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WATCHDOG(4)		 BSD Kernel Interfaces Manual		   WATCHDOG(4)

NAME
     watchdog -- hardware and software watchdog

SYNOPSIS
     #include <sys/watchdog.h>

DESCRIPTION
     The watchdog facility is used for controlling hardware and	software
     watchdogs.

     /dev/fido responds	to a single ioctl(2) call, WDIOCPATPAT.	 It takes a
     single argument which represents a	timeout	value specified	as a power of
     two nanoseconds, or-ed with a flag	selecting active or passive control of
     the watchdog.

     WD_ACTIVE indicates that the watchdog will	be kept	from timing out	from
     userland, for instance by the watchdogd(8)	daemon.	 WD_PASSIVE indicates
     that the watchdog will be kept from timing	out from the kernel.

     The ioctl(2) call will return success if just one of the available
     watchdog(9) implementations supports setting the timeout to the specified
     timeout. This means that at least one watchdog is armed. If the call
     fails, for	instance if none of watchdog(9)	implementations	support	the
     timeout length, all watchdogs are disabled	and must be explicitly re-en-
     abled.

     To	disable	the watchdogs pass WD_TO_NEVER.	 If disarming the watchdog(s)
     failed an error is	returned. The watchdog might still be armed!

RETURN VALUES
     The ioctl returns zero on success and non-zero on failure.

     [EOPNOTSUPP]	No watchdog present in the kernel (timeout value other
			than 0).

     [EOPNOTSUPP]	Watchdog could not be disabled (timeout	value of 0).

     [EINVALID]		Invalid	flag combination passed.

     [EINVALID]		None of	the watchdogs supports the requested timeout
			value.

EXAMPLES
	   #include <paths.h>
	   #include <sys/watchdog.h>

	   #define WDPATH  "/dev/" _PATH_WATCHDOG
	   int wdfd = -1;

	   static void
	   wd_init(void)
	   {
		   wdfd	= open(WDPATH, O_RDWR);
		   if (wdfd == -1)
			   err(1, WDPATH);
	   }
	   static void
	   wd_reset(u_int timeout)
	   {
		   if (ioctl(wdfd, WDIOCPATPAT,	&timeout) == -1)
			   err(1, "WDIOCPATPAT");
	   }

	   /* in main()	*/
	   wd_init();
	   wd_reset(WD_ACTIVE|WD_TO_8SEC);
	   /* potential	freeze point */
	   wd_reset(WD_TO_NEVER);

     Enables a watchdog	to recover from	a potentially freezing piece of	code.

	   options SW_WATCHDOG

     in	your kernel config adds	a software watchdog in the kernel, dropping to
     KDB or panic-ing when firing.

SEE ALSO
     watchdogd(8), watchdog(9)

HISTORY
     The watchdog code first appeared in FreeBSD 5.1.

BUGS
     The WD_PASSIVE option has not yet been implemented.

AUTHORS
     The watchdog facility was written by Poul-Henning Kamp <phk@FreeBSD.org>.
     The software watchdog code	and this manual	page were written by Sean
     Kelly <smkelly@FreeBSD.org>.  Some	contributions were made	by Jeff
     Roberson <jeff@FreeBSD.org>.

BSD				 June 25, 2003				   BSD
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | EXAMPLES | SEE ALSO | HISTORY | BUGS | AUTHORS

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