freebsd-dev/share/man/man9/watchdog.9
Nick Hibma 9079fff550 Align the interfaces for the various watchdogs and make the interface
behave as expected.

Also:
- Return an error if WD_PASSIVE is passed in to the ioctl as only
  WD_ACTIVE is implemented at the moment. See sys/watchdog.h for an
  explanation of the difference between WD_ACTIVE and WD_PASSIVE.
- Remove the I_HAVE_TOTALLY_LOST_MY_SENSE_OF_HUMOR define. If you've
  lost your sense of humor, than don't add a define.

Specific changes:

i80321_wdog.c
  Don't roll your own passive watchdog tickle as this would defeat the
  purpose of an active (userland) watchdog tickle.

ichwd.c / ipmi.c:
  WD_ACTIVE means active patting of the watchdog by a userland process,
  not whether the watchdog is active. See sys/watchdog.h.

kern_clock.c:
  (software watchdog) Remove a check for WD_ACTIVE as this does not make
  sense here. This reverts r1.181.
2006-12-15 21:44:49 +00:00

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.\" $FreeBSD$
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.Dd February 28, 2004
.Dt WATCHDOG 9
.Os
.Sh NAME
.Nm watchdog
.Nd "software and hardware watchdog facility"
.Sh SYNOPSIS
.In sys/watchdog.h
.Ft void
.Fn watchdog_fn "void *private" "u_int cmd" "int *error"
.Fn EVENTHANDLER_REGISTER watchdog_list watchdog_fn private 0
.Fn EVENTHANDLER_DEREGISTER watchdog_list eventhandler_tag
.Sh DESCRIPTION
To implement a watchdog in software or hardware, only a single
function needs to be written and registered on the global
.Va watchdog_list .
.Pp
The function must examine the
.Fa cmd
argument and act on it as
follows:
.Pp
If
.Fa cmd
is zero, the watchdog must be disabled and the
.Fa error
argument left untouched.
.Pp
Else the watchdog should be reset and configured to a timeout of
.Pq 1 << Pq Fa cmd No & Dv WD_INTERVAL
nanoseconds or larger and the
.Fa error
argument be set to zero.
.Pp
If the watchdog cannot be configured to the proposed timeout, it
must be disabled and the
.Fa error
argument set to
.Dv EINVAL .
If the watchdog cannot be disabled, the
.Fa error
argument must be set to
.Dv EOPNOTSUPP .
.Pp
There is no specification of what the watchdog should do when it
times out, but a hardware reset or similar
.Dq "drastic but certain"
behaviour is recommended.
.Sh SEE ALSO
.Xr watchdog 4
.Sh AUTHORS
.An -nosplit
The
.Nm
facility and this manual page was written
.An Poul-Henning Kamp Aq phk@FreeBSD.org .