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From: Segher Boessenkool <segher@kernel.crashing.org>
Subject: Re: [PATCH 15/16] Add device tree for Ebony
Date: Thu, 15 Feb 2007 15:52:38 +0100
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: linuxppc-dev@ozlabs.org, Yoder Stuart-B08248 <stuart.yoder@freescale.com>,
	David Gibson <david@gibson.dropbear.id.au>
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>>> No, the DCR tree, like the interrupt tree in most cases, is
>>> independent of the main tree structure.
>>
>> Yes true; you can hang the UICs from somewhere under the
>> "soc" node or whatever you want.  You need some way to
>> distinguish separate identical devices though; you can't
>> do it by device unit since your devices don't have any
>> (they don't have a "reg" but only a "dcr-reg").  If you
>> would hang them in a DCR tree, you could use the plain
>> "reg" property instead of the "dcr-reg" property and
>> all would be fine (if the DCR binding allows this -- and
>> it better should, it is the standard OF addressing algorithm).
>
> It's not as DCRs are orthogonal to the normal bus tree (yeah, it sucks
> but that's how it is, broken by design :-)

Of course, I know that.  What I'm saying is that devices
where the *only* connection to the system is the DCR ring,
should use normal "reg" properties instead of "dcr-reg"
properties (and normal parent instead of "dcr-parent") to
describe the DCR registers, so that they get a valid unit
address.


Segher