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>.

Debian                                          February 28, 2004                                    WATCHDOG(9)