1.\" $Id$ 2.Dd August 27, 1993 3.Dt CH 4 4.Os FreeBSD 5.Sh NAME 6.Nm ch 7.Nd scsi media-changer (juke box) driver 8.Sh SYNOPSIS 9.Nm device ch 10.Nm device ch1 target 4 lun 0 11.Sh DESCRIPTION 12The 13.Xr ch 14driver provides support for a 15.Em scsi 16juke box. It allows many slots of media to be multiplexed between a number 17of drives. 18.Pp 19A scsi adapter must also be separately configured into the system 20before a scsi changer can be configured. 21.Pp 22As the scsi adapter is probed during boot, the 23.Em SCSI 24bus is scanned for devices. Any devices found which answer as 'Changer' 25type devices will be 'attached' to the 26.Nm 27driver. 28In FreeBSD releases prior to 2.1, the first found will be attached as 29.Em ch0 30and the next, 31.Em ch1 32etc. 33Beginning in 2.1 it is possible to specify what ch unit a device should 34come on line as; refer to 35.Xr scsi 4 36for details on kernel configuration. 37.Pp 38 39.Sh KERNEL CONFIGURATION 40In configuring, if an optional 41.Ar count 42is given in the specification, that number of scsi media changers 43are configured; Most storage for them is allocated only when found 44so a large number of configured devices is cheap. (once the first 45has included the driver). 46 47.Pp 48.Sh IOCTLS 49The following 50.Xr ioctl 2 51call applies to the changer. It is defined in 52in the header file 53.Em sys/chio.h. 54 55.Bl -tag -width DIOCSDINFO 56CHIOOP 57This appears to be a 'do-everything' call. 58.El 59.Sh NOTES 60The 61.Nm 62driver was added to the system by 63 Stefan Grefen (grefen@goofy.zdv.uni-mainz.de) 64who apparently had such a device 65however It appears as though no-one I have heard of has ever used this 66driver. If you use it please let me know so I can test changes. 67Stefan appears to have suffered net.death (or at least net.disconnection). 68I (julian) have never used this device. If you do please re-write this 69man page and send it to me.. 70 71.Sh FILES 72.Bl -tag -width /dev/ch[0-9] -compact 73.It Pa /dev/ch[0-9] 74device entries 75.El 76.Sh DIAGNOSTICS 77None. 78.Sh SEE ALSO 79.Xr sd 4 , 80.Xr st 4 , 81.Xr cd 4 82.Sh HISTORY 83The 84.Nm 85driver appeared in 386BSD 0.1 86 87