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:

quoted

This patch is based on the former Andy Shevchenko's patch:

https://lore.kernel.org/lkml/20210331144526.19439-1-andriy.shevchenko@linux.intel.com/ (local)

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