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Re: [PATCH V3 11/21] pci, acpi: Move ACPI host bridge device companion assignment to core code.

From	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH V3 11/21] pci, acpi: Move ACPI host bridge device companion assignment to core code.
Date	2016-01-27 18:50 +0100
Message-ID	<qVCoa-78y-11@gated-at.bofh.it> (permalink)
References	(3 earlier) <qSZ7z-5Eb-5@gated-at.bofh.it> <qT0dl-6mw-37@gated-at.bofh.it> <qT1j4-7c8-11@gated-at.bofh.it> <qT1VM-7Ky-15@gated-at.bofh.it> <qT2f7-7Ty-1@gated-at.bofh.it>
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On Wed, Jan 20, 2016 at 03:41:56PM +0100, Tomasz Nowicki wrote:
> On 20.01.2016 15:22, Lorenzo Pieralisi wrote:
> >On Wed, Jan 20, 2016 at 02:40:08PM +0100, Tomasz Nowicki wrote:
> >
> >[...]
> >
> >>>>>>+	/* 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.
> >
> 
> I am not able to answer that question, but I see lots of changes in
> this area made by Rafael.

I had a further look and I am not sure why the fwnode_handle* in the
dev member of the acpi_device is not made to point at the fwnode member
of the acpi_device by *default* (acpi_init_device_object() ?), probably
because it is never used as such but certainly Rafael knows, so I would
ask him to clarify please it is unclear to me.

I do not see anything wrong in what you are doing in this patch.

Rafael, any comments ?

Thanks,
Lorenzo

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Re: [PATCH V3 11/21] pci, acpi: Move ACPI host bridge device  companion assignment to core code. Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2016-01-19 17:10 +0100
  Re: [PATCH V3 11/21] pci, acpi: Move ACPI host bridge device  companion assignment to core code. Tomasz Nowicki <tn@semihalf.com> - 2016-01-20 12:30 +0100
    Re: [PATCH V3 11/21] pci, acpi: Move ACPI host bridge device  companion assignment to core code. Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2016-01-20 13:40 +0100
      Re: [PATCH V3 11/21] pci, acpi: Move ACPI host bridge device  companion assignment to core code. Tomasz Nowicki <tn@semihalf.com> - 2016-01-20 14:50 +0100
        Re: [PATCH V3 11/21] pci, acpi: Move ACPI host bridge device  companion assignment to core code. Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2016-01-20 15:30 +0100
          Re: [PATCH V3 11/21] pci, acpi: Move ACPI host bridge device  companion assignment to core code. Tomasz Nowicki <tn@semihalf.com> - 2016-01-20 15:50 +0100
            Re: [PATCH V3 11/21] pci, acpi: Move ACPI host bridge device  companion assignment to core code. Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2016-01-27 18:50 +0100

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