Re: xorg pci probing

[Michael <macallan%NetBSD.org@localhost>]

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Hello,

On Jan 18, 2011, at 6:19 AM, Christoph Egger wrote:

> > On Tue, Jan 18, 2011 at 11:39:35AM +0100, Christoph Egger wrote:
> > > The function pci_device_is_boot_vga() is supposed to return
> > > 'true' for the pci vga device the firmware uses which is not
> > > neccessarily the OS console device (it can be a serial console).
> >
> > Ok. But your function answers "this is the vga device where  
> > wsdisplay0
> > attached" instead - is that a safe bet, especially in case you boot  
> > with
> > a serial console?
>
> According to macallan@  ttyE* is the first graphic device,
> ttyF* the second, ttyG* the third, etc.
>
> So yes, it is safe.

I wouldn't call it 'safe' but 'safe enough'. Most ports will try to  
make sure wsdisplay0 is the firmware console but if the console is a  
serial line there may or may not be a wsdisplay0. On the other hand,  
what X tries to do here, as far as I can tell, is to make sure :0 is  
where the user expects it which would still be wsdisplay0 even in the  
serial console case.

> > I still completely fail to see why X would like to know this detail  
> > and
> > what a wrong answer would mean. If it's just a wrong default display
> > but fixable via config file, it's fine.
>
> The pci probing happens before the config file comes into play.
> That's why the config file has no effect.

I would call that a bug in X though - it should be able to use  
arbitrary PCI devices if there's a driver that can use them, console  
or not, initialized or not ( some drivers can cold boot their hardware  
after all )

> > > > Yes, but the same situation could happen on a desktop. Assume I  
> > > > would
> > > > have such a machine and boot it with serial console. According to  
> > > > your
> > > > logic (as far as I understood it so far), I wouldn't be able to  
> > > > use X.
> > >
> > > Right. The error message "Primary device is not PCI" comes from
> >
> > This is unacceptable. I have a amd64 machine with serial console  
> > that I
> > use to run X, luckily it has only a single vga card right now.
>
> Me too which is an other laptop.

I think the "Primary device is not PCI" error is bogus but that's a  
different story.
If X wants to whine about it that's fine but it shouldn't be fatal.

have fun
Michael

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