Message-ID: <20220112085009.dbasceh3obfok5dc@pengutronix.de>
Date:   Wed, 12 Jan 2022 09:50:09 +0100
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Andrew Lunn <andrew@...n.ch>, Ulf Hansson <ulf.hansson@...aro.org>,
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Subject: Re: [PATCH 1/2] platform: make platform_get_irq_optional() optional

On Wed, Jan 12, 2022 at 09:33:48AM +0100, Geert Uytterhoeven wrote:
> 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.

Is this an ack for renaming platform_get_irq_optional() to
platform_get_irq_silent()?

And then a coccinelle or sparse or ... hook that catches people testing
the return value against 0 would be great.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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