During the atomic pageflip discussions I mentioned that I have some video overlay code for Medfield. Well, here it is, in case someone is interested.
I believe it should be fairly easy to adapt it for "normal" gen3 hardware. I suppose someone might want to use it in the gma driver too.
I replaced some memory management related function calls with comments, since the function calls were only applicable for the specific kernel we used for Medfield.
It has the hooks for the drm_flip stuff, which was used for atomic page flip stuff. The atomic pageflip stuff was implemented rather crudely since I simply made the update_plane() hook arm the overlay as it were, and a subsequent primary plane page flip was needed to trigger the update.
There's also some plane_opts stuff that I proposed way back when. That stuff should these days be handled via plane properties. I also included the fixed point sin/cos implementation I cooked up for calculating the hue adjustments.
So perhaps there's someone with a gen3 hardware and too much time on their hands who would like to poke at this...