1.\" $Id$ 2.\" Copyright (c) 1996 3.\" Julian Elischer <julian@freebsd.org>. All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 16.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25.\" SUCH DAMAGE. 26.\" 27.Dd August 27, 1993 28.Dt CH 4 29.Os FreeBSD 30.Sh NAME 31.Nm ch 32.Nd scsi media-changer (juke box) driver 33.Sh SYNOPSIS 34.Cd device ch 35.Cd device ch1 target 4 lun 0 36.Sh DESCRIPTION 37The 38.Xr ch 39driver provides support for a 40.Em scsi 41juke box. It allows many slots of media to be multiplexed between a number 42of drives. 43.Pp 44A scsi adapter must also be separately configured into the system 45before a scsi changer can be configured. 46.Pp 47As the scsi adapter is probed during boot, the 48.Em SCSI 49bus is scanned for devices. Any devices found which answer as 'Changer' 50type devices will be 'attached' to the 51.Nm 52driver. 53In FreeBSD releases prior to 2.1, the first found will be attached as 54.Em ch0 55and the next, 56.Em ch1 57etc. 58Beginning in 2.1 it is possible to specify what ch unit a device should 59come on line as; refer to 60.Xr scsi 4 61for details on kernel configuration. 62.Pp 63 64.Sh KERNEL CONFIGURATION 65In configuring, if an optional 66.Ar count 67is given in the specification, that number of scsi media changers 68are configured; Most 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 72.Pp 73.Sh IOCTLS 74The following 75.Xr ioctl 2 76call applies to the changer. It is defined in 77in the header file 78.Em sys/chio.h. 79 80.Bl -tag -width DIOCSDINFO 81CHIOOP 82This appears to be a 'do-everything' call. 83.El 84.Sh NOTES 85The 86.Nm 87driver was added to the system by 88 Stefan Grefen (grefen@goofy.zdv.uni-mainz.de) 89who apparently had such a device 90however It appears as though no-one I have heard of has ever used this 91driver. If you use it please let me know so I can test changes. 92Stefan appears to have suffered net.death (or at least net.disconnection). 93I (julian) have never used this device. If you do please re-write this 94man page and send it to me.. 95 96.Sh FILES 97.Bl -tag -width /dev/ch[0-9] -compact 98.It Pa /dev/ch[0-9] 99device entries 100.El 101.Sh DIAGNOSTICS 102None. 103.Sh SEE ALSO 104.Xr cd 4 , 105.Xr sd 4 , 106.Xr st 4 107.Sh HISTORY 108The 109.Nm 110driver appeared in 386BSD 0.1. 111