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From: martyl@rocksvax.UUCP
Newsgroups: comp.sys.ibm.pc
Subject: ioctl on msdos device drivers
Message-ID: <959@rocksvax.UUCP>
Date: Sat, 4-Apr-87 13:33:26 EST
Article-I.D.: rocksvax.959
Posted: Sat Apr  4 13:33:26 1987
Date-Received: Sun, 5-Apr-87 12:48:02 EST
Organization: Xerox: Henrietta, NY
Lines: 30

I just wrote a COM port device driver which buffers both input and output.

I typically use my PC through the RS-232 interface and have a window on
my 6085 to communicate with the PC.  What I want to know is:

How do IOCTL really work?  I've looked in the DOS technical reference
and a number of books, and the general consensus on ioctl seems to be 
"you can send magic bytes to/from device drivers".

Is there any spec on what magic byte operations are supported?

I'm aware of an ioctl function in MSDOS (function 44H).  But how to I
figure out which features are interpreted by msdos and which are 
interpreted by the driver?

What are want to do is be able to turn raw mode on and off (so it can either
understand XON/XOFF or not).  There is a binary bit, but it is defined as
checking for cntl-Z.

I've been able to use this driver to figure out what MS-DOS does (by 
blasting information out to the monitor ram).  However, I'd rather have
a spec I can make sense out of than have to impirically figure out what the
OS does.

Thanks --

marty leisner
xerox corp.
leisner.henr@xerox.com
martyl@rocksvax.uucp