Message-ID: <Ydyf93VD8FrV7GH+@smile.fi.intel.com>
Date:   Mon, 10 Jan 2022 23:07:03 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Cc:     Sergey Shtylyov <s.shtylyov@....ru>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
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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:
> 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.

The problem is not only there, but also in the platform_get_irq() and that
problem is called vIRQ0. Or as Linus put it "_cookie_" for IRQ, which never
ever should be 0.

> As this isn't given with for irqs, I don't think changing the return
> value has much sense. In my eyes the problem with platform_get_irq() and
> platform_get_irq_optional() is that someone considered it was a good
> idea that a global function emits an error message. The problem is,
> that's only true most of the time. (Sometimes the caller can handle an
> error (here: the absence of an irq) just fine, sometimes the generic
> error message just isn't as good as a message by the caller could be.
> (here: The caller could emit "TX irq not found" which is a much nicer
> message than "IRQ index 5 not found".)
> 
> 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 won't fix the issue with vIRQ0.

-- 
With Best Regards,
Andy Shevchenko

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