Re: [PATCH v10 3/4] dtc: Plugin and fixup support

Hi Phil,

On Nov 29, 2016, at 14:57 , Phil Elwell [off-list ref] wrote:

On 29/11/2016 12:24, Pantelis Antoniou wrote:

quoted

First note is that this is exactly what the portable connector is supposed to
do; abstract away the SoC differences.

Second note is that it’s not the overlay application that’s having problems, it’s
your parameter patching method.

The 'spimaxfrequency = <&can0>,"spi-max-frequency:0”’ form could more easily be
done by targeting aliases instead of node labels.

I.e. You can apply the overlay, set an alias to the node and instead of referencing
the label, reference the alias.

But the patching is done before the overlays are applied, in isolation
from the base tree, so that they can still be used with the kernel
configfs overlay mechanism. How do aliases (which associated symbols
with absolute paths) help?

An alias is the standard way to refer to nodes symbolically. They can be overwritten at
runtime without triggering an error.

quoted

Again, this is a stop-gap until the portable connector is done, but what I take out
of this is the need for a parameterization step in which an overlay is modified before
it is applied according to an external parameter.

Yes, absolutely.

Speaking of which, since these overlays are applied at runtime, why not build them with a script
and have a #define passed to the c preprocessor before compiling them?

It doesn’t appear to be a problem doing it this way. 

Phil
—

Regards

— Pantelis