Re: [PATCH 5/5] PCI: Rip out pci_bus_add_devices() from pci_scan_root_bus()

Arnd Bergmann
2014-11-19T12:11:41Z

On Wednesday 19 November 2014 15:32:49 Yijing Wang wrote:
> Just like pci_scan_bus(), we also should rip out
> pci_bus_add_devices() from pci_scan_root_bus().
> Lots platforms first call pci_scan_root_bus(), but
> after that, they call pci_bus_size_bridges() and
> pci_bus_assign_resources(). Place pci_bus_add_devices()
> in pci_scan_root_bus() hurts PCI scan logic.

I think we really need to wait for Bjorn to comment on this patch,
as I mentioned the idea behind pci_scan_root_bus() was to integrate
the scanning part, which you now undo, though I can still see this
working out in the long run.

> Should no functional change.

But you are moving the pci_bus_add_devices() later in a couple of
places. While this seems entirely reasonable, I would consider
it a functional change.

> diff --git a/arch/alpha/kernel/pci.c b/arch/alpha/kernel/pci.c
> index 076c35c..97f9730 100644
> --- a/arch/alpha/kernel/pci.c
> +++ b/arch/alpha/kernel/pci.c
> @@ -334,6 +334,8 @@ common_init_pci(void)
>
> bus = pci_scan_root_bus(NULL, next_busno, alpha_mv.pci_ops,
> hose, &resources);
> + if (bus)
> + pci_bus_add_devices(bus);
> hose->bus = bus;
> hose->need_domain_info = need_domain_info;
> next_busno = bus->busn_res.end + 1;

How about making pci_bus_add_devices() handle a NULL argument to save
the if() here and elsewhere?
> diff --git a/arch/mips/pci/pci.c b/arch/mips/pci/pci.c
> index 1bf60b1..f083688 100644
> --- a/arch/mips/pci/pci.c
> +++ b/arch/mips/pci/pci.c
> @@ -113,6 +113,7 @@ static void pcibios_scanbus(struct pci_controller *hose)
> if (!pci_has_flag(PCI_PROBE_ONLY)) {
> pci_bus_size_bridges(bus);
> pci_bus_assign_resources(bus);
> + pci_bus_add_devices(bus);
> }
> }
> }

This one looks wrong, I think you still want to call pci_bus_add_devices()
even with PCI_PROBE_ONLY set.

> diff --git a/arch/tile/kernel/pci.c b/arch/tile/kernel/pci.c
> index 1f80a88..007466e 100644
> --- a/arch/tile/kernel/pci.c
> +++ b/arch/tile/kernel/pci.c
> @@ -308,6 +308,8 @@ int __init pcibios_init(void)
> pci_add_resource(&resources, &iomem_resource);
> bus = pci_scan_root_bus(NULL, 0, controller->ops,
> controller, &resources);
> + if (bus)
> + pci_bus_add_devices(bus);
> controller->root_bus = bus;
> controller->last_busno = bus->busn_res.end;
> }

Should the pci_bus_add_devices come after setting the bus numbers here?

Arnd