1.\" 2.\" Copyright (c) 2004 Poul-Henning Kamp <phk@FreeBSD.org 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR 15.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT, 18.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24.\" 25.\" $FreeBSD$ 26.\" 27.Dd February 28, 2004 28.Dt watchdog 9 29.Os 30.Sh NAME 31.Nm watchdog 32.Nd "Software and hardware watchdog facility" 33.Sh SYNOPSIS 34.In sys/watchdog.h 35.Ft "void" 36.Fn watchdog_fn "void *private" "u_int cmd" "int *error" 37.Bl -literal 38EVENTHANDLER_REGISTER(watchdog_list, watchdog_fn, private, 0); 39.El 40.Sh DESCRIPTION 41To implement a watchdog in software or hardware, only a single 42function needs to be written and registered on the global 43watchdog_list. 44.Pp 45The function must examine the cmd argument and act on it as 46follows: 47.Pp 48If cmd is zero, the watchdog must be disabled and the error 49argument left untouched. 50.Pp 51Else the watchdog should be reset and configured to a timeout of 52(1<<(cmd & WD_INTERVAL)) 53nanoseconds or larger and the error argument be set to zero. 54.Pp 55If the watchdog can not be configured to the proposed timeout, it 56must be disabled and the error argument left untouched. 57.Pp 58There is no specification of what the watchdog should do when it 59times out, but a hardware reset or similar "drastic but certain" 60behaviour is recommended. 61.Sh SEE ALSO 62.Xr watchdog 4 63.Sh AUTHORS 64.An -nosplit 65The watchdog facility and this manual page was written 66.An Poul-Henning Kamp Aq phk@FreeBSD.org . 67