1.\" $OpenBSD: ch.4,v 1.7 2000/07/10 13:02:25 aaron Exp $ 2.\" 3.\" Copyright (c) 1996 4.\" Julian Elischer <julian@freebsd.org>. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.Dd March 28, 1997 29.Dt CH 4 30.Os 31.Sh NAME 32.Nm ch 33.Nd scsi media-changer (juke box) driver 34.Sh SYNOPSIS 35.Cd "ch? at scsibus? target ? lun ?" 36.Sh DESCRIPTION 37The 38.Nm 39driver provides support for SCSI juke boxes. 40It allows many slots of media to be multiplexed between a number of drives. 41.Pp 42A SCSI adapter and a logical scsibus must also be separately configured 43into the system before a SCSI changer can be configured. 44.Pp 45As the SCSI adapter is probed during boot, the SCSI bus is scanned for devices. 46Any devices found which answer as 47.Qq Changer 48type devices will be 49.Dq attached 50to the 51.Nm 52driver. 53The first device found will be attached as 54.Em ch0 55and the next 56.Em ch1 , 57etc. 58It is also possible to specify what 59.Nm 60unit a device should come on-line as; refer to 61.Xr scsi 4 62for details on kernel configuration. 63.Sh KERNEL CONFIGURATION 64In configuring, if an optional 65.Ar count 66is given in the specification, that number of SCSI media changers 67are configured. 68Most storage for them is allocated only when found 69so a large number of configured devices is cheap (once the first 70has included the driver). 71.Sh IOCTLS 72The following 73.Xr ioctl 2 74call applies to the changer. 75It is defined in the header file 76.Aq Pa sys/chio.h . 77.Bl -tag -width DIOCSDINFO 78.It Dv CHIOOP 79This appears to be a 80.Dq do-everything 81call. 82.El 83.Sh FILES 84.Bl -tag -width /dev/ch[0-9] -compact 85.It Pa /dev/ch[0-9] 86device entries 87.El 88.Sh SEE ALSO 89.Xr cd 4 , 90.Xr scsi 4 , 91.Xr sd 4 , 92.Xr st 4 93.Sh DISCLAIMER 94These manpages were derived from the 95.Fx 96documentation of the generic SCSI drivers. 97Since naming and calling conventions may have diverged or suffered port 98specific changes, please review the appropriate header files and configuration 99file for your port. 100.Sh HISTORY 101The 102.Nm 103driver appeared in 386BSD 0.1. 104