Hi Jesse, Discussion here in Budapest with v4l and embedded graphics folks was extremely fruitful. A few quick things to take away - I'll try to dig through all the stuff I've learned more in-depth later (probably in a blog post or two): - embedded graphics is insane. The output routing/blending/whatever currently shipping hw can do is crazy and kms as-is is nowhere near up to snuff to support this. We've discussed omap4 and a ti chip targeted at video surveillance as use cases. I'll post block diagrams and explanations some when later. - we should immediately stop to call anything an overlay. It's a confusing concept that has a different meaning in every subsystem and for every hw manufacturer. More sensible names are dma fifo engines for things that slurp in planes and make them available to the display subsystem. Blend engines for blocks that take multiple input pipes and overlay/underlay/blend them together. Display subsytem/controller for the aggregate thing including encoders/resizers/outputs and especially the crazy routing network that connects everything. Most of the discussion centered around clearing up the confusion and reaching a mutual understanding between desktop graphics, embedded graphics and v4l people. Two rough ideas emerged though: 1) Splitting the crtc object into two objects: crtc with associated output mode (pixel clock, encoders/connectors) and dma engines (possibly multiple) that feed it. omap 4 has essentially just 4 dma engines that can be freely assigned to the available outputs, so a distinction between normal crtcs and overlay engines just does not make sense. There's the major open question of where to put the various attributes to set up the output pipeline. Also some of these attributes might need to be changed atomicly together with pageflips on a bunch of dma engines all associated with the same crtc on the next vsync, e.g. output position of an overlaid video buffer. 2) The above should be good enough to support halfway sane chips like omap4. But hw with more insane routing capabilities that can also use v4l devices as sources (even video input connectors) media controller might be a good fit. Media controller is designed to expose multimedia pipe routing across different subsystem. But the first version, still marked experimental, only got merged in .39. We discussed a few ideas as how to splice media controller into kms but nothing clear emerged. So a possible kms integration with media controller is rather far away. Yours, Daniel -- Daniel Vetter daniel.vetter@xxxxxxxx - +41 (0) 79 364 57 48 - http://blog.ffwll.ch -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
