From:	"Michael Stewart" <mike AT reggin DOT freeserve DOT co DOT uk>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: 13h forerver (heyy)
Date:	Wed, 28 Jul 1999 10:13:41 +0100
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Eli Zaretskii wrote in message ...
>
>On Wed, 28 Jul 1999, conrad wrote:
>
>> info.size = 320*200;
>> info.address = 0xa0000;
>> __dpmi_physical_address_mapping (&info);
>> my_ds = __dpmi_allocate_ldt_descriptors (1);
>> __dpmi_set_segment_base_address (my_ds, info.address);
>> __dpmi_set_segment_limit (my_ds, (320*200+5)|0xfff);
>
>This is the wrong way of creating a selector for the video RAM.
>__dpmi_physical_address_mapping is for mapping in addresses above 1MB
>mark that by default aren't mapped by the DPMI server.  See section
>18.4 of the DJGPP FAQ for a description and an example of working code
>that sets up a selector for video RAM.
>
>Also, your code doesn't even check for error returns from the DPMI
>functions you call.  No offence, but IMHO such programs really deserve
>to crash...

I wrote (with an awful lot of help from Eli) a small bit of code which may
help here.
If you search for the thread 'Selector code' then for a message posted about
21 June, it should contain the code we produced.

Use it like this:
if (make_ds (my_ds, 0xa0000, 64000)) {
   //error
}

As far as I know it is bug free and fully working.

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