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Date:      Mon, 18 Dec 2006 10:33:01 -0800
From:      Marcel Moolenaar <xcllnt@mac.com>
To:        ppc@FreeBSD.org
Subject:   Adding new PowerPC platforms to the build
Message-ID:  <DE8E70B1-9E3F-41E8-8502-AA374BFB150C@mac.com>

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All,

There has been some mention of activity here about porting FreeBSD to
hardware other than Macintosh. I'm in fact collaborating with Rafal to
add support for e500 (mpc85xx).

In this thread I don't necessarily want to dig deep into the porting
effort, as much as I want to find closure on how we should utilize
the build variables to support differing platforms easily as well as
discuss the mechanics of configuring the kernel.

The most obvious variables we can and/or need to use are MACHINE and
CPUTYPE. For all of the PowerPC ports I expect MACHINE_ARCH to be fixed.
What is important is that CPUTYPE has more relation to the compiler
than it has to the kernel. MACHINE has more relation to the kernel than
anything else. In particular changing MACHINE does not change CPUTYPE
and vice versa.

There's another variable: MACHINE_CPU. It is defined as the oldest CPU
that is supported for a particular architecture. This variable is not
currently used on PowerPC. I don't think it's unreasonable to use this
variable to indicate the kind of features we expect to find on the
target CPU and as such to be able to use it to distinguish between,
say, a PowerPC 7455 and a Book-E?

At this time there's nothing that checks and/or sets CPUTYPE for
PowerPC. As I said, MACHINE_CPU is not used at all.

The big question is: can we make it so that we can use existing
variables to build realeases for 1) Apple hardware, having a Book
III-S ISA processor and 2) embedded hardware with varying drivers and
using a Book III-E ISA processor?

In particular I'd like to see the tinderbox and make release work
without any additional kluging. Would that be possible?

Thoughts?

-- 
Marcel Moolenaar
xcllnt@mac.com





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