Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!apple!well!gurgle
From: gurgle@well.sf.ca.us (Pete Gontier)
Newsgroups: comp.sys.mac.programmer
Subject: Re: trapping for floppy disk
Message-ID: <23818@well.sf.ca.us>
Date: 25 Mar 91 20:45:29 GMT
References: <1991Mar19.164204.8847@hubcap.clemson.edu> <6761@rex.cs.tulane.edu>
Organization: cellular
Lines: 32

In article <6761@rex.cs.tulane.edu> mandel@vax.anes.tulane.edu writes:
>In article <1991Mar19.164204.8847@hubcap.clemson.edu>, mcmac@hubcap.clemson.edu (Scott McAlister) writes:
>>I am working on an init that traps on MountVol.  What I want to do
>>is to distinguish between floppies and hard disks.  Can anybody help 
>>me out?  Sample code would be appreciated.  Thanks in advance.

>I had to figure this out once, and I seem to recall deciphering it from the
>Volume Control Block's vcbDrvNum field. I believe (but it may ONLY be a belief)
>that this was always 1 or 2 for floppies. In any event, if you have to be
>absolutely safe, you can walk the Drive Queue and check the flag bytes of the
>Drive Queue Element for that drive number; byte 1 will tell you if the volume
>is ejectable. See Inside Mac Vol IV pp 176-182 for confusion in greater depth.

Erm... I was waiting for an answer to this one, as well, and I don't
think this is it.

The problem is that at MountVol time, the volume isn't mounted. It's
possible to tail-patch MountVol -- AFTER MountVol, at least you have
a vRefNum and you can run the VCB's looking for it. Then you can get
the handle/pointer to the driver itself and look for its name. "\p.Sony"
is a foolproof way of getting an indication you've a floppy on your
hands, as long as it's smaller than 20M (the original Apple HD20 used
the Sony driver).

However, tail-patching is a no-no. If you head-patch MountVol, you get
the drive number as a parameter, and you can use the strategy proposed
by mandel@vax.anes.tulane.edu once you have the drive number. But I
wouldn't guess that it's fool-proof. I wonder what the drive number of
the ROM disk in some of the newer model Macs is...
-- 
 Pete Gontier, gurgle@well.sf.ca.us
 Software Imagineer, Kiwi Software, Inc.