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 arm-
     ing 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