Hi Hans, On Thursday 27 September 2012 16:33:30 Hans Verkuil wrote: > Hi all, > > During the Linux Plumbers Conference we (i.e. V4L2 and DRM developers) had a > discussion on how to handle the CEC protocol that's part of the HDMI standard. > > The decision was made to create a CEC bus with CEC clients, each represented > by a /dev/cecX device. So this is independent of the V4L or DRM APIs. > > In addition interested subsystems (alsa for the Audio Return Channel, and > possibly networking as well for ethernet over HDMI) can intercept/send CEC > messages as well if needed. Particularly for the CEC additions made in > HDMI 1.4a it is no longer possible to handle the CEC protocol completely in > userspace, but part of the intelligence has to be moved to kernelspace. What kind of "intelligence" are you talking about? I see nothing in HDMI 1.4a or earlier that requires doing stuff in kernelspace besides managing control to the hardware, but I might be missing something. In my opinion ARC is just a control mechanism, and can be dealt with in user- space, since you really want to just have hints about when ARC is enabled/disabled to take appropriate actions on the audio outputs or your system. > > I've started working on this API but I am still at the stage of playing > around with it and thinking about the best way this functionality should > be exposed. At least I managed to get the first CEC packets transferred > today :-) > > It will probably be a few weeks before I post something, but in the meantime > if you want to use CEC and have certain requirements that need to be met, > please let me know. If only so that I can be certain I haven't forgotten > anything. Here is my wish-list, if I may: - allow for a CEC adapter to be in "detached" / "attached" mode, particularly useful if the hardware doing CEC can process a basic set of messages to act a a global wake-up source for the system - allow for a CEC adapter to define several receive modes: unicast and "promiscuous", which is useful for dumping the CEC bus messages - make the CEC adapter API asynchronous for the data path, so it is easy for a driver to report completion of a successfully transmitted/received CEC frame Thank you! -- Florian -- 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
