diff --git a/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/HwcBufferCache.h b/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/HwcBufferCache.h
index 02d7890..97bdc8f 100644
--- a/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/HwcBufferCache.h
+++ b/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/HwcBufferCache.h
@@ -45,7 +45,7 @@
     //
     // outBuffer is set to buffer when buffer is not in the HWC cache;
     // otherwise, outBuffer is set to nullptr.
-    void getHwcBuffer(const sp<GraphicBuffer>& buffer, uint32_t* outSlot,
+    void getHwcBuffer(int slot, const sp<GraphicBuffer>& buffer, uint32_t* outSlot,
                       sp<GraphicBuffer>* outBuffer);
 
 protected:
diff --git a/services/surfaceflinger/CompositionEngine/src/HwcBufferCache.cpp b/services/surfaceflinger/CompositionEngine/src/HwcBufferCache.cpp
index 8613210..a941e09 100644
--- a/services/surfaceflinger/CompositionEngine/src/HwcBufferCache.cpp
+++ b/services/surfaceflinger/CompositionEngine/src/HwcBufferCache.cpp
@@ -48,12 +48,20 @@
     return std::distance(std::begin(mBuffers), iter);
 }
 
-void HwcBufferCache::getHwcBuffer(const sp<GraphicBuffer>& buffer, uint32_t* outSlot,
+void HwcBufferCache::getHwcBuffer(int slot, const sp<GraphicBuffer>& buffer, uint32_t* outSlot,
                                   sp<GraphicBuffer>* outBuffer) {
-    bool cached = getSlot(buffer, outSlot);
+    // if this slot corresponds to a BufferStateLayer, generate the slot
+    if (slot == BufferQueue::INVALID_BUFFER_SLOT) {
+        getSlot(buffer, outSlot);
+    } else if (slot < 0 || slot >= BufferQueue::NUM_BUFFER_SLOTS) {
+        *outSlot = 0;
+    } else {
+        *outSlot = slot;
+    }
 
     auto& [currentCounter, currentBuffer] = mBuffers[*outSlot];
-    if (cached) {
+    wp<GraphicBuffer> weakCopy(buffer);
+    if (currentBuffer == weakCopy) {
         // already cached in HWC, skip sending the buffer
         *outBuffer = nullptr;
         currentCounter = getCounter();
diff --git a/services/surfaceflinger/CompositionEngine/tests/HwcBufferCacheTest.cpp b/services/surfaceflinger/CompositionEngine/tests/HwcBufferCacheTest.cpp
index ac04cb3..b261493 100644
--- a/services/surfaceflinger/CompositionEngine/tests/HwcBufferCacheTest.cpp
+++ b/services/surfaceflinger/CompositionEngine/tests/HwcBufferCacheTest.cpp
@@ -24,9 +24,9 @@
 
 class TestableHwcBufferCache : public impl::HwcBufferCache {
 public:
-    void getHwcBuffer(const sp<GraphicBuffer>& buffer, uint32_t* outSlot,
+    void getHwcBuffer(int slot, const sp<GraphicBuffer>& buffer, uint32_t* outSlot,
                       sp<GraphicBuffer>* outBuffer) {
-        HwcBufferCache::getHwcBuffer(buffer, outSlot, outBuffer);
+        HwcBufferCache::getHwcBuffer(slot, buffer, outSlot, outBuffer);
     }
     bool getSlot(const sp<GraphicBuffer>& buffer, uint32_t* outSlot) {
         return HwcBufferCache::getSlot(buffer, outSlot);
@@ -38,64 +38,88 @@
 public:
     ~HwcBufferCacheTest() override = default;
 
-    TestableHwcBufferCache mCache;
+    void testSlot(const int inSlot, const uint32_t expectedSlot) {
+        uint32_t outSlot;
+        sp<GraphicBuffer> outBuffer;
+
+        // The first time, the output  is the same as the input
+        mCache.getHwcBuffer(inSlot, mBuffer1, &outSlot, &outBuffer);
+        EXPECT_EQ(expectedSlot, outSlot);
+        EXPECT_EQ(mBuffer1, outBuffer);
+
+        // The second time with the same buffer, the outBuffer is nullptr.
+        mCache.getHwcBuffer(inSlot, mBuffer1, &outSlot, &outBuffer);
+        EXPECT_EQ(expectedSlot, outSlot);
+        EXPECT_EQ(nullptr, outBuffer.get());
+
+        // With a new buffer, the outBuffer is the input.
+        mCache.getHwcBuffer(inSlot, mBuffer2, &outSlot, &outBuffer);
+        EXPECT_EQ(expectedSlot, outSlot);
+        EXPECT_EQ(mBuffer2, outBuffer);
+
+        // Again, the second request with the same buffer sets outBuffer to nullptr.
+        mCache.getHwcBuffer(inSlot, mBuffer2, &outSlot, &outBuffer);
+        EXPECT_EQ(expectedSlot, outSlot);
+        EXPECT_EQ(nullptr, outBuffer.get());
+
+        // Setting a slot to use nullptr lookslike works, but note that
+        // the output values make it look like no new buffer is being set....
+        mCache.getHwcBuffer(inSlot, sp<GraphicBuffer>(), &outSlot, &outBuffer);
+        EXPECT_EQ(expectedSlot, outSlot);
+        EXPECT_EQ(nullptr, outBuffer.get());
+    }
+
+    impl::HwcBufferCache mCache;
     sp<GraphicBuffer> mBuffer1{new GraphicBuffer(1, 1, HAL_PIXEL_FORMAT_RGBA_8888, 1, 0)};
     sp<GraphicBuffer> mBuffer2{new GraphicBuffer(1, 1, HAL_PIXEL_FORMAT_RGBA_8888, 1, 0)};
 };
 
-TEST_F(HwcBufferCacheTest, testSlot) {
+TEST_F(HwcBufferCacheTest, cacheWorksForSlotZero) {
+    testSlot(0, 0);
+}
+
+TEST_F(HwcBufferCacheTest, cacheWorksForMaxSlot) {
+    testSlot(BufferQueue::NUM_BUFFER_SLOTS - 1, BufferQueue::NUM_BUFFER_SLOTS - 1);
+}
+
+TEST_F(HwcBufferCacheTest, cacheMapsNegativeSlotToZero) {
+    testSlot(-123, 0);
+}
+
+TEST_F(HwcBufferCacheTest, cacheGeneratesSlotForInvalidBufferSlot) {
     uint32_t outSlot;
     sp<GraphicBuffer> outBuffer;
 
-    // The first time, the output  is the same as the input
-    mCache.getHwcBuffer(mBuffer1, &outSlot, &outBuffer);
+    mCache.getHwcBuffer(BufferQueue::INVALID_BUFFER_SLOT, mBuffer1, &outSlot, &outBuffer);
     EXPECT_EQ(0, outSlot);
     EXPECT_EQ(mBuffer1, outBuffer);
 
-    // The second time with the same buffer, the outBuffer is nullptr.
-    mCache.getHwcBuffer(mBuffer1, &outSlot, &outBuffer);
+    mCache.getHwcBuffer(BufferQueue::INVALID_BUFFER_SLOT, mBuffer1, &outSlot, &outBuffer);
     EXPECT_EQ(0, outSlot);
     EXPECT_EQ(nullptr, outBuffer.get());
 
-    // With a new buffer, the outBuffer is the input.
-    mCache.getHwcBuffer(mBuffer2, &outSlot, &outBuffer);
+    mCache.getHwcBuffer(BufferQueue::INVALID_BUFFER_SLOT, mBuffer2, &outSlot, &outBuffer);
     EXPECT_EQ(1, outSlot);
     EXPECT_EQ(mBuffer2, outBuffer);
 
-    // Again, the second request with the same buffer sets outBuffer to nullptr.
-    mCache.getHwcBuffer(mBuffer2, &outSlot, &outBuffer);
+    mCache.getHwcBuffer(BufferQueue::INVALID_BUFFER_SLOT, mBuffer2, &outSlot, &outBuffer);
     EXPECT_EQ(1, outSlot);
     EXPECT_EQ(nullptr, outBuffer.get());
 
-    // Setting a slot to use nullptr lookslike works, but note that
-    // the output values make it look like no new buffer is being set....
-    mCache.getHwcBuffer(sp<GraphicBuffer>(), &outSlot, &outBuffer);
+    mCache.getHwcBuffer(BufferQueue::INVALID_BUFFER_SLOT, sp<GraphicBuffer>(), &outSlot,
+                        &outBuffer);
     EXPECT_EQ(2, outSlot);
     EXPECT_EQ(nullptr, outBuffer.get());
-}
 
-TEST_F(HwcBufferCacheTest, testGetLeastRecentlyUsedSlot) {
-    int slot;
-    uint32_t outSlot;
-    sp<GraphicBuffer> outBuffer;
-
-    // fill up cache
-    for (int i = 0; i < BufferQueue::NUM_BUFFER_SLOTS; i++) {
-        sp<GraphicBuffer> buf{new GraphicBuffer(1, 1, HAL_PIXEL_FORMAT_RGBA_8888, 1, 0)};
-        mCache.getHwcBuffer(buf, &outSlot, &outBuffer);
-        EXPECT_EQ(buf, outBuffer);
-        EXPECT_EQ(i, outSlot);
-    }
-
-    slot = mCache.getLeastRecentlyUsedSlot();
-    EXPECT_EQ(0, slot);
-
-    mCache.getHwcBuffer(mBuffer1, &outSlot, &outBuffer);
-    EXPECT_EQ(0, outSlot);
+    // note that sending mBuffer1 with explicit slot 1 will overwrite mBuffer2
+    // and also cause mBuffer1 to be stored in two places
+    mCache.getHwcBuffer(1, mBuffer1, &outSlot, &outBuffer);
+    EXPECT_EQ(1, outSlot);
     EXPECT_EQ(mBuffer1, outBuffer);
 
-    slot = mCache.getLeastRecentlyUsedSlot();
-    EXPECT_EQ(1, slot);
+    mCache.getHwcBuffer(BufferQueue::INVALID_BUFFER_SLOT, mBuffer2, &outSlot, &outBuffer);
+    EXPECT_EQ(3, outSlot);
+    EXPECT_EQ(mBuffer2, outBuffer);
 }
 
 } // namespace