On Tue, Aug 04, 2015 at 09:23:27AM -0600, Stephen Warren wrote:
> 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@XXXXXXXX {
> > ...
> > device@XXXXXXXX {
> > ...
> > reg = <0xXXXXXXXX 0x1000>;
> > ...
> > };
> > ...
> > };
> > ...
> > };
> >
> >According to the DT specification the bus@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@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.Okay, that's good. It means there's not even a corner case. =) Thierry
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