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1 1625 jcastillo
        Watchdog Timer Interfaces For The Linux Operating System
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                Alan Cox 
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             Custom Linux Driver And Program Development
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The following watchdog drivers are currently implemented:
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        ICS     WDT501-P
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        ICS     WDT501-P (no fan tachometer)
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        ICS     WDT500-P
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        Software Only
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All four interfaces provide /dev/watchdog, which when open must be written
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to within a minute or the machine will reboot. Each write delays the reboot
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time another minute. In the case of the software watchdog the ability to
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reboot will depend on the state of the machines and interrupts. The hardware
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boards physically pull the machine down off their own onboard timers and
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will reboot from almost anything.
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A second temperature monitoring interface is available on the WDT501P cards
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and provides /dev/temperature. This is the machine internal temperature in
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degrees farenheit. Each read returns a single byte giving the temperature.
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The third interface logs kernel messages on additional alert events.
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Both software and hardware watchdog drivers are available in the standard
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kernel. If you are using the software watchdog, you probably also want
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to use "panic=60" as a boot argument as well.
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Features
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--------
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                WDT501P         WDT500P         Software
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Reboot Timer       X               X                X
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External Reboot    X               X                o
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Temperature        X               o                o
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Fan Speed          X               o                o
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Power Under        X               o                o
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Power Over         X               o                o
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Overheat           X               o                o
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The external event interfaces on the WDT boards are not currently supported.
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Minor numbers are however allocated for it.
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Example Watchdog Driver
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-----------------------
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#include 
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#include 
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#include 
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int main(int argc, const char *argv[])
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{
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        int fd=open("/dev/watchdog",O_WRONLY);
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        if(fd==-1)
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        {
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                perror("watchdog");
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                exit(1);
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        }
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        while(1)
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        {
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                write(fd,"\0",1);
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                sleep(10);
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        }
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}
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Contact Information
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People keep asking about the WDT watchdog timer hardware: The phone contacts
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for Industrial Computer Source are:
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US: 619 677 0877 (sales)  0895 (fax)
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UK: 01243 533900
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France (1) 69.18.74.30
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Industrial Computer Source
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9950 Barnes Canyon Road
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San Diego, CA
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and please mention Linux when enquiring.

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