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Subject: Re: [RFC][PATCH 6/8] Walnut DTS
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Scott Wood <scottwood@freescale.com>
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On Mon, 2007-07-16 at 16:55 -0500, Scott Wood wrote:
> Benjamin Herrenschmidt wrote:
> > I would personally be inclined to define that whatever spec we come up
> > with always require #address-cells/#size-cells for any node that can
> > have either device children or interrupt children, and ban default
> > values alltogether.
> 
> When is #size-cells used in the interrupt tree at all?

It's not, sorry, my fingers typed a bit too fast :-)

> And given the odd behavior of using an interrupt map in an interrupt 
> parent that is not the device parent (you're potentially using keys from 
> different domains that could clash, be a different sizes, etc), if we 
> make any changes in that regard, I'd forbid interrupt maps in interrupt 
> controllers with no device children, and thus #address-cells has no 
> meaning there.

No, interrupt maps are useful in devices with no children in some corner
cases. Remember that a map doesnt need to use the address part of the
source specifier, thus it can be used to do a pure domain->domain
conversion of the irq numbers, what sort of thing. The map has the added
advantage that today, it's the only mechanism that allows you to specify
different interrupt-parents through the same nexus, which is useful for
4xx.

Ben.