gitlab-ci: compile Linux image with support to VGEM

Add VGEM to the Linux image that runs in the CI. There are tests that we
plan to add in the future that need this.

This brings a complication, as we already have VKMS in the image. The
order in which DRM devices are loaded is not always the same, so the
node they receive is non-deterministic. Until now we were sure that VKMS
(the virtual device we use to run the DRM-backend tests in the CI) would
be in "/dev/dri/card0", but now we can't be sure. To deal with this
problem we find the node of each device using a one-liner shell script.

This commit also updates the documentation section that describes
specificities of DRM-backend tests in our test suite.

Signed-off-by: Leandro Ribeiro <leandro.ribeiro@collabora.com>

.gitlab-ci.yml

@@ -43,7 +43,7 @@
 variables:
   FDO_UPSTREAM_REPO: wayland/weston
   FDO_REPO_SUFFIX: "$BUILD_OS/$BUILD_ARCH"
-  FDO_DISTRIBUTION_TAG: '2022-01-22.0-for-axbgr16161616'
+  FDO_DISTRIBUTION_TAG: '2022-02-07.00-add-vgem-to-ci'
 
 
 include:

.gitlab-ci/build-deps.sh

@@ -75,7 +75,8 @@ if [[ -n "$KERNEL_DEFCONFIG" ]]; then
 		--enable CONFIG_DRM \
 		--enable CONFIG_DRM_KMS_HELPER \
 		--enable CONFIG_DRM_KMS_FB_HELPER \
-		--enable CONFIG_DRM_VKMS
+		--enable CONFIG_DRM_VKMS \
+		--enable CONFIG_DRM_VGEM
 	make ARCH=${LINUX_ARCH} oldconfig
 	make ARCH=${LINUX_ARCH}
 

.gitlab-ci/virtme-scripts/run-weston-tests.sh

@@ -7,8 +7,15 @@ chmod -R 0700 /tmp
 
 # set environment variables to run Weston tests
 export XDG_RUNTIME_DIR=/tmp/tests
-export WESTON_TEST_SUITE_DRM_DEVICE=card0
 export LIBSEAT_BACKEND=seatd
+# In our test suite, we use VKMS to run DRM-backend tests. The order in which
+# devices are loaded is not predictable, so the DRM node that VKMS takes can
+# change across each boot. That's why we have this one-liner shell script to get
+# the appropriate node for VKMS.
+export WESTON_TEST_SUITE_DRM_DEVICE=$(basename /sys/devices/platform/vkms/drm/card*)
+# To run tests in the CI that exercise the zwp_linux_dmabuf_v1 implementation in
+# Weston, we use VGEM to allocate buffers.
+export WESTON_TEST_SUITE_ALLOC_DEVICE=$(basename /sys/devices/platform/vgem/drm/card*)
 
 # ninja test depends on meson, and meson itself looks for its modules on folder
 # $HOME/.local/lib/pythonX.Y/site-packages (the Python version may differ).

doc/sphinx/toc/test-suite.rst

@@ -218,10 +218,19 @@ DRM-backend tests
 
 DRM-backend tests require a DRM device, so they are a special case. To select a
 device the test suite will simply look at the environment variable
-``WESTON_TEST_SUITE_DRM_DEVICE``. So the first thing the user has to do in order
-to run DRM-backend tests is to set this environment variable with the card that
-should run the tests. For instance, in order to run DRM-backend tests with
-``card0`` we need to run ``export WESTON_TEST_SUITE_DRM_DEVICE=card0``.
+``WESTON_TEST_SUITE_DRM_DEVICE``. In Weston's CI, we set this variable to the
+DRM node that VKMS takes (``cardX`` - X can change across each bot, as the order
+in which devices are loaded is not predictable).
+
+**IMPORTANT**: our DRM-backend tests are written specifically to run on top of
+VKMS (KMS driver created to be used by headless machines in test suites, so it
+aims to be more configurable and predictable than real hardware). We don't
+guarantee that these tests will work on real hardware.
+
+But if users want to run DRM-backend tests using real hardware anyway, the first
+thing they need to do is to set this environment variable with the DRM node of
+the card that should run the tests. For instance, in order to run DRM-backend
+tests with ``card0`` we need to run ``export WESTON_TEST_SUITE_DRM_DEVICE=card0``.
 
 Note that the card should not be in use by a desktop environment (or any other
 program that requires master status), as there can only be one user at a time