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

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Date:   Fri, 9 Sep 2022 12:20:45 +0200
From:   Robert Richter <rrichter@....com>
To:     Dan Williams <dan.j.williams@...el.com>
CC:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Alison Schofield <alison.schofield@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Ben Widawsky <bwidawsk@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        <linux-cxl@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Len Brown <lenb@...nel.org>,
        Linux PCI <linux-pci@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH 06/15] PCI/ACPI: Link host bridge to its ACPI fw node

On 08.09.22 12:45:16, Dan Williams wrote:
> Rafael J. Wysocki wrote:
> > On Thu, Sep 8, 2022 at 8:05 AM Dan Williams <dan.j.williams@...el.com> wrote:
> > >
> > > 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.
> > 
> > It is needed and it is present on x86 AFAICS (see my last reply in this thread).
> > 
> > This seems to be addressing an ARM64-specific issue.
> > 
> 
> Ah, ok, thanks for pointing that out.

No, it is x86. And true, it is set. So this series is actually working
without this patch. It can be dropped.

Now, I just checked my logs. The reason I was adding this is that
during code development I modified the code to have bridge->dev.parent
set. Then, the fwnode is not linked. I later dropped that change but
kept this patch.

Thanks for catching this.

-Robert