Re: [RFC v2 6/7] PCI: arm64: Allow pci_config_window::parent to be NULL

Bjorn Helgaas
2021-05-06T22:28:03Z

Make your subject something like this so it matches previous practice:

arm64: PCI: ...

The "::" notation probably comes from C++, but doesn't really apply in
C. In C, we would say "cfg.parent" or "cfg->parent".

But pci_config_window and cfg->parent are probably too low-level for
the subject anyway. Seems like it should mention Hyper-V, for
instance.

On Mon, May 03, 2021 at 10:46:34PM +0800, Boqun Feng wrote:
> This is purely a hack, for ARM64 Hyper-V guest, there is no
> corresponding ACPI device for the root bridge, so the best we can
> provide is an all-zeroed pci_config_window, and in this case make
> pcibios_root_bridge_prepare() act as the ACPI device is NULL.

Why is there no ACPI device? Is this a needless arch dependency? Or
is this related to using DT instead of ACPI?

The cover letter hints that this might be related to
PCI_DOMAINS_GENERIC=y, but that doesn't sound like a very convincing
reason (and the cover letter can provide an overview, but the commit
logs of individual patches shouldn't assume knowledge of the cover
letter).

> Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
> ---
> arch/arm64/kernel/pci.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kernel/pci.c b/arch/arm64/kernel/pci.c
> index e9a6eeb6a694..f159df903ccb 100644
> --- a/arch/arm64/kernel/pci.c
> +++ b/arch/arm64/kernel/pci.c
> @@ -83,7 +83,7 @@ int pcibios_root_bridge_prepare(struct pci_host_bridge *bridge)
> {
> if (!acpi_disabled) {
> struct pci_config_window *cfg = bridge->bus->sysdata;
> - struct acpi_device *adev = to_acpi_device(cfg->parent);
> + struct acpi_device *adev = cfg->parent ? to_acpi_device(cfg->parent) : NULL;
> struct device *bus_dev = &bridge->bus->dev;
>
> ACPI_COMPANION_SET(&bridge->dev, adev);
> --
> 2.30.2
>