Date:   Wed, 12 Jan 2022 09:33:48 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
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Subject: Re: [PATCH 1/2] platform: make platform_get_irq_optional() optional

Hi Andrew,

On Mon, Jan 10, 2022 at 10:20 PM Andrew Lunn <andrew@...n.ch> wrote:
> On Mon, Jan 10, 2022 at 09:10:14PM +0100, Uwe Kleine-König wrote:
> > On Mon, Jan 10, 2022 at 10:54:48PM +0300, Sergey Shtylyov wrote:
> > > This patch is based on the former Andy Shevchenko's patch:
> > >
> > > https://lore.kernel.org/lkml/20210331144526.19439-1-andriy.shevchenko@linux.intel.com/
> > >
> > > Currently platform_get_irq_optional() returns an error code even if IRQ
> > > resource simply has not been found. It prevents the callers from being
> > > error code agnostic in their error handling:
> > >
> > >     ret = platform_get_irq_optional(...);
> > >     if (ret < 0 && ret != -ENXIO)
> > >             return ret; // respect deferred probe
> > >     if (ret > 0)
> > >             ...we get an IRQ...
> > >
> > > All other *_optional() APIs seem to return 0 or NULL in case an optional
> > > resource is not available. Let's follow this good example, so that the
> > > callers would look like:
> > >
> > >     ret = platform_get_irq_optional(...);
> > >     if (ret < 0)
> > >             return ret;
> > >     if (ret > 0)
> > >             ...we get an IRQ...
> >
> > The difference to gpiod_get_optional (and most other *_optional) is that
> > you can use the NULL value as if it were a valid GPIO.
> >
> > As this isn't given with for irqs, I don't think changing the return
> > value has much sense.
>
> We actually want platform_get_irq_optional() to look different to all
> the other _optional() methods because it is not equivalent. If it
> looks the same, developers will assume it is the same, and get
> themselves into trouble.

Developers already assume it is the same, and thus forget they have
to check against -ENXIO instead of zero.

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

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