[7884] in linux-scsi channel archive
Re: Another multi-lun CD changer (was: ... simultaneous access problem)
daemon@ATHENA.MIT.EDU (Eric Youngdale)
Sat Jan 22 07:36:36 2000
Message-ID: <000c01bf640e$5588ed60$2017a8c0@eric.home>
From: "Eric Youngdale" <eric@andante.org>
To: "Brendan Miller" <brmiller@netgate.net>,
"Ishikawa" <ishikawa@yk.rim.or.jp>
Cc: "LINUX SCSI" <linux-scsi@vger.rutgers.edu>
Date: Fri, 21 Jan 2000 07:52:10 -0500
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----- Original Message -----
From: "Brendan Miller" <brmiller@netgate.net>
To: "Ishikawa" <ishikawa@yk.rim.or.jp>
Cc: "Eric Youngdale" <eric@andante.org>; "LINUX SCSI"
<linux-scsi@vger.rutgers.edu>
Sent: Friday, January 21, 2000 3:01 AM
Subject: Re: Another multi-lun CD changer (was: ... simultaneous access
problem)
> > If you did it WITHOUT blacklisting and succeed, I need
> > to dig into the scsi code and check if the meaning of the flag
> > is somehow treated in a reverse manner or whatever.
> >
>
> Well, I was looking through scsi.c to see what all those device flags
> mean. I got to a part where it says:
>
> /*
> * If we want to only allow I/O to one of the luns attached to this
device
> * at a time, then we set this flag.
> */
> if (bflags & BLIST_SINGLELUN)
> SDpnt->single_lun = 1;
>
> Should I interpret this that the SINGLELUN flag means "only talk to one
> LUN at a time"? Maybe this is part of the problem, since your problems
> begin when doing simultaneous access...
Yes, BLIST_SINGLELUN is the one you want. It was designed for this
purpose.
> How do you know if a device can only handle a single lun communication
> at a time? A lot of the devices "with special flags" have SINGLELUN
> enabled. How is this determined? What is the effect on the usability?
They are all changers :-).
> As for my "5 LUNS" problem, Eric said there already was a MAX5LUN
> employed for some Regal device. Is this the hack that avoids having
> to specify "max_scsi_luns=5" in the boot prompt?
Yes. Look at REGAL again - the flags they use are both SINGLELUN and
5LUNS. This is exactly the same set of flags that you need to be using.
-Eric
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