Regression: Weston crashes always on start to HDCP property assert

Between following commits:

• 18e0cf85 at 2019-08-23 21:14:35 UTC build: reopen master for regular development
• fbfcc304 at 2019-08-26 10:48:22 UTC man: Declare drm-backend support for HDCP

Weston started to crash on every startup.

Setup:

• HW: J4205 (haven't tested on others)
• OS: Latest ClearLinux (haven't tested on others)
• SW: latest git versions of drm-tip v5.3-rc6 kernel, Mesa, libwayland and Weston

Weston is built with following options (mainly to disable features where ClearLinux doesn't have libs matching Ubuntu 18.04 build machine):

  -Dimage-jpeg=false -Dimage-webp=false \
  -Dsimple-dmabuf-drm=auto -Dbackend-drm-screencast-vaapi=false \
  -Dpipewire=false -Dbackend-rdp=false -Dremoting=false

This is the crash output from journalctl:

weston[412]:                Build: 7.0.0-7-gfbfcc304
weston[412]: [08:34:30.724] Command line: /opt/install/bin/weston --tty=7 --idle-time=0 --xwayland
weston[412]: [08:34:30.724] OS: Linux, 5.3.0-rc6, #1 SMP PREEMPT Mon Aug 26 20:11:23 EEST 2019, x86_64
weston[412]: [08:34:30.724] Starting with no config file.
...
weston[412]: [08:34:30.782] Failed to obtain a high priority context.
weston[412]: [08:34:30.782] GL version: OpenGL ES 3.2 Mesa 19.3.0-devel (git-2e1be771e4)
weston[412]: [08:34:30.782] GLSL version: OpenGL ES GLSL ES 3.20
weston[412]: [08:34:30.782] GL vendor: Intel Open Source Technology Center
weston[412]: [08:34:30.782] GL renderer: Mesa DRI Intel(R) HD Graphics 505 (Broxton)
...
weston[412]: [08:34:30.890] DRM: head 'DP-1' found, connector 100 is disconnected.
weston[412]: [08:34:30.920] DRM: head 'DP-2' found, connector 105 is connected, EDID make 'DEL', model 'DELL U2312HM', serial '59DJP1AAATCL'
weston[412]: [08:34:30.922] DRM: head 'HDMI-A-1' found, connector 112 is disconnected.
...
weston[412]: [08:34:30.924] Output 'DP-2' enabled with head(s) DP-2
...
weston[412]: weston: libweston/backend-drm/kms.c:909: drm_head_set_hdcp_property: Assertion `ret == 0'
systemd[1]: Created slice system-systemd\x2dcoredump.slice.
systemd[1]: Started Process Core Dump (PID 434/UID 0).
systemd[1]: weston.service: Main process exited, code=dumped, status=6/ABRT
systemd[1]: weston.service: Failed with result 'core-dump'.
...
systemd-coredump[435]: Process 412 (weston) of user 1000 dumped core.

    Stack trace of thread 412:
    #0  0x00007f8e72b1c185 raise (libc.so.6)
    #1  0x00007f8e72afb8a7 abort (libc.so.6)
    #2  0x00007f8e72afb777 n/a (libc.so.6)
    #3  0x00007f8e72b0cd86 __assert_fail (libc.so.6)
    #4  0x00007f8e720c5d65 drm_head_set_hdcp_property (drm-backend.so)
    #5  0x00007f8e720beeb6 drm_repaint_flush (drm-backend.so)
    #6  0x00007f8e7319eb2b output_repaint_timer_handler (libweston-7.so.0)
    #7  0x00007f8e72d6a809 wl_event_source_timer_dispatch (libwayland-server.so.0)
    #8  0x00007f8e72d6aec2 wl_event_loop_dispatch (libwayland-server.so.0)
    #9  0x00007f8e72d69ada wl_display_run (libwayland-server.so.0)
    #10 0x000055fb4814edd1 main (weston)
    #11 0x00007f8e72afd193 __libc_start_main (libc.so.6)
    #12 0x000055fb48150c2a _start (weston)

    Stack trace of thread 430:
    #0  0x00007f8e72be793f __fxstatat64 (libc.so.6)
    #1  0x00007f8e6f806fc2 fstatat64 (i965_dri.so)
    #2  0x00007f8e6f80710a unlink_lru_file_from_directory (i965_dri.so)
    #3  0x00007f8e6f8076a0 evict_lru_item (i965_dri.so)
    #4  0x00007f8e6f80f907 util_queue_thread_func (i965_dri.so)
    #5  0x00007f8e6f80f397 impl_thrd_routine (i965_dri.so)
    #6  0x00007f8e72cd37bf n/a (libpthread.so.0)
    #7  0x00007f8e72bf95c3 __clone (libc.so.6)
systemd[1]: systemd-coredump@0-434-0.service: Succeeded.