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.Fn EVENTHANDLER_REGISTER watchdog_list watchdog_fn private 0 38.Fn EVENTHANDLER_DEREGISTER watchdog_list eventhandler_tag 39.Sh DESCRIPTION 40To implement a watchdog in software or hardware, only a single 41function needs to be written and registered on the global 42.Va watchdog_list . 43.Pp 44The function must examine the 45.Fa cmd 46argument and act on it as 47follows: 48.Pp 49If 50.Fa cmd 51is zero, the watchdog must be disabled and the 52.Fa error 53argument left untouched. 54.Pp 55Else the watchdog should be reset and configured to a timeout of 56.Pq 1 << Pq Fa cmd No & Dv WD_INTERVAL 57nanoseconds or larger and the 58.Fa error 59argument be set to zero. 60.Pp 61If the watchdog cannot be configured to the proposed timeout, it 62must be disabled and the 63.Fa error 64argument set to 65.Dv EINVAL . 66If the watchdog cannot be disabled, the 67.Fa error 68argument must be set to 69.Dv EOPNOTSUPP . 70.Pp 71There is no specification of what the watchdog should do when it 72times out, but a hardware reset or similar 73.Dq "drastic but certain" 74behaviour is recommended. 75.Sh SEE ALSO 76.Xr watchdog 4 77.Sh AUTHORS 78.An -nosplit 79The 80.Nm 81facility and this manual page was written 82.An Poul-Henning Kamp Aq phk@FreeBSD.org . 83