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Re: [Qemu-devel] [PATCH/RFC] Set a (distinguishable) subsystem id for Ci

From: Paul Brook
Subject: Re: [Qemu-devel] [PATCH/RFC] Set a (distinguishable) subsystem id for Cirrus VGA
Date: Fri, 10 Aug 2007 19:16:02 +0100
User-agent: KMail/1.9.7

On Friday 10 August 2007, Jeremy Katz wrote:
> On Fri, 2007-08-10 at 17:28 +0100, Paul Brook wrote:
> > On Thursday 09 August 2007, Jeremy Katz wrote:
> > > The attached adds a PCI subsystem vendor ID of 0x514D (QM ascii->hex)
> > > for the Cirrus emulation so that you can tell that the system is
> > > running under qemu.  This will make it so that, eg, we can detect that
> > > in X and know that resolutions > 800x600 won't blow up a monitor.
> >
> > I'd rather not. If you want autodetection to work then implement vesa DDC
> > emulation.
> The Cirrus hardware never supported it, so it's basically going to be
> making up all new code for the emulation, the drivers, etc.

My sources say otherwise.
The current Xorg cirrus driver clearly has DDC (aka i2c) support, and there's 
a patch for linux framebuffer support here: http://lkml.org/lkml/2006/7/4/230

qemu already have a generic i2c framework, and i2c EEPROM devices (used to 
hold the EDID), so all you need to implement is the cirrus host bits.
It's not entirely trivial as the card sees to just expose the raw signal 
lines. However i2c is fairly straightforward, so it shouldn't be that hard to 


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