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From: Segher Boessenkool <segher@kernel.crashing.org>
Subject: Re: [PATCH 2/3] Derive ebc ranges property from EBC registers
Date: Wed, 16 May 2007 15:28:16 +0200
To: David Gibson <dwg@au1.ibm.com>
Cc: linuxppc-dev@ozlabs.org
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>> Do we want a "ranges;" here as a placeholder?  I don't see where it's
>> absolutely required, but it makes me feel better for some reason...
>
> Absolutely not.  An empty ranges property indicates that the child bus
> address space is the same as the parent bus address space.

Or a subset of it, anyway; both address domains have to
use the same representation in "reg" properties, and the
mapping has to be 1-1.

A missing "ranges" property means there is no direct
mapping, which is more correct in this case, and perfectly
valid.

> If we're
> using the chip-select/offset addressing form for the EBC peripherals,
> that's manifestly not the case.

This would be a nice use case for the

	ranges = ??;

syntax when/if that gets added to DTC and the kernel
and bootwrapper parsers for DTBs.


Segher