Re: [PATCH 1/2] platform: make platform_get_irq_optional() optional

[Uwe Kleine-König]

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@xxxxxxxxxxxxxxx/
> 
> 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. 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().

Best regards
Uwe

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

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