[RFC PATCH 0/4] Add device-tree support to kexec-tools for ARM

Simon Horman horms at verge.net.au
Thu Sep 6 05:09:14 EDT 2012

Hi Will,

On Thu, Sep 06, 2012 at 10:01:28AM +0100, Will Deacon wrote:
> Hi guys,
> On Thu, Sep 06, 2012 at 04:29:02AM +0100, Simon Horman wrote:
> > On Wed, Sep 05, 2012 at 03:34:09PM +0100, Matthew Leach wrote:
> > > Also, I use a
> > > different segment for the dtb rather than appending it to the
> > > zImage; I think this approach would be better as it is less
> > > restrictive, however a kernel patch is required to set r2 to the
> > > appropriate address on entry to the new kernel. What are your
> > > thoughts?
> > 
> > I would prefer to avoid requiring kernel changes unless necessary -
> > the kernels some of the boards I work with require DT since 3.5.
> > However, I am happy to discuss this further, there certainly is
> > merit to a clean implementation.
> I had a quick look at both the approaches and it looks like Matthew requires
> changes to the host kernel (to load the dtb correctly) and Simon requires
> changes to the target kernel (to pick up the dtb correctly).

Could you explain a little why you feel my patch requires a change to
the target kernel?

> I would personally prefer changing the host, as the target should ideally
> have no knowledge about the kexec. Given that kexec has not supported DT on
> ARM so far and these patches have no affect on the existing ATAG mechanism,
> I don't think there is a problem with making changes to the kernel.


> I also wouldn't like to hedge my bets on CONFIG_ARM_APPENDED_DTB staying
> around forever -- it's intended as convenience for legacy bootloaders rather
> than something that should be used in preference to passing the dtb via r2.

Also agreed.

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