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WATCHDOG(9)		 BSD Kernel Developer's Manual		   WATCHDOG(9)

NAME
     watchdog — software and hardware watchdog facility

SYNOPSIS
     #include <sys/watchdog.h>

     void
     watchdog_fn(void *private, u_int cmd, int *error);

     EVENTHANDLER_REGISTER(watchdog_list, watchdog_fn, private, 0);

     EVENTHANDLER_DEREGISTER(watchdog_list, eventhandler_tag);

DESCRIPTION
     To implement a watchdog in software or hardware, only a single function
     needs to be written and registered on the global watchdog_list.

     The function must examine the cmd argument and act on it as follows:

     If cmd is zero, the watchdog must be disabled and the error argument left
     untouched.	 If the watchdog cannot be disabled, the error argument must
     be set to EOPNOTSUPP.

     Else the watchdog should be reset and configured to a timeout of (1 <<
     (cmd & WD_INTERVAL)) nanoseconds or larger and the error argument be set
     to zero to signal arming of a watchdog.

     If the watchdog cannot be configured to the proposed timeout, it must be
     disabled and the error argument left as is (to avoid hiding the arming of
     another watchdog).

     There is no specification of what the watchdog should do when it times
     out, but a hardware reset or similar “drastic but certain” behaviour is
     recommended.

SEE ALSO
     watchdog(4)

AUTHORS
     The watchdog facility and this manual page was written Poul-Henning Kamp
     ⟨phk@FreeBSD.org⟩.

BSD			       February 28, 2004			   BSD

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