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.\" -*- nroff -*-
.\"
.\" Copyright (c) 2000 Alexander Langer
.\"
.\" All rights reserved.
.\"
.\" This program is free software.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd March 1, 2001
.Dt MODULE 9
.Os
.Sh NAME
.Nm module
.Nd structure describing a kernel module
.Sh DESCRIPTION
Each module in the kernel is described by a
.Vt module_t
structure.
The structure contains the name of the device, a unique ID number,
a pointer to an event handler function and to an argument,
which is given to the event handler,
as well as some kernel internal data.
.Pp
The
.Xr DECLARE_MODULE 9
macro
registers the module with the system.
.Pp
When the module is loaded, the event handler function is called with
the
.Fa what
argument set to
.Dv MOD_LOAD .
.Pp
On unload it is first called with
.Fa what
set to MOD_QUIESCE .
If the unload was not forced, a non-zero return will prevent the
unload from happening.
.Pp
If the unload continues
.Fa what
is set to
.Dv MOD_UNLOAD .
If the module returns non-zero to this, the unload will not happen.
.Pp
The difference between MOD_QUIESCE and MOD_UNLOAD is that the module
should fail MOD_QUIESCE if it is currently in use, whereas MOD_UNLOAD
should only fail if it is impossible to unload the module, for instance
because there are memory references to the module which cannot be revoked.
.Pp
When the system is shutting down,
.Fa what
contains the value of
.Dv MOD_SHUTDOWN .
.Pp
The module should return EOPNOTSUPP for unrecognized values of
.Fa what .
.Sh EXAMPLES
.Bd -literal
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/module.h>
static int foo_handler(module_t mod, int /*modeventtype_t*/ what,
void *arg);
static moduledata_t mod_data= {
"foo",
foo_handler,
0
};
MODULE_VERSION(foo, 1);
MODULE_DEPEND(foo, bar, 1, 3, 4);
DECLARE_MODULE(foo, mod_data, SI_SUB_EXEC, SI_ORDER_ANY);
.Ed
.Sh SEE ALSO
.Xr DECLARE_MODULE 9 ,
.Xr DEV_MODULE 9 ,
.Xr DRIVER_MODULE 9 ,
.Xr MODULE_DEPEND 9 ,
.Xr MODULE_VERSION 9 ,
.Xr SYSCALL_MODULE 9
.Pp
.Pa /usr/share/examples/kld
.Sh AUTHORS
This man page was written by
.An Alexander Langer Aq alex@FreeBSD.org .
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