Ping again. Added a CC to Ville whom I inexplicably forgot to add when I sent the v5 patch series. Regards, Hans On 01/12/17 08:23, Hans Verkuil wrote: > Ping! > > I really like to get this in for 4.16 so I can move forward with hooking > this up for nouveau/amd. > > Regards, > > Hans > > On 11/20/2017 12:42 PM, Hans Verkuil wrote: >> This patch series adds support for the DisplayPort CEC-Tunneling-over-AUX >> feature. This patch series is based on the 4.14 mainline release but applies >> as well to drm-next. >> >> This patch series has been tested with my NUC7i5BNK, a Samsung USB-C to >> HDMI adapter and a Club 3D DisplayPort MST Hub + modified UpTab DP-to-HDMI >> adapter (where the CEC pin is wired up). >> >> Please note this comment at the start of drm_dp_cec.c: >> >> ---------------------------------------------------------------------- >> Unfortunately it turns out that we have a chicken-and-egg situation >> here. Quite a few active (mini-)DP-to-HDMI or USB-C-to-HDMI adapters >> have a converter chip that supports CEC-Tunneling-over-AUX (usually the >> Parade PS176 or MegaChips MCDP2900), but they do not wire up the CEC pin, >> thus making CEC useless. >> >> Sadly there is no way for this driver to know this. What happens is >> that a /dev/cecX device is created that is isolated and unable to see >> any of the other CEC devices. Quite literally the CEC wire is cut >> (or in this case, never connected in the first place). >> >> I suspect that the reason so few adapters support this is that this >> tunneling protocol was never supported by any OS. So there was no >> easy way of testing it, and no incentive to correctly wire up the >> CEC pin. >> >> Hopefully by creating this driver it will be easier for vendors to >> finally fix their adapters and test the CEC functionality. >> >> I keep a list of known working adapters here: >> >> https://hverkuil.home.xs4all.nl/cec-status.txt >> >> Please mail me (hverkuil@xxxxxxxxx) if you find an adapter that works >> and is not yet listed there. >> >> Note that the current implementation does not support CEC over an MST hub. >> As far as I can see there is no mechanism defined in the DisplayPort >> standard to transport CEC interrupts over an MST device. It might be >> possible to do this through polling, but I have not been able to get that >> to work. >> ---------------------------------------------------------------------- >> >> I really hope that this work will provide an incentive for vendors to >> finally connect the CEC pin. It's a shame that there are so few adapters >> that work (I found only two USB-C to HDMI adapters that work, and no >> (mini-)DP to HDMI adapters at all). >> >> Hopefully if this gets merged there will be an incentive for vendors >> to make adapters where this actually works. It is a very nice feature >> for HTPC boxes. >> >> The main reason why this v5 is delayed by 2 months is due to the fact >> that I needed some dedicated time to investigate what happens when an >> MST hub is in use. It turns out that this is not working. There is no >> mechanism defined in the DisplayPort standard to transport the CEC >> interrupt back up the MST chain. I was actually able to send a CEC >> message but the interrupt that tells when the transmit finished is >> unavailable. >> >> I attempted to implement this via polling, but I got weird errors >> and was not able to read the DP_DEVICE_SERVICE_IRQ_VECTOR_ESI1 >> register. I decided to give up on this for now and just disable CEC >> for DP-to-HDMI adapters after an MST hub. I plan to revisit this >> later since it would be neat to make this work as well. Although it >> might not be possible at all. >> >> If anyone is interested, work-in-progress for this is here: >> >> https://git.linuxtv.org/hverkuil/media_tree.git/log/?h=dp-cec-mst >> >> Note that I removed the Tested-by tag from Carlos Santa due to the >> almost complete rework of the third patch. Carlos, can you test this again? >> >> Regards, >> >> Hans >> >> Changes since v4: >> >> - Updated comment at the start of drm_dp_cec.c >> - Add edid pointer to drm_dp_cec_configure_adapter >> - Reworked the last patch (adding CEC to i915) based on Ville's comments >> and my MST testing: >> - register/unregister CEC in intel_dp_connector_register/unregister >> - add comment and check if connector is registered in long_pulse >> - unregister CEC if an MST 'connector' is detected. >> >> _______________________________________________ >> dri-devel mailing list >> dri-devel@xxxxxxxxxxxxxxxxxxxxx >> https://lists.freedesktop.org/mailman/listinfo/dri-devel >> > > _______________________________________________ > dri-devel mailing list > dri-devel@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/dri-devel > _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
