First of all a Happy New Year for all of you! And secondly: can this v5 patch series be reviewed/merged? It's been waiting for that for a very long time now... Regards, Hans On 12/11/17 09:57, Hans Verkuil wrote: > 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 > _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
