From mboxrd@z Thu Jan 1 00:00:00 1970 From: jeremy.kerr@canonical.com (Jeremy Kerr) Date: Wed, 19 May 2010 16:50:53 +0800 Subject: Boot interface for device trees on ARM In-Reply-To: References: <201005181054.32325.jeremy.kerr@canonical.com> <20100518084954.GC25892@yookeroo> Message-ID: <201005191650.55978.jeremy.kerr@canonical.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Nicolas, > Exact. For example, on ARM the machine ID is also used to figure out > the MMU mapping needed to be able to simply be able to debug the very > early assembly boot stage when there isn't even a stack available. I get the impression that this is the only thing that we need the io_pg_offset for - setting up the debug page mapping, for very early printk output. If this is the case, I would much rather have it as a compile-time constant when doing this early debug; this is what I have been doing for DT boot in my tree (however, I would like to move it to something more configurable). In the cases where we need to debug the pre-C stuff (ie, machine bringup), I think we can live with a compile-time constant, rather than having to define a special 'exception' in the DT boot interface to handle this. Or is there another early use of the mdesc that I'm not aware of? Cheers, Jeremy