"magic" handling of memory nodes

On 04/24/2014 05:33 AM, Leif Lindholm wrote:

Hi,

Following on the special handling of nodes called memory at 0, I went to
have a look at the various platforms that do not actually declare a
device_type = "memory" for their "memory" nodes.

Firstly, we currently have 162(ish, I did a sloppy grep) such .dts{i}
files in the kernel tree.

Secondly, the only reason these platforms could ever have worked is
because they include .dtsi files that define a memory node with a
type explicitly set. Since this node already exists, its contents get
overridden, but the type tag remains. Of course, this only happens
with nodes called explicitly "memory" - but it happens regardless of
what other things they contain.

That's precisely how DT includes/overrides are supposed to work, and is
entirely expected and normal.

Since skeleton.dtsi already says:

        memory { device_type = "memory"; reg = <0 0>; };

... then any .dts which includes that already has the device_type
property set, so there's no need to repeat that property. Subsequent
changes to /memory/reg have no impact on /memory/device_type; any new
node definitions simply over-write any previous definitions of a
redefined property, but leave unmentioned properties unchanged (unless
you /delete-property/).

If skeleton.dtsi were changed to remove that property then yes a lot of
files would then need to set it, but why would it be removed?