Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Tue, 4 Jan 2022 12:24:33 +0100 | Subject | Re: [PATCH] platform: finally disallow IRQ0 in platform_get_irq() and its ilk |
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Hi Marc,
On Tue, Jan 4, 2022 at 11:48 AM Marc Zyngier <maz@kernel.org> wrote: > On Tue, 04 Jan 2022 09:47:21 +0000, > Geert Uytterhoeven <geert@linux-m68k.org> wrote: > > On Tue, Jan 4, 2022 at 10:26 AM Marc Zyngier <maz@kernel.org> wrote: > > > [Adding Geert] > > > > > > On Sat, 06 Nov 2021 20:26:47 +0000, > > > Sergey Shtylyov <s.shtylyov@omp.ru> wrote: > > > > The commit a85a6c86c25b ("driver core: platform: Clarify that IRQ 0 is > > > > invalid") only calls WARN() when IRQ0 is about to be returned, however > > > > using IRQ0 is considered invalid (according to Linus) outside the arch/ > > > > code where it's used by the i8253 drivers. Many driver subsystems treat > > > > 0 specially (e.g. as an indication of the polling mode by libata), so > > > > the users of platform_get_irq[_byname]() in them would have to filter > > > > out IRQ0 explicitly and this (quite obviously) doesn't scale... > > > > Let's finally get this straight and return -EINVAL instead of IRQ0! > > > > > > > > Fixes: a85a6c86c25b ("driver core: platform: Clarify that IRQ 0 is invalid") > > > > Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru> > > > > > > --- driver-core.orig/drivers/base/platform.c > > > > +++ driver-core/drivers/base/platform.c > > > > @@ -231,7 +231,8 @@ int platform_get_irq_optional(struct pla > > > > out_not_found: > > > > ret = -ENXIO; > > > > out: > > > > - WARN(ret == 0, "0 is an invalid IRQ number\n"); > > > > + if (WARN(!ret, "0 is an invalid IRQ number\n")) > > > > + return -EINVAL; > > > > return ret; > > > > } > > > > EXPORT_SYMBOL_GPL(platform_get_irq_optional); > > > > @@ -445,7 +446,8 @@ static int __platform_get_irq_byname(str > > > > > > > > r = platform_get_resource_byname(dev, IORESOURCE_IRQ, name); > > > > if (r) { > > > > - WARN(r->start == 0, "0 is an invalid IRQ number\n"); > > > > + if (WARN(!r->start, "0 is an invalid IRQ number\n")) > > > > + return -EINVAL; > > > > return r->start; > > > > } > > > > > > Geert recently mentioned that a few architectures (such as sh?) still > > > use IRQ0 as something valid in limited cases. > > > > https://lore.kernel.org/all/CAMuHMdUg3=q7gyaVHP0XcYUOo3PQUUv8Hc8wp5faVQ+bTBpg4A@mail.gmail.com > > > > TL;DR: Probably only smsc911x Ethernet on the AP-SH4A-3A and > > AP-SH4AD-0A boards, which should trigger the warning since v5.8. > > > > > From my PoV, this patch is fine, but please be prepared to fix things > > > in a couple of years when someone decides to boot a recent kernel on > > > their pet dinosaur. With that in mind: > > > > > > Acked-by: Marc Zyngier <maz@kernel.org> > > > > TBH, I don't see much point in this patch, as the WARN() has been > > there since a while, and the end goal is to return zero instead of > > -ENXIO for no interrupt, right? > > I think the end-goal is to never return 0. Either we return a valid > interrupt number, or we return an error. It should be the > responsibility of the caller to decide what they want to do in the > error case.
This is platform_get_irq_optional(). All other *_optional() APIs return 0 (or NULL[1]) in case the optional resource is not available.
[1] Most (all?) return pointers, NULL, or a negative error code.
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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