On Fri, Oct 7, 2011 at 3:50 PM, Bjorn Helgaas <bhelgaas@xxxxxxxxxx> wrote: > On Wed, Aug 31, 2011 at 8:48 PM, Deng-Cheng Zhu <dczhu@xxxxxxxx> wrote: >> (Resending the patch set to include more arch maintainers.) >> >> Change the pci_create_bus() interface to pass in available resources to get them >> settled down early. This is to avoid possible resource conflicts while doing >> pci_scan_slot() in pci_scan_child_bus(). Note that pcibios_fixup_bus() can get >> rid of such conflicts, but it's done AFTER scanning slots. >> >> In addition, MIPS PCI resources are now fixed using this new interface. > > Jesse, I assume these are headed for the 3.2 merge window, right? I tried to build on these patches to convert x86 to using the new pci_create_bus() interface, but I couldn't figure out a nice way to handle an arbitrary number of resources. We made pci_create_bus() take a "struct pci_bus_resource *" (https://lkml.org/lkml/2011/8/26/88): struct pci_bus *pci_create_bus(struct device *parent, int bus, struct pci_ops *ops, void *sysdata, struct pci_bus_resource *bus_res); Where pci_bus_resource looks like this: struct pci_bus_resource { struct list_head list; struct resource *res; unsigned int flags; }; Conceptually, we're passing a list of resources to pci_create_bus(), which I think is the right thing. But I think the best way to do that is by passing a pointer to a struct list_head, not a pointer to a pci_bus_resource. If we pass a pci_bus_resource, we're basically using that as a container for a list (as per include/linux/list.h), but it's not a well-formed list. Normally a list contains one list_head per element, plus an extra list_head for the head of the list. There's a nice drawing on page 296 of http://lwn.net/images/pdf/LDD3/ch11.pdf. The list built in your MIPS patch (https://lkml.org/lkml/2011/8/26/89) consists of two pci_bus_resource structs (each with a list_head), but there's no third list_head for the head of the list. I think if you tried to use list_for_each_entry() to iterate through the list, it would not work correctly. I'll post a slightly modified series to show what I mean. Take a look and see if it makes sense to you. Bjorn
