# \[RFC v2 6/7\] PCI: arm64: Allow pci\_config\_window::parent to be NULL

- From: Boqun Feng \<hidden\>
- Date: 2021-05-03 14:48:07 
- List: linux-hyperv
- Page: https://ratatoskr.run/linux-hyperv/2021/05/6356262
- Thread: https://ratatoskr.run/linux-arm-kernel/2021/05/6356256/t.md

```text
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.

Signed-off-by: Boqun Feng <redacted>
---
 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

```