On 02/04/2018 02:13 PM, Laurent Pinchart wrote:
> Hi Hans,
> On Sunday, 4 February 2018 15:06:42 EET Hans Verkuil wrote:
>> Hi Mauro,
>> I'm working on adding proper compliance tests for the MC but I think
>> something is missing in the G_TOPOLOGY ioctl w.r.t. pads.
>> In several v4l-subdev ioctls you need to pass the pad. There the pad is an
>> index for the corresponding entity. I.e. an entity has 3 pads, so the pad
>> argument is [0-2].
>> The G_TOPOLOGY ioctl returns a pad ID, which is > 0x01000000. I can't use
>> that in the v4l-subdev ioctls, so how do I translate that to a pad index in
>> my application?
>> It seems to be a missing feature in the API. I assume this information is
>> available in the core, so then I would add a field to struct media_v2_pad
>> with the pad index for the entity.
>> Next time we add new public API features I want to see compliance tests
>> before accepting it. It's much too easy to overlook something, either in
>> the design or in a driver or in the documentation, so this is really,
>> really needed IMHO.
> I agree with you, and would even like to go one step beyond by requiring an 
> implementation in a real use case, not just in a compliance or test tool.
> On the topic of the G_TOPOLOGY API, it's pretty clear it was merged too 
> hastily. We could try to fix it, but given all the issues we haven't solved 
> yet, I believe a new version of the API would be better.

It's actually not too bad as an API speaking as an end-user. It's simple and
efficient. But this pad issue is a real problem.



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