NAME    [Toc]    [Back]

     ch - scsi media-changer (juke box) driver

SYNOPSIS    [Toc]    [Back]

     ch? at scsibus? target ? lun ?

DESCRIPTION    [Toc]    [Back]

     The ch driver provides support for SCSI juke boxes.  It  allows many slots
     of media to be multiplexed between a number of drives.

     A SCSI adapter and a logical scsibus must also be separately
configured
     into the system before a SCSI changer can be configured.

     As the SCSI adapter is probed during boot, the SCSI  bus  is
scanned for
     devices.   Any  devices found which answer as "Changer" type
devices will
     be ``attached'' to the ch driver.  The  first  device  found
will be attached
 as ch0 and the next ch1, etc.  It is also possible to
specify what
     ch unit a device should come on-line as;  refer  to  scsi(4)
for details on
     kernel configuration.

KERNEL CONFIGURATION    [Toc]    [Back]

     In  configuring, if an optional 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).

IOCTLS    [Toc]    [Back]

     The following ioctl(2) call applies to the changer.   It  is
defined in the
     header file <sys/chio.h>.

     CHIOOP      This appears to be a ``do-everything'' call.

FILES    [Toc]    [Back]

     /dev/ch[0-9]  device entries

SEE ALSO    [Toc]    [Back]

     cd(4), intro(4), scsi(4), sd(4), st(4)

DISCLAIMER    [Toc]    [Back]

     These  manpages  were derived from the 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.

HISTORY    [Toc]    [Back]

     The ch driver appeared in 386BSD 0.1.

OpenBSD     3.6                          March      28,      1997