Allocating Resource for Legacy VGA Buffer

Li-Ta Lo ollie at
Sat Dec 4 10:34:00 CET 2004

On Fri, 2004-12-03 at 19:20, Eric W. Biederman wrote:
> Li-Ta Lo <ollie at> writes:
> > Eric,
> > 
> > I tried to allocate a MEM resource for legacy VGA framebuffer (0xA0000 -
> > 0xBFFFF) on AMDK8 NB Fun 1. I find a new mem_pair and assigned base 
> > and size of the resource as the code show in the bottom. But at the run 
> > time the resrouce allocation code still try to allocate that resource
> > to  0xA0000 to 0x002ffffff. Why it does not care about the 
> > resource->size field nor the FIXED flag ?
> The resource allocator should and it does in other cases.
> Hmm.  You don't even allocate this resource in read_resources
> so the resource allocator might should not even see it.  
> The IORESOURCE_PREFETCH is not correct for that area though.
> Setting up write-combining MSRs would be a very bad thing
> to have happen.  Which is what IORESOURCE_PREFETCH implies is
> legal.

The problem is I have no way to know which node/link the
VGA connects to at the read_resources time. So I can not
return a correct resource which these info embedded.

I tried to extend the pci_read_resources() to include the
memory resource 0xa0000-0xbfffff as the read_resources()
method of the VGA device. It does not work neither. The
read_resources() does return one more resource but the
bridges ignore it. Did I miss something ?


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