Re: [RFR 2/2] drm/panel: Add simple panel support

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

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On 17/10/13 15:17, Laurent Pinchart wrote:
> Hi Tomi,
> 
> On Thursday 17 October 2013 14:59:41 Tomi Valkeinen wrote:
>> On 17/10/13 14:51, Laurent Pinchart wrote:
>>>> I'm not sure if there's a specific need for the port or endpoint nodes
>>>> in cases like the above. Even if we have common properties describing
>>>> the endpoint, I guess they could just be in the parent node.
>>>>
>>>> panel {
>>>> 	remote = <&dc>;
>>>> 	common-video-property = <asd>;
>>>> };
>>>>
>>>> The above would imply one port and one endpoint. Would that work? If we
>>>> had a function like parse_endpoint(node), we could just point it to
>>>> either a real endpoint node, or to the device's node.
>>>
>>> You reference the display controller here, not a specific display
>>> controller output. Don't most display controllers have several outputs ?
>>
>> Sure. Then the display controller could have more verbose description.
>> But the panel could still have what I wrote above, except the 'remote'
>> property would point to a real endpoint node inside the dispc node, not
>> to the dispc node.
>>
>> This would, of course, need some extra code to handle the different
>> cases, but just from DT point of view, I think all the relevant
>> information is there.
> 
> There's many ways to describe the same information in DT. While we could have 
> DT bindings that use different descriptions for different devices and still 
> support all of them in our code, why should we opt for that option that will 
> make the implementation much more complex when we can describe connections in 
> a simple and generic way ?

My suggestion was simple and generic. I'm not proposing per-device
custom bindings.

My point was, if we can describe the connections as I described above,
which to me sounds possible, we can simplify the panel DT data for 99.9%
of the cases.

To me, the first of these looks much nicer:

panel {
	remote = <&remote-endpoint>;
	common-video-property = <asd>;
};

panel {
	port {
		endpoint {
			remote = <&remote-endpoint>;
			common-video-property = <asd>;
		};
	};
};

If that can be supported in the SW by adding complexity to a few
functions, and it covers practically all the panels, isn't it worth it?

Note that I have not tried this, so I don't know if there are issues.
It's just a thought. Even if there's need for a endpoint node, perhaps
the port node can be made optional.

 Tomi



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