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    SubjectRe: [PATCH] irqdomain: print a warning if domains contain IRQ 0
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    On Thu, 19 Apr 2012 08:23:12 +1000, Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:
    > On Wed, 2012-04-18 at 15:40 +0200, Linus Walleij wrote:
    > > From: Linus Walleij <linus.walleij@linaro.org>
    > >
    > > Some of the clients using IRQ domains from the ARM VIC
    > > (arch/arm/common/vic.c) don't know that their (hardware) IRQ 0
    > > is silently ignored by the IRQ core, they will just notice
    > > that they're not getting this IRQ anymore. So print a warning
    > > if a domain contains IRQ 0 (NO_IRQ) so we get some noise about
    > > it atleast.
    >
    > I don't understand. HW IRQ 0 is not ignored and works perfectly
    > fine on "normal" remapped domains. Or is this specific to "legacy
    > domains" ? In this case pls make it clear in the subject :-)

    This is indeed specific to the legacy domain. I think the patch is
    good and it will help weed out unintended irq0 users. However, it
    requires the following additional fix I think. It will need to be
    tested to make sure it doesn't break PowerPC ISA users.

    g.

    diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
    index d0995bd..31f1f88 100644
    --- a/include/linux/irqdomain.h
    +++ b/include/linux/irqdomain.h
    @@ -138,7 +138,7 @@ static inline struct irq_domain *irq_domain_add_legacy_isa(
    const struct irq_domain_ops *ops,
    void *host_data)
    {
    - return irq_domain_add_legacy(of_node, NUM_ISA_INTERRUPTS, 0, 0, ops,
    + return irq_domain_add_legacy(of_node, NUM_ISA_INTERRUPTS-1, 1, 1, ops,
    host_data);
    }
    extern struct irq_domain *irq_find_host(struct device_node *node);

    > > ---
    > > kernel/irq/irqdomain.c | 4 +++-
    > > 1 file changed, 3 insertions(+), 1 deletion(-)
    > >
    > > diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
    > > index 0e0ba5f..1444454 100644
    > > --- a/kernel/irq/irqdomain.c
    > > +++ b/kernel/irq/irqdomain.c
    > > @@ -136,8 +136,10 @@ struct irq_domain *irq_domain_add_legacy(struct device_node *of_node,
    > > int hwirq = first_hwirq + i;
    > >
    > > /* IRQ0 gets ignored */
    > > - if (!irq)
    > > + if (!irq) {
    > > + pr_warn("trying to register IRQ 0 (NO_IRQ) in an irq domain\n");
    > > continue;
    > > + }
    > >
    > > /* Legacy flags are left to default at this point,
    > > * one can then use irq_create_mapping() to
    >
    >

    --
    Grant Likely, B.Sc, P.Eng.
    Secret Lab Technologies,Ltd.


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