Re: [PATCH v4 3/3] dtc: Document the dynamic plugin internals

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Hi Jan,

> On Mar 3, 2015, at 15:42 , Jan Lübbe <jlu@xxxxxxxxxxxxxx> wrote:
> 
> Hi Pantelis,
> 
> On Fr, 2015-02-27 at 20:55 +0200, Pantelis Antoniou wrote:
>> +3.b) The Device Tree fragments must be compiled with the same option but they
>> +must also have a tag (/plugin/) that allows undefined references to labels
>> +that are not present at compilation time to be recorded so that the runtime
>> +loader can fix them.
>> +
>> +So the bar peripheral's DTS format would be of the form:
>> +
>> +/plugin/;	/* allow undefined label references and record them */
>> +/ {
>> +	....	/* various properties for loader use; i.e. part id etc. */
>> +	fragment@0 {
>> +		target = <&ocp>;
>> +		__overlay__ {
>> +			/* bar peripheral */
>> +			bar {
>> +				compatible = "corp,bar";
>> +				... /* various properties and child nodes */
>> +			}
>> +		};
>> +	};
>> +};
>> +
>> +Note that there's a target property that specifies the location where the
>> +contents of the overlay node will be placed, and it references the label
>> +in the foo.dts file.
> 
> The kernel overlay code also supports using 'target-path="/path";'
> instead of 'target=<phandle>;' to work with base DTBs which have no
> __symbols__ node. Shouldn't this be mentioned here as well?
> 

The kernel documentation entries contain all relevant information. This is just the DTC
support patch, and as such they only need a rough outline of what the actual in-kernel
resolver and overlay handler code does.

tl;dr DTC has no notion of either target or target-path properties.

> Thanks,
> Jan
> -- 
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> 

Regards

— Pantelis

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