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

Andy Shevchenko
2022-01-10T21:08:44Z

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