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