Re: [PATCH] perf/arm-smmuv3: Propagate errors from optional IRQ lookup

[Bui Duc Phuc]

Hi Will,

> > > Not sure about this. If it's optional, why should we bail the probe if
> > > we don't manage to get an irq? Surely it's better to continue without
> > > the interrupt in that case?
> > >
> >
> > platform_get_irq_optional() returns -ENXIO when no IRQ is available.
> > Other negative return values indicate errors, including -EPROBE_DEFER.
> > In the case of -EPROBE_DEFER, we should propagate the error so that
> > the probe can be retried later.
>
> Thanks, The -EPROBE_DEFER case seems more compelling, so perhaps we should
> check for the expliitly (because it won't fail the probe altogether)?
>

The idea of the _optional getters is that only the "not present" case
is turned into a special value (-ENXIO here, NULL for
devm_clk_get_optional()), while real errors are still reported to the
caller.

Besides -EPROBE_DEFER, platform_get_irq_optional() can return other
negative error values depending on how the IRQ is obtained. These
indicate an actual error rather than the IRQ simply being absent.
Ignoring them would leave the device running without its interrupt
and no indication of what went wrong.

So I'd rather keep:

-----------------------------------------------------
irq = platform_get_irq_optional(pdev, 0);
if (irq < 0 && irq != -ENXIO)
        return irq;
-----------------------------------------------------

and continue without the IRQ only for -ENXIO. This is also the usual
pattern for platform_get_irq_optional() users.

Best regards,
Phuc