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+.\"	$OpenBSD: ch.4,v 1.1 1997/06/04 07:37:57 grr Exp $
+.\"	$FreeBSD$
+.\" Copyright (c) 1996
+.\"	Julian Elischer <julian@freebsd.org>.  All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\"
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.Dd March 28, 1997
+.Dt CH 4
+.Os OpenBSD
+.Sh NAME
+.Nm ch
+.Nd scsi media-changer (juke box) driver
+.Sh SYNOPSIS
+.Cd "ch? at scsibus? target ? lun ?"
+.Sh DESCRIPTION
+The
+.Xr ch
+driver provides support for a 
+.Em scsi
+juke box. It allows many slots of media to be multiplexed between a number
+of drives.
+.Pp
+A scsi adapter and a logical scsibuss must also be separately configured
+into the system before a scsi changer can be configured.
+.Pp
+As the scsi adapter is probed during boot, the 
+.Em SCSI
+bus is scanned for devices. Any devices found which answer as 'Changer'
+type devices will be 'attached' to the 
+.Nm
+driver.
+The first device found will be attached as
+.Em ch0
+and the next, 
+.Em ch1
+etc.
+It is also possible to specify what ch unit a device should
+come on line as; refer to
+.Xr scsi 4
+for details on kernel configuration.
+.Pp
+
+.Sh KERNEL CONFIGURATION
+In configuring, if an optional
+.Ar count
+is given in the specification, that number of scsi media changers
+are configured; Most storage for them is allocated only when found
+so a large number of configured devices is cheap. (once the first
+has included the driver).
+
+.Pp
+.Sh IOCTLS
+The following 
+.Xr ioctl 2
+call applies to the changer. It is defined in
+in the header file
+.Em sys/chio.h.
+
+.Bl -tag -width DIOCSDINFO
+CHIOOP	
+This appears to be a 'do-everything' call.
+.El
+.Sh NOTES
+The 
+.Nm
+driver was added to the system by
+   Stefan Grefen (grefen@goofy.zdv.uni-mainz.de)
+who apparently had such a device
+however It appears as though no-one I have heard of has ever used this
+driver. If you use it please let me know so I can test changes.
+Stefan appears to have suffered net.death (or at least net.disconnection).
+I (julian) have never used this device. If you do please re-write this
+man page and send it to me..
+
+.Sh FILES
+.Bl -tag -width /dev/ch[0-9] -compact
+.It Pa /dev/ch[0-9]
+device entries
+.El
+.Sh DIAGNOSTICS
+None.
+.Sh SEE ALSO
+.Xr cd 4 ,
+.Xr sd 4 ,
+.Xr st 4
+.Sh DISCLAIMER
+These manpages were derived from the
+.Tn FreeBSD
+documentation of the generic scsi drivers.  Since naming and calling
+conventions may have diverged or suffered port specific changes, please
+review the appropriate header files and configuration file for your port.
+.Sh HISTORY
+The
+.Nm
+driver appeared in 386BSD 0.1.