From: Neil Goldberg <ngoldber AT mitre DOT org>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Device Driver programming with DJGPP
Date: Tue, 10 Aug 1999 08:59:13 +0100
Organization: The MITRE Corporation
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

Javier Reyes wrote:
> 
> Hi Guys,
> 
> I need to program a very simple device driver for a PCI card. I just
> need to be able to read and write to/from memory at 0xF0000000. Can
> anyone tell me where to find the source code sample to do it ?
> 
> Thanks in advance,
> 
> Javier
> 
> PS: Please reply to me if possible.
I sent two replies. You have to something from both of them. Let's try
this again, from start to finish so there's no confusion.

This should work fine:

#include "dpmi.h"
#include "go32.h"
//Include your other headers...
some function
{

//Yadda Yadda Yadda, get all your preliminary stuff..

__dpmi_meminfo MABuffer;
//Buffer with all your info...
MABuffer.size = total_interface_size_in_bytes;
MABuffer.address = 0xF0000000; //That's what you want, right?

__dpmi_physical_address_mapping(&MABuffer);
//Replace MABuffer.address with an equivalent linear address.

int selector = __dpmi_allocate_ldt_descriptors(1);
__dpmi_set_segment_base_address(selector, MABuffer.address);
__dpmi_set_segment_limit(selector, total_pages_size_in_bytes);
//Set up your selector to point to this buffer
/*The physical region 0xF0000000 is now mapped into linear, protected
memory and now you've got a selector to access it*/

//Here's your code that uses the selector to access your PCI card (use
_far* functions or movedata, etc.)

__dpmi_free_ldt_descriptor(selector);
//Free the selector at the end.
}

If anything bad happens with that code,
give me all the specifics (all values, selectors, sizes, addresses to
map,
etc). It'll help me to see what went wrong.


moogla