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. 54If the watchdog cannot be disabled, the 55.Fa error 56argument must be set to 57.Dv EOPNOTSUPP . 58.Pp 59Else the watchdog should be reset and configured to a timeout of 60.Pq 1 << Pq Fa cmd No & Dv WD_INTERVAL 61nanoseconds or larger and the 62.Fa error 63argument be set to zero to signal arming of a watchdog. 64.Pp 65If the watchdog cannot be configured to the proposed timeout, it 66must be disabled and the 67.Fa error 68argument left as is (to avoid hiding the arming of another watchdog). 69.Pp 70There is no specification of what the watchdog should do when it 71times out, but a hardware reset or similar 72.Dq "drastic but certain" 73behaviour is recommended. 74.Sh SEE ALSO 75.Xr watchdog 4 76.Sh AUTHORS 77.An -nosplit 78The 79.Nm 80facility and this manual page was written 81.An Poul-Henning Kamp Aq Mt phk@FreeBSD.org . 82