Media controller update based on Hans' v4l-dvb-mc tree

Hi everybody,

here's a set of patches to clean up and extend Hans' initial media controller implementation.

Patches prefixed by v4l deal with the v4l core code and update existing drivers when required by an API change. The core now offers two functions to deal with entities and links:

- v4l2_entity_init() will initialize an entity. For subdevices the v4l2_subdev_init() performs part of the entity initialization as well, which leads me to believe that the API is currently ill-defined.

- v4l2_entity_connect() creates a link between two entities. All possible links should be created using that function before the subdevice is registered.

As I don't own any ivtv hardware the media controller code was difficult to test so I've implemented media controller support in the UVC driver for testing purpose. The code can be found in patches prefixed by uvc.

This is mostly playground code. There are known and unknown bugs (especially in the ivtv driver as I haven't been able to test that code; v4l2_entity_connect is definitely called with bad parameters in there) as well as design issues. There's a lot of code missing. I'm mostly interested in getting feedback on the changes, especially the new v4l2_entity_pad and v4l2_entity_link objects. Feel free to comment on the public userspace API too, I realized after changing it to mimic the new kernel API that the way the previous API exposed "local" and "remote" pads instead of pads and links is probably more space efficient.

I'll keep playing with the code and I'll start porting the OMAP3 camera driver to the in-progress media controller API. I'll discover problems (and hopefully solutions) along the way so another round of patches can be expected later, maybe in a week. Of course I'll appreciate comments before that, as the earlier I get feedback the easier it will be to incorporate it in the code. No pressure though, I know that a few developers have left for the kernel summit in Japan.

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Regards,

Laurent Pinchart