On Fri, Jan 12, 2018 at 05:19:44PM +0100, Hans Verkuil wrote: > Hi Ville, > > For some strange reason your email disappeared from the Cc list. Perhaps it's > the > ä that confuses something somewhere. > > So I'll just forward this directly to you. > > Can you please take a look? This patch series has been in limbo for too long.
IIRC last I looked we still had some ragistration race to deal with. Was that fixed? Also I think we got stuck on leaving the zombie device lingering around when the display is disconnected. I couldn't understand why that is at all useful since you anyway remove the device eventually. Adding the lists back to cc so I don't have to repeat myself there... > > Regards, > > Hans > > > -------- Forwarded Message -------- > Subject: Re: [PATCHv5 0/3] drm/i915: add DisplayPort CEC-Tunneling-over-AUX > support > Date: Tue, 9 Jan 2018 13:46:44 +0100 > From: Hans Verkuil <hverk...@xs4all.nl> > To: linux-me...@vger.kernel.org > CC: Daniel Vetter <daniel.vet...@ffwll.ch>, Carlos Santa > <carlos.sa...@intel.com>, dri-devel@lists.freedesktop.org > > 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 (hverk...@xs4all.nl) 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@lists.freedesktop.org > >>> https://lists.freedesktop.org/mailman/listinfo/dri-devel > >>> > >> > >> _______________________________________________ > >> dri-devel mailing list > >> dri-devel@lists.freedesktop.org > >> https://lists.freedesktop.org/mailman/listinfo/dri-devel > >> > > > > _______________________________________________ > > dri-devel mailing list > > dri-devel@lists.freedesktop.org > > https://lists.freedesktop.org/mailman/listinfo/dri-devel > > > > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Ville Syrjälä Intel OTC _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
