On Mon October 8 2012 17:06:20 Florian Fainelli wrote: > 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. Most notably: handling the new hotplug message. That's something that kernel drivers need to know. Some ARC messages might be relevant for ALSA drivers as well, but I need to look into those more carefully. Also remote control messages might optionally be handled through an input driver. > 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 I have hardware that can do that, so I want to look into supporting this. > - allow for a CEC adapter to define several receive modes: unicast and > "promiscuous", which is useful for dumping the CEC bus messages I don't think I have hardware for that, but it shouldn't be difficult to add. > - 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 Already done. Regards, Hans -- 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
