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