On Fri, Dec 10, 2021 at 08:39:38PM +0300, Sergey Shtylyov wrote: > On 12/10/21 2:28 PM, Andy Shevchenko wrote: > > >>>>>>>>> While at it, drop redundant check for 0 as platform_get_irq() spills > >>>>>>>>> out a big WARN() in such case. > >>>>>>>> > >>>>>>>> And? IRQ0 is still returned! :-( > >>>>>>> > >>>>>>> It should not be returned in the first place. > >>>>>> > >>>>>> But it still is, despite the WARN(), right? > >>>>> > >>>>> So, you admit that there is a code which does that? > >>>> > >>>> I admit *what*?! That platfrom_get_irq() and its ilk return IRQ0 while they > >>>> shouldn't? =) > >>> > >>> That there is a code beneath platform_get_irq() that returns 0, yes. > >> > >> Look at the ACPI-specific GpioInt handling code (just above the out_not_found label) -- > >> I'm not sure the check there is correct -- I'm not very familiar with ACPI, you seem to > >> know it much better. :-) > > > > And what is your point here exactly? > > You're saying IRQ0 shouldn't be returned (by the ACPI code) -- from this fragment > we can see that it may be returned... Please, provide your analysis, I really don't see how it's possible. If you prove that, we must fix the severe bug then. > > If == 0 case happens, it will be > > immediately WARN() and reported (I hope) > > Well, "hope dies last"... :-) Believe, big WARNs are quite likely to be reported if not by humans, then by CIs and fuzzers. So, the hope is rather to word 'immediately'. > > since it will mean bug in the code. > > > >> Also, 0 can be specified via the normal IRQ resource. I know of e.g. the Alchemy MIPS SoCs > >> that have IRQ0 used by UART0; luckily, currently SoC IRQs are mapped starting at Linux IRQ8 > >> (but it wasn't the case in the 2.6.1x time frame where we had issue with the serial driver)... > > > > You mixed up HW IRQ with vIRQ. > > I didn't. Linux expects the vIRQs (I called them Linux IRQs). In the 2.6.1x time frame > those corresponded 1:1 on Alchemy. Also, there's 8259 which is always mapped at vIRQ0 (or > the legacy drivers won't work). > > > The former one may be 0 and it's completely valid case, while > > the second one is not. > > Well, request_irq() happilly takes vIRQ0. Moreover, there are 8253 drivers in e.g. the arch/x86/ > (PPC and MIPS too) which do use vIRQ0. This is an exception which is not in the scope here. Let me remind that the topic here is libahci_platform and platform_get_irq(). > >>>>> That code should be fixed first. Have you sent a patch? > >>>> > >>>> Which code?! You got me totally muddled. =) > >>> > >>> Above mentioned. > >> > >> What needs to be fixed in this case is the interrupt controller driver. > > > > What do you mean by that? > > You better ask Linus... ;-) If you cite somebody you have to understand what they said, right? Lemme repeat the question, what do you mean by that? In your own words, please. > > vIRQ is handled by IRQ core, IRQ controller driver > > just a mere provider of the resource. And those exceptions for vIRQ == 0 > > shouldn't be propagated to the platform code or so. > > >> Quoting Linus > >> (imprecisely :-)), IRQ #s should be either mapped starting with #1 or IRQ0 remapped at > >> the end of the controller's interrupt range... I currently have no information on the > >> platforms requiring such kind of fixing (Alchemy don't seem to need it now)... > > Well, actually that Linus' quote predates drivers/irqchip/, so I must confess this > argument was wrong... :-) > > > Again, do not mix vIRQ (about which Linus ranted) and HW IRQ. ... > >>>>>>>>> - if (!irq) > >>>>>>>>> - return -EINVAL; > >>>>>>>> > >>>>>>>> This is prermature -- let's wait till my patch that stops returning IRQ0 from > >>>>>>>> platform_get_irq() and friends gets merged.... > >>>>>>> > >>>>>>> What patch? > >>>>>> > >>>>>> https://marc.info/?l=linux-kernel&m=163623041902285 > >>>>>> > >>>>>>> Does it fix platform_get_irq_optional()? > >>>>>> > >>>>>> Of course! :-) > >>>>> > >>>>> Can you share link to lore.kernel.org, please? > >>>>> It will make much easier to try and comment. > >>>> > >>>> I don't know how to uise it yet, and I'm a little busy with other IRQ0 issues ATM, > > > >> A little bit, I meant to type. > > > > No problem. I just haven't got what other IRQ0 issues except fixing > > platform_get_irq_optional() et al. could be possibly needed... > > There is other IRQ0 issue which is very old already... Is it big secret? What is that issue? -- With Best Regards, Andy Shevchenko
