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    SubjectRe: [PATCH v3 3/3] gpio: add Intel SCH GPIO controller driver
    David Brownell wrote:
    > On Sunday 21 February 2010, Denis Turischev wrote:
    >> v2: there is no acpi_check_region, it will be implemented in mfd-core
    >> v3: patch refreshed against the latest Linus tree
    >
    > Could such call really address the GPIO conflict issue I mentioned?
    >
    > The AML bytecodes I looked at were writing directly to Southbridge
    > GPIO registers (or reading them), or relying on ACPI to mediate the
    > GPIO interrupts. ISTR that button drivers, and code to switch into
    > or out of low power states, were good sources of such bad examples.

    I'm really not an ACPI expert, but as far as I understand possibility of
    such conflicts largely depends on particular board/BIOS implementation.
    On the hardware we have such conflict cannot happen, unless there are
    bugs in ACPI we are not yet aware of. :)

    > Calls like that should clearly be able to handle cases where ACPI
    > has a "Real" Driver (tm) ... e.g. for SMBus hardware.
    >
    > I'm not sure what a good solution for this would be, short of just
    > not using ACPI ... which may not be practical, given the limited
    > degree of x86 board/system support for Linux.
    >
    > I mention this mostly because when I looked at the issue in the
    > context of an ICHx GPIO driver, I didn't see a good solution to
    > the problem then ... and nothing seems to have changed meanwhile.

    I've looked at two x86 drivers in drivers/gpiolib (cs5535 and langwell)
    and there's no treatment of ACPI in either of them. Since SCH is defined
    by Intel as "embedded" product, having a GPIO driver for it seems
    logical even despite problems you mention.

    > - Dave
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    --
    Sincerely yours,
    Mike.



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