On Mon, Apr 07, 2014 at 05:16:13PM +0300, Marcel Apfelbaum wrote: > On Mon, 2014-04-07 at 17:09 +0300, Michael S. Tsirkin wrote: > > On Mon, Apr 07, 2014 at 04:51:54PM +0300, Marcel Apfelbaum wrote: > [...] > > > > > I don't think we'll need that for the SHPC bridge. > > > > > > > > Why not? > > > Because "has shpc" => not an PCIe port. (as far as I know) > > > Anyway, why have shpc capability but no I/O or mem to support it? > ^^^ > [...] > > > > > > AFAIK the spec does not list reset value for this register. > > IIRC QEMU resets both to 0. > Thanks, what do you think about the above ? ^^^ > While I am not against it, it seems redundant. > It has shpc => it needs I/O or mem space. > > Marcel
Fair enough but it can have shpc and memory without io, or shpc and io without memory. > > > > > > > > - read back value > > > > > > > > value 0 means bridge does not support I/O. > > > > > > > > > > > > A similar trick should work for other optional resources. > > > > > > > > > > > > > For express it indeed makes sense to avoid claiming IO address space. > > > > > I'd try to find something more automatic though, where you don't need > > > > > some kind of "disable io for this express port" config option. > > > > > > > > Won't same trick as above work? > > > > > > > > > For express ports which can only have a single device underneath we > > > > > can > > > > > check whenever we have a device and if one is present already don't > > > > > bother claiming extra resources for hotplug. > > > > > > > > > > > > + for (cap = pci_config_readb(pci->bdf, PCI_CAPABILITY_LIST); > > > > > > > cap; > > > > > > > + cap = pci_config_readb(pci->bdf, cap + > > > > > > > PCI_CAP_LIST_NEXT)) > > > > > > > + if (pci_config_readb(pci->bdf, cap + PCI_CAP_LIST_ID) == > > > > > > > cap_id) > > > > > > > + return cap; > > > > > > > > > > > > I would also limit this to 256 iterations, to make sure > > > > > > we dont' get into an infinite loop with a broken device. > > > > > > > > > > Good point. > > > > > > > > > > cheers, > > > > > Gerd > > > > > > > > > > > > >
