From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ian Campbell <ian.campbell@citrix.com>
Subject: Re: [PATCH v3 22/24] tools/libxl: arm: Use an higher
 value for the GIC phandle
Date: Mon, 23 Feb 2015 14:36:30 +0000
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To: Julien Grall <julien.grall@linaro.org>
Cc: Wei Liu <wei.liu2@citrix.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, Ian Jackson <ian.jackson@eu.citrix.com>, tim@xen.org, stefano.stabellini@citrix.com, xen-devel@lists.xenproject.org
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On Thu, 2015-01-29 at 13:48 +0000, Julien Grall wrote:
> On 29/01/15 12:28, Stefano Stabellini wrote:
> > On Thu, 29 Jan 2015, Julien Grall wrote:
> >> On 29/01/15 11:07, Stefano Stabellini wrote:
> >>> On Tue, 13 Jan 2015, Julien Grall wrote:
> >>>> The partial device tree may contains phandle. The Device Tree Compiler
> >>>> tends to allocate the phandle from 1.
> >>>>
> >>>> Reserve the ID 65000 for the GIC phandle. I think we can safely assume
> >>>> that the partial device tree will never contain a such ID.
> >>>>
> >>>> Signed-off-by: Julien Grall <julien.grall@linaro.org>
> >>>> Cc: Ian Jackson <ian.jackson@eu.citrix.com>
> >>>> Cc: Wei Liu <wei.liu2@citrix.com>
> >>>>
> >>>
> >>> Shouldn't we at least check that the partial device tree doesn't contain
> >>> a conflicting phandle?
> >>
> >> I don't think so. This will unlikely happen, and if it happens the guest
> >> will crash with an obvious error.
> > 
> > It is good that the error is obvious.
> > 
> > But how expensive is to check for it?
> 
> I would have to check the validity of the properties (name + value
> size). At least the properties "linux,phandle" and "phandle" should be
> checked.
> 
> Though I could do in copy_properties but I find it hackish.

Can't you just track the largest phandle ever seen during
copy_properties and then use N+1 for the GIC?

> > Think about the poor user that ends up in this situation: the fact that
> > is unlikely only makes it harder for a user to figure out what to do to
> > fix it.
> 
> The poor use will have to write his device tree by hand to hit this
> error ;).

Or use a new version of dtc which does things differently for some
reason.

> So using the right phandle is not a huge drawback.
> 
> Regards,
>