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Subject: Re: Obtaining the physical address of a pointer using PMODE
Date: Wed, 16 Nov 2005 10:06:45 -0700
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Thread-Topic: Re: Obtaining the physical address of a pointer using PMODE
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From: "Schumacher, Gordon" <gordon_schumacher AT maxtor DOT com>
To: "DJGPP List \(E-mail\)" <djgpp AT delorie DOT com>
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# From: "Roland Zitzke" <NZEONTQYRAHL AT spammotel DOT com>
# Sent: Tuesday, November 15, 2005 12:16 PM
# To: djgpp AT delorie DOT com
# Subject: Re: Obtaining the physical address of a pointer using PMODE
#
# Hi,
# I read somewhere, that the pmode/dj extender has a fixed mapping of
# pointers to physical memory.
# Thus, if I write something like
# unsigned char* p = malloc(1024);
# how can I obtain the physical location of the data pointed to by p,
# provided that I use pmode?
# Background is that I need this to allocate a DMA buffer and I do not
# necessarily need virtual memory in my application.
#
# Thanks and regards
# Roland

Try this thread:

http://www.delorie.com/djgpp/mail-archives/browse.cgi?p=djgpp/2001/04/13/12:21:37
http://www.delorie.com/djgpp/mail-archives/browse.cgi?p=djgpp/2001/04/14/01:01:55
http://www.delorie.com/djgpp/mail-archives/browse.cgi?p=djgpp/2001/05/09/17:04:12
http://www.delorie.com/djgpp/mail-archives/browse.cgi?p=djgpp/2001/05/09/16:33:37

Charles Sandmann gave us some example code, and put it at
ftp://clio.rice.edu/djgpp/cwsdma.zip.  He was talking about cleaning
it up and making it more publicized; I don't know if that ever happened.

But hopefully that's a good start.  If you get stuck, I still have the
e-mail thread that went on when we were tackling this same problem.