minigbm: add unit test for minigbm public apis

This is the first change to add unit tests for the public APIs in
minigbm.
Only tests 3 APIs here for now, and just added some very simple input
for each api testing.

The ultimate goal would be cover more APIs and the input combinations.

BUG=b:304380938
TEST=cros_workon_make --board=guybrush minigbm --test
TEST=cros_run_unit_tests --board guybrush --packages "minigbm"
TEST=CQ

Change-Id: Id15806b7bc6cd9c4764bf08becec6546d72bb117
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/minigbm/+/4923791
Commit-Queue: Dawn Han <dawnhan@google.com>
Reviewed-by: Yiwei Zhang <zzyiwei@chromium.org>
Tested-by: Dawn Han <dawnhan@google.com>

Makefile

@@ -12,6 +12,10 @@ CPPFLAGS += -D_GNU_SOURCE=1
 CFLAGS += -std=c99 -Wall -Wsign-compare -Wpointer-arith -Wcast-qual \
 	  -Wcast-align -D_GNU_SOURCE=1 -D_FILE_OFFSET_BITS=64
 
+# Dependencies that all gtest based unittests should have.
+UNITTEST_LIBS := -lcap -lgtest -lgmock
+UNITTEST_DEPS := gbm_unittest.o testrunner.o gbm.o dri.o drv_array_helpers.o drv_helpers.o drv.o backend_mock.o virtgpu_cross_domain.o virtgpu_virgl.o virtgpu.o msm.o vc4.o amdgpu.o i915.o mediatek.o dumb_driver.o
+
 ifdef DRV_AMDGPU
 	CFLAGS += $(shell $(PKG_CONFIG) --cflags libdrm_amdgpu)
 	LDLIBS += -ldrm_amdgpu -ldl
@@ -52,6 +56,13 @@ all: CC_LIBRARY($(MINIGBM_FILENAME))
 
 clean: CLEAN($(MINIGBM_FILENAME))
 
+CXX_BINARY(gbm_unittest): CXXFLAGS += -Wno-write-strings \
+						$(GTEST_CXXFLAGS)
+CXX_BINARY(gbm_unittest): LDLIBS += $(UNITTEST_LIBS)
+CXX_BINARY(gbm_unittest): $(UNITTEST_DEPS)
+clean: CLEAN(gbm_unittest)
+tests: TEST(CXX_BINARY(gbm_unittest))
+
 install: all
 	mkdir -p $(DESTDIR)/$(LIBDIR)
 	install -D -m 755 $(OUT)/$(MINIGBM_FILENAME) $(DESTDIR)/$(LIBDIR)

backend_mock.c

@@ -0,0 +1,16 @@
+/*
+ * Copyright 2023 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "drv_priv.h"
+
+static int backend_mock_init(struct driver *drv) {
+	return 0;
+}
+
+const struct backend backend_mock = {
+	.name = "Mock Backend",
+	.init = backend_mock_init,
+};

drv.c

@@ -56,6 +56,8 @@ extern const struct backend backend_virtgpu;
 extern const struct backend backend_udl;
 extern const struct backend backend_vkms;
 
+extern const struct backend backend_mock;
+
 static const struct backend *drv_backend_list[] = {
 #ifdef DRV_AMDGPU
 	&backend_amdgpu,
@@ -72,7 +74,7 @@ static const struct backend *drv_backend_list[] = {
 	&backend_evdi,	    &backend_komeda,	&backend_marvell, &backend_mediatek,
 	&backend_meson,	    &backend_nouveau,	&backend_radeon,  &backend_rockchip,
 	&backend_sun4i_drm, &backend_synaptics, &backend_udl,	  &backend_virtgpu,
-	&backend_vkms
+	&backend_vkms,	    &backend_mock
 };
 
 void drv_preload(bool load)

gbm_unittest.cc

@@ -0,0 +1,82 @@
+/* Copyright 2023 The ChromiumOS Authors
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ *
+ * Test gbm.h module code using gtest.
+ */
+
+#include <drm/drm_fourcc.h>
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+#include <xf86drm.h>
+
+#include "gbm.h"
+
+class MockDrm
+{
+ public:
+	MOCK_METHOD(drmVersionPtr, drmGetVersion, (int fd));
+	MOCK_METHOD(void, drmFreeVersion, (drmVersionPtr v));
+};
+
+// Define a mock version of drmGetVersion
+drmVersionPtr drmGetVersion(int fd)
+{
+	drmVersionPtr mock_version = new drmVersion();
+	mock_version->name = "Mock Backend";
+	return mock_version;
+}
+
+// Define a mock version of drmFreeVersion
+void drmFreeVersion(drmVersionPtr v)
+{
+	delete(v);
+}
+
+/* TODO : This is a protocol to add unit tests for the public APIs in minigbm.
+ *
+ * The ultimate goal would be cover more APIs and the input combinations.
+ * Set fd to 0 for now, it doesn't have any particular meaning
+ */
+
+TEST(gbm_unit_test, create_device)
+{
+	MockDrm mock_drm; // Create a mock object
+
+	EXPECT_CALL(mock_drm, drmGetVersion(testing::_))
+	    .WillRepeatedly(testing::Invoke(&mock_drm, &MockDrm::drmGetVersion));
+
+	struct gbm_device *gbm_device = gbm_create_device(0);
+
+	ASSERT_TRUE(gbm_device);
+
+	gbm_device_destroy(gbm_device);
+}
+
+TEST(gbm_unit_test, valid_fd)
+{
+	MockDrm mock_drm; // Create a mock object
+
+	EXPECT_CALL(mock_drm, drmGetVersion(testing::_))
+	    .WillRepeatedly(testing::Invoke(&mock_drm, &MockDrm::drmGetVersion));
+	struct gbm_device *gbm_device = gbm_create_device(99);
+	int fd = gbm_device_get_fd(gbm_device);
+
+	ASSERT_EQ(fd, 99);
+
+	gbm_device_destroy(gbm_device);
+}
+
+TEST(gbm_unit_test, valid_backend_name)
+{
+	MockDrm mock_drm; // Create a mock object
+
+	EXPECT_CALL(mock_drm, drmGetVersion(testing::_))
+	    .WillRepeatedly(testing::Invoke(&mock_drm, &MockDrm::drmGetVersion));
+	struct gbm_device *gbm_device = gbm_create_device(0);
+	const char *backend_name = gbm_device_get_backend_name(gbm_device);
+
+	ASSERT_STREQ(backend_name, "Mock Backend");
+
+	gbm_device_destroy(gbm_device);
+}

testrunner.cc

@@ -0,0 +1,15 @@
+/* Copyright 2023 The ChromiumOS Authors
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ *
+ * Main entrypoint for gtest.
+ */
+
+#include <gtest/gtest.h>
+
+int main(int argc, char **argv)
+{
+	testing::InitGoogleTest(&argc, argv);
+
+	return RUN_ALL_TESTS();
+}