Linux 4.19 To Feature Support For HDMI CEC With DP/USB-C To HDMI Adapters
Written by Michael Larabel in Linux Kernel on 18 July 2018 at 07:30 PM EDT. 2 Comments
Adding to the big batch of feature additions and improvements queuing in DRM-Next for the upcoming Linux 4.19 kernel merge window is another round of drm-misc-next improvements.

While the drm-misc-next material consists of the random DRM core and small driver changes not big enough to otherwise warrant their own individual pull requests to DRM-Next, for Linux 4.19 this "misc" material has been fairly exciting. Last week's drm-misc-next pull request introduced the Virtual KMS (VKMS) driver that offers exciting potential. With this week's drm-misc-next pull are further improvements to the VKMS code for frame-buffer and plane helpers, among other additions.

But what's more significant this week is the merging of the "DisplayPort CEC-Tunneling-over-AUX" patches that have been in development for many months. What this DisplayPort CEC-Tunneling-over-AUX support means is basically supporting HDMI CEC with DisplayPort/USB-C to HDMI adapters. HDMI CEC is the awesome standard that allows most HDMI-enabled devices to be controlled over the HDMI link from a central device. This "Consumer Electronics Control" specification is marketed by different vendors under a variety of names but allows for conveniently allowing one remote control / controller to send command and control connected devices.

The HDMI CEC support within the mainline Linux kernel has gotten into shape nicely over the past number of kernel series. But one area that was still lacking is supporting DP/USB-C to HDMI adapters, but now that code is in place with this DisplayPort CEC-Tunneling-over-AUX functionality and exposed with a new DRM_DP_CEC Kconfig build switch. But it's worth noting that not all of these adapters support HDMI CEC, unfortunately, so some of the adapters may outright just not work with CEC.

The complete list of patches as part of today's drm-misc-next pull can be found via this pull request.
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