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

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Hi Phil,

> On Nov 29, 2016, at 14:57 , Phil Elwell <phil@xxxxxxxxxxxxxxx> wrote:
> 
> On 29/11/2016 12:24, Pantelis Antoniou wrote:
>> 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.

>> 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

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