Re: [RFC v2 6/7] PCI: arm64: Allow pci_config_window::parent to be NULL
From: Bjorn Helgaas <helgaas@kernel.org>
Date: 2021-05-06 22:25:35
Also in:
linux-arm-kernel, linux-hyperv, linux-pci, lkml
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).
quoted hunk ↗ jump to hunk
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