linux-kernel - Re: [PATCH] thermal: rcar_thermal: Use platform_get_irq

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Date:   Mon, 20 Dec 2021 15:26:44 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Niklas Söderlund <niklas.soderlund@...natech.se>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Amit Kucheria <amitk@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Linux PM list <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Prabhakar <prabhakar.csengg@...il.com>
Subject: Re: [PATCH] thermal: rcar_thermal: Use platform_get_irq_optional() to
 get the interrupt

Hi Daniel,

On Mon, Dec 20, 2021 at 3:19 PM Daniel Lezcano
<daniel.lezcano@...aro.org> wrote:
> On 20/12/2021 14:48, Geert Uytterhoeven wrote:
> > On Mon, Dec 20, 2021 at 1:29 PM Daniel Lezcano
> > <daniel.lezcano@...aro.org> wrote:
> >> On 18/12/2021 15:41, Lad Prabhakar wrote:
> >>> platform_get_resource(pdev, IORESOURCE_IRQ, ..) relies on static
> >>> allocation of IRQ resources in DT core code, this causes an issue
> >>> when using hierarchical interrupt domains using "interrupts" property
> >>> in the node as this bypasses the hierarchical setup and messes up the
> >>> irq chaining.
> >>>
> >>> In preparation for removal of static setup of IRQ resource from DT core
> >>> code use platform_get_irq_optional().
> >>>
> >>> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>

> >>> --- a/drivers/thermal/rcar_thermal.c
> >>> +++ b/drivers/thermal/rcar_thermal.c
> >>> @@ -445,7 +445,7 @@ static int rcar_thermal_probe(struct platform_device *pdev)
> >>>       struct rcar_thermal_common *common;
> >>>       struct rcar_thermal_priv *priv;
> >>>       struct device *dev = &pdev->dev;
> >>> -     struct resource *res, *irq;
> >>> +     struct resource *res;
> >>>       const struct rcar_thermal_chip *chip = of_device_get_match_data(dev);
> >>>       int mres = 0;
> >>>       int i;
> >>> @@ -467,9 +467,16 @@ static int rcar_thermal_probe(struct platform_device *pdev)
> >>>       pm_runtime_get_sync(dev);
> >>>
> >>>       for (i = 0; i < chip->nirqs; i++) {
> >>> -             irq = platform_get_resource(pdev, IORESOURCE_IRQ, i);
> >>> -             if (!irq)
> >>> +             int irq;
> >>> +
> >>> +             irq = platform_get_irq_optional(pdev, i);
> >>> +             if (irq <= 0 && irq != -ENXIO) {
> >>> +                     ret = irq ? irq : -ENXIO;
> >>> +                     goto error_unregister;
> >>> +             }
> >>> +             if (irq == -ENXIO)
> >>>                       continue;
> >>
> >> Why not invert the conditions?
> >>
> >>                 if (irq == -ENXIO)
> >>                         continue;
> >
> > And this can be break.
> >
> >>
> >>                 if (irq <= 0) {
> >>                         ret = irq ? irq : -ENXIO;
> >
> > irq == 0 cannot happen.
> >
> >>                         goto out_unregister;
> >>                 }
>
> Sorry, I don't get the two comments. May be I missed something but it
> seems for me the results are the same with the inverted conditions or not.
>
> if (irq <= 0 && irq != -ENXIO)
>         goto out;
>
> if (irq == -ENXIO)
>         continue;
>
> Can be changed to:
>
> if (irq != -ENXIO)
>         if (irq <= 0)
>                 goto out;
>
> if (irq == -ENXIO)
>         continue;
>
> Can be changed to:
>
>
> if (irq == -ENXIO)
>         continue;
>
> if (irq != -ENXIO)
>         if (irq <= 0)
>                 goto out;
>
> The second condition is always true because the first condition is the
> opposite of the second condition, if the second condition block is
> reached, that means irq != -ENXIO, so we can remove the second condition
> and that results into:
>
> if (irq == -ENXIO)
>         continue;
>
> if (irq <= 0)
>         goto out;
>
>
> Did I miss your point ?

I think so, as I don't see your point, neither ;-)

I meant (a) there is no need to continue the loop when there are no
more interrupts present, and (b) irq == 0 cannot happen, so the cod
can be simplified to:

    if (irq == -ENXIO)
            break;
    if (irq < 0) {
            ret = irq;
            goto out_unregister;
    }

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-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