NetBSD-5.0.2/share/man/man4/man4.i386/io.4

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.\" $NetBSD: io.4,v 1.4 2002/01/15 01:42:01 wiz Exp $
.\"
.\" Copyright (c) 1996 Joerg Wunsch
.\"
.\" All rights reserved.
.\"
.\" This program is free software.
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.\" $FreeBSD: src/share/man/man4/man4.i386/io.4,v 1.6.2.2 2000/12/12 10:00:55 ru Exp $
.\"
.Dd January 1, 1996
.Dt IO 4 i386
.Os
.Sh NAME
.Nm io
.Nd I/O privilege file
.Sh DESCRIPTION
.Bf -symbolic
This device is obsolete and is provided for compatibility purposes
only; use
.Xr i386_iopl 2
instead.
.Ef
.Pp
After opening
.Pa /dev/io
for writing
the process is granted full I/O privileges; closing the returned file
descriptor does
.Em not
result in revocation of these privileges.
The new I/O privileges can be useful in order to write userland
programs that handle some hardware directly.
.Pp
The entire access control is handled by the file access permissions
of
.Pa /dev/io ,
so care should be taken in granting rights for this device.
.Pp
I/O privilege on access to
.Pa /dev/io
is only granted if the kernel was built with the
.Dv COMPAT_10
option.
.Sh FILES
.Bl -tag -width Pa -compact
.It Pa /dev/io
.El
.Sh SEE ALSO
.Xr mem 4
.Sh HISTORY
The
.Nm
file appeared in
.Nx 1.0
after it was in the kernel for some time.