Re: [Minios-devel] [UNIKRAFT PATCHv4 4/9] plat/common: Introduce fdt_{address, size}_cells_or_parent helpers

[Julien Grall <julien.grall@xxxxxxx>]

On 10/04/2019 06:43, Jia He wrote:
> Hi Sharan
>
> After I dig more on it, I would like to rework this patch 4/9.
>
> Please see the comments from libfdt author [1]
>
> "
>
>    * #address-cells and #size-cells describe the format of addresses
>      for children of this node, not this node itself.  So if you're
>      looking to parse 'reg' for this node, you *always* need to look at
>      the parent, not just as a fallback.
>
>    * #address-cells and #size-cells are *not* inherited.  If they're
>      missing in a node, then the format for its children's addresses is
>      2 cell addresses and 2 cell sizes, it is *not* correct to look at
>      the next parent up for these properties.
> "
As I pointed out earlier on, the Device-Tree spec requires to return 1 is 
#size-cells is missing. This is different from the libfdt implementation. So ...
> So, seems I should
>
> parent = fdt_parent_offset(fdt, nodeoffset);
> naddr = fdt_address_cells(parent, nodeoffset);
> nsize = fdt_size_cells(parent, nodeoffset);
... this would return the wrong value if #size-cells is no present.

Cheers,

--
Julien Grall

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