--- DF-3946 guest compile-test (DragonFly cc, raw DRM atomic ioctl decl)
$ cc -O2 -Wall -o trigger_dce110_headplane trigger_dce110_headplane.c
BUILD_RC=0

--- DF-3946 guest run (no DRI adapter in QEMU guest)
$ ./trigger_dce110_headplane /dev/dri/card0
open(/dev/dri/card0): No such file or directory (no display adapter - hardware-gated trigger)
RUN_RC=2