diff --git a/services/audioflinger/PatchPanel.cpp b/services/audioflinger/PatchPanel.cpp
index 42a5a90..0caa0af 100644
--- a/services/audioflinger/PatchPanel.cpp
+++ b/services/audioflinger/PatchPanel.cpp
@@ -110,9 +110,7 @@
     status_t status = NO_ERROR;
     audio_patch_handle_t halHandle = AUDIO_PATCH_HANDLE_NONE;
 
-    if (patch->num_sources == 0 || patch->num_sources > AUDIO_PATCH_PORTS_MAX ||
-            (patch->num_sinks == 0 && patch->num_sources != 2) ||
-            patch->num_sinks > AUDIO_PATCH_PORTS_MAX) {
+    if (!audio_patch_is_valid(patch) || (patch->num_sinks == 0 && patch->num_sources != 2)) {
         return BAD_VALUE;
     }
     // limit number of sources to 1 for now or 2 sources for special cross hw module case.
diff --git a/services/audiopolicy/managerdefault/AudioPolicyManager.cpp b/services/audiopolicy/managerdefault/AudioPolicyManager.cpp
index 7154cb2..87cacf8 100644
--- a/services/audiopolicy/managerdefault/AudioPolicyManager.cpp
+++ b/services/audiopolicy/managerdefault/AudioPolicyManager.cpp
@@ -2834,8 +2834,7 @@
     }
     ALOGV("createAudioPatch() num sources %d num sinks %d", patch->num_sources, patch->num_sinks);
 
-    if (patch->num_sources == 0 || patch->num_sources > AUDIO_PATCH_PORTS_MAX ||
-            patch->num_sinks == 0 || patch->num_sinks > AUDIO_PATCH_PORTS_MAX) {
+    if (!audio_patch_is_valid(patch)) {
         return BAD_VALUE;
     }
     // only one source per audio patch supported for now
diff --git a/services/audiopolicy/tests/Android.mk b/services/audiopolicy/tests/Android.mk
index cfa9ab1..b739b88 100644
--- a/services/audiopolicy/tests/Android.mk
+++ b/services/audiopolicy/tests/Android.mk
@@ -29,3 +29,26 @@
 LOCAL_MULTILIB := $(AUDIOSERVER_MULTILIB)
 
 include $(BUILD_NATIVE_TEST)
+
+# system/audio.h utilities test
+
+include $(CLEAR_VARS)
+
+LOCAL_SHARED_LIBRARIES := \
+  libbase \
+  liblog \
+  libmedia_helper \
+  libutils
+
+LOCAL_SRC_FILES := \
+  systemaudio_tests.cpp \
+
+LOCAL_MODULE := systemaudio_tests
+
+LOCAL_MODULE_TAGS := tests
+
+LOCAL_CFLAGS := -Werror -Wall
+
+LOCAL_MULTILIB := $(AUDIOSERVER_MULTILIB)
+
+include $(BUILD_NATIVE_TEST)
diff --git a/services/audiopolicy/tests/systemaudio_tests.cpp b/services/audiopolicy/tests/systemaudio_tests.cpp
new file mode 100644
index 0000000..abaae52
--- /dev/null
+++ b/services/audiopolicy/tests/systemaudio_tests.cpp
@@ -0,0 +1,117 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <gtest/gtest.h>
+
+#define LOG_TAG "SysAudio_Test"
+#include <log/log.h>
+#include <media/PatchBuilder.h>
+#include <system/audio.h>
+
+using namespace android;
+
+TEST(SystemAudioTest, PatchInvalid) {
+    audio_patch patch{};
+    ASSERT_FALSE(audio_patch_is_valid(&patch));
+    patch.num_sources = AUDIO_PATCH_PORTS_MAX + 1;
+    patch.num_sinks = 1;
+    ASSERT_FALSE(audio_patch_is_valid(&patch));
+    patch.num_sources = 1;
+    patch.num_sinks = AUDIO_PATCH_PORTS_MAX + 1;
+    ASSERT_FALSE(audio_patch_is_valid(&patch));
+    patch.num_sources = 0;
+    patch.num_sinks = 1;
+    ASSERT_FALSE(audio_patch_is_valid(&patch));
+}
+
+TEST(SystemAudioTest, PatchValid) {
+    const audio_port_config src = {
+        .id = 1, .role = AUDIO_PORT_ROLE_SOURCE, .type = AUDIO_PORT_TYPE_DEVICE };
+    // It's OK not to have sinks.
+    ASSERT_TRUE(audio_patch_is_valid((PatchBuilder{}).addSource(src).patch()));
+    const audio_port_config sink = {
+        .id = 2, .role = AUDIO_PORT_ROLE_SINK, .type = AUDIO_PORT_TYPE_DEVICE };
+    ASSERT_TRUE(audio_patch_is_valid((PatchBuilder{}).addSource(src).addSink(sink).patch()));
+    ASSERT_TRUE(audio_patch_is_valid(
+                    (PatchBuilder{}).addSource(src).addSource(src).addSink(sink).patch()));
+    ASSERT_TRUE(audio_patch_is_valid(
+                    (PatchBuilder{}).addSource(src).addSink(sink).addSink(sink).patch()));
+    ASSERT_TRUE(audio_patch_is_valid(
+                    (PatchBuilder{}).addSource(src).addSource(src).
+                    addSink(sink).addSink(sink).patch()));
+}
+
+TEST(SystemAudioTest, PatchHwAvSync) {
+    audio_port_config device_src_cfg = {
+        .id = 1, .role = AUDIO_PORT_ROLE_SOURCE, .type = AUDIO_PORT_TYPE_DEVICE };
+    ASSERT_FALSE(audio_port_config_has_hw_av_sync(&device_src_cfg));
+    device_src_cfg.config_mask |= AUDIO_PORT_CONFIG_FLAGS;
+    ASSERT_FALSE(audio_port_config_has_hw_av_sync(&device_src_cfg));
+    device_src_cfg.flags.input = AUDIO_INPUT_FLAG_HW_AV_SYNC;
+    ASSERT_TRUE(audio_port_config_has_hw_av_sync(&device_src_cfg));
+
+    audio_port_config device_sink_cfg = {
+        .id = 1, .role = AUDIO_PORT_ROLE_SINK, .type = AUDIO_PORT_TYPE_DEVICE };
+    ASSERT_FALSE(audio_port_config_has_hw_av_sync(&device_sink_cfg));
+    device_sink_cfg.config_mask |= AUDIO_PORT_CONFIG_FLAGS;
+    ASSERT_FALSE(audio_port_config_has_hw_av_sync(&device_sink_cfg));
+    device_sink_cfg.flags.output = AUDIO_OUTPUT_FLAG_HW_AV_SYNC;
+    ASSERT_TRUE(audio_port_config_has_hw_av_sync(&device_sink_cfg));
+
+    audio_port_config mix_sink_cfg = {
+        .id = 1, .role = AUDIO_PORT_ROLE_SINK, .type = AUDIO_PORT_TYPE_MIX };
+    ASSERT_FALSE(audio_port_config_has_hw_av_sync(&mix_sink_cfg));
+    mix_sink_cfg.config_mask |= AUDIO_PORT_CONFIG_FLAGS;
+    ASSERT_FALSE(audio_port_config_has_hw_av_sync(&mix_sink_cfg));
+    mix_sink_cfg.flags.input = AUDIO_INPUT_FLAG_HW_AV_SYNC;
+    ASSERT_TRUE(audio_port_config_has_hw_av_sync(&mix_sink_cfg));
+
+    audio_port_config mix_src_cfg = {
+        .id = 1, .role = AUDIO_PORT_ROLE_SOURCE, .type = AUDIO_PORT_TYPE_MIX };
+    ASSERT_FALSE(audio_port_config_has_hw_av_sync(&mix_src_cfg));
+    mix_src_cfg.config_mask |= AUDIO_PORT_CONFIG_FLAGS;
+    ASSERT_FALSE(audio_port_config_has_hw_av_sync(&mix_src_cfg));
+    mix_src_cfg.flags.output = AUDIO_OUTPUT_FLAG_HW_AV_SYNC;
+    ASSERT_TRUE(audio_port_config_has_hw_av_sync(&mix_src_cfg));
+}
+
+TEST(SystemAudioTest, PatchEqual) {
+    const audio_patch patch1{}, patch2{};
+    // Invalid patches are not equal.
+    ASSERT_FALSE(audio_patches_are_equal(&patch1, &patch2));
+    const audio_port_config src = {
+        .id = 1, .role = AUDIO_PORT_ROLE_SOURCE, .type = AUDIO_PORT_TYPE_DEVICE };
+    const audio_port_config sink = {
+        .id = 2, .role = AUDIO_PORT_ROLE_SINK, .type = AUDIO_PORT_TYPE_DEVICE };
+    ASSERT_FALSE(audio_patches_are_equal(
+                    (PatchBuilder{}).addSource(src).patch(),
+                    (PatchBuilder{}).addSource(src).addSink(sink).patch()));
+    ASSERT_TRUE(audio_patches_are_equal(
+                    (PatchBuilder{}).addSource(src).addSink(sink).patch(),
+                    (PatchBuilder{}).addSource(src).addSink(sink).patch()));
+    ASSERT_FALSE(audio_patches_are_equal(
+                    (PatchBuilder{}).addSource(src).addSink(sink).patch(),
+                    (PatchBuilder{}).addSource(src).addSource(src).addSink(sink).patch()));
+    audio_port_config sink_hw_av_sync = sink;
+    sink_hw_av_sync.config_mask |= AUDIO_PORT_CONFIG_FLAGS;
+    sink_hw_av_sync.flags.output = AUDIO_OUTPUT_FLAG_HW_AV_SYNC;
+    ASSERT_FALSE(audio_patches_are_equal(
+                    (PatchBuilder{}).addSource(src).addSink(sink).patch(),
+                    (PatchBuilder{}).addSource(src).addSink(sink_hw_av_sync).patch()));
+    ASSERT_TRUE(audio_patches_are_equal(
+                    (PatchBuilder{}).addSource(src).addSink(sink_hw_av_sync).patch(),
+                    (PatchBuilder{}).addSource(src).addSink(sink_hw_av_sync).patch()));
+}