From:	"Malcolm Herring" <malcolm DOT herring AT btinternet DOT com>
Newsgroups:	comp.os.msdos.djgpp
References:	<Pine DOT SUN DOT 3 DOT 91 DOT 1000515105456 DOT 9209P-100000 AT is>
Subject:	Re: DPMI GPF problem
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Date:	Mon, 15 May 2000 18:15:36 -0700
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That did the trick! Thanks!

"Eli Zaretskii" <eliz AT is DOT elta DOT co DOT il> wrote in message
news:Pine DOT SUN DOT 3 DOT 91 DOT 1000515105456 DOT 9209P-100000 AT is...
>
> On Sun, 14 May 2000, Malcolm Herring wrote:
>
> > 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.
>
> Your code has a number of bugs.  First, it sets the segment limit
> incorrectly:
>
> >     __dpmi_set_segment_limit(sel, mmem.address + 65535);
>
> This should be:
>
>      __dpmi_set_segment_limit(sel, 65535);
>
> >  _movedatal(_my_ds(), (int)&prng, sel, mmem.address, 1);
>
> This is also wrong: the 4th argument is an *offset* into the segment,
> so it starts from zero, not from mmem.address.
>
> Btw, section 18.7 of the DJGPP FAQ list explains how to do this and
> includes working code that does it.  I suggest to use that code as a
> basis for your program.
>
> If something in the FAQ is unclear, please ask specific questions.
>
> >     __dpmi_set_descriptor_access_rights(sel,
> > __dpmi_get_descriptor_access_rights(_my_ds()));
>
> This call is unnecessary: the segment descriptor already has the same
> rights as DS by default.
>

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