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From: Arnd Bergmann <arnd@arndb.de>
To: linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC part1 PATCH 1/7] ACPI: Make ACPI core running without PCI on ARM64
Date: Thu, 5 Dec 2013 23:04:22 +0100
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Cc: Hanjun Guo <hanjun.guo@linaro.org>, Matthew Garrett <mjg59@srcf.ucam.org>,
        Mark Rutland <mark.rutland@arm.com>, linaro-kernel@lists.linaro.org,
        "Russell King - ARM Linux" <linux@arm.linux.org.uk>,
        Al Stone <al.stone@linaro.org>,
        Graeme Gregory <graeme.gregory@linaro.org>, patches@linaro.org,
        Olof Johansson <olof@lixom.net>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Linus Walleij <linus.walleij@linaro.org>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>, linux-kernel@vger.kernel.org,
        Will Deacon <will.deacon@arm.com>, linaro-acpi@lists.linaro.org,
        linux-acpi@vger.kernel.org, Rob Herring <rob.herring@calxeda.com>,
        Grant Likely <grant.likely@linaro.org>,
        Jon Masters <jonathan@jonmasters.org>,
        Bjorn Helgaas <bhelgaas@google.com>
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On Wednesday 04 December 2013, Hanjun Guo wrote:
> On 2013年12月04日 00:41, Matthew Garrett wrote:
> > Given the number of #ifdefs you're adding, wouldn't it make more sense
> > to just add stub functions to include/linux/pci.h?
> 
> Thanks for the suggestion :)
> 
> I can add stub functions in include/linux/pci.h for raw_pci_read()/
> raw_pci_write(), then can remove #ifdefs for acpi_os_read/write_pci_configuration().

Actually I wonder about the usefulness of this patch in either form: Since ACPI
on ARM64 is only for servers, I would very much expect them to always come with
PCI, either physical host bridges with attached devices, or logical PCI functions
used to describe the on-SoC I/O devices. Even in case of virtual machines, you'd
normally use PCI as the method to communicate data about the virtio channels.

Can you name a realistic use-case where you'd want ACPI but not PCI?

	Arnd