Copyright (c) 2004 Poul-Henning Kamp <phk@FreeBSD.org>
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
$FreeBSD: releng/10.2/share/man/man9/watchdog.9 233648 2012-03-29 05:02:12Z eadler $
.Dd February 28, 2004 .Dt WATCHDOG 9 .Os .Sh NAME .Nm watchdog .Nd "software and hardware watchdog facility" .Sh SYNOPSIS n sys/watchdog.h .Ft void .Fn watchdog_fn "void *private" "u_int cmd" "int *error" .Fn EVENTHANDLER_REGISTER watchdog_list watchdog_fn private 0 .Fn EVENTHANDLER_DEREGISTER watchdog_list eventhandler_tag .Sh DESCRIPTION To implement a watchdog in software or hardware, only a single function needs to be written and registered on the global .Va watchdog_list .
p The function must examine the .Fa cmd argument and act on it as follows:
p If .Fa cmd is zero, the watchdog must be disabled and the .Fa error argument left untouched. If the watchdog cannot be disabled, the .Fa error argument must be set to .Dv EOPNOTSUPP .
p Else the watchdog should be reset and configured to a timeout of
q 1 << Pq Fa cmd No & Dv WD_INTERVAL nanoseconds or larger and the .Fa error argument be set to zero to signal arming of a watchdog.
p If the watchdog cannot be configured to the proposed timeout, it must be disabled and the .Fa error argument left as is (to avoid hiding the arming of another watchdog).
p There is no specification of what the watchdog should do when it times out, but a hardware reset or similar .Dq "drastic but certain" behaviour is recommended. .Sh SEE ALSO .Xr watchdog 4 .Sh AUTHORS .An -nosplit The .Nm facility and this manual page was written .An Poul-Henning Kamp Aq phk@FreeBSD.org .