Subject: Re: MTRR vesafb and wrong X performance
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Gerd Knorr <kraxel@bytesex.org>
Cc: Dave Jones <davej@redhat.com>, Andrew Morton <akpm@osdl.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Date: Mon, 29 Nov 2004 17:22:24 +0000
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On Llu, 2004-11-29 at 17:34, Gerd Knorr wrote:
> Thats kida silly, but as I've found some simliar construct in the old
> code I left it in to avoid breaking stuff.  Guess there is a reason that
> this was there.  I'll take that as proof that broken BIOSes exist which
> don't fill screen_info.lfb_size correctly ;)

Indeed. Also some report less than the full amount because they only
support VGA modes in the lower bits of memory and others like Intel
ICH/GCH based systems report 1Mb because in essence the question has no
right answer.

> Maybe it works better to walk the PCI device list, find the correct
> gfx card using the framebuffer start address, then double-check the
> size by looking at the PCI ressources?

Very very few cards have a PCI resource map that gives useful size
information because they have apertures and are sometimes also windowed
or not all CPU accessible.

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