On Thu, Jan 20, 2022 at 08:57:18AM +0100, Uwe Kleine-König wrote: > On Wed, Jan 19, 2022 at 08:51:29PM +0200, Andy Shevchenko wrote: > > On Sat, Jan 15, 2022 at 04:45:39PM +0100, Uwe Kleine-König wrote: > > > On Fri, Jan 14, 2022 at 03:04:38PM +0200, Andy Shevchenko wrote: > > > > On Thu, Jan 13, 2022 at 08:43:58PM +0100, Uwe Kleine-König wrote: > > > > > > 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. > > > > > > > > And similar number of people are on the other side. > > > > > > If someone already opposed to the renaming (and not only the name) I > > > must have missed that. > > > > > > So you think it's a good idea to keep the name > > > platform_get_irq_optional() despite the "not found" value returned by it > > > isn't usable as if it were a normal irq number? > > > > I meant that on the other side people who are in favour of Sergey's patch. > > Since that I commented already that I opposed the renaming being a standalone > > change. > > > > Do you agree that we have several issues with platform_get_irq*() APIs? > > > > 1. The unfortunate naming > > unfortunate naming for the currently implemented semantic, yes. Yes. > > 2. The vIRQ0 handling: a) WARN() followed by b) returned value 0 > > I'm happy with the vIRQ0 handling. Today platform_get_irq() and it's > silent variant returns either a valid and usuable irq number or a > negative error value. That's totally fine. It might return 0. Actually it seems that the WARN() can only be issued in two cases: - SPARC with vIRQ0 in one of the array member - fallback to ACPI for GPIO IRQ resource with index 0 But the latter is bogus, because it would mean a bug in the ACPI code. The bottom line here is the SPARC case. Anybody familiar with the platform can shed a light on this. If there is no such case, we may remove warning along with ret = 0 case from platfrom_get_irq(). > > 3. The specific cookie for "IRQ not found, while no error happened" case > > Not sure what you mean here. I have no problem that a situation I can > cope with is called an error for the query function. I just do error > handling and continue happily. So the part "while no error happened" is > irrelevant to me. I meant that instead of using special error code, 0 is very much good for the cases when IRQ is not found. It allows to distinguish -ENXIO from the low layer from -ENXIO with this magic meaning. > Additionally I see the problems: > > 4. The semantic as implemented in Sergey's patch isn't better than the > current one. I disagree on this. See above on why. > platform_get_irq*() is still considerably different from > (clk|gpiod)_get* because the not-found value for the _optional variant > isn't usuable for the irq case. For clk and gpio I get rid of a whole if > branch, for irq I only change the if-condition. (And if that change is > considered good or bad seems to be subjective.) You are mixing up two things: - semantics of the pointer - semantics of the cookie Like I said previously the mistake is in putting an equal sign between apples and oranges (or in terms of Python, which is a good example here, None and False objects, where in both case 0 is magic and Python `if X`, `while `X` will work in the same way, the `typeof(X)` is different semantically). > For the idea to add a warning to platform_get_irq_optional for all but > -ENXIO (and -EPROBE_DEFER), I see the problem: > > 5. platform_get_irq*() issuing an error message is only correct most of > the time and given proper error handling in the caller (which might be > able to handle not only -ENXIO but maybe also -EINVAL[1]) the error message > is irritating. Today platform_get_irq() emits an error message for all > but -EPROBE_DEFER. As soon as we find a driver that handles -EINVAL we > need a function platform_get_irq_variant1 to be silent for -EINVAL, > -EPROBE_DEFER and -ENXIO (or platform_get_irq_variant2 that is only > silent for -EINVAL and -EPROBE_DEFER?) > > IMHO a query function should always be silent and let the caller do the > error handling. And if it's only because > > mydev: IRQ index 0 not found > > is worse than > > mydev: neither TX irq not a muxed RX/TX irq found > > . Also "index 0" is irritating for devices that are expected to have > only a single irq (i.e. the majority of all devices). Yeah, ack the #5. > Yes, I admit, we can safe some code by pushing the error message in a > query function. But that doesn't only have advantages. > [1] Looking through the source I wonder: What are the errors that can happen > in platform_get_irq*()? (calling everything but a valid irq number > an error) Looking at many callers, they only seem to expect "not > found" and some "probe defer" (even platform_get_irq() interprets > everything but -EPROBE_DEFER as "IRQ index %u not found\n".) > IMHO before we should consider to introduce a platform_get_irq*() > variant with improved semantics, some cleanup in the internals of > the irq lookup are necessary. -- With Best Regards, Andy Shevchenko
