1.\" 2.\" Copyright (c) 1996 Joerg Wunsch 3.\" 4.\" All rights reserved. 5.\" 6.\" This program is free software. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 17.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR 18.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 19.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 20.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT, 21.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 22.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27.\" 28.\" $FreeBSD: src/share/man/man4/man4.i386/io.4,v 1.6.2.2 2000/12/12 10:00:55 ru Exp $ 29.\" 30.Dd January 1, 1996 31.Dt IO 4 i386 32.Os 33.Sh NAME 34.Nm io 35.Nd I/O privilege file 36.Sh DESCRIPTION 37.Bf -symbolic 38This device is obsolete and is provided for compatibility purposes 39only; use 40.Xr i386_iopl 2 41instead. 42.Ef 43.Pp 44After opening 45.Pa /dev/io 46for writing 47the process is granted full I/O privileges; closing the returned file 48descriptor does 49.Em not 50result in revocation of these privileges. 51The new I/O privileges can be useful in order to write userland 52programs that handle some hardware directly. 53.Pp 54The entire access control is handled by the file access permissions 55of 56.Pa /dev/io , 57so care should be taken in granting rights for this device. 58.Pp 59I/O privilege on access to 60.Pa /dev/io 61is only granted if the kernel was built with the 62.Dv COMPAT_10 63option. 64.Sh FILES 65.Bl -tag -width Pa -compact 66.It Pa /dev/io 67.El 68.Sh SEE ALSO 69.Xr mem 4 70.Sh HISTORY 71The 72.Nm 73file appeared in 74.Nx 1.0 75after it was in the kernel for some time. 76