From:	"XtReMe" <xtreme AT x-project DOT demon DOT nl>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Linear frame buffer size
Date:	Sun, 28 Feb 1999 18:02:38 +0100
Message-ID:	<920221317.3421.0.rover.d4ee0fa5@news.demon.nl>
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To:	djgpp AT delorie DOT com
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Reply-To:	djgpp AT delorie DOT com

Hi!
I have this little problem setting up the Linear Frame Buffer with VESA 2
Here's what I did:

VESAModeInfo VMI;
__dpmi_meminfo VESAPhysical;
int VESASelector;
int vesa_setlinear ()
{
    VESAPhysical.address = VMI.PhysBasePtr;
    VESAPhysical.size = VMI.height * VMI.bytes_per_scanline;
    if (!__dpmi_physical_address_mapping (&VESAPhysical))
        return 1;

    if (!__dpmi_allocate_ldt_descriptors (1))
        return 2;

    if (!__dpmi_set_descriptor_access_rights (VESASelector, 0xC0F2))
        return 3;

    if (!__dpmi_set_segment_base_address (VESASelector,
VESAPhysical.address))
        return 4;

    if (!__dpmi_set_segment_limit (VESASelector, VESAPhysical.size))
        return 5;

    return 0;
}

It all works fine, except for __dpmi_set_segment_limit (). When the
frame buffer gets real big, like 640 * 480 * 24 bpp or 1024 * 786 * 16,
I get __dpmi_error 8, which is the DOS error : Not enough memory.
But I have a 4 MB video card and it sets the mode correctly without any
errors. But when I don't allocate a ldt descriptor and just access the
frame buffer directly with the selector _dos_ds starting from the returned
physical base ptr, it works! But I don't want it this way. Why does dpmi
return that there's not enough memory? Does anyone has a sollution?

Thanx

XtReMe
xtreme AT x-project DOT demon DOT nl

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