#include <sys/eventhandler.h>
EVENTHANDLER_DECLARE (name type);
EVENTHANDLER_INVOKE (name ...); eventhandler_tag
EVENTHANDLER_REGISTER (name func arg priority);
EVENTHANDLER_DEREGISTER (name tag); eventhandler_tag
Fo eventhandler_register
Fa struct eventhandler_list *list
Fa const char *name
Fa void *func
Fa void *arg
Fa int priority
Fc Ft void
Fo eventhandler_deregister
Fa struct eventhandler_list *list
Fa eventhandler_tag tag
Fc Ft struct eventhandler_list *
eventhandler_find_list (const char *name); void
eventhandler_prune_list (struct eventhandler_list *list);
DESCRIPTION
The
mechanism provides a way for kernel subsystems to register interest in
kernel events and have their callback functions invoked when these
events occur.
The normal way to use this subsystem is via the macro interface.
The macros that can be used for working with event handlers and callback
function lists are:
Fn EVENTHANDLER_DECLARE
This macro declares an event handler named by argument
Fa name
with callback functions of type
Fa type .
Fn EVENTHANDLER_REGISTER
This macro registers a callback function
Fa func
with event handler
Fa name .
When invoked, function
Fa func
will be invoked with argument
Fa arg
as its first parameter along with any additional parameters passed in
via macro
EVENTHANDLER_INVOKE ();
(see below).
Callback functions are invoked in order of priority.
The relative priority of each callback among other callbacks
associated with an event is given by argument
Fa priority ,
which is an integer ranging from
EVENTHANDLER_PRI_FIRST
(highest priority), to
EVENTHANDLER_PRI_LAST
(lowest priority).
The symbol
EVENTHANDLER_PRI_ANY
may be used if the handler does not have a specific priority
associated with it.
If registration is successful,
EVENTHANDLER_REGISTER ();
returns a cookie of type
Vt eventhandler_tag .
Fn EVENTHANDLER_DEREGISTER
This macro removes a previously registered callback associated with tag
Fa tag
from the event handler named by argument
Fa name .
Fn EVENTHANDLER_INVOKE
This macro is used to invoke all the callbacks associated with event
handler
Fa name .
This macro is a variadic one.
Additional arguments to the macro after the
Fa name
parameter are passed as the second and subsequent arguments to each
registered callback function.
The macros are implemented using the following functions:
Fn eventhandler_register
The
eventhandler_register ();
function is used to register a callback with a given event.
The arguments expected by this function are:
Fa list
A pointer to an existing event handler list, or
NULL
If
Fa list
is
NULL
the event handler list corresponding to argument
Fa name
is used.
Fa name
The name of the event handler list.
Fa func
A pointer to a callback function.
Argument
Fa arg
is passed to the callback function
Fa func
as its first argument when it is invoked.
Fa priority
The relative priority of this callback among all the callbacks
registered for this event.
Valid values are those in the range
EVENTHANDLER_PRI_FIRST
to
EVENTHANDLER_PRI_LAST
The
eventhandler_register ();
function returns a
Fa tag
that can later be used with
eventhandler_deregister ();
to remove the particular callback function.
Fn eventhandler_deregister
The
eventhandler_deregister ();
function removes the callback associated with tag
Fa tag
from the event handler list pointed to by
Fa list .
This function is safe to call from inside an event handler
callback.
Fn eventhandler_find_list
The
eventhandler_find_list ();
function returns a pointer to event handler list structure corresponding
to event
Fa name .
Fn eventhandler_prune_list
The
eventhandler_prune_list ();
function removes all deregistered callbacks from the event list
Fa list .
Kernel Event Handlers
The following event handlers are present in the kernel:
Vt acpi_sleep_event
Callbacks invoked when the system is being sent to sleep.
Vt acpi_wakeup_event
Callbacks invoked when the system is being woken up.
Vt dev_clone
Callbacks invoked when a new entry is created under
/dev
Vt ifaddr_event
Callbacks invoked when an address is set up on a network interface.
Vt if_clone_event
Callbacks invoked when an interface is cloned.
Vt ifnet_arrival_event
Callbacks invoked when a new network interface appears.
Vt ifnet_departure_event
Callbacks invoked when a network interface is taken down.
Vt power_profile_change
Callbacks invoked when the power profile of the system changes.
Vt process_exec
Callbacks invoked when a process performs an
exec ();
operation.
Vt process_exit
Callbacks invoked when a process exits.
Vt process_fork
Callbacks invoked when a process forks a child.
Vt shutdown_pre_sync
Callbacks invoked at shutdown time, before file systems are synchronized.
Vt shutdown_post_sync
Callbacks invoked at shutdown time, after all file systems are synchronized.
Vt shutdown_final
Callbacks invoked just before halting the system.
Vt vm_lowmem
Callbacks invoked when virtual memory is low.
Vt watchdog_list
Callbacks invoked when the system watchdog timer is reinitialized.
RETURN VALUES
The macro
EVENTHANDLER_REGISTER ();
and function
eventhandler_register ();
return a cookie of type
Vt eventhandler_tag ,
which may be used in a subsequent call to
EVENTHANDLER_DEREGISTER ();
or
eventhandler_deregister (.);
The
eventhandler_find_list ();
function
returns a pointer to an event handler list corresponding to parameter
Fa name ,
or
NULL
if no such list was found.
HISTORY
The
facility first appeared in
Fx 4.0 .
AUTHORS
This manual page was written by
An Joseph Koshy Aq [email protected] .
