt.io=0x240 wdt.irq=11 | |
26 | ||
27 | Other "wdt" driver parameters are: | |
28 | heartbeat Watchdog heartbeat in seconds (default 60) | |
29 | nowayout Watchdog cannot be stopped once started (kernel | |
30 | build parameter) | |
31 | tachometer WDT501-P Fan Tachometer support (0=disable, default=0) | |
32 | type WDT501-P Card type (500 or 501, default=500) | |
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33 | |
34 | Features | |
35 | -------- | |
36 | WDT501P WDT500P | |
37 | Reboot Timer X X | |
38 | External Reboot X X | |
39 | I/O Port Monitor o o | |
40 | Temperature X o | |
41 | Fan Speed X o | |
42 | Power Under X o | |
43 | Power Over X o | |
44 | Overheat X o | |
45 | ||
46 | The external event interfaces on the WDT boards are not currently supported. | |
47 | Minor numbers are however allocated for it. | |
48 | ||
49 | ||
50 | Example Watchdog Driver: see Documentation/watchdog/src/watchdog-simple.c |