linux-kernel - RE: [PATCH 06/15] PCI/ACPI: Link host bridge to its ACPI fw node

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Date:   Wed, 7 Sep 2022 23:05:11 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Robert Richter <rrichter@....com>,
        Alison Schofield <alison.schofield@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        "Ira Weiny" <ira.weiny@...el.com>,
        Ben Widawsky <bwidawsk@...nel.org>,
        "Dan Williams" <dan.j.williams@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>
CC:     <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Len Brown <lenb@...nel.org>, Robert Richter <rrichter@....com>,
        <linux-pci@...r.kernel.org>, <linux-acpi@...r.kernel.org>
Subject: RE: [PATCH 06/15] PCI/ACPI: Link host bridge to its ACPI fw node

Robert Richter wrote:
> A lookup of a host bridge's corresponding acpi device (struct
> acpi_device) is not possible, for example:
> 
> 	adev = ACPI_COMPANION(&host_bridge->dev);
> 
> This could be useful to find a host bridge's fwnode handle and to
> determine and call additional host bridge ACPI parameters and methods
> such as HID/CID or _UID.

When is this explicitly needed. "Could be useful" is interesting, but it
needs to have a practical need.

> 
> Make this work by linking the host bridge to its ACPI fw node.
> 
> Signed-off-by: Robert Richter <rrichter@....com>
> ---
>  drivers/acpi/pci_root.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> index d57cf8454b93..846c979e4c29 100644
> --- a/drivers/acpi/pci_root.c
> +++ b/drivers/acpi/pci_root.c
> @@ -1083,6 +1083,7 @@ struct pci_bus *acpi_pci_root_create(struct acpi_pci_root *root,
>  		goto out_release_info;
>  
>  	host_bridge = to_pci_host_bridge(bus->bridge);
> +	host_bridge->dev.fwnode = acpi_fwnode_handle(device);
>  	if (!(root->osc_control_set & OSC_PCI_EXPRESS_NATIVE_HP_CONTROL))
>  		host_bridge->native_pcie_hotplug = 0;
>  	if (!(root->osc_control_set & OSC_PCI_SHPC_NATIVE_HP_CONTROL))
> -- 
> 2.30.2
>