Re: [PATCH v19 2/2] PCI: Add a quirk for AMD PCIe root ports w/ USB4 controllers

[Lukas Wunner <lukas@wunner.de>]

On Thu, Sep 14, 2023 at 09:33:54PM -0500, Mario Limonciello wrote:
> +static bool child_has_amd_usb4(struct pci_dev *pdev)
> +{
> +	struct pci_dev *child = NULL;
> +
> +	while ((child = pci_get_class(PCI_CLASS_SERIAL_USB_USB4, child))) {
> +		if (child->vendor != PCI_VENDOR_ID_AMD)
> +			continue;
> +		if (pcie_find_root_port(child) != pdev)
> +			continue;
> +		return true;
> +	}
> +
> +	return false;
> +}

What's the purpose of the pcie_find_root_port() check?  PCI is a hierarchy,
not a graph, so a device cannot have any other Root Port but the one below
which you're searching.

If the purpose is to check that the port is a Root Port (if the PCI IDs
you're using in the DECLARE_PCI_FIXUP_* clauses match non-Root Ports),
check for pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT.  (No need to
check for that in every loop iteration obviously, just check once in
the fixup.)

Thanks,

Lukas