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.Dd February 28, 2004 26.Dt WATCHDOG 9 27.Os 28.Sh NAME 29.Nm watchdog 30.Nd "software and hardware watchdog facility" 31.Sh SYNOPSIS 32.In sys/watchdog.h 33.Ft void 34.Fn watchdog_fn "void *private" "u_int cmd" "int *error" 35.Fn EVENTHANDLER_REGISTER watchdog_list watchdog_fn private 0 36.Fn EVENTHANDLER_DEREGISTER watchdog_list eventhandler_tag 37.Sh DESCRIPTION 38To implement a watchdog in software or hardware, only a single 39function needs to be written and registered on the global 40.Va watchdog_list . 41.Pp 42The function must examine the 43.Fa cmd 44argument and act on it as 45follows: 46.Pp 47If 48.Fa cmd 49is zero, the watchdog must be disabled and the 50.Fa error 51argument left untouched. 52If the watchdog cannot be disabled, the 53.Fa error 54argument must be set to 55.Dv EOPNOTSUPP . 56.Pp 57Else the watchdog should be reset and configured to a timeout of 58.Pq 1 << Pq Fa cmd No & Dv WD_INTERVAL 59nanoseconds or larger and the 60.Fa error 61argument be set to zero to signal arming of a watchdog. 62.Pp 63If the watchdog cannot be configured to the proposed timeout, it 64must be disabled and the 65.Fa error 66argument left as is (to avoid hiding the arming of another watchdog). 67.Pp 68There is no specification of what the watchdog should do when it 69times out, but a hardware reset or similar 70.Dq "drastic but certain" 71behaviour is recommended. 72.Sh SEE ALSO 73.Xr watchdog 4 74.Sh AUTHORS 75.An -nosplit 76The 77.Nm 78facility and this manual page was written 79.An Poul-Henning Kamp Aq Mt phk@FreeBSD.org . 80