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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Mon, 27 Dec 2021 10:45:09 +0100
Message-ID: <CAMuHMdWSAOEAvqvr1UqKKmVDMzY3Tb8Y_4XowFPBN6L3TESqYA@mail.gmail.com>
Subject: Re: [PATCH] irqchip/renesas-irqc: Use platform_get_irq_optional() to
 get the interrupt
To:     Andy Shevchenko <andy.shevchenko@gmail.com>
Cc:     "Lad, Prabhakar" <prabhakar.csengg@gmail.com>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Marc Zyngier <maz@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Hi Andy,

On Sun, Dec 26, 2021 at 9:49 AM Andy Shevchenko
<andy.shevchenko@gmail.com> wrote:
> On Sun, Dec 26, 2021 at 1:59 AM Lad, Prabhakar
> <prabhakar.csengg@gmail.com> wrote:
> > On Sat, Dec 25, 2021 at 5:40 PM Andy Shevchenko
> > <andy.shevchenko@gmail.com> wrote:
> > > On Sat, Dec 25, 2021 at 7:28 PM Lad, Prabhakar
> > > <prabhakar.csengg@gmail.com> wrote:
> > > > On Sat, Dec 25, 2021 at 4:46 PM Andy Shevchenko
> > > > <andy.shevchenko@gmail.com> wrote:
> > > > > On Thu, Dec 16, 2021 at 9:52 AM Lad Prabhakar
> > > > > <prabhakar.mahadev-lad.rj@bp.renesas.com> wrote:
> > >
> > > > > ret = platform_get_irq_optional(...);
> > > > > if (ret < 0 && ret != -ENXIO)
> > > > >   return ret;
> > > > > if (ret > 0)
> > > > >   ...we got it...
> > > > >
> > > > > It will allow the future API fix of platform_get_irq_optional() to be
> > > > > really optional.
> > > > >
> > > > Later patch [0] (merged into -next) does check for -ENXIO first.
> > > >
> > > > [0] https://lore.kernel.org/lkml/20211216182121.5323-1-prabhakar.mahadev-lad.rj@bp.renesas.com/t/
> > >
> > > The problem is that it doesn't consider 0 as no IRQ.
> > >
> > Can you please point me to the discussion/patch where this API change
> > is considered/discussed. Just to clarify now the new API for
> > platform_get_irq_optional() will return "0" in case there is no
> > interrupt and not not -ENXIO anymore?
>
> The longest one happened here:
> https://lore.kernel.org/linux-ide/20211209145937.77719-1-andriy.shevchenko@linux.intel.com/T/#u
>
> It has links to some other discussions on the topic.
>
> > When will this patch be merged for the new api, so that I can base my
> > patches on top of it to avoid more changes?
>
> You can simply imply that, I dunno when it gets merged (from my point
> of view the users should be fixed first, and since you are adding
> users, the burden is increasing).

Not only users (drivers), but also providers (architecture-specific code).
IRQ zero is still valid on some architectures, e.g. on SH[1].

[1] https://lore.kernel.org/linux-renesas-soc/CAMuHMdUg3=q7gyaVHP0XcYUOo3PQUUv8Hc8wp5faVQ+bTBpg4A@mail.gmail.com/

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds