linux-kernel - Re: [PATCH] irqchip/renesas-irqc: Use platform_get_irq

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Message-ID: <CAHp75Vd5gGLoVBbiZ1FBWs4fMgq=c4xU2NspQXEpnCf6=b4tCg@mail.gmail.com>
Date:   Mon, 27 Dec 2021 12:03:32 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     "Lad, Prabhakar" <prabhakar.csengg@...il.com>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] irqchip/renesas-irqc: Use platform_get_irq_optional() to
 get the interrupt

On Mon, Dec 27, 2021 at 11:56 AM Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
>
> On Mon, Dec 27, 2021 at 11:45 AM Geert Uytterhoeven
> <geert@...ux-m68k.org> wrote:
> >
> > Hi Andy,
> >
> > On Sun, Dec 26, 2021 at 9:49 AM Andy Shevchenko
> > <andy.shevchenko@...il.com> wrote:
> > > On Sun, Dec 26, 2021 at 1:59 AM Lad, Prabhakar
> > > <prabhakar.csengg@...il.com> wrote:
> > > > On Sat, Dec 25, 2021 at 5:40 PM Andy Shevchenko
> > > > <andy.shevchenko@...il.com> wrote:
> > > > > On Sat, Dec 25, 2021 at 7:28 PM Lad, Prabhakar
> > > > > <prabhakar.csengg@...il.com> wrote:
> > > > > > On Sat, Dec 25, 2021 at 4:46 PM Andy Shevchenko
> > > > > > <andy.shevchenko@...il.com> wrote:
> > > > > > > On Thu, Dec 16, 2021 at 9:52 AM Lad Prabhakar
> > > > > > > <prabhakar.mahadev-lad.rj@...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].
>
> Are we talking about vIRQ?
> And users are fine with a big warning?
>
> My understanding is that the architecture code there is broken. It
> needs to be fixed to use IRQ domains and all that machinery instead of
> what it does.
>
> 0 is "no IRQ" in Linux.
>
> > [1] https://lore.kernel.org/linux-renesas-soc/CAMuHMdUg3=q7gyaVHP0XcYUOo3PQUUv8Hc8wp5faVQ+bTBpg4A@mail.gmail.com/

And to the point of the scope of this change, why should we obfuscate
the code in the case we know that it's not the case? You pointed out
to the ethernet driver. How does it related here?

-- 
With Best Regards,
Andy Shevchenko