Re: [kvm-unit-tests PATCH 1/2] devicetree: search up tree in dt_get_nr_cells

[Thomas Huth <thuth@redhat.com>]

On 10.05.2016 19:32, Andrew Jones wrote:
> Search up the tree until we find #address-cells/#size-cells.
> Also only assign outputs if both address and size are found.
> 
> Signed-off-by: Andrew Jones <drjones@redhat.com>
> ---
>  lib/devicetree.c | 17 +++++++++++++----
>  lib/devicetree.h |  3 ++-
>  2 files changed, 15 insertions(+), 5 deletions(-)
> 
> diff --git a/lib/devicetree.c b/lib/devicetree.c
> index a5c7f7c69ddfd..d3751e2b7e7f9 100644
> --- a/lib/devicetree.c
> +++ b/lib/devicetree.c
> @@ -24,21 +24,30 @@ int dt_get_nr_cells(int fdtnode, u32 *nr_address_cells, u32 *nr_size_cells)
>  {
>  	const struct fdt_property *prop;
>  	u32 *nr_cells;
> -	int len;
> +	int len, nac, nsc;
> +
> +	while (1) {
> +		prop = fdt_get_property(fdt, fdtnode, "#address-cells", &len);
> +		if (prop != NULL || len != -FDT_ERR_NOTFOUND)
> +			break;
> +		fdtnode = fdt_parent_offset(fdt, fdtnode);
> +	}

Why do you need this search? ePAPR clearly states:

"The #address-cells and #size-cells properties are not inherited from
ancestors in the device tree. They shall be explicitly defined."

So as far as I can see, it should always be enough to look up the
properties in the parent of the node, no need for a recursion here?

 Thomas