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    SubjectRe: [PATCH v2] gpio: Add Avionic Design N-bit GPIO expander support
    On Fri, Aug 10, 2012 at 10:35 AM, Thierry Reding
    <> wrote:
    >> Consult the following article on LWN:
    >> Then grep your gitlog and you'll see we got rid of it from ARM.
    > Then why is there still the following in arch/arm/include/asm/irq.h?
    > /*
    > * Use this value to indicate lack of interrupt
    > * capability
    > */
    > #ifndef NO_IRQ
    > #define NO_IRQ ((unsigned int)(-1))
    > #endif

    That's a question for Russell but I think it's basically there for
    old platforms, on a "don't use it"-basis. (Maybe a comment could
    be good.)

    As you see non-sparse platforms can redefine NO_IRQS in their
    <mach/irqs.h> file, but in practice things like the VIC and GIC
    drivers have been switched over to using irqdomain which
    in turn does *not* allow IRQ 0 to be used, so most platforms
    are indirectly disallowed to use IRQ 0 anyway. In fact I think
    some of them are just broken now.

    >> If this driver is for some other arch like openrisc I might accept
    >> it but please reconsider.
    > There's nothing in the driver that makes it ARM specific, so it could be
    > used on other platforms just as well.

    The linked article makes it clear that the direction for the entire
    kernel is to get rid of NO_IRQ and !irq is used all over the place.

    > But as I also said in my previous
    > mail, in this particular case the value for the interrupt comes from the
    > call to irq_of_parse_and_map(), which will return 0 on failure,
    > regardless of the architecture, so there is actually no problem.

    OK cool.

    Linus Walleij

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