Messages in this thread | | | Date | Tue, 19 Apr 2011 18:09:19 -0500 | From | Scott Wood <> | Subject | Re: [PATCH v3] uio/pdrv_genirq: Add OF support |
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On Wed, 20 Apr 2011 00:00:18 +0200 "Hans J. Koch" <hjk@hansjkoch.de> wrote:
> On Tue, Apr 19, 2011 at 12:08:16AM -0600, Grant Likely wrote: > > PowerPC and x86 will return 0 for an unassigned IRQ, as will most platforms. > > That might be right for these architectures. On ARM SoCs, IRQ0 is often a > normal irq like any other (e.g. "Audio DMA Controller 1" on Telechips TCC8000).
It's true on at least some powerpc and x86 interrupt controllers as well. ARM isn't special. :-)
I'm not sure what goes on on x86, as I see a real " 0:" in /proc/interrupts. But on powerpc, Linux's IRQ numberspace is decoupled from that of any IRQ controller. This is mainly to accommodate multiple IRQ controllers with their own numberspaces in the same system; being able to avoid irq 0 is just a bonus.
-Scott
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