Path: utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!wuarchive!usc!ucsd!ucbvax!hoptoad!tim
From: tim@hoptoad.uucp (Tim Maroney)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Opening Drivers
Message-ID: <9310@hoptoad.uucp>
Date: 16 Dec 89 22:50:00 GMT
References: <7421@hubcap.clemson.edu>
Reply-To: tim@hoptoad.UUCP (Tim Maroney)
Organization: Eclectic Software, San Francisco
Lines: 27

In article <7421@hubcap.clemson.edu> mikeoro@hubcap.clemson.edu (Michael
K O'Rourke) writes:
>First, I know that there are a certain number of "slots" for use by
>drivers and da's.  Does my driver have to be numbered as one of those
>slots?  For instance, I am opening the driver from an INIT and the driver
>will continue to run in the background while the machine is running.  Am
>i going to have to look thru the system file at boot time to see if there
>is an empty slot, renumber my driver and then open it?

Close.  Check the unit table, not the system file.  Walk over the unit
table in a way similar to that of Tech Note #71.  Look for an empty
DCE entry.  You may then install yourself as the driver with the
reference number corresponding to the empty slot.  Use the _DrvrInstall
trap documented in Tech Note #108.

>I read the device
>manager stuff but am still confused on this point.  My guess is that the
>refNum passed by OpenDriver() will give me the slot i am in.  Is this correct?

It doesn't give you the slot number, but it gives you a reference number
from which the slot number can readily be derived; the slot number is
-1 * (refNum + 1).
-- 
Tim Maroney, Mac Software Consultant, sun!hoptoad!tim, tim@toad.com

"Those who restrain desire, do so because theirs is weak enough to be
 restrained..." - Blake, "The Marriage of Heaven and Hell"