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    SubjectRe: [PATCH] platform: finally disallow IRQ0 in platform_get_irq() and its ilk
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    Hello!

    On 1/4/22 12:26 PM, Marc Zyngier wrote:

    [...]
    >> The commit a85a6c86c25b ("driver core: platform: Clarify that IRQ 0 is
    >> invalid") only calls WARN() when IRQ0 is about to be returned, however
    >> using IRQ0 is considered invalid (according to Linus) outside the arch/
    >> code where it's used by the i8253 drivers. Many driver subsystems treat
    >> 0 specially (e.g. as an indication of the polling mode by libata), so
    >> the users of platform_get_irq[_byname]() in them would have to filter
    >> out IRQ0 explicitly and this (quite obviously) doesn't scale...
    >> Let's finally get this straight and return -EINVAL instead of IRQ0!
    >>
    >> Fixes: a85a6c86c25b ("driver core: platform: Clarify that IRQ 0 is invalid")
    >> Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru>
    >>
    >> ---
    >> The patch is against the 'driver-core-linus' branch of Greg Kroah-Hartman's
    >> 'driver-core.git' repo.
    >>
    >> drivers/base/platform.c | 6 ++++--
    >> 1 file changed, 4 insertions(+), 2 deletions(-)
    >>
    >> Index: driver-core/drivers/base/platform.c
    >> ===================================================================
    >> --- driver-core.orig/drivers/base/platform.c
    >> +++ driver-core/drivers/base/platform.c
    >> @@ -231,7 +231,8 @@ int platform_get_irq_optional(struct pla
    >> out_not_found:
    >> ret = -ENXIO;
    >> out:
    >> - WARN(ret == 0, "0 is an invalid IRQ number\n");
    >> + if (WARN(!ret, "0 is an invalid IRQ number\n"))
    >> + return -EINVAL;
    >> return ret;
    >> }
    >> EXPORT_SYMBOL_GPL(platform_get_irq_optional);
    >> @@ -445,7 +446,8 @@ static int __platform_get_irq_byname(str
    >>
    >> r = platform_get_resource_byname(dev, IORESOURCE_IRQ, name);
    >> if (r) {
    >> - WARN(r->start == 0, "0 is an invalid IRQ number\n");
    >> + if (WARN(!r->start, "0 is an invalid IRQ number\n"))
    >> + return -EINVAL;
    >> return r->start;
    >> }
    >
    > Geert recently mentioned that a few architectures (such as sh?) still
    > use IRQ0 as something valid in limited cases.

    Yeah, valid IRQ0 on some SH boards -- which I believe could soon be addressed.

    > From my PoV, this patch is fine, but please be prepared to fix things
    > in a couple of years when someone decides to boot a recent kernel on
    > their pet dinosaur. With that in mind:

    Of course, I'm prepared.

    >
    > Acked-by: Marc Zyngier <maz@kernel.org>

    Thank you!

    MBR, Sergey

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