[U-Boot] [PATCH] fdt: Fix fdtdec_get_addr_size() for 64-bit

[Stephen Warren]

On 08/04/2015 08:26 AM, Thierry Reding wrote:
... [ discussion of new fdtdec_get_addr_size() implementation]
> So what this does is really fix parsing of address and size cells in the
> general case, though it would still fail for values of #address-cells or
> #size-cells bigger than 2 (because we don't have a datatype that would
> be able to contain such large values).
>
> Note that there's also still a corner case that this doesn't handle. The
> DT specification states, if I remember correctly, that #address-cells
> and #size-cells are inherited. That means with the current code we will
> wrongly parse something like this:
>
> 	/ {
> 		...
> 		#address-cells = <1>;
> 		#size-cells = <1>;
> 		...
> 		bus at XXXXXXXX {
> 			...
> 			device at XXXXXXXX {
> 				...
> 				reg = <0xXXXXXXXX 0x1000>;
> 				...
> 			};
> 			...
> 		};
> 		...
> 	};
>
> According to the DT specification the bus at XXXXXXXX node would inherit
> #address-cells = <1> and #size-cells = <1> from the root node. However
> with libfdt what really happens is that since bus at XXXXXXXX does not have
> either property it will default to 2 in both cases. I'm not sure if this
> really is a problem. Typically nodes are not nested that deeply, or if
> they are then, typically, they explicitly contain #address-cells and
> #size-cells properties.

I don't think #address-cells/#size-cells do actually get inherited. 
Admittedly some other properties (e.g. interrupt-parent) do, but 
according to:

https://lists.ozlabs.org/pipermail/linuxppc-dev/2008-January/049113.html
[PATCH] powerpc: #address-cells & #size-cells properties not inherited

... and my vague memory, these two don't.

You can search Google for e.g. "#address-cells inherited" and find a 
number of similar assertions.