On Thu, May 03, 2012 at 10:39:42AM -0600, Bjorn Helgaas wrote: >> >> >> >> >> +-------------------------------|------------------------------+ >> | | | >> | +----+----+ | >> | | virtual | | >> | | PCI-PCI | | >> | | bridge | | >> | +----+----+ >> | | | >> | |Bus#3 >> | | | >> | +----------------------------------------+ | >> | | | | | >> | | | | | >> | |03:00.0 |03:01.0 |03:02.0 | >> | +----+----+ +----+----+ +----++---+ | >> | | virtual | | virtual | | virtual | | >> | | PCI-PCI | | PCI-PCI | | PCI-PCI | | >> | | bridge | | bridge | | bridge | | >> | +----+----+ +----+----+ +----+----+ | >> | | | | | >> | | | | | >> +----------|--------------------|-------------------|----------+ >> | Bus#4? | | >> v v v >> I read the code of pci_scan_child_bus(), in this function it will call pci_scan_slot() like this. for (devfn = 0; devfn < 0x100; devfn += 8) pci_scan_slot(bus, devfn); I think this scheme is based on the PCI LB specification. If the bus->self is ari enabled, one call of pci_scan_slot(bus, 0) will scan all the functions under this bus. Then next 2^5-1 times of pci_scan_slot() will configure the function which has already been configured, or even empty function. My idea is if the bus is ari enabled, just one call of pci_scan_slot() will be called. Do you think this works? Or may I miss some real case? >> So the link itself is Bus#4? > >Exactly. > >> If there is no device under this link, will Bus#4 appear in kernel? > >Yes, I'm pretty sure we build the bus 04 pci_bus structure, then scan >bus 04 for devices. Even if we find none, the pci_bus struct for bus >04 remains. > >> And then the PCIe switch is represented by 4 pci_dev structure and each >> is bridge type? > >Yes. And each has an associated pci_bus struct for its secondary bus. > >Bjorn -- Richard Yang Help you, Help me -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
