projects / linux-block.git / blame
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|---|---|---|
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1 | ============================================================ |
| 2 | WDT Watchdog Timer Interfaces For The Linux Operating System | |
| 3 | ============================================================ | |
| 4 | ||
| 4d389dce AC |
5 | Last Reviewed: 10/05/2007 |
| 6 | ||
| cc2a2d19 | 7 | Alan Cox <alan@lxorguk.ukuu.org.uk> |
| 4d389dce | 8 | |
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9 | - ICS WDT501-P |
| 10 | - ICS WDT501-P (no fan tachometer) | |
| 11 | - ICS WDT500-P | |
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12 | |
| 13 | All the interfaces provide /dev/watchdog, which when open must be written | |
| 14 | to within a timeout or the machine will reboot. Each write delays the reboot | |
| 15 | time another timeout. In the case of the software watchdog the ability to | |
| 16 | reboot will depend on the state of the machines and interrupts. The hardware | |
| 17 | boards physically pull the machine down off their own onboard timers and | |
| 18 | will reboot from almost anything. | |
| 19 | ||
| 4724ba57 | 20 | A second temperature monitoring interface is available on the WDT501P cards. |
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21 | This provides /dev/temperature. This is the machine internal temperature in |
| 22 | degrees Fahrenheit. Each read returns a single byte giving the temperature. | |
| 23 | ||
| 24 | The third interface logs kernel messages on additional alert events. | |
| 25 | ||
| 4724ba57 | 26 | The ICS ISA-bus wdt card cannot be safely probed for. Instead you need to |
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27 | pass IO address and IRQ boot parameters. E.g.:: |
| 28 | ||
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29 | wdt.io=0x240 wdt.irq=11 |
| 30 | ||
| 31 | Other "wdt" driver parameters are: | |
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32 | |
| 33 | =========== ====================================================== | |
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34 | heartbeat Watchdog heartbeat in seconds (default 60) |
| 35 | nowayout Watchdog cannot be stopped once started (kernel | |
| cc2a2d19 | 36 | build parameter) |
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37 | tachometer WDT501-P Fan Tachometer support (0=disable, default=0) |
| 38 | type WDT501-P Card type (500 or 501, default=500) | |
| cc2a2d19 | 39 | =========== ====================================================== |
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40 | |
| 41 | Features | |
| 42 | -------- | |
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43 | |
| 44 | ================ ======= ======= | |
| 45 | WDT501P WDT500P | |
| 46 | ================ ======= ======= | |
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47 | Reboot Timer X X |
| 48 | External Reboot X X | |
| 49 | I/O Port Monitor o o | |
| 50 | Temperature X o | |
| 51 | Fan Speed X o | |
| 52 | Power Under X o | |
| 53 | Power Over X o | |
| 54 | Overheat X o | |
| cc2a2d19 | 55 | ================ ======= ======= |
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56 | |
| 57 | The external event interfaces on the WDT boards are not currently supported. | |
| 58 | Minor numbers are however allocated for it. | |
| 59 | ||
| 60 | ||
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61 | Example Watchdog Driver: |
| 62 | ||
| 63 | see samples/watchdog/watchdog-simple.c |