On Fri, Apr 28, 2017 at 02:28:38PM +0200, Arnd Bergmann wrote:
> On Wed, Apr 26, 2017 at 1:17 PM, Lorenzo Pieralisi
> <lorenzo.pieralisi@xxxxxxx> wrote:
> > Current pci_scan_root_bus() interface is made up of two main
> > code paths:
> >
> > - pci_create_root_bus()
> > - pci_scan_child_bus()
> >
> > pci_create_root_bus() is a wrapper function that allows to create
> > a struct pci_host_bridge structure, initialize it with the passed
> > parameters and register it with the kernel.
> >
> > As the struct pci_host_bridge require additional struct members,
> > pci_create_root_bus() parameters list has grown in time, making
> > it unwieldy to add further parameters to it in case the struct
> > pci_host_bridge gains more members fields to augment its functionality.
> >
> > Since PCI core code provides functions to allocate struct
> > pci_host_bridge, instead of forcing the pci_create_root_bus() interface
> > to add new parameters to cater for new struct pci_host_bridge
> > functionality, it is more suitable to add an interface in PCI
> > core code to scan a PCI bus straight from a struct pci_host_bridge
> > created and customized by each specific PCI host controller driver.
> >
> > Add a pci_scan_root_bus_bridge() function to allow PCI host controller
> > drivers to create and initialize struct pci_host_bridge and scan
> > the resulting bus.
> >
> > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> > Cc: Arnd Bergmann <arnd@xxxxxxxx>
> > Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
>
> Good idea, yes. To avoid growing the number of interfaces too
> much, should we change the existing users of pci_register_host_bridge
> in host drivers over to this entry point, and make the other one
> local to probe.c then?
Yes, the problem is that there are drivers (ie pcie-iproc.c) that
require the struct pci_bus (created by pci_register_host_bridge())
to fiddle with it to check link status and THEN scan the bus (so
the pci_register_host_bridge() call can't be embedded in the scan
interface - the driver requires struct pci_bus for pci_ops to work
before scanning the bus itself).
I will see how I can accommodate this change because you definitely
have a point.
> > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> > index 7e4ffc4..c7a7f72 100644
> > --- a/drivers/pci/probe.c
> > +++ b/drivers/pci/probe.c
> > @@ -2412,6 +2412,44 @@ void pci_bus_release_busn_res(struct pci_bus *b)
> > res, ret ? "can not be" : "is");
> > }
> >
> > +int pci_scan_root_bus_bridge(struct pci_host_bridge *bridge)
> > +{
> > + struct resource_entry *window;
> > + bool found = false;
> > + struct pci_bus *b;
> > + int max, bus, ret;
> > +
> > + if (!bridge)
> > + return -EINVAL;
> > +
> > + resource_list_for_each_entry(window, &bridge->windows)
> > + if (window->res->flags & IORESOURCE_BUS) {
> > + found = true;
> > + break;
> > + }
> > +
> > + ret = pci_register_host_bridge(bridge);
> > + if (ret < 0)
> > + return ret;
> > +
> > + b = bridge->bus;
> > + bus = bridge->busnr;
> > +
> > + if (!found) {
> > + dev_info(&b->dev,
> > + "No busn resource found for root bus, will use [bus %02x-ff]\n",
> > + bus);
> > + pci_bus_insert_busn_res(b, bus, 255);
> > + }
> > +
> > + max = pci_scan_child_bus(b);
> > +
> > + if (!found)
> > + pci_bus_update_busn_res_end(b, max);
> > +
> > + return 0;
> > +}
> > +
>
> We probably want an EXPORT_SYMBOL() here as well.
Yep, sure.
Thanks for having a look !
Lorenzo
