1.\" $NetBSD: io.4,v 1.4 2002/01/15 01:42:01 wiz Exp $ 2.\" 3.\" Copyright (c) 1996 Joerg Wunsch 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: src/share/man/man4/man4.i386/io.4,v 1.6.2.2 2000/12/12 10:00:55 ru Exp $ 30.\" 31.Dd January 1, 1996 32.Dt IO 4 i386 33.Os 34.Sh NAME 35.Nm io 36.Nd I/O privilege file 37.Sh DESCRIPTION 38.Bf -symbolic 39This device is obsolete and is provided for compatibility purposes 40only; use 41.Xr i386_iopl 2 42instead. 43.Ef 44.Pp 45After opening 46.Pa /dev/io 47for writing 48the process is granted full I/O privileges; closing the returned file 49descriptor does 50.Em not 51result in revocation of these privileges. 52The new I/O privileges can be useful in order to write userland 53programs that handle some hardware directly. 54.Pp 55The entire access control is handled by the file access permissions 56of 57.Pa /dev/io , 58so care should be taken in granting rights for this device. 59.Pp 60I/O privilege on access to 61.Pa /dev/io 62is only granted if the kernel was built with the 63.Dv COMPAT_10 64option. 65.Sh FILES 66.Bl -tag -width Pa -compact 67.It Pa /dev/io 68.El 69.Sh SEE ALSO 70.Xr mem 4 71.Sh HISTORY 72The 73.Nm 74file appeared in 75.Nx 1.0 76after it was in the kernel for some time. 77