Subject: Re: [PATCH v2] of: WARN on deprecated #address-cells/#size-cells handling

From: Michael Ellerman <[email-masked]>
Date: Thu, 14 Nov 2024 13:07:49 +1100

Geert Uytterhoeven <[email-masked]> writes:
> On Thu, Nov 7, 2024 at 12:37 PM Michael Ellerman <[email-masked]> wrote:
>> "Rob Herring (Arm)" <[email-masked]> writes:
>> > While OpenFirmware originally allowed walking parent nodes and default
>> > root values for #address-cells and #size-cells, FDT has long required
>> > explicit values. It's been a warning in dtc for the root node since the
>> > beginning (2005) and for any parent node since 2007. Of course, not all
>> > FDT uses dtc, but that should be the majority by far. The various
>> > extracted OF devicetrees I have dating back to the 1990s (various
>> > PowerMac, OLPC, PASemi Nemo) all have explicit root node properties.
>>
>> I have various old device trees that have been given to me over the
>> years, and as far as I can tell they all have these properties (some of
>> them are partial trees so it's hard to be 100% sure).
>
> Apparently CHRP LongTrail only had #address-cells in the root node.
> Interestingly, /cpus does have a (zero) @size-cells property.
> http://g33rt.be/migrated/Linux/PPC/root.html
> http://g33rt.be/migrated/Linux/PPC/DeviceTree.html
>
> No idea if any of them are still alive.

OK. We could fix that up in prom_init() if necessary - there's already a
bunch of workarounds in there for longtrail.

cheers