LinuxKPI: pci: implement pci_upstream_bridge()

[bz]

Summary

Currently we point back to ourselves on pdev->bus->self rather than
the parent PCI bridge.

We keep this as status-quo with an extra comment and only on-demand
allocate a pci_dev for the parent bridge if we are asked for in
pci_upstream_bridge().
When releasing the pci_dev we check if pdev->bus->self has changed
and call pci_dev_put() to release the reference count on the parent
bridge as well.

This code moves pci_is_root_bus() higher up in pci.h but no functional
change there.

Sponsored by: The FreeBSD Foundation
MFC after: 3 days

Test Plan

Adding x11 to reviewers as this conflicts with the
implementation there.

I'll also need to MFC this.

[bz]

Sorry to add you here but I know you to know PCI very well; I found pci_find_pcie_root_port() but nothing which just walks up the PCI bridge tree step by step as a function to the next step so I am going with what other people also have done in sys/dev/ and got two up and check the class on that parent. Is that sane? I wonder if we should indeed (in the future) add a function and then replace then 2-3 places throughout the tree with that...?

[bz]

x11 I opened a pull request which will remove the conflict : https://github.com/freebsd/drm-kmod/pull/152/commits/a35463b86a3babd4b580dab5f447d215478036ee If possible please apply to the devel/current/13 versions so this could proceed once reviewed.

[jhb]

sys/compat/linuxkpi/common/include/linux/pci.h

500

Won't this second case (pdev->bus->self == NULL) never get this far because pci_is_root_bus() would be true and return NULL instead?

[bz]

sys/compat/linuxkpi/common/include/linux/pci.h

500

Correct; I'll remove the second condition :-)

[bz]

Remove 2nd condition from if() clause as it cannot happen here.

[bz]

Thank you @wulf for handling the drm-kmod bits! Much appreciated.

Anyone any comments on this? If I don't hear back I'll probably commit it Tuesday morning UTC.

[bz]

This fell through. ANyone trying to use a last chance to review? I'd love to at least get the linux_pci.c part of the change in.

[• hselasky]

Change looks good. I've added some comments.

sys/compat/linuxkpi/common/include/linux/pci.h

505

goto done;

508

goto done;

511

goto done;

518

done:

[bz]

Goto done, goto done, goto done, are we done now?