1.\" $NetBSD: nullop.9,v 1.1 2010/07/25 21:05:13 jruoho Exp $ 2.\" 3.\" Copyright (c) 2010 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by Jukka Ruohonen. 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 NETBSD FOUNDATION, INC. AND CONTRIBUTORS 19.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 20.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 21.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 22.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 23.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 24.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 25.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 26.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 27.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 28.\" POSSIBILITY OF SUCH DAMAGE. 29.\" 30.Dd July 25, 2010 31.Dt NULLOP 9 32.Os 33.Sh NAME 34.Nm nullop 35.Nd dummy functions 36.Sh SYNOPSIS 37.In sys/systm.h 38.Ft int 39.Fn nullop "void *v" 40.Ft void 41.Fn voidop "void" 42.Ft int 43.Fn enodev "void" 44.Ft int 45.Fn enxio "void" 46.Ft int 47.Fn enoioctl "void" 48.Ft int 49.Fn enosys "void" 50.Ft int 51.Fn eopnotsupp "void" 52.Sh DESCRIPTION 53The 54.Fn nullop 55function provides a generic 56.Dq null operation . 57It always returns the value 0. 58The 59.Fn voidop 60function takes no arguments and does nothing. 61.Pp 62The 63.Fn enodev , 64.Fn enxio , 65.Fn enoioctl , 66.Fn enosys , 67and 68.Fn eopnotsupp 69functions always fail, returning 70.Er ENODEV , 71.Er ENXIO , 72.Er ENOTTY , 73.Er ENOSYS , 74and 75.Er EOPNOTSUPP , 76respectively. 77.Sh EXAMPLES 78The following example demonstrates a case where 79.Fn nullop 80may be useful: 81.Bd -literal -offset indent 82uint64_t xc; 83 84\&... 85 86xc = xc_broadcast(0, (xcfunc_t)nullop, NULL, NULL); 87xc_wait(xc); 88.Ed 89