Date:   Fri, 14 Jan 2022 10:58:51 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Cc:     Sergey Shtylyov <s.shtylyov@....ru>,
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Subject: Re: [PATCH] driver core: platform: Rename platform_get_irq_optional()
 to platform_get_irq_silent()

Hi Uwe,

On Thu, Jan 13, 2022 at 11:43 PM Uwe Kleine-König
<u.kleine-koenig@...gutronix.de> wrote:
> On Thu, Jan 13, 2022 at 11:57:43PM +0300, Sergey Shtylyov wrote:
> > On 1/13/22 11:17 PM, Mark Brown wrote:
> > >> The subsystems regulator, clk and gpio have the concept of a dummy
> > >> resource. For regulator, clk and gpio there is a semantic difference
> > >> between the regular _get() function and the _get_optional() variant.
> > >> (One might return the dummy resource, the other won't. Unfortunately
> > >> which one implements which isn't the same for these three.) The
> > >> difference between platform_get_irq() and platform_get_irq_optional() is
> > >> only that the former might emit an error message and the later won't.
> >
> >    This is only a current difference but I'm still going to return 0 ISO
> > -ENXIO from latform_get_irq_optional(), no way I'd leave that -ENXIO there
> > alone... :-)
>
> This would address a bit of the critic in my commit log. But as 0 isn't
> a dummy value like the dummy values that exist for clk, gpiod and
> regulator I still think that the naming is a bad idea because it's not
> in the spirit of the other *_get_optional functions.
>
> Seeing you say that -ENXIO is a bad return value for
> platform_get_irq_optional() and 0 should be used instead, I wonder why
> not changing platform_get_irq() to return 0 instead of -ENXIO, too.
> This question is for now only about a sensible semantic. That actually
> changing platform_get_irq() is probably harder than changing
> platform_get_irq_optional() is a different story.
>
> If only platform_get_irq_optional() is changed and given that the
> callers have to do something like:
>
>         if (this_irq_exists()):
>                 ... (e.g. request_irq)
>         else:
>                 ... (e.g. setup polling)
>
> I really think it's a bad idea that this_irq_exists() has to be
> different for platform_get_irq() vs. platform_get_irq_optional().

For platform_get_irq(), the IRQ being absent is an error condition,
hence it should return an error code.
For platform_get_irq_optional(), the IRQ being absent is not an error
condition, hence it should not return an error code, and 0 is OK.

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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