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    SubjectRe: [PATCH V6 08/13] PCI: generic, thunder: update to use generic ECAM API
    On Sat, Apr 16, 2016 at 1:01 PM, Arnd Bergmann <arnd@arndb.de> wrote:
    > On Saturday 16 April 2016 12:50:13 Jayachandran C wrote:
    >> >
    >> > I still think it would be better to keep the loadable PCI host drivers
    >> > separate from the ACPI PCI infrastructure. There are a number of
    >> > simplifications that we want to do to the DT based drivers in the long
    >> > run, so it's better if that code is not shared at this level. Abstracting
    >> > out the ECAM code is fine, but at that point you should be able to just
    >> > call it from the ACPI layer.
    >>
    >> The issue is not with this patch (in my opinion). This patch is just
    >> re-arranging how thunder specific data is maintained. Earlier it was
    >> a container_of gen_pci, now it is ->priv of pci_config_window.
    >>
    >> I can see the issue in patches 12 and 13 of this patchset which adds
    >> ACPI fixups into the thunder OF driver.
    >
    > Right, I commented on this one, because it seems to rearrange the code
    > in order to do the later one.

    Patches 11- 13 are not from me, and I am not completely on board
    on the approach of adding the sections.We can look at reworking this.

    >> The simple approach when doing modular PCI drivers would be to make
    >> pci-thunder-*.c like pci-host-common.c, to be compiled in if configured.
    >> The fie will contain all the Thunder quirks and can export
    >> pci_thunder_ecam_ops.
    >
    > I would argue that we should not export anything from drivers/pci/host,
    > those should really be standalone drivers that do not interact with other
    > subsystems.

    pci-host-common.c goes against being standalone. The files calling
    pci_host_common_probe() are expected to have custom ECAM ops
    the way it is written now. We need to have a reasonable way to share
    those ECAM ops if needed by ACPI.

    > How much code would you need to duplicate from thunder-ecam to have
    > the same functionality available in ACPI? My expectation is that it's
    > not really that much more compared to the code you need for sharing
    > a single implementation, but you get a lower complexity here, which
    > makes it easier to understand and to rework.

    Like I wrote above, the sharing is really simple because both generic
    ACPI and pci-host-common.c have been written for "ECAM with quirks".

    The whole pci-thunder-*.c is to support thunder PCI quirks since the
    generic OF is handled by pci-host-common.c and generic ECAM is now
    separated - duplicating the whole file for ACPI will be bad.

    Any suggestions on how to do this better would be really welcome.

    Thanks,
    JC.

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