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Date: Sat, 11 May 1996 03:44:41 -0700 (PDT)
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To: bde@zeta.org.au
CC: jgreco@brasil.moneng.mei.com, current@freebsd.org, nisha@cs.berkeley.edu
In-reply-to: <199605101430.AAA17773@godzilla.zeta.org.au> (message from Bruce Evans on Sat, 11 May 1996 00:30:45 +1000)
Subject: Re: more than 32 scsi disks on a single machine ?
From: asami@cs.berkeley.edu (Satoshi Asami)
Sender: owner-current@freebsd.org
X-Loop: FreeBSD.org
Precedence: bulk

 * You mostly preserved compatibility with the existing device nodes, provided
 * everything uses the dk macros and functions.

Well if they don't use them, they just won't be able to see disks >
32. :>

 * I use 6 TYPE bits in the floppy driver.  Committing this has been
 * waiting about 1.5 years because I don't want to rearrange everyone's fd
 * minors.  Please bits from the top of the original TYPE.  PART2 should be
 * taking from the top too.

You mean both UNIT2 and PART2 should have been taken from the highest
bit?  Well I guess that's ok as long as there isn't a device that uses 
both (Julian, what was the PART2 for?)....  By the way, should I avoid 
the MSB for sign-extension problems?

 * 			     Watch out for the scsictl bit in MAKEDEV.

According to MAKEDEV, scsictl is 0x20000000.  We'll run into it in a
major way if we try to take some (contiguous) bits from the top.

 * `unit' is now evaluated multiply and there are too many columns.

I can put in a \ for the columns, but I didn't think multiple
evaluation of units was bad.  I thought people aren't supposed to do
mkmakeminor(unit++, slice, part) kind of stuff with macros anyway.
Should I use a gcc extension or something to save the value of unit to 
a temporary variable?

 * `dev' is now evaluated multiply and there are too many columns.

Ok ok.... ;)

 * The type bits now overlap ...

You mean with the 6 bits you are using?

 * scsictl should have been a `type' bit.  Maybe it is :-).

Well it *is* in there. :)

 * devfs should be finished so that minor numbers become irrelevant.

I think that's the best solution too!  (Ok, letting someone else do
the work, my favorite means of accomplishing the goal. :)

Satoshi