This fixes a bug uncovered by a recent driver core change that
modified the implementation of the ACPI_COMPANION_SET() macro to
strictly rely on its second argument to be either NULL or a valid
pointer to struct acpi_device.
As it turns out, pcibios_root_bridge_prepare() on x86 and ia64
works with the assumption that the only code path calling
pci_create_root_bus() is pci_acpi_scan_root() and therefore
the sysdata argument passed to it will always match the
expectations of pcibios_root_bridge_prepare(). That need not
be the case, however, and in particular it is not the case for
the Xen pcifront driver that passes a pointer to its own private
data strcture as sysdata to pci_scan_bus_parented() which then
passes it to pci_create_root_bus() and it ends up being used
incorrectly by pcibios_root_bridge_prepare().
/
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Merge tag 'acpi-pci-4.1-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
Pull PCI / ACPI fix from Rafael Wysocki:
"This fixes a bug uncovered by a recent driver core change that
modified the implementation of the ACPI_COMPANION_SET() macro to
strictly rely on its second argument to be either NULL or a valid
pointer to struct acpi_device.
As it turns out, pcibios_root_bridge_prepare() on x86 and ia64 works
with the assumption that the only code path calling pci_create_root_bus()
is pci_acpi_scan_root() and therefore the sysdata argument passed to
it will always match the expectations of pcibios_root_bridge_prepare().
That need not be the case, however, and in particular it is not the
case for the Xen pcifront driver that passes a pointer to its own
private data strcture as sysdata to pci_scan_bus_parented() which then
passes it to pci_create_root_bus() and it ends up being used incorrectly
by pcibios_root_bridge_prepare()"
* tag 'acpi-pci-4.1-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
PCI / ACPI: Do not set ACPI companions for host bridges with parents
aaa20fc233