I think force-modesetting isn't great has a property. As the time goes, we find that most people uses kmssink in a way one would use decklinkvideosink. It's basically the "new" way, even though still a bit limited, to handle a video output. In this regard, the typical use case is to fix the output mode using well known names, like 1080p60, 1080i60, etc. Basically, the API exposed by decklinkvideosink.

So my proposal is to replace "force-modesetting" with a mode property. We could have special values to indicate "current", for the currently configured mode (our default), "automatic", to try and match the video resolution with the output, or an alternative of type "best-match". And then, a list of modes.

The decklinkvideosink just hardcodes a fixed list of modes, we could do that, but then we'd need to improve it everything a DRM driver introduce a new mode. Maybe we could find a compromise, keep "mode" as a string and match it to one of the enumerated modes for the connector.