On Monday 08 October 2012 17:49:00 Hans Verkuil wrote: > 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. Ok, then maybe just stick to the standard CEC_UI_* key codes, and let people having proprietary UI functions do the rest in user-space, or write their own 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. Definitively not, just let a driver writer specify a flag to advertise this capability and have a getter/setter to specify the receive mode. > > > - 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. Great, thanks! -- Florian _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
