On Wed, Nov 27, 2024 at 3:47 PM Segher Boessenkool <segher@xxxxxxxxxxxxxxxxxxx> wrote: > > On Tue, Nov 26, 2024 at 02:36:32PM +1100, Michael Ellerman wrote: > > Michael Ellerman <mpe@xxxxxxxxxxxxxx> writes: > > > "Rob Herring (Arm)" <robh@xxxxxxxxxx> 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). > > > > > > So LGTM. > > > > Turns out I was wrong. > > > > The warning about #size-cells hits on some powermacs, possible fixup > > patch here: > > > > https://lore.kernel.org/linuxppc-dev/20241126025710.591683-1-mpe@xxxxxxxxxxxxxx/ > > The Open Firmware specification is extremely clear that a "missing" > "#size-cells" property means this bus has the default value of 1. And the default for #address-cells is 2, but yet every architecture except Sparc has that wrong. If I have a node without #size-cells, is the default of 1 used or do we check parent nodes? My read of the spec would be the former, but the kernel does the latter. > https://www.openfirmware.info/data/docs/of1275.pdf (page 186). > > DTC or FDT might want to do things differently, but expecting decades > older stuff to conform to its ill-conceived unnecessarily super wordy > stuff is, well, not a plan that is likely to work very well :-) That is not the intention. The intention is to identify what doesn't conform and exclude those systems from this check (or apply a fixup if that works). Rob
