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?
- The unfortunate naming
unfortunate naming for the currently implemented semantic, yes.
Yes.
- 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().
- 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:
- 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:
- 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.