Re: pci: Arch hook to determine config space size

[Grant Grundler]

On Mon, Jan 31, 2005 at 01:40:04PM -0600, Brian King wrote:
> CC'ing the linux-pci mailing list...

thanks...

> > This patch adds an arch hook so
> > that individual archs can indicate if the underlying system supports
> > expanded config space accesses or not.

> >@@ -653,6 +653,8 @@ static int pci_cfg_space_size(struct pci
> > 			goto fail;
> > 	}
> > 
> >+	if (!pcibios_exp_cfg_space(dev))
> >+		goto fail;
> > 	if (pci_read_config_dword(dev, 256, &status) != PCIBIOS_SUCCESSFUL)
> > 		goto fail;

pci_read_config_dword lands in arch specific code.
See drivers/pci/access.c:PCI_OP_READ() macro.

I'm missing what pcibios_exp_cfg_space() does that can't be handled by
the bus_ops supplied by pci_scan_bus().

I would expect the pci_read_config_dword to fail for being out of bounds.
Is that wrong?
Or is bus_ops not feasible in this case because pcibios needs access
to pci_dev?

If it's feasible, maybe the right place to add this hook is to
pci_read_config_dword which is also handed the pci_dev. And add
another function pointer to bus_ops (which could be NULL) to check
chipset support for Expanded Config space before calling
pci_bus_read_config_dword. Thats cleaner than adding a hook
before each use of pci_read_config_dword.

hth,
grant
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