"magic" handling of memory nodes

[swarren@wwwdotorg.org (Stephen Warren)]

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?