355 lines
11 KiB
Groff
355 lines
11 KiB
Groff
.\" Copyright (c) 2004 Joseph Koshy
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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 AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\" $FreeBSD$
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.\"
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.Dd March 27, 2017
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.Dt EVENTHANDLER 9
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.Os
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.Sh NAME
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.Nm EVENTHANDLER
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.Nd kernel event handling functions
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.Sh SYNOPSIS
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.In sys/eventhandler.h
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.Fn EVENTHANDLER_DECLARE name type
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.Fn EVENTHANDLER_DEFINE name func arg priority
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.Fn EVENTHANDLER_INVOKE name ...
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.Ft eventhandler_tag
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.Fn EVENTHANDLER_REGISTER name func arg priority
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.Fn EVENTHANDLER_DEREGISTER name tag
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.Ft eventhandler_tag
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.Fo eventhandler_register
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.Fa "struct eventhandler_list *list"
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.Fa "const char *name"
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.Fa "void *func"
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.Fa "void *arg"
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.Fa "int priority"
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.Fc
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.Ft void
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.Fo eventhandler_deregister
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.Fa "struct eventhandler_list *list"
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.Fa "eventhandler_tag tag"
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.Fc
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.Ft "struct eventhandler_list *"
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.Fn eventhandler_find_list "const char *name"
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.Ft void
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.Fn eventhandler_prune_list "struct eventhandler_list *list"
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.Sh DESCRIPTION
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The
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.Nm
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mechanism provides a way for kernel subsystems to register interest in
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kernel events and have their callback functions invoked when these
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events occur.
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.Pp
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Callback functions are invoked in order of priority.
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The relative priority of each callback among other callbacks
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associated with an event is given by argument
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.Fa priority ,
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which is an integer ranging from
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.Dv EVENTHANDLER_PRI_FIRST
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(highest priority), to
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.Dv EVENTHANDLER_PRI_LAST
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(lowest priority).
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The symbol
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.Dv EVENTHANDLER_PRI_ANY
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may be used if the handler does not have a specific priority
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associated with it.
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.Pp
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The normal way to use this subsystem is via the macro interface.
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The macros that can be used for working with event handlers and callback
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function lists are:
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.Bl -tag -width indent
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.It Fn EVENTHANDLER_DECLARE
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This macro declares an event handler named by argument
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.Fa name
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with callback functions of type
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.Fa type .
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.It Fn EVENTHANDLER_DEFINE
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This macro uses
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.Xr SYSINIT 9
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to register a callback function
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.Fa func
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with event handler
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.Fa name .
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When invoked, function
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.Fa func
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will be invoked with argument
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.Fa arg
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as its first parameter along with any additional parameters passed in
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via macro
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.Fn EVENTHANDLER_INVOKE
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(see below).
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.It Fn EVENTHANDLER_REGISTER
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This macro registers a callback function
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.Fa func
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with event handler
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.Fa name .
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When invoked, function
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.Fa func
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will be invoked with argument
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.Fa arg
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as its first parameter along with any additional parameters passed in
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via macro
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.Fn EVENTHANDLER_INVOKE
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(see below).
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If registration is successful,
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.Fn EVENTHANDLER_REGISTER
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returns a cookie of type
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.Vt eventhandler_tag .
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.It Fn EVENTHANDLER_DEREGISTER
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This macro removes a previously registered callback associated with tag
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.Fa tag
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from the event handler named by argument
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.Fa name .
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.It Fn EVENTHANDLER_INVOKE
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This macro is used to invoke all the callbacks associated with event
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handler
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.Fa name .
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This macro is a variadic one.
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Additional arguments to the macro after the
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.Fa name
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parameter are passed as the second and subsequent arguments to each
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registered callback function.
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.El
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.Pp
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The macros are implemented using the following functions:
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.Bl -tag -width indent
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.It Fn eventhandler_register
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The
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.Fn eventhandler_register
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function is used to register a callback with a given event.
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The arguments expected by this function are:
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.Bl -tag -width ".Fa priority"
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.It Fa list
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A pointer to an existing event handler list, or
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.Dv NULL .
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If
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.Fa list
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is
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.Dv NULL ,
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the event handler list corresponding to argument
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.Fa name
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is used.
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.It Fa name
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The name of the event handler list.
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.It Fa func
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A pointer to a callback function.
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Argument
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.Fa arg
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is passed to the callback function
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.Fa func
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as its first argument when it is invoked.
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.It Fa priority
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The relative priority of this callback among all the callbacks
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registered for this event.
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Valid values are those in the range
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.Dv EVENTHANDLER_PRI_FIRST
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to
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.Dv EVENTHANDLER_PRI_LAST .
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.El
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.Pp
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The
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.Fn eventhandler_register
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function returns a
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.Fa tag
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that can later be used with
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.Fn eventhandler_deregister
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to remove the particular callback function.
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.It Fn eventhandler_deregister
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The
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.Fn eventhandler_deregister
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function removes the callback associated with tag
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.Fa tag
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from the event handler list pointed to by
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.Fa list .
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This function is safe to call from inside an event handler
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callback.
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.It Fn eventhandler_find_list
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The
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.Fn eventhandler_find_list
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function returns a pointer to event handler list structure corresponding
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to event
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.Fa name .
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.It Fn eventhandler_prune_list
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The
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.Fn eventhandler_prune_list
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function removes all deregistered callbacks from the event list
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.Fa list .
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.El
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.Ss Kernel Event Handlers
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The following event handlers are present in the kernel:
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.Bl -tag -width indent
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.It Vt acpi_sleep_event
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Callbacks invoked when the system is being sent to sleep.
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.It Vt acpi_wakeup_event
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Callbacks invoked when the system is being woken up.
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.It Vt app_coredump_start
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Callbacks invoked at start of application core dump.
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.It Vt app_coredump_progress
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Callbacks invoked during progress of application core dump.
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.It Vt app_coredump_finish
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Callbacks invoked at finish of application core dump.
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.It Vt app_coredump_error
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Callbacks invoked on error of application core dump.
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.It Vt bpf_track
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Callbacks invoked when a BPF listener attaches to/detaches from network interface.
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.It Vt cpufreq_levels_changed
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Callback invoked when cpu frequency levels have changed.
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.It Vt cpufreq_post_change
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Callback invoked after cpu frequency has changed.
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.It Vt cpufreq_pre_change
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Callback invoked before cpu frequency has changed.
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.It Vt dcons_poll
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Callback invoked to poll for dcons changes.
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.It Vt dev_clone
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Callbacks invoked when a new entry is created under
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.Pa /dev .
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.It Vt group_attach_event
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Callback invoked when an interfance has been added to an interface group.
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.It Vt group_change_event
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Callback invoked when an change has been made to an interface group.
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.It Vt group_detach_event
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Callback invoked when an interfance has been removed from an interface group.
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.It Vt ifaddr_event
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Callbacks invoked when an address is set up on a network interface.
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.It Vt if_clone_event
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Callbacks invoked when an interface is cloned.
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.It Vt iflladdr_event
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Callback invoked when an if link layer address event has happened.
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.It Vt ifnet_arrival_event
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Callbacks invoked when a new network interface appears.
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.It Vt ifnet_departure_event
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Callbacks invoked when a network interface is taken down.
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.It Vt ifnet_link_event
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Callback invoked when an interfance link event has happened.
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.It Vt kld_load
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Callbacks invoked after a linker file has been loaded.
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.It Vt kld_unload
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Callbacks invoked after a linker file has been successfully unloaded.
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.It Vt kld_unload_try
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Callbacks invoked before a linker file is about to be unloaded.
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These callbacks may be used to return an error and prevent the unload from
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proceeding.
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.It Vt lle_event
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Callback invoked when an link layer event has happened.
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.It Vt nmbclusters_change
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Callback invoked when the number of mbuf clusters has changed.
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.It Vt nmbufs_change
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Callback invoked when the number of mbufs has changed.
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.It Vt maxsockets_change
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Callback invoked when the maximum number of sockets has changed.
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.It Vt mountroot
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Callback invoked when root has been mounted.
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.It Vt power_profile_change
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Callbacks invoked when the power profile of the system changes.
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.It Vt power_resume
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Callback invoked when the system has resumed.
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.It Vt power_suspend
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Callback invoked just before the system is suspended.
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.It Vt process_ctor
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Callback invoked when a process is created.
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.It Vt process_dtor
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Callback invoked when a process is destroyed.
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.It Vt process_exec
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Callbacks invoked when a process performs an
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.Fn exec
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operation.
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.It Vt process_exit
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Callbacks invoked when a process exits.
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.It Vt process_fini
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Callback invoked when a process memory is destroyed.
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This is never called.
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.It Vt process_fork
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Callbacks invoked when a process forks a child.
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.It Vt process_init
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Callback invoked when a process is initalized.
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.It Vt random_adaptor_attach
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Callback invoked when a new random module has been loaded.
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.It Vt register_framebuffer
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Callback invoked when a new frame buffer is registered.
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.It Vt route_redirect_event
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Callback invoked when a route gets redirected to a new location.
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.It Vt shutdown_pre_sync
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Callbacks invoked at shutdown time, before file systems are synchronized.
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.It Vt shutdown_post_sync
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Callbacks invoked at shutdown time, after all file systems are synchronized.
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.It Vt shutdown_final
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Callbacks invoked just before halting the system.
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.It Vt tcp_offload_listen_start
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Callback invoked for TCP Offload to start listening for new connections.
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.It Vt tcp_offload_listen_stop
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Callback invoked ror TCP Offload to stop listening for new connections.
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.It Vt thread_ctor
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Callback invoked when a thread object is created.
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.It Vt thread_dtor
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Callback invoked when a thread object is destroyed.
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.It Vt thread_init
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Callback invoked when a thread object is initalized.
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.It Vt thread_fini
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Callback invoked when a thread object is deinitalized.
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.It Vt usb_dev_configured
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Callback invoked when a USB device is configured
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.It Vt unregister_framebuffer
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Callback invoked when a frame buffer is deregistered.
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.It Vt vfs_mounted
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Callback invoked when a file system is mounted.
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.It Vt vfs_unmounted
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Callback invoked when a file system is unmounted.
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.It Vt vlan_config
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Callback invoked when the vlan configuration has changed.
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.It Vt vlan_unconfig
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Callback invoked when a vlan is destroyed.
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.It Vt vm_lowmem
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Callbacks invoked when virtual memory is low.
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.It Vt watchdog_list
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Callbacks invoked when the system watchdog timer is reinitialized.
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.El
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.Sh RETURN VALUES
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The macro
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.Fn EVENTHANDLER_REGISTER
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and function
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.Fn eventhandler_register
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return a cookie of type
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.Vt eventhandler_tag ,
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which may be used in a subsequent call to
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.Fn EVENTHANDLER_DEREGISTER
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or
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.Fn eventhandler_deregister .
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.Pp
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The
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.Fn eventhandler_find_list
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function
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returns a pointer to an event handler list corresponding to parameter
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.Fa name ,
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or
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.Dv NULL
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if no such list was found.
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.Sh HISTORY
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The
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.Nm
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facility first appeared in
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.Fx 4.0 .
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.Sh AUTHORS
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This manual page was written by
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.An Joseph Koshy Aq Mt jkoshy@FreeBSD.org .
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