Re: [PATCH V7 11/12] Documentation: bridge: Add documentation for ps8622 DT properties

[Tomi Valkeinen <tomi.valkeinen-l0cyMroinI0@public.gmane.org>]

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On 23/09/14 09:04, Thierry Reding wrote:

> I certainly agree that it's useful to have standard ways to describe at
> least various aspects. For example I think it would be useful to add
> standard properties for a bridge's connections, such as "bridge" or
> "panel" to allow bridge chaining and attaching them to panels.

I don't see a need for such properties. Do you have examples where they
would be needed?

The driver for the respective device does know if it's a bridge or a
panel, so that information is there as soon as the driver has loaded.

> But I think that should be the end of it. Mandating anything other than
> that will just complicate things and limit what people can do in the
> binding.
> 
> One of the disadvantages of the video graph bindings is that they are
> overly vague in that they don't carry information about what type a
> device is. Bindings then have to require additional meta-data, at which
> point it's become far easier to describe things with a custom property
> that already provides context.

I don't see why the graphs and such metadata are connected in any way.
They are separate issues. If we need such metadata, it needs to be added
in any case. That is not related to the graphs.

>> Yes, there's always one active input and one output for this bridge.
>> What the video graphs would bring is to have the possibility to have
>> multiple inputs and outputs, of which a single ones could be active at a
>> time. The different inputs and outputs could even have different
>> settings required (say, first output requires this bit set, but when
>> using second output that bit must be cleared).
> 
> As discussed elsewhere this should be handled at a different level then.
> DT should describe the hardware and this particular bridge device simply
> doesn't have a means to connect more than a single input or more than a
> single output.

Well, I can't say about this particular bridge, but afaik you can
connect a parallel RGB signal to multiple panels just like that, without
any muxing.

If a mux is needed, I agree that there should be a device for that mux.
But we still need a way to have multiple different "configuration sets"
for the bridge, as I explained in the earlier mail.

 Tomi



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