diff --git a/graphics/composer/aidl/include/android/hardware/graphics/composer3/ComposerClientReader.h b/graphics/composer/aidl/include/android/hardware/graphics/composer3/ComposerClientReader.h
index 27dce76..76ba24b 100644
--- a/graphics/composer/aidl/include/android/hardware/graphics/composer3/ComposerClientReader.h
+++ b/graphics/composer/aidl/include/android/hardware/graphics/composer3/ComposerClientReader.h
@@ -19,8 +19,8 @@
 #include <algorithm>
 #include <limits>
 #include <memory>
+#include <optional>
 #include <unordered_map>
-#include <unordered_set>
 #include <vector>
 
 #include <inttypes.h>
@@ -41,8 +41,15 @@
 
 class ComposerClientReader {
   public:
+    explicit ComposerClientReader(std::optional<int64_t> display = {}) : mDisplay(display) {}
+
     ~ComposerClientReader() { resetData(); }
 
+    ComposerClientReader(ComposerClientReader&&) = default;
+
+    ComposerClientReader(const ComposerClientReader&) = delete;
+    ComposerClientReader& operator=(const ComposerClientReader&) = delete;
+
     // Parse and execute commands from the command queue.  The commands are
     // actually return values from the server and will be saved in ReturnData.
     void parse(std::vector<CommandResultPayload>&& results) {
@@ -85,6 +92,7 @@
 
     void hasChanges(int64_t display, uint32_t* outNumChangedCompositionTypes,
                     uint32_t* outNumLayerRequestMasks) const {
+        LOG_ALWAYS_FATAL_IF(mDisplay && display != *mDisplay);
         auto found = mReturnData.find(display);
         if (found == mReturnData.end()) {
             *outNumChangedCompositionTypes = 0;
@@ -100,6 +108,7 @@
 
     // Get and clear saved changed composition types.
     std::vector<ChangedCompositionLayer> takeChangedCompositionTypes(int64_t display) {
+        LOG_ALWAYS_FATAL_IF(mDisplay && display != *mDisplay);
         auto found = mReturnData.find(display);
         if (found == mReturnData.end()) {
             return {};
@@ -111,6 +120,7 @@
 
     // Get and clear saved display requests.
     DisplayRequest takeDisplayRequests(int64_t display) {
+        LOG_ALWAYS_FATAL_IF(mDisplay && display != *mDisplay);
         auto found = mReturnData.find(display);
         if (found == mReturnData.end()) {
             return {};
@@ -122,6 +132,7 @@
 
     // Get and clear saved release fences.
     std::vector<ReleaseFences::Layer> takeReleaseFences(int64_t display) {
+        LOG_ALWAYS_FATAL_IF(mDisplay && display != *mDisplay);
         auto found = mReturnData.find(display);
         if (found == mReturnData.end()) {
             return {};
@@ -133,6 +144,7 @@
 
     // Get and clear saved present fence.
     ndk::ScopedFileDescriptor takePresentFence(int64_t display) {
+        LOG_ALWAYS_FATAL_IF(mDisplay && display != *mDisplay);
         auto found = mReturnData.find(display);
         if (found == mReturnData.end()) {
             return {};
@@ -144,6 +156,7 @@
 
     // Get what stage succeeded during PresentOrValidate: Present or Validate
     std::optional<PresentOrValidate::Result> takePresentOrValidateStage(int64_t display) {
+        LOG_ALWAYS_FATAL_IF(mDisplay && display != *mDisplay);
         auto found = mReturnData.find(display);
         if (found == mReturnData.end()) {
             return std::nullopt;
@@ -154,6 +167,7 @@
 
     // Get the client target properties requested by hardware composer.
     ClientTargetPropertyWithBrightness takeClientTargetProperty(int64_t display) {
+        LOG_ALWAYS_FATAL_IF(mDisplay && display != *mDisplay);
         auto found = mReturnData.find(display);
 
         // If not found, return the default values.
@@ -177,32 +191,38 @@
     void parseSetError(CommandError&& error) { mErrors.emplace_back(error); }
 
     void parseSetChangedCompositionTypes(ChangedCompositionTypes&& changedCompositionTypes) {
+        LOG_ALWAYS_FATAL_IF(mDisplay && changedCompositionTypes.display != *mDisplay);
         auto& data = mReturnData[changedCompositionTypes.display];
         data.changedLayers = std::move(changedCompositionTypes.layers);
     }
 
     void parseSetDisplayRequests(DisplayRequest&& displayRequest) {
+        LOG_ALWAYS_FATAL_IF(mDisplay && displayRequest.display != *mDisplay);
         auto& data = mReturnData[displayRequest.display];
         data.displayRequests = std::move(displayRequest);
     }
 
     void parseSetPresentFence(PresentFence&& presentFence) {
+        LOG_ALWAYS_FATAL_IF(mDisplay && presentFence.display != *mDisplay);
         auto& data = mReturnData[presentFence.display];
         data.presentFence = std::move(presentFence.fence);
     }
 
     void parseSetReleaseFences(ReleaseFences&& releaseFences) {
+        LOG_ALWAYS_FATAL_IF(mDisplay && releaseFences.display != *mDisplay);
         auto& data = mReturnData[releaseFences.display];
         data.releasedLayers = std::move(releaseFences.layers);
     }
 
     void parseSetPresentOrValidateDisplayResult(const PresentOrValidate&& presentOrValidate) {
+        LOG_ALWAYS_FATAL_IF(mDisplay && presentOrValidate.display != *mDisplay);
         auto& data = mReturnData[presentOrValidate.display];
         data.presentOrValidateState = std::move(presentOrValidate.result);
     }
 
     void parseSetClientTargetProperty(
             const ClientTargetPropertyWithBrightness&& clientTargetProperty) {
+        LOG_ALWAYS_FATAL_IF(mDisplay && clientTargetProperty.display != *mDisplay);
         auto& data = mReturnData[clientTargetProperty.display];
         data.clientTargetProperty = std::move(clientTargetProperty);
     }
@@ -222,6 +242,7 @@
 
     std::vector<CommandError> mErrors;
     std::unordered_map<int64_t, ReturnData> mReturnData;
+    const std::optional<int64_t> mDisplay;
 };
 
 }  // namespace aidl::android::hardware::graphics::composer3
diff --git a/graphics/composer/aidl/include/android/hardware/graphics/composer3/ComposerClientWriter.h b/graphics/composer/aidl/include/android/hardware/graphics/composer3/ComposerClientWriter.h
index 775ae9f..0c8742f 100644
--- a/graphics/composer/aidl/include/android/hardware/graphics/composer3/ComposerClientWriter.h
+++ b/graphics/composer/aidl/include/android/hardware/graphics/composer3/ComposerClientWriter.h
@@ -19,8 +19,6 @@
 #include <algorithm>
 #include <limits>
 #include <memory>
-#include <unordered_map>
-#include <unordered_set>
 #include <vector>
 
 #include <inttypes.h>
@@ -63,10 +61,15 @@
   public:
     static constexpr std::optional<ClockMonotonicTimestamp> kNoTimestamp = std::nullopt;
 
-    ComposerClientWriter() { reset(); }
+    explicit ComposerClientWriter(int64_t display) : mDisplay(display) { reset(); }
 
     ~ComposerClientWriter() { reset(); }
 
+    ComposerClientWriter(ComposerClientWriter&&) = default;
+
+    ComposerClientWriter(const ComposerClientWriter&) = delete;
+    ComposerClientWriter& operator=(const ComposerClientWriter&) = delete;
+
     void reset() {
         mDisplayCommand.reset();
         mLayerCommand.reset();
@@ -229,6 +232,7 @@
     std::optional<DisplayCommand> mDisplayCommand;
     std::optional<LayerCommand> mLayerCommand;
     std::vector<DisplayCommand> mCommands;
+    const int64_t mDisplay;
 
     Buffer getBuffer(uint32_t slot, const native_handle_t* bufferHandle, int fence) {
         Buffer bufferCommand;
@@ -254,6 +258,7 @@
 
     DisplayCommand& getDisplayCommand(int64_t display) {
         if (!mDisplayCommand.has_value() || mDisplayCommand->display != display) {
+            LOG_ALWAYS_FATAL_IF(display != mDisplay);
             flushLayerCommand();
             flushDisplayCommand();
             mDisplayCommand.emplace();
diff --git a/graphics/composer/aidl/vts/VtsComposerClient.h b/graphics/composer/aidl/vts/VtsComposerClient.h
index 6358b85..1883336 100644
--- a/graphics/composer/aidl/vts/VtsComposerClient.h
+++ b/graphics/composer/aidl/vts/VtsComposerClient.h
@@ -35,6 +35,7 @@
 #include <string>
 #include <thread>
 #include <unordered_map>
+#include <unordered_set>
 #include "GraphicsComposerCallback.h"
 
 using aidl::android::hardware::graphics::common::Dataspace;
diff --git a/graphics/composer/aidl/vts/VtsHalGraphicsComposer3_ReadbackTest.cpp b/graphics/composer/aidl/vts/VtsHalGraphicsComposer3_ReadbackTest.cpp
index 46dde09..6fa3392 100644
--- a/graphics/composer/aidl/vts/VtsHalGraphicsComposer3_ReadbackTest.cpp
+++ b/graphics/composer/aidl/vts/VtsHalGraphicsComposer3_ReadbackTest.cpp
@@ -53,6 +53,7 @@
         const auto& [status, displays] = mComposerClient->getDisplays();
         ASSERT_TRUE(status.isOk());
         mDisplays = displays;
+        mWriter.reset(new ComposerClientWriter(getPrimaryDisplayId()));
 
         setTestColorModes();
 
@@ -200,15 +201,15 @@
 
     void writeLayers(const std::vector<std::shared_ptr<TestLayer>>& layers) {
         for (const auto& layer : layers) {
-            layer->write(mWriter);
+            layer->write(*mWriter);
         }
         execute();
     }
 
     void execute() {
-        const auto& commands = mWriter.getPendingCommands();
+        const auto& commands = mWriter->getPendingCommands();
         if (commands.empty()) {
-            mWriter.reset();
+            mWriter->reset();
             return;
         }
 
@@ -216,7 +217,7 @@
         ASSERT_TRUE(status.isOk()) << "executeCommands failed " << status.getDescription();
 
         mReader.parse(std::move(results));
-        mWriter.reset();
+        mWriter->reset();
     }
 
     bool getHasReadbackBuffer() {
@@ -236,7 +237,7 @@
     std::vector<VtsDisplay> mDisplays;
     // use the slot count usually set by SF
     std::vector<ColorMode> mTestColorModes;
-    ComposerClientWriter mWriter;
+    std::unique_ptr<ComposerClientWriter> mWriter;
     ComposerClientReader mReader;
     std::unique_ptr<TestRenderEngine> mTestRenderEngine;
     common::PixelFormat mPixelFormat;
@@ -297,7 +298,7 @@
 
         writeLayers(layers);
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+        mWriter->validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
         execute();
         // if hwc cannot handle and asks for composition change,
         // just succeed the test
@@ -306,7 +307,7 @@
             return;
         }
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.presentDisplay(getPrimaryDisplayId());
+        mWriter->presentDisplay(getPrimaryDisplayId());
         execute();
         ASSERT_TRUE(mReader.takeErrors().empty());
 
@@ -349,14 +350,14 @@
                 getDisplayHeight(), common::PixelFormat::RGBA_8888);
         layer->setDisplayFrame({0, 0, getDisplayWidth(), getDisplayHeight()});
         layer->setZOrder(10);
-        layer->setDataspace(ReadbackHelper::getDataspaceForColorMode(mode), mWriter);
+        layer->setDataspace(ReadbackHelper::getDataspaceForColorMode(mode), *mWriter);
         ASSERT_NO_FATAL_FAILURE(layer->setBuffer(expectedColors));
 
         std::vector<std::shared_ptr<TestLayer>> layers = {layer};
 
         writeLayers(layers);
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+        mWriter->validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
         execute();
 
         if (!mReader.takeChangedCompositionTypes(getPrimaryDisplayId()).empty()) {
@@ -365,7 +366,7 @@
         }
         ASSERT_TRUE(mReader.takeErrors().empty());
 
-        mWriter.presentDisplay(getPrimaryDisplayId());
+        mWriter->presentDisplay(getPrimaryDisplayId());
         execute();
 
         ASSERT_TRUE(mReader.takeErrors().empty());
@@ -395,7 +396,7 @@
         layer->setColor(BLUE);
         layer->setDisplayFrame(coloredSquare);
         layer->setZOrder(10);
-        layer->write(mWriter);
+        layer->write(*mWriter);
 
         // This following buffer call should have no effect
         const auto usage = static_cast<uint32_t>(common::BufferUsage::CPU_WRITE_OFTEN) |
@@ -403,8 +404,8 @@
         const auto& [graphicBufferStatus, graphicBuffer] = allocateBuffer(usage);
         ASSERT_TRUE(graphicBufferStatus);
         const auto& buffer = graphicBuffer->handle;
-        mWriter.setLayerBuffer(getPrimaryDisplayId(), layer->getLayer(), /*slot*/ 0, buffer,
-                               /*acquireFence*/ -1);
+        mWriter->setLayerBuffer(getPrimaryDisplayId(), layer->getLayer(), /*slot*/ 0, buffer,
+                                /*acquireFence*/ -1);
 
         // expected color for each pixel
         std::vector<Color> expectedColors(
@@ -415,7 +416,7 @@
                                       getDisplayHeight(), mPixelFormat, mDataspace);
         ASSERT_NO_FATAL_FAILURE(readbackBuffer.setReadbackBuffer());
 
-        mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+        mWriter->validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
         execute();
 
         if (!mReader.takeChangedCompositionTypes(getPrimaryDisplayId()).empty()) {
@@ -423,7 +424,7 @@
             return;
         }
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.presentDisplay(getPrimaryDisplayId());
+        mWriter->presentDisplay(getPrimaryDisplayId());
         execute();
         ASSERT_TRUE(mReader.takeErrors().empty());
 
@@ -533,7 +534,7 @@
                                                        getDisplayHeight(), PixelFormat::RGBA_FP16);
         layer->setDisplayFrame({0, 0, getDisplayWidth(), getDisplayHeight()});
         layer->setZOrder(10);
-        layer->setDataspace(ReadbackHelper::getDataspaceForColorMode(mode), mWriter);
+        layer->setDataspace(ReadbackHelper::getDataspaceForColorMode(mode), *mWriter);
 
         std::vector<std::shared_ptr<TestLayer>> layers = {layer};
 
@@ -542,7 +543,7 @@
         ASSERT_NO_FATAL_FAILURE(readbackBuffer.setReadbackBuffer());
         writeLayers(layers);
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+        mWriter->validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
         execute();
 
         auto changedCompositionTypes = mReader.takeChangedCompositionTypes(getPrimaryDisplayId());
@@ -572,17 +573,17 @@
             int32_t clientFence;
             const auto unlockStatus = graphicBuffer->unlockAsync(&clientFence);
             ASSERT_EQ(::android::OK, unlockStatus);
-            mWriter.setClientTarget(getPrimaryDisplayId(), /*slot*/ 0, buffer, clientFence,
-                                    clientDataspace, std::vector<common::Rect>(1, damage));
-            layer->setToClientComposition(mWriter);
-            mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+            mWriter->setClientTarget(getPrimaryDisplayId(), /*slot*/ 0, buffer, clientFence,
+                                     clientDataspace, std::vector<common::Rect>(1, damage));
+            layer->setToClientComposition(*mWriter);
+            mWriter->validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
             execute();
             changedCompositionTypes = mReader.takeChangedCompositionTypes(getPrimaryDisplayId());
             ASSERT_TRUE(changedCompositionTypes.empty());
         }
         ASSERT_TRUE(mReader.takeErrors().empty());
 
-        mWriter.presentDisplay(getPrimaryDisplayId());
+        mWriter->presentDisplay(getPrimaryDisplayId());
         execute();
 
         ASSERT_TRUE(mReader.takeErrors().empty());
@@ -631,9 +632,9 @@
         deviceLayer->setDisplayFrame({0, 0, static_cast<int32_t>(deviceLayer->getWidth()),
                                       static_cast<int32_t>(deviceLayer->getHeight())});
         deviceLayer->setZOrder(10);
-        deviceLayer->setDataspace(ReadbackHelper::getDataspaceForColorMode(mode), mWriter);
+        deviceLayer->setDataspace(ReadbackHelper::getDataspaceForColorMode(mode), *mWriter);
         ASSERT_NO_FATAL_FAILURE(deviceLayer->setBuffer(deviceColors));
-        deviceLayer->write(mWriter);
+        deviceLayer->write(*mWriter);
 
         PixelFormat clientFormat = PixelFormat::RGBA_8888;
         auto clientUsage = static_cast<uint32_t>(
@@ -651,8 +652,8 @@
                                     getDisplayHeight()};
         clientLayer->setDisplayFrame(clientFrame);
         clientLayer->setZOrder(0);
-        clientLayer->write(mWriter);
-        mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+        clientLayer->write(*mWriter);
+        mWriter->validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
         execute();
 
         auto changedCompositionTypes = mReader.takeChangedCompositionTypes(getPrimaryDisplayId());
@@ -678,16 +679,16 @@
         int32_t clientFence;
         const auto unlockStatus = graphicBuffer->unlockAsync(&clientFence);
         ASSERT_EQ(::android::OK, unlockStatus);
-        mWriter.setClientTarget(getPrimaryDisplayId(), /*slot*/ 0, buffer, clientFence,
-                                clientDataspace, std::vector<common::Rect>(1, clientFrame));
-        clientLayer->setToClientComposition(mWriter);
-        mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+        mWriter->setClientTarget(getPrimaryDisplayId(), /*slot*/ 0, buffer, clientFence,
+                                 clientDataspace, std::vector<common::Rect>(1, clientFrame));
+        clientLayer->setToClientComposition(*mWriter);
+        mWriter->validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
         execute();
         changedCompositionTypes = mReader.takeChangedCompositionTypes(getPrimaryDisplayId());
         ASSERT_TRUE(changedCompositionTypes.empty());
         ASSERT_TRUE(mReader.takeErrors().empty());
 
-        mWriter.presentDisplay(getPrimaryDisplayId());
+        mWriter->presentDisplay(getPrimaryDisplayId());
         execute();
         ASSERT_TRUE(mReader.takeErrors().empty());
         ASSERT_NO_FATAL_FAILURE(readbackBuffer.checkReadbackBuffer(expectedColors));
@@ -718,7 +719,7 @@
                                                        getDisplayHeight(), PixelFormat::RGBA_8888);
         layer->setDisplayFrame({0, 0, getDisplayWidth(), getDisplayHeight()});
         layer->setZOrder(10);
-        layer->setDataspace(ReadbackHelper::getDataspaceForColorMode(mode), mWriter);
+        layer->setDataspace(ReadbackHelper::getDataspaceForColorMode(mode), *mWriter);
         ASSERT_NO_FATAL_FAILURE(layer->setBuffer(expectedColors));
 
         std::vector<std::shared_ptr<TestLayer>> layers = {layer};
@@ -729,14 +730,14 @@
 
         writeLayers(layers);
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+        mWriter->validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
         execute();
         if (!mReader.takeChangedCompositionTypes(getPrimaryDisplayId()).empty()) {
             GTEST_SUCCEED();
             return;
         }
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.presentDisplay(getPrimaryDisplayId());
+        mWriter->presentDisplay(getPrimaryDisplayId());
         execute();
         ASSERT_TRUE(mReader.takeErrors().empty());
 
@@ -757,11 +758,11 @@
 
         writeLayers(layers);
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+        mWriter->validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
         execute();
         ASSERT_TRUE(mReader.takeErrors().empty());
         ASSERT_TRUE(mReader.takeChangedCompositionTypes(getPrimaryDisplayId()).empty());
-        mWriter.presentDisplay(getPrimaryDisplayId());
+        mWriter->presentDisplay(getPrimaryDisplayId());
         execute();
         ASSERT_TRUE(mReader.takeErrors().empty());
 
@@ -798,7 +799,7 @@
 
         writeLayers(layers);
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+        mWriter->validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
         execute();
         if (!mReader.takeChangedCompositionTypes(getPrimaryDisplayId()).empty()) {
             GTEST_SUCCEED();
@@ -806,7 +807,7 @@
         }
         ASSERT_TRUE(mReader.takeErrors().empty());
 
-        mWriter.presentDisplay(getPrimaryDisplayId());
+        mWriter->presentDisplay(getPrimaryDisplayId());
         execute();
         ASSERT_TRUE(mReader.takeErrors().empty());
 
@@ -846,7 +847,7 @@
                                                        getDisplayHeight(), PixelFormat::RGBA_8888);
         layer->setDisplayFrame({0, 0, getDisplayWidth(), getDisplayHeight()});
         layer->setZOrder(10);
-        layer->setDataspace(ReadbackHelper::getDataspaceForColorMode(mode), mWriter);
+        layer->setDataspace(ReadbackHelper::getDataspaceForColorMode(mode), *mWriter);
         layer->setSourceCrop({0, static_cast<float>(getDisplayHeight() / 2),
                               static_cast<float>(getDisplayWidth()),
                               static_cast<float>(getDisplayHeight())});
@@ -862,14 +863,14 @@
         ASSERT_NO_FATAL_FAILURE(readbackBuffer.setReadbackBuffer());
         writeLayers(layers);
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+        mWriter->validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
         execute();
         if (!mReader.takeChangedCompositionTypes(getPrimaryDisplayId()).empty()) {
             GTEST_SUCCEED();
             return;
         }
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.presentDisplay(getPrimaryDisplayId());
+        mWriter->presentDisplay(getPrimaryDisplayId());
         execute();
         ASSERT_TRUE(mReader.takeErrors().empty());
         ASSERT_NO_FATAL_FAILURE(readbackBuffer.checkReadbackBuffer(expectedColors));
@@ -920,13 +921,13 @@
 
         writeLayers(layers);
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+        mWriter->validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
         execute();
         if (!mReader.takeChangedCompositionTypes(getPrimaryDisplayId()).empty()) {
             GTEST_SUCCEED();
             return;
         }
-        mWriter.presentDisplay(getPrimaryDisplayId());
+        mWriter->presentDisplay(getPrimaryDisplayId());
         execute();
         ASSERT_TRUE(mReader.takeErrors().empty());
 
@@ -942,11 +943,11 @@
 
         writeLayers(layers);
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+        mWriter->validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
         execute();
         ASSERT_TRUE(mReader.takeChangedCompositionTypes(getPrimaryDisplayId()).empty());
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.presentDisplay(getPrimaryDisplayId());
+        mWriter->presentDisplay(getPrimaryDisplayId());
         execute();
         ASSERT_TRUE(mReader.takeErrors().empty());
 
@@ -980,7 +981,7 @@
     // Preconditions to successfully run are knowing the max brightness and successfully applying
     // the max brightness
     ASSERT_GT(maxBrightnessNits, 0.f);
-    mWriter.setDisplayBrightness(getPrimaryDisplayId(), /*brightness*/ 1.f, maxBrightnessNits);
+    mWriter->setDisplayBrightness(getPrimaryDisplayId(), /*brightness*/ 1.f, maxBrightnessNits);
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 
@@ -1030,7 +1031,7 @@
 
         writeLayers(layers);
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+        mWriter->validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
         execute();
         if (!mReader.takeChangedCompositionTypes(getPrimaryDisplayId()).empty()) {
             GTEST_SUCCEED()
@@ -1038,7 +1039,7 @@
                     << toString(mode);
             continue;
         }
-        mWriter.presentDisplay(getPrimaryDisplayId());
+        mWriter->presentDisplay(getPrimaryDisplayId());
         execute();
         ASSERT_TRUE(mReader.takeErrors().empty());
 
@@ -1088,7 +1089,7 @@
                                                        getDisplayHeight(), PixelFormat::RGBA_8888);
         layer->setDisplayFrame({0, 0, getDisplayWidth(), getDisplayHeight()});
         layer->setZOrder(10);
-        layer->setDataspace(Dataspace::UNKNOWN, mWriter);
+        layer->setDataspace(Dataspace::UNKNOWN, *mWriter);
         ASSERT_NO_FATAL_FAILURE(layer->setBuffer(topLayerPixelColors));
 
         layer->setBlendMode(blendMode);
@@ -1165,14 +1166,14 @@
         ASSERT_NO_FATAL_FAILURE(readbackBuffer.setReadbackBuffer());
         writeLayers(mLayers);
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+        mWriter->validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
         execute();
         if (!mReader.takeChangedCompositionTypes(getPrimaryDisplayId()).empty()) {
             GTEST_SUCCEED();
             return;
         }
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.presentDisplay(getPrimaryDisplayId());
+        mWriter->presentDisplay(getPrimaryDisplayId());
         execute();
         ASSERT_TRUE(mReader.takeErrors().empty());
 
@@ -1210,14 +1211,14 @@
         ASSERT_NO_FATAL_FAILURE(readbackBuffer.setReadbackBuffer());
         writeLayers(mLayers);
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+        mWriter->validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
         execute();
         if (!mReader.takeChangedCompositionTypes(getPrimaryDisplayId()).empty()) {
             GTEST_SUCCEED();
             return;
         }
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.presentDisplay(getPrimaryDisplayId());
+        mWriter->presentDisplay(getPrimaryDisplayId());
         execute();
         ASSERT_TRUE(mReader.takeErrors().empty());
         ASSERT_NO_FATAL_FAILURE(readbackBuffer.checkReadbackBuffer(expectedColors));
@@ -1250,14 +1251,14 @@
         ASSERT_NO_FATAL_FAILURE(readbackBuffer.setReadbackBuffer());
         writeLayers(mLayers);
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+        mWriter->validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
         execute();
         if (!mReader.takeChangedCompositionTypes(getPrimaryDisplayId()).empty()) {
             GTEST_SUCCEED();
             return;
         }
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.presentDisplay(getPrimaryDisplayId());
+        mWriter->presentDisplay(getPrimaryDisplayId());
         execute();
         ASSERT_TRUE(mReader.takeErrors().empty());
         ASSERT_NO_FATAL_FAILURE(readbackBuffer.checkReadbackBuffer(expectedColors));
@@ -1323,7 +1324,7 @@
                                       getDisplayHeight(), mPixelFormat, mDataspace);
         ASSERT_NO_FATAL_FAILURE(readbackBuffer.setReadbackBuffer());
         mLayer->setTransform(Transform::FLIP_H);
-        mLayer->setDataspace(ReadbackHelper::getDataspaceForColorMode(mode), mWriter);
+        mLayer->setDataspace(ReadbackHelper::getDataspaceForColorMode(mode), *mWriter);
 
         std::vector<Color> expectedColors(
                 static_cast<size_t>(getDisplayWidth() * getDisplayHeight()));
@@ -1334,14 +1335,14 @@
 
         writeLayers(mLayers);
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+        mWriter->validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
         execute();
         if (!mReader.takeChangedCompositionTypes(getPrimaryDisplayId()).empty()) {
             GTEST_SUCCEED();
             return;
         }
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.presentDisplay(getPrimaryDisplayId());
+        mWriter->presentDisplay(getPrimaryDisplayId());
         execute();
         ASSERT_TRUE(mReader.takeErrors().empty());
 
@@ -1369,7 +1370,7 @@
         ASSERT_NO_FATAL_FAILURE(readbackBuffer.setReadbackBuffer());
 
         mLayer->setTransform(Transform::FLIP_V);
-        mLayer->setDataspace(ReadbackHelper::getDataspaceForColorMode(mode), mWriter);
+        mLayer->setDataspace(ReadbackHelper::getDataspaceForColorMode(mode), *mWriter);
 
         std::vector<Color> expectedColors(
                 static_cast<size_t>(getDisplayWidth() * getDisplayHeight()));
@@ -1380,14 +1381,14 @@
 
         writeLayers(mLayers);
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+        mWriter->validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
         execute();
         if (!mReader.takeChangedCompositionTypes(getPrimaryDisplayId()).empty()) {
             GTEST_SUCCEED();
             return;
         }
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.presentDisplay(getPrimaryDisplayId());
+        mWriter->presentDisplay(getPrimaryDisplayId());
         execute();
         ASSERT_TRUE(mReader.takeErrors().empty());
         ASSERT_NO_FATAL_FAILURE(readbackBuffer.checkReadbackBuffer(expectedColors));
@@ -1414,7 +1415,7 @@
         ASSERT_NO_FATAL_FAILURE(readbackBuffer.setReadbackBuffer());
 
         mLayer->setTransform(Transform::ROT_180);
-        mLayer->setDataspace(ReadbackHelper::getDataspaceForColorMode(mode), mWriter);
+        mLayer->setDataspace(ReadbackHelper::getDataspaceForColorMode(mode), *mWriter);
 
         std::vector<Color> expectedColors(
                 static_cast<size_t>(getDisplayWidth() * getDisplayHeight()));
@@ -1426,14 +1427,14 @@
 
         writeLayers(mLayers);
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+        mWriter->validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
         execute();
         if (!mReader.takeChangedCompositionTypes(getPrimaryDisplayId()).empty()) {
             GTEST_SUCCEED();
             return;
         }
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.presentDisplay(getPrimaryDisplayId());
+        mWriter->presentDisplay(getPrimaryDisplayId());
         execute();
         ASSERT_TRUE(mReader.takeErrors().empty());
         ASSERT_NO_FATAL_FAILURE(readbackBuffer.checkReadbackBuffer(expectedColors));
diff --git a/graphics/composer/aidl/vts/VtsHalGraphicsComposer3_TargetTest.cpp b/graphics/composer/aidl/vts/VtsHalGraphicsComposer3_TargetTest.cpp
index ed8a06c..fa66812 100644
--- a/graphics/composer/aidl/vts/VtsHalGraphicsComposer3_TargetTest.cpp
+++ b/graphics/composer/aidl/vts/VtsHalGraphicsComposer3_TargetTest.cpp
@@ -33,9 +33,11 @@
 #include <ui/GraphicBuffer.h>
 #include <ui/PixelFormat.h>
 #include <algorithm>
+#include <iterator>
 #include <numeric>
 #include <string>
 #include <thread>
+#include <unordered_map>
 #include "GraphicsComposerCallback.h"
 #include "VtsComposerClient.h"
 
@@ -1078,17 +1080,23 @@
     }
 
     void execute() {
-        const auto& commands = mWriter.getPendingCommands();
-        if (commands.empty()) {
-            mWriter.reset();
-            return;
+        std::vector<CommandResultPayload> payloads;
+        for (auto& [_, writer] : mWriters) {
+            const auto& commands = writer.getPendingCommands();
+            if (commands.empty()) {
+                writer.reset();
+                continue;
+            }
+
+            auto [status, results] = mComposerClient->executeCommands(commands);
+            ASSERT_TRUE(status.isOk()) << "executeCommands failed " << status.getDescription();
+            writer.reset();
+
+            payloads.reserve(payloads.size() + results.size());
+            payloads.insert(payloads.end(), std::make_move_iterator(results.begin()),
+                            std::make_move_iterator(results.end()));
         }
-
-        auto [status, results] = mComposerClient->executeCommands(commands);
-        ASSERT_TRUE(status.isOk()) << "executeCommands failed " << status.getDescription();
-
-        mReader.parse(std::move(results));
-        mWriter.reset();
+        mReader.parse(std::move(payloads));
     }
 
     static inline auto toTimePoint(nsecs_t time) {
@@ -1152,6 +1160,7 @@
         const auto& [status, layer] =
                 mComposerClient->createLayer(display.getDisplayId(), kBufferSlotCount);
         EXPECT_TRUE(status.isOk());
+        auto& writer = getWriter(display.getDisplayId());
         {
             const auto buffer = allocate(::android::PIXEL_FORMAT_RGBA_8888);
             ASSERT_NE(nullptr, buffer);
@@ -1160,15 +1169,15 @@
 
             configureLayer(display, layer, Composition::DEVICE, display.getFrameRect(),
                            display.getCrop());
-            mWriter.setLayerBuffer(display.getDisplayId(), layer, /*slot*/ 0, buffer->handle,
-                                   /*acquireFence*/ -1);
-            mWriter.setLayerDataspace(display.getDisplayId(), layer, common::Dataspace::UNKNOWN);
+            writer.setLayerBuffer(display.getDisplayId(), layer, /*slot*/ 0, buffer->handle,
+                                  /*acquireFence*/ -1);
+            writer.setLayerDataspace(display.getDisplayId(), layer, common::Dataspace::UNKNOWN);
 
-            mWriter.validateDisplay(display.getDisplayId(), ComposerClientWriter::kNoTimestamp);
+            writer.validateDisplay(display.getDisplayId(), ComposerClientWriter::kNoTimestamp);
             execute();
             ASSERT_TRUE(mReader.takeErrors().empty());
 
-            mWriter.presentDisplay(display.getDisplayId());
+            writer.presentDisplay(display.getDisplayId());
             execute();
             ASSERT_TRUE(mReader.takeErrors().empty());
         }
@@ -1177,15 +1186,15 @@
             const auto buffer = allocate(::android::PIXEL_FORMAT_RGBA_8888);
             ASSERT_NE(nullptr, buffer->handle);
 
-            mWriter.setLayerBuffer(display.getDisplayId(), layer, /*slot*/ 0, buffer->handle,
-                                   /*acquireFence*/ -1);
-            mWriter.setLayerSurfaceDamage(display.getDisplayId(), layer,
-                                          std::vector<Rect>(1, {0, 0, 10, 10}));
-            mWriter.validateDisplay(display.getDisplayId(), ComposerClientWriter::kNoTimestamp);
+            writer.setLayerBuffer(display.getDisplayId(), layer, /*slot*/ 0, buffer->handle,
+                                  /*acquireFence*/ -1);
+            writer.setLayerSurfaceDamage(display.getDisplayId(), layer,
+                                         std::vector<Rect>(1, {0, 0, 10, 10}));
+            writer.validateDisplay(display.getDisplayId(), ComposerClientWriter::kNoTimestamp);
             execute();
             ASSERT_TRUE(mReader.takeErrors().empty());
 
-            mWriter.presentDisplay(display.getDisplayId());
+            writer.presentDisplay(display.getDisplayId());
             execute();
         }
 
@@ -1194,11 +1203,12 @@
 
     sp<::android::Fence> presentAndGetFence(
             std::optional<ClockMonotonicTimestamp> expectedPresentTime) {
-        mWriter.validateDisplay(getPrimaryDisplayId(), expectedPresentTime);
+        auto& writer = getWriter(getPrimaryDisplayId());
+        writer.validateDisplay(getPrimaryDisplayId(), expectedPresentTime);
         execute();
         EXPECT_TRUE(mReader.takeErrors().empty());
 
-        mWriter.presentDisplay(getPrimaryDisplayId());
+        writer.presentDisplay(getPrimaryDisplayId());
         execute();
         EXPECT_TRUE(mReader.takeErrors().empty());
 
@@ -1230,7 +1240,8 @@
         FRect cropRect{0, 0, (float)getPrimaryDisplay().getDisplayWidth(),
                        (float)getPrimaryDisplay().getDisplayHeight()};
         configureLayer(getPrimaryDisplay(), layer, Composition::DEVICE, displayFrame, cropRect);
-        mWriter.setLayerDataspace(getPrimaryDisplayId(), layer, common::Dataspace::UNKNOWN);
+        auto& writer = getWriter(getPrimaryDisplayId());
+        writer.setLayerDataspace(getPrimaryDisplayId(), layer, common::Dataspace::UNKNOWN);
         return layer;
     }
 
@@ -1330,8 +1341,9 @@
         ASSERT_NE(nullptr, buffer2);
 
         const auto layer = createOnScreenLayer();
-        mWriter.setLayerBuffer(getPrimaryDisplayId(), layer, /*slot*/ 0, buffer1->handle,
-                               /*acquireFence*/ -1);
+        auto& writer = getWriter(getPrimaryDisplayId());
+        writer.setLayerBuffer(getPrimaryDisplayId(), layer, /*slot*/ 0, buffer1->handle,
+                              /*acquireFence*/ -1);
         const sp<::android::Fence> presentFence1 =
                 presentAndGetFence(ComposerClientWriter::kNoTimestamp);
         presentFence1->waitForever(LOG_TAG);
@@ -1341,8 +1353,8 @@
             expectedPresentTime += *framesDelay * vsyncPeriod;
         }
 
-        mWriter.setLayerBuffer(getPrimaryDisplayId(), layer, /*slot*/ 0, buffer2->handle,
-                               /*acquireFence*/ -1);
+        writer.setLayerBuffer(getPrimaryDisplayId(), layer, /*slot*/ 0, buffer2->handle,
+                              /*acquireFence*/ -1);
         const auto setExpectedPresentTime = [&]() -> std::optional<ClockMonotonicTimestamp> {
             if (!framesDelay.has_value()) {
                 return ComposerClientWriter::kNoTimestamp;
@@ -1363,17 +1375,18 @@
 
     void configureLayer(const VtsDisplay& display, int64_t layer, Composition composition,
                         const Rect& displayFrame, const FRect& cropRect) {
-        mWriter.setLayerCompositionType(display.getDisplayId(), layer, composition);
-        mWriter.setLayerDisplayFrame(display.getDisplayId(), layer, displayFrame);
-        mWriter.setLayerPlaneAlpha(display.getDisplayId(), layer, /*alpha*/ 1);
-        mWriter.setLayerSourceCrop(display.getDisplayId(), layer, cropRect);
-        mWriter.setLayerTransform(display.getDisplayId(), layer, static_cast<Transform>(0));
-        mWriter.setLayerVisibleRegion(display.getDisplayId(), layer,
-                                      std::vector<Rect>(1, displayFrame));
-        mWriter.setLayerZOrder(display.getDisplayId(), layer, /*z*/ 10);
-        mWriter.setLayerBlendMode(display.getDisplayId(), layer, BlendMode::NONE);
-        mWriter.setLayerSurfaceDamage(display.getDisplayId(), layer,
-                                      std::vector<Rect>(1, displayFrame));
+        auto& writer = getWriter(display.getDisplayId());
+        writer.setLayerCompositionType(display.getDisplayId(), layer, composition);
+        writer.setLayerDisplayFrame(display.getDisplayId(), layer, displayFrame);
+        writer.setLayerPlaneAlpha(display.getDisplayId(), layer, /*alpha*/ 1);
+        writer.setLayerSourceCrop(display.getDisplayId(), layer, cropRect);
+        writer.setLayerTransform(display.getDisplayId(), layer, static_cast<Transform>(0));
+        writer.setLayerVisibleRegion(display.getDisplayId(), layer,
+                                     std::vector<Rect>(1, displayFrame));
+        writer.setLayerZOrder(display.getDisplayId(), layer, /*z*/ 10);
+        writer.setLayerBlendMode(display.getDisplayId(), layer, BlendMode::NONE);
+        writer.setLayerSurfaceDamage(display.getDisplayId(), layer,
+                                     std::vector<Rect>(1, displayFrame));
     }
     // clang-format off
     const std::array<float, 16> kIdentity = {{
@@ -1384,12 +1397,20 @@
     }};
     // clang-format on
 
-    ComposerClientWriter mWriter;
+    ComposerClientWriter& getWriter(int64_t display) {
+        auto [it, _] = mWriters.try_emplace(display, display);
+        return it->second;
+    }
+
     ComposerClientReader mReader;
+
+  private:
+    std::unordered_map<int64_t, ComposerClientWriter> mWriters;
 };
 
 TEST_P(GraphicsComposerAidlCommandTest, SetColorTransform) {
-    mWriter.setColorTransform(getPrimaryDisplayId(), kIdentity.data());
+    auto& writer = getWriter(getPrimaryDisplayId());
+    writer.setColorTransform(getPrimaryDisplayId(), kIdentity.data());
     execute();
 }
 
@@ -1397,7 +1418,8 @@
     const auto& [status, layer] =
             mComposerClient->createLayer(getPrimaryDisplayId(), kBufferSlotCount);
     EXPECT_TRUE(status.isOk());
-    mWriter.setLayerColorTransform(getPrimaryDisplayId(), layer, kIdentity.data());
+    auto& writer = getWriter(getPrimaryDisplayId());
+    writer.setLayerColorTransform(getPrimaryDisplayId(), layer, kIdentity.data());
     execute();
 
     const auto errors = mReader.takeErrors();
@@ -1413,8 +1435,9 @@
     ASSERT_TRUE(status.isOk());
     bool brightnessSupport = std::find(capabilities.begin(), capabilities.end(),
                                        DisplayCapability::BRIGHTNESS) != capabilities.end();
+    auto& writer = getWriter(getPrimaryDisplayId());
     if (!brightnessSupport) {
-        mWriter.setDisplayBrightness(getPrimaryDisplayId(), /*brightness*/ 0.5f, -1.f);
+        writer.setDisplayBrightness(getPrimaryDisplayId(), /*brightness*/ 0.5f, -1.f);
         execute();
         const auto errors = mReader.takeErrors();
         EXPECT_EQ(1, errors.size());
@@ -1423,23 +1446,23 @@
         return;
     }
 
-    mWriter.setDisplayBrightness(getPrimaryDisplayId(), /*brightness*/ 0.0f, -1.f);
+    writer.setDisplayBrightness(getPrimaryDisplayId(), /*brightness*/ 0.0f, -1.f);
     execute();
     EXPECT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setDisplayBrightness(getPrimaryDisplayId(), /*brightness*/ 0.5f, -1.f);
+    writer.setDisplayBrightness(getPrimaryDisplayId(), /*brightness*/ 0.5f, -1.f);
     execute();
     EXPECT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setDisplayBrightness(getPrimaryDisplayId(), /*brightness*/ 1.0f, -1.f);
+    writer.setDisplayBrightness(getPrimaryDisplayId(), /*brightness*/ 1.0f, -1.f);
     execute();
     EXPECT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setDisplayBrightness(getPrimaryDisplayId(), /*brightness*/ -1.0f, -1.f);
+    writer.setDisplayBrightness(getPrimaryDisplayId(), /*brightness*/ -1.0f, -1.f);
     execute();
     EXPECT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setDisplayBrightness(getPrimaryDisplayId(), /*brightness*/ 2.0f, -1.f);
+    writer.setDisplayBrightness(getPrimaryDisplayId(), /*brightness*/ 2.0f, -1.f);
     execute();
     {
         const auto errors = mReader.takeErrors();
@@ -1447,7 +1470,7 @@
         EXPECT_EQ(IComposerClient::EX_BAD_PARAMETER, errors[0].errorCode);
     }
 
-    mWriter.setDisplayBrightness(getPrimaryDisplayId(), /*brightness*/ -2.0f, -1.f);
+    writer.setDisplayBrightness(getPrimaryDisplayId(), /*brightness*/ -2.0f, -1.f);
     execute();
     {
         const auto errors = mReader.takeErrors();
@@ -1460,8 +1483,9 @@
     EXPECT_TRUE(mComposerClient->setClientTargetSlotCount(getPrimaryDisplayId(), kBufferSlotCount)
                         .isOk());
 
-    mWriter.setClientTarget(getPrimaryDisplayId(), /*slot*/ 0, nullptr, /*acquireFence*/ -1,
-                            Dataspace::UNKNOWN, std::vector<Rect>());
+    auto& writer = getWriter(getPrimaryDisplayId());
+    writer.setClientTarget(getPrimaryDisplayId(), /*slot*/ 0, nullptr, /*acquireFence*/ -1,
+                           Dataspace::UNKNOWN, std::vector<Rect>());
 
     execute();
 }
@@ -1481,24 +1505,28 @@
 
     const auto buffer = allocate(::android::PIXEL_FORMAT_RGBA_8888);
     const auto handle = buffer->handle;
-    mWriter.setOutputBuffer(display.display, /*slot*/ 0, handle, /*releaseFence*/ -1);
+    auto& writer = getWriter(display.display);
+    writer.setOutputBuffer(display.display, /*slot*/ 0, handle, /*releaseFence*/ -1);
     execute();
 }
 
 TEST_P(GraphicsComposerAidlCommandTest, ValidDisplay) {
-    mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+    auto& writer = getWriter(getPrimaryDisplayId());
+    writer.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
     execute();
 }
 
 TEST_P(GraphicsComposerAidlCommandTest, AcceptDisplayChanges) {
-    mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
-    mWriter.acceptDisplayChanges(getPrimaryDisplayId());
+    auto& writer = getWriter(getPrimaryDisplayId());
+    writer.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+    writer.acceptDisplayChanges(getPrimaryDisplayId());
     execute();
 }
 
 TEST_P(GraphicsComposerAidlCommandTest, PresentDisplay) {
-    mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
-    mWriter.presentDisplay(getPrimaryDisplayId());
+    auto& writer = getWriter(getPrimaryDisplayId());
+    writer.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+    writer.presentDisplay(getPrimaryDisplayId());
     execute();
 }
 
@@ -1519,6 +1547,7 @@
     const auto& [renderIntentsStatus, renderIntents] =
             mComposerClient->getRenderIntents(getPrimaryDisplayId(), ColorMode::NATIVE);
     EXPECT_TRUE(renderIntentsStatus.isOk());
+    auto& writer = getWriter(getPrimaryDisplayId());
     for (auto intent : renderIntents) {
         EXPECT_TRUE(mComposerClient->setColorMode(getPrimaryDisplayId(), ColorMode::NATIVE, intent)
                             .isOk());
@@ -1536,10 +1565,10 @@
         FRect cropRect{0, 0, (float)getPrimaryDisplay().getDisplayWidth(),
                        (float)getPrimaryDisplay().getDisplayHeight()};
         configureLayer(getPrimaryDisplay(), layer, Composition::CURSOR, displayFrame, cropRect);
-        mWriter.setLayerBuffer(getPrimaryDisplayId(), layer, /*slot*/ 0, handle,
-                               /*acquireFence*/ -1);
-        mWriter.setLayerDataspace(getPrimaryDisplayId(), layer, Dataspace::UNKNOWN);
-        mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+        writer.setLayerBuffer(getPrimaryDisplayId(), layer, /*slot*/ 0, handle,
+                              /*acquireFence*/ -1);
+        writer.setLayerDataspace(getPrimaryDisplayId(), layer, Dataspace::UNKNOWN);
+        writer.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
         execute();
         if (!mReader.takeChangedCompositionTypes(getPrimaryDisplayId()).empty()) {
             GTEST_SUCCEED() << "Composition change requested, skipping test";
@@ -1547,18 +1576,18 @@
         }
 
         ASSERT_TRUE(mReader.takeErrors().empty());
-        mWriter.presentDisplay(getPrimaryDisplayId());
+        writer.presentDisplay(getPrimaryDisplayId());
         execute();
         ASSERT_TRUE(mReader.takeErrors().empty());
 
         const auto buffer2 = allocate(::android::PIXEL_FORMAT_RGBA_8888);
         const auto handle2 = buffer2->handle;
         ASSERT_NE(nullptr, handle2);
-        mWriter.setLayerBuffer(getPrimaryDisplayId(), layer, /*slot*/ 0, handle2,
-                               /*acquireFence*/ -1);
-        mWriter.setLayerSurfaceDamage(getPrimaryDisplayId(), layer,
-                                      std::vector<Rect>(1, {0, 0, 10, 10}));
-        mWriter.presentDisplay(getPrimaryDisplayId());
+        writer.setLayerBuffer(getPrimaryDisplayId(), layer, /*slot*/ 0, handle2,
+                              /*acquireFence*/ -1);
+        writer.setLayerSurfaceDamage(getPrimaryDisplayId(), layer,
+                                     std::vector<Rect>(1, {0, 0, 10, 10}));
+        writer.presentDisplay(getPrimaryDisplayId());
         execute();
     }
 }
@@ -1572,15 +1601,16 @@
     const auto handle = buffer->handle;
     ASSERT_NE(nullptr, handle);
 
-    mWriter.setLayerBuffer(getPrimaryDisplayId(), layer, /*slot*/ 0, handle, /*acquireFence*/ -1);
+    auto& writer = getWriter(getPrimaryDisplayId());
+    writer.setLayerBuffer(getPrimaryDisplayId(), layer, /*slot*/ 0, handle, /*acquireFence*/ -1);
 
     Rect displayFrame{0, 0, getPrimaryDisplay().getDisplayWidth(),
                       getPrimaryDisplay().getDisplayHeight()};
     FRect cropRect{0, 0, (float)getPrimaryDisplay().getDisplayWidth(),
                    (float)getPrimaryDisplay().getDisplayHeight()};
     configureLayer(getPrimaryDisplay(), layer, Composition::CURSOR, displayFrame, cropRect);
-    mWriter.setLayerDataspace(getPrimaryDisplayId(), layer, Dataspace::UNKNOWN);
-    mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+    writer.setLayerDataspace(getPrimaryDisplayId(), layer, Dataspace::UNKNOWN);
+    writer.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
 
     execute();
 
@@ -1588,15 +1618,15 @@
         GTEST_SUCCEED() << "Composition change requested, skipping test";
         return;
     }
-    mWriter.presentDisplay(getPrimaryDisplayId());
+    writer.presentDisplay(getPrimaryDisplayId());
     ASSERT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setLayerCursorPosition(getPrimaryDisplayId(), layer, /*x*/ 1, /*y*/ 1);
+    writer.setLayerCursorPosition(getPrimaryDisplayId(), layer, /*x*/ 1, /*y*/ 1);
     execute();
 
-    mWriter.setLayerCursorPosition(getPrimaryDisplayId(), layer, /*x*/ 0, /*y*/ 0);
-    mWriter.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
-    mWriter.presentDisplay(getPrimaryDisplayId());
+    writer.setLayerCursorPosition(getPrimaryDisplayId(), layer, /*x*/ 0, /*y*/ 0);
+    writer.validateDisplay(getPrimaryDisplayId(), ComposerClientWriter::kNoTimestamp);
+    writer.presentDisplay(getPrimaryDisplayId());
     execute();
 }
 
@@ -1608,7 +1638,8 @@
     const auto& [layerStatus, layer] =
             mComposerClient->createLayer(getPrimaryDisplayId(), kBufferSlotCount);
     EXPECT_TRUE(layerStatus.isOk());
-    mWriter.setLayerBuffer(getPrimaryDisplayId(), layer, /*slot*/ 0, handle, /*acquireFence*/ -1);
+    auto& writer = getWriter(getPrimaryDisplayId());
+    writer.setLayerBuffer(getPrimaryDisplayId(), layer, /*slot*/ 0, handle, /*acquireFence*/ -1);
     execute();
 }
 
@@ -1620,15 +1651,16 @@
     Rect empty{0, 0, 0, 0};
     Rect unit{0, 0, 1, 1};
 
-    mWriter.setLayerSurfaceDamage(getPrimaryDisplayId(), layer, std::vector<Rect>(1, empty));
+    auto& writer = getWriter(getPrimaryDisplayId());
+    writer.setLayerSurfaceDamage(getPrimaryDisplayId(), layer, std::vector<Rect>(1, empty));
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setLayerSurfaceDamage(getPrimaryDisplayId(), layer, std::vector<Rect>(1, unit));
+    writer.setLayerSurfaceDamage(getPrimaryDisplayId(), layer, std::vector<Rect>(1, unit));
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setLayerSurfaceDamage(getPrimaryDisplayId(), layer, std::vector<Rect>());
+    writer.setLayerSurfaceDamage(getPrimaryDisplayId(), layer, std::vector<Rect>());
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 }
@@ -1641,15 +1673,16 @@
     Rect empty{0, 0, 0, 0};
     Rect unit{0, 0, 1, 1};
 
-    mWriter.setLayerBlockingRegion(getPrimaryDisplayId(), layer, std::vector<Rect>(1, empty));
+    auto& writer = getWriter(getPrimaryDisplayId());
+    writer.setLayerBlockingRegion(getPrimaryDisplayId(), layer, std::vector<Rect>(1, empty));
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setLayerBlockingRegion(getPrimaryDisplayId(), layer, std::vector<Rect>(1, unit));
+    writer.setLayerBlockingRegion(getPrimaryDisplayId(), layer, std::vector<Rect>(1, unit));
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setLayerBlockingRegion(getPrimaryDisplayId(), layer, std::vector<Rect>());
+    writer.setLayerBlockingRegion(getPrimaryDisplayId(), layer, std::vector<Rect>());
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 }
@@ -1659,15 +1692,16 @@
             mComposerClient->createLayer(getPrimaryDisplayId(), kBufferSlotCount);
     EXPECT_TRUE(layerStatus.isOk());
 
-    mWriter.setLayerBlendMode(getPrimaryDisplayId(), layer, BlendMode::NONE);
+    auto& writer = getWriter(getPrimaryDisplayId());
+    writer.setLayerBlendMode(getPrimaryDisplayId(), layer, BlendMode::NONE);
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setLayerBlendMode(getPrimaryDisplayId(), layer, BlendMode::PREMULTIPLIED);
+    writer.setLayerBlendMode(getPrimaryDisplayId(), layer, BlendMode::PREMULTIPLIED);
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setLayerBlendMode(getPrimaryDisplayId(), layer, BlendMode::COVERAGE);
+    writer.setLayerBlendMode(getPrimaryDisplayId(), layer, BlendMode::COVERAGE);
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 }
@@ -1677,11 +1711,12 @@
             mComposerClient->createLayer(getPrimaryDisplayId(), kBufferSlotCount);
     EXPECT_TRUE(layerStatus.isOk());
 
-    mWriter.setLayerColor(getPrimaryDisplayId(), layer, Color{1.0f, 1.0f, 1.0f, 1.0f});
+    auto& writer = getWriter(getPrimaryDisplayId());
+    writer.setLayerColor(getPrimaryDisplayId(), layer, Color{1.0f, 1.0f, 1.0f, 1.0f});
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setLayerColor(getPrimaryDisplayId(), layer, Color{0.0f, 0.0f, 0.0f, 0.0f});
+    writer.setLayerColor(getPrimaryDisplayId(), layer, Color{0.0f, 0.0f, 0.0f, 0.0f});
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 }
@@ -1691,19 +1726,20 @@
             mComposerClient->createLayer(getPrimaryDisplayId(), kBufferSlotCount);
     EXPECT_TRUE(layerStatus.isOk());
 
-    mWriter.setLayerCompositionType(getPrimaryDisplayId(), layer, Composition::CLIENT);
+    auto& writer = getWriter(getPrimaryDisplayId());
+    writer.setLayerCompositionType(getPrimaryDisplayId(), layer, Composition::CLIENT);
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setLayerCompositionType(getPrimaryDisplayId(), layer, Composition::DEVICE);
+    writer.setLayerCompositionType(getPrimaryDisplayId(), layer, Composition::DEVICE);
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setLayerCompositionType(getPrimaryDisplayId(), layer, Composition::SOLID_COLOR);
+    writer.setLayerCompositionType(getPrimaryDisplayId(), layer, Composition::SOLID_COLOR);
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setLayerCompositionType(getPrimaryDisplayId(), layer, Composition::CURSOR);
+    writer.setLayerCompositionType(getPrimaryDisplayId(), layer, Composition::CURSOR);
     execute();
 }
 
@@ -1734,9 +1770,10 @@
 
         configureLayer(display, layer, Composition::DISPLAY_DECORATION, display.getFrameRect(),
                           display.getCrop());
-        mWriter.setLayerBuffer(display.getDisplayId(), layer, /*slot*/ 0, decorBuffer->handle,
-                               /*acquireFence*/ -1);
-        mWriter.validateDisplay(display.getDisplayId(), ComposerClientWriter::kNoTimestamp);
+        auto& writer = getWriter(display.getDisplayId());
+        writer.setLayerBuffer(display.getDisplayId(), layer, /*slot*/ 0, decorBuffer->handle,
+                              /*acquireFence*/ -1);
+        writer.validateDisplay(display.getDisplayId(), ComposerClientWriter::kNoTimestamp);
         execute();
         if (support) {
             ASSERT_TRUE(mReader.takeErrors().empty());
@@ -1753,7 +1790,8 @@
             mComposerClient->createLayer(getPrimaryDisplayId(), kBufferSlotCount);
     EXPECT_TRUE(layerStatus.isOk());
 
-    mWriter.setLayerDataspace(getPrimaryDisplayId(), layer, Dataspace::UNKNOWN);
+    auto& writer = getWriter(getPrimaryDisplayId());
+    writer.setLayerDataspace(getPrimaryDisplayId(), layer, Dataspace::UNKNOWN);
     execute();
 }
 
@@ -1762,7 +1800,8 @@
             mComposerClient->createLayer(getPrimaryDisplayId(), kBufferSlotCount);
     EXPECT_TRUE(layerStatus.isOk());
 
-    mWriter.setLayerDisplayFrame(getPrimaryDisplayId(), layer, Rect{0, 0, 1, 1});
+    auto& writer = getWriter(getPrimaryDisplayId());
+    writer.setLayerDisplayFrame(getPrimaryDisplayId(), layer, Rect{0, 0, 1, 1});
     execute();
 }
 
@@ -1771,11 +1810,12 @@
             mComposerClient->createLayer(getPrimaryDisplayId(), kBufferSlotCount);
     EXPECT_TRUE(layerStatus.isOk());
 
-    mWriter.setLayerPlaneAlpha(getPrimaryDisplayId(), layer, /*alpha*/ 0.0f);
+    auto& writer = getWriter(getPrimaryDisplayId());
+    writer.setLayerPlaneAlpha(getPrimaryDisplayId(), layer, /*alpha*/ 0.0f);
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setLayerPlaneAlpha(getPrimaryDisplayId(), layer, /*alpha*/ 1.0f);
+    writer.setLayerPlaneAlpha(getPrimaryDisplayId(), layer, /*alpha*/ 1.0f);
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 }
@@ -1794,7 +1834,8 @@
             mComposerClient->createLayer(getPrimaryDisplayId(), kBufferSlotCount);
     EXPECT_TRUE(layerStatus.isOk());
 
-    mWriter.setLayerSidebandStream(getPrimaryDisplayId(), layer, handle);
+    auto& writer = getWriter(getPrimaryDisplayId());
+    writer.setLayerSidebandStream(getPrimaryDisplayId(), layer, handle);
     execute();
 }
 
@@ -1803,7 +1844,8 @@
             mComposerClient->createLayer(getPrimaryDisplayId(), kBufferSlotCount);
     EXPECT_TRUE(layerStatus.isOk());
 
-    mWriter.setLayerSourceCrop(getPrimaryDisplayId(), layer, FRect{0.0f, 0.0f, 1.0f, 1.0f});
+    auto& writer = getWriter(getPrimaryDisplayId());
+    writer.setLayerSourceCrop(getPrimaryDisplayId(), layer, FRect{0.0f, 0.0f, 1.0f, 1.0f});
     execute();
 }
 
@@ -1812,39 +1854,40 @@
             mComposerClient->createLayer(getPrimaryDisplayId(), kBufferSlotCount);
     EXPECT_TRUE(layerStatus.isOk());
 
-    mWriter.setLayerTransform(getPrimaryDisplayId(), layer, static_cast<Transform>(0));
+    auto& writer = getWriter(getPrimaryDisplayId());
+    writer.setLayerTransform(getPrimaryDisplayId(), layer, static_cast<Transform>(0));
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setLayerTransform(getPrimaryDisplayId(), layer, Transform::FLIP_H);
+    writer.setLayerTransform(getPrimaryDisplayId(), layer, Transform::FLIP_H);
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setLayerTransform(getPrimaryDisplayId(), layer, Transform::FLIP_V);
+    writer.setLayerTransform(getPrimaryDisplayId(), layer, Transform::FLIP_V);
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setLayerTransform(getPrimaryDisplayId(), layer, Transform::ROT_90);
+    writer.setLayerTransform(getPrimaryDisplayId(), layer, Transform::ROT_90);
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setLayerTransform(getPrimaryDisplayId(), layer, Transform::ROT_180);
+    writer.setLayerTransform(getPrimaryDisplayId(), layer, Transform::ROT_180);
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setLayerTransform(getPrimaryDisplayId(), layer, Transform::ROT_270);
+    writer.setLayerTransform(getPrimaryDisplayId(), layer, Transform::ROT_270);
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setLayerTransform(getPrimaryDisplayId(), layer,
-                              static_cast<Transform>(static_cast<int>(Transform::FLIP_H) |
-                                                     static_cast<int>(Transform::ROT_90)));
+    writer.setLayerTransform(getPrimaryDisplayId(), layer,
+                             static_cast<Transform>(static_cast<int>(Transform::FLIP_H) |
+                                                    static_cast<int>(Transform::ROT_90)));
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setLayerTransform(getPrimaryDisplayId(), layer,
-                              static_cast<Transform>(static_cast<int>(Transform::FLIP_V) |
-                                                     static_cast<int>(Transform::ROT_90)));
+    writer.setLayerTransform(getPrimaryDisplayId(), layer,
+                             static_cast<Transform>(static_cast<int>(Transform::FLIP_V) |
+                                                    static_cast<int>(Transform::ROT_90)));
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 }
@@ -1857,15 +1900,16 @@
     Rect empty{0, 0, 0, 0};
     Rect unit{0, 0, 1, 1};
 
-    mWriter.setLayerVisibleRegion(getPrimaryDisplayId(), layer, std::vector<Rect>(1, empty));
+    auto& writer = getWriter(getPrimaryDisplayId());
+    writer.setLayerVisibleRegion(getPrimaryDisplayId(), layer, std::vector<Rect>(1, empty));
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setLayerVisibleRegion(getPrimaryDisplayId(), layer, std::vector<Rect>(1, unit));
+    writer.setLayerVisibleRegion(getPrimaryDisplayId(), layer, std::vector<Rect>(1, unit));
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setLayerVisibleRegion(getPrimaryDisplayId(), layer, std::vector<Rect>());
+    writer.setLayerVisibleRegion(getPrimaryDisplayId(), layer, std::vector<Rect>());
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 }
@@ -1875,11 +1919,12 @@
             mComposerClient->createLayer(getPrimaryDisplayId(), kBufferSlotCount);
     EXPECT_TRUE(layerStatus.isOk());
 
-    mWriter.setLayerZOrder(getPrimaryDisplayId(), layer, /*z*/ 10);
+    auto& writer = getWriter(getPrimaryDisplayId());
+    writer.setLayerZOrder(getPrimaryDisplayId(), layer, /*z*/ 10);
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setLayerZOrder(getPrimaryDisplayId(), layer, /*z*/ 0);
+    writer.setLayerZOrder(getPrimaryDisplayId(), layer, /*z*/ 0);
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 }
@@ -1901,6 +1946,7 @@
      *  white (D65)     0.3127  0.3290
      */
 
+    auto& writer = getWriter(getPrimaryDisplayId());
     std::vector<PerFrameMetadata> aidlMetadata;
     aidlMetadata.push_back({PerFrameMetadataKey::DISPLAY_RED_PRIMARY_X, 0.680f});
     aidlMetadata.push_back({PerFrameMetadataKey::DISPLAY_RED_PRIMARY_Y, 0.320f});
@@ -1914,7 +1960,7 @@
     aidlMetadata.push_back({PerFrameMetadataKey::MIN_LUMINANCE, 0.1f});
     aidlMetadata.push_back({PerFrameMetadataKey::MAX_CONTENT_LIGHT_LEVEL, 78.0});
     aidlMetadata.push_back({PerFrameMetadataKey::MAX_FRAME_AVERAGE_LIGHT_LEVEL, 62.0});
-    mWriter.setLayerPerFrameMetadata(getPrimaryDisplayId(), layer, aidlMetadata);
+    writer.setLayerPerFrameMetadata(getPrimaryDisplayId(), layer, aidlMetadata);
     execute();
 
     const auto errors = mReader.takeErrors();
@@ -1931,19 +1977,20 @@
     const auto& [layerStatus, layer] =
             mComposerClient->createLayer(getPrimaryDisplayId(), kBufferSlotCount);
 
-    mWriter.setLayerBrightness(getPrimaryDisplayId(), layer, 0.2f);
+    auto& writer = getWriter(getPrimaryDisplayId());
+    writer.setLayerBrightness(getPrimaryDisplayId(), layer, 0.2f);
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setLayerBrightness(getPrimaryDisplayId(), layer, 1.f);
+    writer.setLayerBrightness(getPrimaryDisplayId(), layer, 1.f);
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setLayerBrightness(getPrimaryDisplayId(), layer, 0.f);
+    writer.setLayerBrightness(getPrimaryDisplayId(), layer, 0.f);
     execute();
     ASSERT_TRUE(mReader.takeErrors().empty());
 
-    mWriter.setLayerBrightness(getPrimaryDisplayId(), layer, -1.f);
+    writer.setLayerBrightness(getPrimaryDisplayId(), layer, -1.f);
     execute();
     {
         const auto errors = mReader.takeErrors();
@@ -1951,7 +1998,7 @@
         EXPECT_EQ(IComposerClient::EX_BAD_PARAMETER, errors[0].errorCode);
     }
 
-    mWriter.setLayerBrightness(getPrimaryDisplayId(), layer, std::nanf(""));
+    writer.setLayerBrightness(getPrimaryDisplayId(), layer, std::nanf(""));
     execute();
     {
         const auto errors = mReader.takeErrors();
@@ -2116,8 +2163,9 @@
     ASSERT_NE(nullptr, buffer->handle);
 
     const auto layer = createOnScreenLayer();
-    mWriter.setLayerBuffer(getPrimaryDisplayId(), layer, /*slot*/ 0, buffer->handle,
-                           /*acquireFence*/ -1);
+    auto& writer = getWriter(getPrimaryDisplayId());
+    writer.setLayerBuffer(getPrimaryDisplayId(), layer, /*slot*/ 0, buffer->handle,
+                          /*acquireFence*/ -1);
     int32_t vsyncIdleCount = mComposerClient->getVsyncIdleCount();
     auto earlyVsyncIdleTime = systemTime() + std::chrono::nanoseconds(2s).count();
     EXPECT_TRUE(