From:	"Malcolm Herring" <malcolm DOT herring AT btinternet DOT com>
Newsgroups:	comp.os.msdos.djgpp
Subject:	DPMI GPF problem
Date:	Sun, 14 May 2000 14:37:47 -0700
Organization:	BT Internet
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To:	djgpp AT delorie DOT com
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Reply-To:	djgpp AT delorie DOT com

I need to map to a physical address range to access a memory-mapped device.
The following code fragments is how I have tried to do it, but this results
in a GPF when 'movedatal' is called.

Help, anybody? - TIA

#include <dos.h>
#include <stdio.h>
#include <dpmi.h>
#include <sys/movedata.h>
...
__dpmi_meminfo mmem;
unsigned int sel;

unsigned long sram;
...
    unsigned long prng, test;
...
    mmem.size = 65536;
    mmem.address = sram;
    if (__dpmi_physical_address_mapping(&mmem) != 0) {
 printf("Address mapping failed\n");
 exit(-1);
    }
    sel = __dpmi_allocate_ldt_descriptors(1);
    __dpmi_set_segment_base_address(sel, mmem.address);
    __dpmi_set_segment_limit(sel, mmem.address + 65535);
    __dpmi_set_descriptor_access_rights(sel,
__dpmi_get_descriptor_access_rights(_my_ds()));
...
 _movedatal(_my_ds(), (int)&prng, sel, mmem.address, 1);

- Raw text -