linux-kernel - Re: [PATCH 1/2] platform: make platform_get_irq

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Message-ID: <YdyilpjC6rtz6toJ@lunn.ch>
Date:   Mon, 10 Jan 2022 22:18:14 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Cc:     Sergey Shtylyov <s.shtylyov@....ru>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org, Ulf Hansson <ulf.hansson@...aro.org>,
        Vignesh Raghavendra <vigneshr@...com>,
        Jiri Slaby <jirislaby@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>, linux-iio@...r.kernel.org,
        Linus Walleij <linus.walleij@...aro.org>,
        Amit Kucheria <amitk@...nel.org>, alsa-devel@...a-project.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Sebastian Reichel <sre@...nel.org>,
        linux-phy@...ts.infradead.org,
        Thierry Reding <thierry.reding@...il.com>,
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        Brian Norris <computersforpeace@...il.com>,
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Subject: Re: [PATCH 1/2] platform: make platform_get_irq_optional() optional

On Mon, Jan 10, 2022 at 09:10:14PM +0100, Uwe Kleine-König wrote:
> Hello,
> 
> 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.

> My suggestion would be to keep the return value of
> platform_get_irq_optional() as is, but rename it to
> platform_get_irq_silent() to get rid of the expectation invoked by
> the naming similarity that motivated you to change
> platform_get_irq_optional().

This is a good idea.

     Andrew