On Mon, Apr 07, 2014 at 11:44:51PM +0100, Bjorn Helgaas wrote: > On Mon, Apr 7, 2014 at 4:07 AM, Liviu Dudau <Liviu.Dudau@xxxxxxx> wrote: > > On Mon, Apr 07, 2014 at 10:14:18AM +0100, Benjamin Herrenschmidt wrote: > >> On Mon, 2014-04-07 at 09:46 +0100, Liviu Dudau wrote: > >> > > >> > *My* strategy is to get rid of pci_domain_nr(). I don't see why we need > >> > to have arch specific way of providing the number, specially after looking > >> > at the existing implementations that return a value from a variable that > >> > is never touched or incremented. My guess is that pci_domain_nr() was > >> > created to work around the fact that there was no domain_nr maintainance in > >> > the generic code. > >> > >> Well, there was no generic host bridge structure. There is one now, it should > >> go there. > > > > Exactly! Hence my patch. After it gets accepted I will go through architectures > > and remove their version of pci_domain_nr(). > > Currently the arch has to supply pci_domain_nr() because that's the > only way for the generic code to learn the domain. After you add > pci_create_root_bus_in_domain(), the arch can supply the domain that > way, and we won't need the arch-specific pci_domain_nr(). Right? > That makes more sense to me; thanks for the explanation. > > Let me try to explain my concern about the > pci_create_root_bus_in_domain() interface. We currently have these > interfaces: > > pci_scan_root_bus() > pci_scan_bus() > pci_scan_bus_parented() > pci_create_root_bus() > > pci_scan_root_bus() is a higher-level interface than > pci_create_root_bus(), so I'm trying to migrate toward it because it > lets us remove a little code from the arch, e.g., pci_scan_child_bus() > and pci_bus_add_devices(). > > I think we can only remove the arch-specific pci_domain_nr() if that > arch uses pci_create_root_bus_in_domain(). When we convert an arch > from using scan_bus interfaces to using > pci_create_root_bus_in_domain(), we will have to move the rest of the > scan_bus code (pci_scan_child_bus(), pci_bus_add_devices()) back into > the arch code. > > One alternative is to add an _in_domain() variant of each of these > interfaces, but that doesn't seem very convenient either. My idea of > passing in a structure would also require adding variants, so there's > not really an advantage there, but I am thinking of the next > unification effort, e.g., for NUMA node info. I don't really want to > have to change all the _in_domain() interfaces to also take yet > another parameter for the node number. Bjorn, I'm coming around to your way of thinking and I want to suggest a strategy for adding the domain number into the PCI framework. My understanding is that when pci_host_bridge structure was introduced you were trying to keep the APIs unchanged and hence the creation of a bridge was hidden inside the pci_create_root_bus() function. If we want to store the domain_nr information in the host bridge structure, together with a pointer to sysdata, then we need to break up the creation of the pci_host_bridge from the creation of a root bus. At that moment, pci_scan_root_bus() will need to be changed to accept a pci_host_bridge pointer, while pci_scan_bus() and pci_scan_bus_parented() will create the host bridge in the body of their function. Did I understood correctly this time your intentions? Do you agree with this plan? Best regards, Liviu > > Bjorn > -- > 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 > -- ==================== | I would like to | | fix the world, | | but they're not | | giving me the | \ source code! / --------------- ¯\_(ツ)_/¯ -- 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
