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Subject: RE: [PATCH 15/16] Add device tree for Ebony
Date: Wed, 14 Feb 2007 13:08:01 -0700
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From: "Yoder Stuart-B08248" <stuart.yoder@freescale.com>
To: "Segher Boessenkool" <segher@kernel.crashing.org>,
	"Josh Boyer" <jwboyer@jdub.homelinux.org>
Cc: linuxppc-dev@ozlabs.org, David Gibson <david@gibson.dropbear.id.au>
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=20
> >> Hmm.  There are two "soc" devices here, one nested under the
> >> first??
> >>
> >> I'm assuming these are two levels of busses the opb bus is attached
> >> to the plb bus.  Is the "soc" device_type the right way to
> >> do this?
> >
> > Right, OPB hangs off of PLB in this case.  I dunno if "soc" is the=20
> > right
> > device type for them though.
>=20
> I would use device_type "plb" (or "plb4") and "opb" I think.
> Similar to how PCI and ISA etc. busses are represented.

I think we should avoid making up new device_types unlesss it
really is necessary.

Is it really necessary to distinguish between devices on
the PLB or OPB?

As I undestand it the "soc" device type is a logical container
for a group of devices in an SOC, not necessarily a group
of devices on the same bus.  Could we simply list all those
devices under an "soc" node at the same level.

If for some reason the bus hierarchy distinction _is_ required,
my suggestion would be to create new generic device type for
representing an internal bus.   The "device_type" is supposed
to be somewhat general-- "network", "serial", etc.

We could create something like "soc-bus" or "internal-bus" with
a compatible field that identifies the type of bus.

The general philosophy is a general device_type prooperty and
a specific compatible property.

Stuart Yoder