On Wed, May 11, 2016 at 11:28:36AM +0200, Thomas Huth wrote:
> On 11.05.2016 11:04, Andrew Jones wrote:
> > On Wed, May 11, 2016 at 09:02:39AM +0200, Thomas Huth wrote:
> >> 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@xxxxxxxxxx>
> >>> ---
> >>> 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."
> >
> > You are right.
> >
> > My skimming of Documentation/devicetree/booting-without-of.txt was
> > sloppy and I missed basically the same quote
> >
> > "Note that the parent's parent definitions of #address-cells and
> > #size-cells are not inherited so every node with children must
> > specify them."
> >
> >>
> >> 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?
> >
> > So, yes, I should look in the current node, and then the parent, and
> > then just assert.
>
> AFAIK the #address-cells and #size-cells properties of the current node
> only apply to the _children_ of the current node, but not to itself. I
> think you always have to look at the parent to find out the correct
> value for the current node.
Thanks for this clarification. I'll rework this API to allow fetching
a node's *-cells proprieties (when you know the node you're asking
about is the parent, and you just want get this information) and for
asking for a child-node's *-cells when doing translation (which means
getting it from the parent).
drew
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