[RFC][PATCH 6/8] Walnut DTS

Segher Boessenkool segher at kernel.crashing.org
Tue Jul 17 00:34:45 EST 2007

>>> +		#address-cells = <0>;
>>> +		#size-cells = <0>;
>> No need for these.
> Isn't a good practice to put #address-cells in interrupt controller
> nodes?

It is not.

> If the device tree has an interrupt map defined the interrupt
> parent 'unit interrupt specifier' has to be interpreted according
> to the #address-cells of the interrupt parent.

And "#address-cells" is defaulted to 0 if it is absent,
for the purpose of interrupt mapping (but not for its
other purposes).  Typically, such interrupt controllers
don't have device tree children so it doesn't make sense
to give them an "#address-cells" anyway.

> It seems like
> typical practice in the current DTS files to explicitly define this
> in the interrupt controller.

That "typical practice" is inspired by the need to explicitly
put #address-cells and #size-cells into the device tree if you
want Linux to properly parse the device tree, even if the default
values would work perfectly (if Linux would work correctly,
that is).

> Of course this particular device tree doesn't have an interrupt
> map...
> #size-cells is not needed.

There are no child nodes, and no binding that says there can
be any; neither #address-cells not #size-cells should be there.


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