1996-09-23 22:24:39 +00:00
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.\" $Id$
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1995-01-25 09:18:56 +00:00
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.Dd August 27, 1993
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.Dt CH 4
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.Os FreeBSD
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.Sh NAME
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.Nm ch
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.Nd scsi media-changer (juke box) driver
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.Sh SYNOPSIS
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1995-03-01 22:32:38 +00:00
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.Nm device ch
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.Nm device ch1 target 4 lun 0
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1995-01-25 09:18:56 +00:00
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.Sh DESCRIPTION
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The
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.Xr ch
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driver provides support for a
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.Em scsi
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juke box. It allows many slots of media to be multiplexed between a number
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of drives.
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.Pp
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1996-01-30 13:52:50 +00:00
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A scsi adapter must also be separately configured into the system
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1995-01-25 09:18:56 +00:00
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before a scsi changer can be configured.
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.Pp
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As the scsi adapter is probed during boot, the
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.Em SCSI
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bus is scanned for devices. Any devices found which answer as 'Changer'
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type devices will be 'attached' to the
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.Nm
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1995-03-01 22:32:38 +00:00
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driver.
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In FreeBSD releases prior to 2.1, the first found will be attached as
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1995-01-25 09:18:56 +00:00
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.Em ch0
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and the next,
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.Em ch1
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etc.
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1995-03-01 22:32:38 +00:00
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Beginning in 2.1 it is possible to specify what ch unit a device should
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come on line as; refer to
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.Xr scsi 4
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for details on kernel configuration.
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1995-01-25 09:18:56 +00:00
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.Pp
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.Sh KERNEL CONFIGURATION
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In configuring, if an optional
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.Ar count
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is given in the specification, that number of scsi media changers
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are configured; Most storage for them is allocated only when found
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so a large number of configured devices is cheap. (once the first
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has included the driver).
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.Pp
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.Sh IOCTLS
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The following
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.Xr ioctl 2
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call applies to the changer. It is defined in
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in the header file
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.Em sys/chio.h.
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.Bl -tag -width DIOCSDINFO
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CHIOOP
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This appears to be a 'do-everything' call.
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.El
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.Sh NOTES
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The
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.Nm
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driver was added to the system by
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Stefan Grefen (grefen@goofy.zdv.uni-mainz.de)
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who apparently had such a device
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however It appears as though no-one I have heard of has ever used this
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driver. If you use it please let me know so I can test changes.
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Stefan appears to have suffered net.death (or at least net.disconnection).
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I (julian) have never used this device. If you do please re-write this
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man page and send it to me..
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.Sh FILES
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.Bl -tag -width /dev/ch[0-9] -compact
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.It Pa /dev/ch[0-9]
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device entries
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.El
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.Sh DIAGNOSTICS
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None.
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.Sh SEE ALSO
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1996-09-23 22:24:39 +00:00
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.Xr sd 4 ,
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.Xr st 4 ,
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1995-01-25 09:18:56 +00:00
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.Xr cd 4
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.Sh HISTORY
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The
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.Nm
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driver appeared in 386BSD 0.1
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