Re: Bug in "genirq: record trigger type"

From: David Brownell
Date: Tue Oct 21 2008 - 04:01:43 EST

On Monday 20 October 2008, Benjamin Herrenschmidt wrote:
> This one is obviously broken and breaks booting on a whole bunch of
> machines (including powermac's and thus my G5, it's never good when my
> own machine breaks !).
> Nice to see 3 SOB's and one Ack and nobody caught the obvious bug :-)

As you saw, that one's fixed. Chris' patch unfortunately didn't
get integrated right away.

I'm a bit more curious about another potential issue though ... as
described in the patch comment:

- Make set_irq_type() usage match request_irq() usage:
* IRQ_TYPE_NONE should be a NOP; succeed, so irq_chip methods
won't have to handle that case any more (many do it wrong).

It might be a bit more accurate to say irq_chip.set_type() methods
are *inconsistent* in handling IRQ_TYPE_NONE. Previously the
set_irq_type() method would pass that down to irq_chip code.

I had observed two behaviors, but I thought I observed a third one
in some of the PowerPC code:

(1) ignore it ... matching request_irq() usage
(2) return an error ... nasty
(3) assign some irq_chip-specific trigger mode

That third behavior might cause a bit of trouble, but I think
it was only used during platform init. Someone more attuned
to PowerPC might want to check ...

- Dave

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