On Wed, Jan 20, 2016 at 02:40:08PM +0100, Tomasz Nowicki wrote:

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+	/* Root bridge device needs to be sure of parent ACPI type */
+	ACPI_COMPANION_SET(&device->dev, device);

I do not understand why the code above is needed, can you elaborate
please ?

This makes sure that device->dev can be identified as ACPI device,
so we can use to_acpi_device_node() and assign companion safely
below.

I do not follow. If you refer to the fwnode handle type, that is
already set by ACPI core code (before acpi_pci_root_add() is called,
in acpi_init_device_object()).

acpi_init_device_object() sets ACPI fwnode handle type only for
"device", but not for "device->dev" which is what is passed as an
argument to pci_create_root_bus().

Without ACPI_COMPANION_SET(&device->dev, device) here, no one can be
sure if we have ACPI device in pci_create_root_bus().

Ok, got it. The question is whether this should be done in ACPI
core instead (is there a reason why it should *not* be done ?), but I
now understand your point.

Thanks,
Lorenzo