We should integrate and test the HDCP support.

There's a userspace component at https://github.com/intel/hdcp which suggests that drm-tip kernel is needed, but this may well be stale information and the patches could be in PKT or upstream already.

https://github.com/freedesktop/xorg-intel-gpu-tools/blob/master/tests/kms_content_protection.c is apparently a related tool for exercising the kernel support.