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From: vishniac@wanginst.UUCP (Ephraim Vishniac)
Newsgroups: net.micro.mac
Subject: Undocumented driver control codes?
Message-ID: <984@wanginst.UUCP>
Date: Mon, 26-Aug-85 09:46:10 EDT
Article-I.D.: wanginst.984
Posted: Mon Aug 26 09:46:10 1985
Date-Received: Wed, 28-Aug-85 20:11:36 EDT
Distribution: net
Organization: Wang Institute, Tyngsboro, Ma.  01879
Lines: 33

In the course of debugging a ramdisk driver, I've found that there are
several undocumented(?) control codes that the finder uses to interact with
disk drivers.  The clearly documented ones are:
	1 = kill (abort operation in progress and any queued operations)
	7 = eject (spit disk)
	8 = set tag buffer

The undocumented ones are:
	6 = erase (whole disk?  some fixed number of sectors?  some given
			number of sectors?)
	$14 = ?
	$15 = ?

Code 6 is used only when the disk is erased.  Codes 14 and 15 seem to be used
whenever the volume is mounted.  The .Sony driver does not support any of
these - it just returns -$11 (controlErr) for any code except 1, 7, or 8.
The Assimilation process ramdisk acts on code 6 by erasing as many sectors
as given by the word at ApplScratch in low ram.  I don't think that's right.
My disk behaves acceptably if I erase the boot, map, and directory sectors
in response to a 6.

Does anyone know what $14 and $15 are supposed to do?  Does anyone know
*for certain* what 6 is supposed to do?

Also, a bug in Macsbug:  when disassembling moveq instructions with negative
contants, the constant is complemented.  For example, moveq #-$11,d0 would
disassemble as moveq #-$6f,d0.  (And vice-versa!)

-- 
Ephraim Vishniac
  [apollo, bbncca, cadmus, decvax, harvard, linus, masscomp]!wanginst!vishniac
  vishniac%Wang-Inst@Csnet-Relay