This message has been earlier sent to the V4L mailing list Linux Media Mailing List <linux-media@xxxxxxxxxxxxxxx> When replying, please add it to CC. This is a discussion proposal for the V4L mini summit, that is going to take place in June in Helsinki, Finland. Any opinions very welcome. V4L(2) video output vs. framebuffer. Problem: Currently the standard way to provide graphical output on various (embedded) displays like LCDs is to use a framebuffer driver. The interface is well supported and widely adopted in the user-space, many applications, including the X-server, various libraries like directfb, gstreamer, mplayer, etc. In the kernel space, however, the subsystem has a number of problems. It is unmaintained. The infrastructure is not being further developed, every specific hardware driver is being supported by the respective architecture community. But as video output hardware evolves, more complex displays and buses appear and have to be supported, the subsystem shows its aging. For example, there is currently no way to write reusable across multiple platforms display drivers. OTOH V4L2 has a standard video output driver support, it is not very widely used, in the userspace I know only of gstreamer, that somehow supports video-output v4l2 devices in latest versions. But, being a part of the v4l2 subsystem, these drivers already now can take a full advantage of all v4l2 APIs, including the v4l2-subdev API for the driver reuse. So, how can we help graphics driver developers on the one hand by providing them with a capable driver framework (v4l2) and on the other hand by simplifying the task of interfacing to the user-space? How about a v4l2-output - fbdev translation layer? You write a v4l2-output driver and get a framebuffer device free of charge... TBH, I haven't given this too much of a thought, but so far I don't see anything that would make this impossible in principle. The video buffer management is quite different between the two systems, but maybe we can teach video-output drivers to work with just one buffer too? Anyway, feel free to tell me why this is an absolutely impossible / impractical idea;) Thanks Guennadi --- Guennadi Liakhovetski, Ph.D. Freelance Open-Source Software Developer http://www.open-technology.de/ -- To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
