1.\" -*- nroff -*- 2.\" 3.\" Copyright (c) 2000 Alexander Langer 4.\" 5.\" All rights reserved. 6.\" 7.\" This program is free software. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR 19.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 20.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 21.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT, 22.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 23.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 24.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 25.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 26.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 27.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 28.\" 29.\" $FreeBSD$ 30.\" 31.Dd November 11, 2021 32.Dt MODULE 9 33.Os 34.Sh NAME 35.Nm module 36.Nd structure describing a kernel module 37.Sh DESCRIPTION 38Each module in the kernel is described by a 39.Vt module_t 40structure. 41The structure contains the name of the device, a unique ID number, 42a pointer to an event handler function and to an argument, 43which is given to the event handler, 44as well as some kernel internal data. 45If the event handler function is 46.Dv NULL , 47the module will use a no-operation function handler instead. 48.Pp 49The 50.Xr DECLARE_MODULE 9 51macro 52registers the module with the system. 53.Pp 54When the module is loaded, the event handler function is called with 55the 56.Fa what 57argument set to 58.Dv MOD_LOAD . 59.Pp 60On unload it is first called with 61.Fa what 62set to 63.Dv MOD_QUIESCE . 64If the unload was not forced, a non-zero return will prevent the 65unload from happening. 66.Pp 67If the unload continues 68.Fa what 69is set to 70.Dv MOD_UNLOAD . 71If the module returns non-zero to this, the unload will not happen. 72.Pp 73The difference between 74.Dv MOD_QUIESCE 75and 76.Dv MOD_UNLOAD 77is that the module should fail 78.Dv MOD_QUIESCE 79if it is currently in use, whereas 80.Dv MOD_UNLOAD 81should only fail if it is impossible to unload the module, for instance 82because there are memory references to the module which cannot be revoked. 83.Pp 84When the system is shutting down, 85.Fa what 86contains the value of 87.Dv MOD_SHUTDOWN . 88.Pp 89The module should return 90.Er EOPNOTSUPP 91for unsupported and unrecognized values of 92.Fa what . 93.Sh EXAMPLES 94.Bd -literal 95#include <sys/param.h> 96#include <sys/kernel.h> 97#include <sys/module.h> 98 99static int foo_handler(module_t mod, int /*modeventtype_t*/ what, 100 void *arg); 101 102static moduledata_t mod_data= { 103 "foo", 104 foo_handler, 105 NULL 106}; 107 108MODULE_VERSION(foo, 1); 109MODULE_DEPEND(foo, bar, 1, 3, 4); 110 111DECLARE_MODULE(foo, mod_data, SI_SUB_EXEC, SI_ORDER_ANY); 112.Ed 113.Sh SEE ALSO 114.Xr DECLARE_MODULE 9 , 115.Xr DEV_MODULE 9 , 116.Xr DRIVER_MODULE 9 , 117.Xr MODULE_DEPEND 9 , 118.Xr MODULE_PNP_INFO 9 , 119.Xr MODULE_VERSION 9 , 120.Xr SYSCALL_MODULE 9 121.Pp 122.Pa /usr/share/examples/kld 123.Sh AUTHORS 124This manual page was written by 125.An Alexander Langer Aq Mt alex@FreeBSD.org . 126