On 11/28/16 19:10, David Gibson wrote:
> On Mon, Nov 28, 2016 at 06:05:39PM +0200, Pantelis Antoniou wrote:
>> There exists a syntactic sugar version of overlays which
>> make them simpler to write for the trivial case of a single target.
It also works for multiple targets. (See the example I provided in
my comment to v10.)
>>
>> Document it in the device tree object internals.
>>
>> Signed-off-by: Pantelis Antoniou <pantelis.antoniou@xxxxxxxxxxxx>
>
> I'm with Frank that I think this, rather than being regarded mere
> syntactic sugar, should be considered the primary way of describing
> overlays.
>
> Obviously we need to support the fully written out version as well.
If we need to support the fully written out version, can we make that
a discouraged, non-preferred method? Maybe require an option to
enable compiling this style of dts?
I can imagine some reasons to support the fully written out version,
but can we document what those reasons are?
-Frank
>
>> ---
>> Documentation/dt-object-internal.txt | 16 ++++++++++++++++
>> 1 file changed, 16 insertions(+)
>>
>> diff --git a/Documentation/dt-object-internal.txt b/Documentation/dt-object-internal.txt
>> index 026d4ee..d5b841e 100644
>> --- a/Documentation/dt-object-internal.txt
>> +++ b/Documentation/dt-object-internal.txt
>> @@ -300,3 +300,19 @@ local reference is being made. No matter how phandles are allocated from dtc
>> the run time loader must apply an offset to each phandle in every dynamic
>> DT object loaded. The __local_fixups__ node records the place of every
>> local reference so that the loader can apply the offset.
>> +
>> +There is an alternative syntax to the expanded form for overlays with phandle
>> +targets which makes the format similar to the one using in .dtsi include files.
>> +
>> +So for the &ocp target example above one can simply write:
>> +
>> +/dts-v1/ /plugin/;
>> +&ocp {
>> + /* bar peripheral */
>> + bar {
>> + compatible = "corp,bar";
>> + ... /* various properties and child nodes */
>> + }
>> +};
>> +
>> +The resulting dtb object is identical.
>
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