From: "Alan" <LMail AT optonline DOT net>
Newsgroups: comp.os.msdos.djgpp
Subject: Physical Address Mapping Problem
Lines: 59
X-Priority: 3
X-MSMail-Priority: Normal
X-Newsreader: Microsoft Outlook Express 5.50.4522.1200
X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4522.1200
Message-ID: <rpW26.50336$nM5.8360195@news02.optonline.net>
Date: Fri, 29 Dec 2000 06:44:39 GMT
NNTP-Posting-Host: 167.206.69.80
X-Trace: news02.optonline.net 978072279 167.206.69.80 (Fri, 29 Dec 2000 01:44:39 EST)
NNTP-Posting-Date: Fri, 29 Dec 2000 01:44:39 EST
Organization: Optimum Online
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Reply-To: djgpp AT delorie DOT com

I'm trying to map the physical address of a PCI board, whose BAR0 register
contains 0xE1410000.  So, it should be a memory mapped.  Probing the BAR
with 0xFFFFFFFF gives a length of 512 bytes.

I wrote a quick test to see if I could address the memory:

The register at offset 0xFC is a 32 bit r/w register.  When read, the upper
16 bits return all zeros.  After a reset, the register should read back
0x00000100.  An NT driver and a VxWorks driver both read back the correct
value.  Unfortunately, the output of this test program is:

MC1=0xFFFFFFFF

Hmmm...  Anyone have any idea what I'm doing wrong?

I'm running DOS 6.22 and I've tried it both with and without Himem.sys and
emm386.exe.  I always get the same result.

Thanks in advance for your time!


#include <stdio.h>
#include <io.h>
#include <dpmi.h>

int main ()
{
 int  CaptureSelector;
 char Buf[256];
 __dpmi_meminfo mi;

 /* Map the physical device address to linear memory.  */
 mi.address=0xE1410000;
 mi.size=0x200;
 if (__dpmi_physical_address_mapping (&mi) == -1)
  return 1;

 /* Now mi.address holds the linear address.  */

 /* Allocate an LDT descriptor and set it up to span the entire
   device on-board memory.  */
 CaptureSelector=__dpmi_allocate_ldt_descriptors (1);
 if (CaptureSelector == -1)
  return 2;

 if (__dpmi_set_segment_base_address (CaptureSelector, mi.address) == -1)
  return 3;

 if (__dpmi_set_segment_limit (CaptureSelector, mi.size - 1) == -1)
  return 4;

 sprintf (Buf, "MC1=0x%08X\r\n\n", _farpeekl (CaptureSelector, 0xFC));
 _write (2, Buf, strlen (Buf));

 return 0;

}