[PATCH v6 3/3] drm: Add GUD USB Display driver

[Noralf Trønnes]

Den 20.02.2021 18.27, skrev Noralf Trønnes:
> 
> 
> Den 19.02.2021 22.42, skrev Peter Stuge:

>>
>> More generally it's not very typical in USB to report the data size
>> separately from the data itself, if reporting size explicitly at all.
>>
>> Sizes can be part of the data structure itself (like in descriptors) but
>> on the application layer (like here) it's convenient to just decide a
>> sensible fixed maximum size and let the host try to always transfer
>> that size while accepting short transfers. Unlike read() a short
>> transfer only ever happens if and when a device intends for it,
>> so that's like an in-band handshake but "for free".
>>
>> Oh, and does/should the GUD EDID change if the panel "behind" the device
>> CPU on a hotpluggable connector changes? It wouldn't be great to require
>> GUD driver reprobe in that case. But maybe DRM requires that anyway?
>>
> 
> If gud_connector_status_req.status has changed since last poll or
> GUD_CONNECTOR_STATUS_CHANGED is set, DRM will notify userspace which
> will reprobe the connector. connector->epoch_counter++ in
> gud_connector_status_request() triggers that.
> 
>>
>> I'm sorry I didn't spot this pattern earlier, I understand that it's late
>> in the game and that changing it needs the gadget to change as well, but I
>> do really think this is a worthwhile change throughout the protocol.
>>
> 
> I see what you mean, I'll give it a try.
> 

Peter, please have a look at this diff and see if I'm on the right track
here: https://gist.github.com/notro/a43a93a3aa0cc75d930890b7b254fc0a

I want to avoid waisting a patch version cycle by being way off.

Noralf.