Re: [PATCH] driver core: platform: Rename platform_get_irq_optional() to platform_get_irq_silent()

Uwe Kleine-König
2022-01-13T23:07:25Z

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On Thu, Jan 13, 2022 at 01:42:57PM -0800, Florian Fainelli wrote:
>
>
> On 1/13/2022 11:43 AM, Uwe Kleine-König wrote:
> > The subsystems regulator, clk and gpio have the concept of a dummy
> > resource. For regulator, clk and gpio there is a semantic difference
> > between the regular _get() function and the _get_optional() variant.
> > (One might return the dummy resource, the other won't. Unfortunately
> > which one implements which isn't the same for these three.) The
> > difference between platform_get_irq() and platform_get_irq_optional() is
> > only that the former might emit an error message and the later won't.
> >
> > To prevent people's expectations that there is a semantic difference
> > between these too, rename platform_get_irq_optional() to
> > platform_get_irq_silent() to make the actual difference more obvious.
> >
> > The #define for the old name can and should be removed once all patches
> > currently in flux still relying on platform_get_irq_optional() are
> > fixed.
> >
> > Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> > ---
> > Hello,
> >
> > On Thu, Jan 13, 2022 at 02:45:30PM +0000, Mark Brown wrote:
> > > On Thu, Jan 13, 2022 at 12:08:31PM +0100, Uwe Kleine-König wrote:
> > >
> > > > This is all very unfortunate. In my eyes b) is the most sensible
> > > > sense, but the past showed that we don't agree here. (The most annoying
> > > > part of regulator_get is the warning that is emitted that regularily
> > > > makes customers ask what happens here and if this is fixable.)
> > >
> > > Fortunately it can be fixed, and it's safer to clearly specify things.
> > > The prints are there because when the description is wrong enough to
> > > cause things to blow up we can fail to boot or run messily and
> > > forgetting to describe some supplies (or typoing so they haven't done
> > > that) and people were having a hard time figuring out what might've
> > > happened.
> >
> > Yes, that's right. I sent a patch for such a warning in 2019 and pinged
> > occationally. Still waiting for it to be merged :-\
> > (https://lore.kernel.org/r/20190625100412.11815-1-u.kleine-koenig@pengutronix.de)
> >
> > > > I think at least c) is easy to resolve because
> > > > platform_get_irq_optional() isn't that old yet and mechanically
> > > > replacing it by platform_get_irq_silent() should be easy and safe.
> > > > And this is orthogonal to the discussion if -ENOXIO is a sensible return
> > > > value and if it's as easy as it could be to work with errors on irq
> > > > lookups.
> > >
> > > It'd certainly be good to name anything that doesn't correspond to one
> > > of the existing semantics for the API (!) something different rather
> > > than adding yet another potentially overloaded meaning.
> >
> > It seems we're (at least) three who agree about this. Here is a patch
> > fixing the name.
>
> From an API naming perspective this does not make much sense anymore with
> the name chosen, it is understood that whent he function is called
> platform_get_irq_optional(), optional applies to the IRQ. An optional IRQ is
> something people can reason about because it makes sense.

The problem I see is that the semantic is different to the other
available *_get_optional() functions. And this isn't fixable for irqs.
So better don't use that naming scheme.

> What is a a "silent" IRQ however? It does not apply to the object it is
> trying to fetch to anymore, but to the message that may not be printed in
> case the resource failed to be obtained, because said resource is optional.
> Woah, that's quite a stretch.

I'm surprised that the semantic isn't obvious, but ok, I can accept
that.Can you maek a constructive suggestion here? What name pair would
you choose for the two functions functions under discussion?

(BTW, my favourite would be that platform_get_irq() doesn't emit an
error message and the caller is reliable for emitting that. But I think
it's too late for this approach.)

> Following the discussion and original 2 patches set from Sergey, it is not
> entirely clear to me anymore what is it that we are trying to fix.

(I think) Sergey's focus is:

platform_get_irq_optional() returning -ENXIO is ugly, other
functions return -ENOENT and other *_get_optional() functions
return NULL for "This resource doesn't exist". So let's return 0
in this case.

My focus is:

There cannot be an "optional irq" where the driver doesn't have
to care if the irq actually exist or not. So the pattern with
*_get_optional() isn't sensible for irqs and if changing the
returned value meaning "This resource doesn't exist" is sensible
for platform_get_irq_optional(), I claim it's sensible for
platform_get_irq(), too.

So the semantic difference between platform_get_irq() and
platform_get_irq_optional() is only that one emits an error
message and the other doesn't. So this function pair should use
a different naming than get + get_optional as this naming evokes
expectations that must be wrong as there cannot be a dummy irq
value.

> I nearly forgot, I would paint it blue, sky blue, not navy blue, not light
> blue ;)

no way. green is the ultimate blue for platform_get_irq() :-)

Best regards
Uwe

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

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