Messages in this thread | | | Date | Wed, 16 Dec 2009 18:49:04 +0100 | From | Uwe Kleine-König <> | Subject | Re: [PATCH 6/7] spi/mpc8xxx: don't check platform_get_irq's return value against zero |
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Hello,
[Note the email address used for David Vrabel isn't valid any more, this mail uses his last used address.]
On Wed, Dec 16, 2009 at 07:32:29PM +0300, Anton Vorontsov wrote: > On Wed, Dec 16, 2009 at 05:10:08PM +0100, Uwe Kleine-König wrote: > > platform_get_irq returns -ENXIO on failure, so !irq was probably > > always true. Better use (int)irq <= 0. Note that a return value of > > zero is still handled as error even though this could mean irq0. > > > > This is a followup to 305b3228f9ff4d59f49e6d34a7034d44ee8ce2f0 that > > changed the return value of platform_get_irq from 0 to -ENXIO on error. > > > > Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> > > --- > > Noooooo... :-( > > Please revert 305b3228f9ff4d59f49e6d34a7034d44ee8ce2f0 instead, > and fix platforms to remap HWIRQ0 to something that is not VIRQ0. > > IRQ0 is invalid for everything that is outside of arch/*. > > http://lkml.org/lkml/2005/11/22/159 > http://lkml.org/lkml/2005/11/22/213 > http://lkml.org/lkml/2005/11/22/227 First note that my check is safe with both variants (e.g. it does the right thing independent of the error being signaled by 0 or -ESOMETHING.)
Then arch/arm/mach-pxa/devices.c has:
static struct resource pxa27x_resource_ssp3[] = { ... [1] = { .start = IRQ_SSP3, .end = IRQ_SSP3, .flags = IORESOURCE_IRQ, }, ... }
with IRQ_SSP3 being zero (sometimes). The driver is implemented in arch/arm/mach-pxa/ssp.c and uses platform_get_irq. So according to your definition it's allowed (arch/* only). Still this would break if you revert 305b3228f9.
Actually I don't care much, but as platform_get_irq returns an int I think it's fine for it to signal an error using a value < 0 as irqs are not negative.
My position regarding irq0 is: If a variable holds either a valid irq or a value indicating "no irq", then feel free to use 0 as "no irq" and a value > 0 for a valid irq (without offset). If you want irq0 here, you're out of luck. But if you have a variable holding a valid irq only (that is, there is no doubt if the value is valid or not) I see no reason to dogmatically prohibit irq0.
I'm a bit annoyed as this is the third time[1] this month this irq0 discussion pops up for me. I think people see that irq0 is involved somehow, start wailing and stop seeing the issues being fixed.
Best regards Uwe
[1] one is: http://thread.gmane.org/gmane.linux.kernel/924739 the other wasn't on lkml, only mm-commits. Cannot find it on the net now. -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ | -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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