Re: [coreboot] Patch set updated for coreboot: 6709bdd Fix multipleVGA cards resource conflict on Windows

[She, Kerry]

Hello, Ron
> -----Original Message-----
> From: coreboot-bounces+kerry.she=[e-mail] [mailto:coreboot-
> bounces+kerry.she=[e-mail]] On Behalf Of ron minnich
> Sent: Monday, December 19, 2011 1:07 PM
> To: Kerry Sheh
> Cc: [e-mail]
> Subject: Re: [coreboot] Patch set updated for coreboot: 6709bdd Fix
> multipleVGA cards resource conflict on Windows
> > /* It isn't safe to enable multiple VGA cards.
> > * Windows will report resource conflict when more than
>
> one
> > * VGA-compatible legacy graphic card in the system.
> > */
> >
> > +#if CONFIG_VGA_BRIDGE_SETUP == 1
> > extern device_t vga_pri;
> > if (((dev->class >> 16) == PCI_BASE_CLASS_DISPLAY) &&
> > (dev != vga_pri)) {
> > if (((vga_pri->class >> 8) ==
>
> PCI_CLASS_DISPLAY_VGA) &&
> > ((dev->class >> 8) ==
>
> PCI_CLASS_DISPLAY_VGA)) {
> > dev->command &= ~(PCI_COMMAND_IO |
>
> PCI_COMMAND_MEMORY);
> > }
> > }
> >
> > +#endif
>
> What do Linux or *BSD do in the same situation? Do they handle it cleanly?

Linux VGA Arbiter module(vgaarb) will handle this explicitly.
So dual vga card would works together, even coreboot not disable IO& MEM decoding on the second vga card.
thanks
> thanks
>
> ron

Patch set updated for coreboot: 6709bdd Fix multipleVGA cards resource conflict on Windows

[ron minnich]

On Sun, Dec 18, 2011 at 10:01 PM, She, Kerry  wrote:
> Hello, Ron
> > I asked:
> > What do Linux or *BSD do in the same situation? Do they handle it cleanly?
>
> Linux VGA Arbiter module(vgaarb) will handle this explicitly.
> So dual vga card would works together, even coreboot not disable IO& MEM decoding on the second vga card.

OK, then,  my concern about this patch is that you are making a
compile-time decision in  coreboot to fix a problem with one operating
system (Windows) that will impact other operating systems that don't
have the problem.

I wonder if a better way to manage this is via a CMOS (aka NVRAM)
setting. I kind of hate to limit coreboot because Windows is limited.
But I'm a n00b in a sense, having just come back onto this project, so
I'm happy to be told I'm wrong :-)

ron
p.s. For those who don't know me, I've been out of coreboot for 2
years, having been heavily involved from 1999 (when I started
LinuxBIOS) to 2009. Changing circumstances mean I get to work on it
again, which is nice.