linux-kernel - Re: console font limits

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Date:	Thu, 3 May 2007 23:58:55 -0400
From:	Daniel Hazelton <dhazelton@...er.net>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Kyle Moffett <mrmacman_g4@....com>,
	Jan Engelhardt <jengelh@...ux01.gwdg.de>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Albert Cahalan <acahalan@...il.com>,
	"Antonino A. Daplas" <adaplas@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>, aeb@....nl
Subject: Re: console font limits

On Thursday 03 May 2007 20:39:05 H. Peter Anvin wrote:
> Kyle Moffett wrote:
> > Actually I think the real problem was that "KD_GRAPHICS" got overloaded
> > to mean "some userspace program is probably poking at the GPU in very
> > direct ways possibly including /dev/mem".  As such it really isn't safe
> > at all for the kernel to write stuff to the screen in that situation;
> > you could turn a panic()+reboot-after-30-secs into an unrecoverable hard
> > PCI bus lockup.  IIRC there were at least a couple chipsets which had
> > that problem with X.  If we can implement enough APIs for X to do all of
> > its stuff from userspace without iopl() or /dev/mem then we could
> > probably bring back the option for dumping oopses to screen in
> > KD_GRAPHICS mode, but otherwise it'll just cause more headaches.
>
> It never meant anything *BUT* that, to the best of my knowledge.  That
> was certainly the original meaning of KD_GRAPHICS.

I started work last year on making the framebuffer layer use the DRM internals 
for all controls, providing a unified kernel and userspace system for 
accessing the graphics devices. It never got anywhere because I couldn't 
figure out a simple system for figuring out which driver (out of the numerous 
ones that could potentially be compiled into the kernel) to actually give 
control to. (I know I could have just looped over them all and figured it out 
that way, but that is far from elegant)

I guess I could start on that work again - shouldn't take me all that long to 
recover the stuff I lost when a blackout caused my hard drive to get 
corrupted beyond recovery (and the automated journal replay didn't do a 
damned thing - I think it actually *added* to the corruption, but I don't 
think any filesystem would have survived that)

DRH
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