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Subject: Re: DLT exchanger
In-Reply-To: <199703271913.LAA11872@lestat.nas.nasa.gov> from Jason Thorpe at "Mar 27, 97 11:13:18 am"
To: thorpej@nas.nasa.gov
Date: Thu, 27 Mar 1997 10:29:59 -1000 (HST)
Cc: arman@bico.co.id, freebsd-hackers@freebsd.org, freebsd-scsi@freebsd.org
From: "David Langford" <langfod@dihelix.com>
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>On Thu, 27 Mar 1997 23:30:19 +0700 (JVT) 
> Arman Hazairin Hasan <arman@BICO.co.id> wrote:
>
> >  Does any body knows the SCSI control command for DLT exchanger.
> >  I want to write a script that control the 'arm' of DLT exchanger
> >  in order to move the cartridge from repository to it's drive.
>
>If you're using FreeBSD-current, I believe you can use the chio(1)
>command if you have the "ch" driver in your kernel.  (Can't say for
>sure, since I don't run FreeBSD, but I think my driver was finally
>committed :-)
>Jason R. Thorpe                                       thorpej@nas.nasa.gov

Yes, it was!!! :)  I never did publicy thank the FreeBSD team for doing this.
So, if you guys are reading this THANK YOU!!!! 

The driver works well on the cheapo 4mm Archive/Seagate drive.
The thing that took me awhile to realize was that you had to be very
explicit with chio. You cannot tell it to move a tape into the drive
and expect it to return the one it already has.

Here is the stupid short write-up I did for someone:

The thing to keep in mind is that the tape changer is a robot.
Robots are dumb. Robots only do what you tell them to.
Unlike Douglas Adams you cannot have tape and no-tape at the same time.
You cannot hold two tapes in either the tape drive or the tape slot.

When tape starts it holds all tapes in holders and none it the drive.
Here is me moving tape from the third slot into the drive and back.
Then I move tape in the first slot into the drive.
Rule of thumb is:  chio "from" "to"

www /root% chio status
picker 0: 
slot 0: <ACCESS,FULL>
slot 1: <ACCESS,FULL>
slot 2: <ACCESS,FULL>
slot 3: <ACCESS,FULL>
drive 0: <ACCESS>
www /root% chio move slot 3 drive 0
www /root% chio status
picker 0: 
slot 0: <ACCESS,FULL>
slot 1: <ACCESS,FULL>
slot 2: <ACCESS,FULL>
slot 3: <ACCESS>
drive 0: <ACCESS,FULL>
www /root% chio move drive 0 slot 3
www /root% chio status
picker 0: 
slot 0: <ACCESS,FULL>
slot 1: <ACCESS,FULL>
slot 2: <ACCESS,FULL>
slot 3: <ACCESS,FULL>
drive 0: <ACCESS>
www /root% chio move slot 0 drive 0
www /root% chio status
picker 0: 
slot 0: <ACCESS>
slot 1: <ACCESS,FULL>
slot 2: <ACCESS,FULL>
slot 3: <ACCESS,FULL>
drive 0: <ACCESS,FULL>

-David Langford
 langfod@dihelix.com