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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 01:17:30 +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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> The device type specifies the programming model of the node for OF, 
> that
> is the set of words the driver will provide to OF. So that's something
> we don't necessarily care much about for non-OF implementation but 
> still
> we should avoid going too far from that model either (after all,
> somebody can very well want to use a real OF on a board with a SoC).

Exactly.  The "separate device tree" imitates a real OF,
so you will lose much of its value if you start to deviate
from how real OF works.

> The device type is also used by the kernel in some areas. For example,
> the spec specifies that PCI host controllers and P2P bridges have a
> device-type of "pci" and the kernel relies heavily on that. Same for
> ISA. It thus makes sense to continue that practice with other bus 
> types.

Yep, for peripheral busses the kernel's needs are quite the
same as the firmware's needs so it makes sense that both use
device_type.


Segher