Ping! Adding Ville to the CC list, I think I forgot to add you, sorry about that. Regards, Hans On 06/12/2018 01:18 PM, Hans Verkuil wrote: > From: Hans Verkuil <hans.verkuil@xxxxxxxxx> > > This patch series adds support for the DisplayPort CEC-Tunneling-over-AUX > feature. This patch series is based on the current media master branch > (https://git.linuxtv.org/media_tree.git/log/) but it applies fine on top > of the current mainline tree. > > This patch series has been tested with my NUC7i5BNK, a Google 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). The latter is to check that > replacing a USB-C to HDMI adapter by a USB-C MST Hub works correctly. > CEC for MST is currently not supported. > > 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), 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). > > 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 three USB-C to HDMI adapters that work, and no > (mini-)DP to HDMI adapters at all). It is a very nice feature for HTPC > boxes. > > Apologies for the long delay between v5 and this v6: too many other > projects needed my attention. > > The main change since v5 is that the CEC adapter is now unregistered > after a user-defined time (by default 1 second) if the EDID is unset. > If the EDID comes back within that time, then the existing CEC adapter > is used as this is assumed to be a HPD off-and-on toggle from the > display. The delay can also be set to 0 through a module option. In > that case the CEC adapter will never be unregistered as long as the > connector remains registered (or if a new HDMI adapter was connected > with different capabilities from the previous adapter). > > Note that I removed the Tested-by tag from Carlos Santa due to the > substantial rework of the code. Carlos, can you test this again? > > Regards, > > Hans > > Changes since v5: > > - Moved the logic of when to unregister a CEC adapter to the drm core > code, since this is independent of the actual driver implementation. > - Simplified the calls the driver needs to make: the core code is > informed when a connector is (un)registered, when the EDID is > unset or set and when a DP short pulse is seen and you need to check > if that is for a CEC interrupt. > - Added the drm_dp_cec_unregister_delay module option to set the delay > between unsetting the EDID and unregistering the CEC adapter. > > 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. > > Hans Verkuil (3): > drm: add support for DisplayPort CEC-Tunneling-over-AUX > drm-kms-helpers.rst: document the DP CEC helpers > drm/i915: add DisplayPort CEC-Tunneling-over-AUX support > > Documentation/gpu/drm-kms-helpers.rst | 9 + > drivers/gpu/drm/Kconfig | 10 + > drivers/gpu/drm/Makefile | 1 + > drivers/gpu/drm/drm_dp_cec.c | 423 ++++++++++++++++++++++++++ > drivers/gpu/drm/drm_dp_helper.c | 1 + > drivers/gpu/drm/i915/intel_dp.c | 17 +- > include/drm/drm_dp_helper.h | 56 ++++ > 7 files changed, 515 insertions(+), 2 deletions(-) > create mode 100644 drivers/gpu/drm/drm_dp_cec.c >
