BQ: Add support for single buffer mode

- Adds a single buffer mode to BufferQueue. In this mode designate the
  first dequeued buffer as the shared buffer. All calls to dequeue()
  and acquire() will then return the shared buffer, allowing the
  producer and consumer to share it.
- Modify the buffer slot state tracking. Add a new SHARED state for
  the shared buffer in single buffer mode. Also track how many times
  a buffer has been dequeued/queued/acquired as it's possible for a
  shared buffer to be both dequeued and acquired at the same time, or
  dequeued/acquired multiple times. This tracking is needed to know
  when to drop the buffer out of the SHARED state after single buffer
  mode has been disabled.
- Add plumbing for enabling/disabling single buffer mode from Surface.

Bug 24940410

Change-Id: I3fc550c74bacb5523c049a227111356257386853

1 files changed, 151 insertions, 61 deletions

diff --git a/libs/gui/BufferQueueProducer.cpp b/libs/gui/BufferQueueProducer.cpp
index 9ef8ff715f..268c9da0de 100644
--- a/libs/gui/BufferQueueProducer.cpp
+++ b/libs/gui/BufferQueueProducer.cpp
@@ -66,9 +66,9 @@ status_t BufferQueueProducer::requestBuffer(int slot, sp<GraphicBuffer>* buf) {
         BQ_LOGE("requestBuffer: slot index %d out of range [0, %d)",
                 slot, BufferQueueDefs::NUM_BUFFER_SLOTS);
         return BAD_VALUE;
-    } else if (mSlots[slot].mBufferState != BufferSlot::DEQUEUED) {
+    } else if (!mSlots[slot].mBufferState.isDequeued()) {
         BQ_LOGE("requestBuffer: slot %d is not owned by the producer "
-                "(state = %d)", slot, mSlots[slot].mBufferState);
+                "(state = %s)", slot, mSlots[slot].mBufferState.string());
         return BAD_VALUE;
     }
 
@@ -96,7 +96,7 @@ status_t BufferQueueProducer::setMaxDequeuedBufferCount(
 
         // There must be no dequeued buffers when changing the buffer count.
         for (int s = 0; s < BufferQueueDefs::NUM_BUFFER_SLOTS; ++s) {
-            if (mSlots[s].mBufferState == BufferSlot::DEQUEUED) {
+            if (mSlots[s].mBufferState.isDequeued()) {
                 BQ_LOGE("setMaxDequeuedBufferCount: buffer owned by producer");
                 return BAD_VALUE;
             }
@@ -196,7 +196,7 @@ status_t BufferQueueProducer::waitForFreeSlotThenRelock(const char* caller,
 
         // Free up any buffers that are in slots beyond the max buffer count
         for (int s = maxBufferCount; s < BufferQueueDefs::NUM_BUFFER_SLOTS; ++s) {
-            assert(mSlots[s].mBufferState == BufferSlot::FREE);
+            assert(mSlots[s].mBufferState.isFree());
             if (mSlots[s].mGraphicBuffer != NULL) {
                 mCore->freeBufferLocked(s);
                 *returnFlags |= RELEASE_ALL_BUFFERS;
@@ -206,15 +206,11 @@ status_t BufferQueueProducer::waitForFreeSlotThenRelock(const char* caller,
         int dequeuedCount = 0;
         int acquiredCount = 0;
         for (int s = 0; s < maxBufferCount; ++s) {
-            switch (mSlots[s].mBufferState) {
-                case BufferSlot::DEQUEUED:
-                    ++dequeuedCount;
-                    break;
-                case BufferSlot::ACQUIRED:
-                    ++acquiredCount;
-                    break;
-                default:
-                    break;
+            if (mSlots[s].mBufferState.isDequeued()) {
+                ++dequeuedCount;
+            }
+            if (mSlots[s].mBufferState.isAcquired()) {
+                ++acquiredCount;
             }
         }
 
@@ -240,7 +236,12 @@ status_t BufferQueueProducer::waitForFreeSlotThenRelock(const char* caller,
             BQ_LOGV("%s: queue size is %zu, waiting", caller,
                     mCore->mQueue.size());
         } else {
-            if (!mCore->mFreeBuffers.empty()) {
+            // If in single buffer mode and a shared buffer exists, always
+            // return it.
+            if (mCore->mSingleBufferMode && mCore->mSingleBufferSlot !=
+                    BufferQueueCore::INVALID_BUFFER_SLOT) {
+                *found = mCore->mSingleBufferSlot;
+            } else if (!mCore->mFreeBuffers.empty()) {
                 auto slot = mCore->mFreeBuffers.begin();
                 *found = *slot;
                 mCore->mFreeBuffers.erase(slot);
@@ -348,6 +349,13 @@ status_t BufferQueueProducer::dequeueBuffer(int *outSlot,
             // requested attributes, we free it and attempt to get another one.
             if (!mCore->mAllowAllocation) {
                 if (buffer->needsReallocation(width, height, format, usage)) {
+                    if (mCore->mSingleBufferMode &&
+                            mCore->mSingleBufferSlot == found) {
+                        BQ_LOGE("dequeueBuffer: cannot re-allocate a shared"
+                                "buffer");
+                        return BAD_VALUE;
+                    }
+
                     mCore->freeBufferLocked(found);
                     found = BufferItem::INVALID_BUFFER_SLOT;
                     continue;
@@ -360,7 +368,15 @@ status_t BufferQueueProducer::dequeueBuffer(int *outSlot,
 
         attachedByConsumer = mSlots[found].mAttachedByConsumer;
 
-        mSlots[found].mBufferState = BufferSlot::DEQUEUED;
+        mSlots[found].mBufferState.dequeue();
+
+        // If single buffer mode has just been enabled, cache the slot of the
+        // first buffer that is dequeued and mark it as the shared buffer.
+        if (mCore->mSingleBufferMode && mCore->mSingleBufferSlot ==
+                BufferQueueCore::INVALID_BUFFER_SLOT) {
+            mCore->mSingleBufferSlot = found;
+            mSlots[found].mBufferState.mShared = true;
+        }
 
         const sp<GraphicBuffer>& buffer(mSlots[found].mGraphicBuffer);
         if ((buffer == NULL) ||
@@ -373,6 +389,7 @@ status_t BufferQueueProducer::dequeueBuffer(int *outSlot,
             mSlots[found].mEglFence = EGL_NO_SYNC_KHR;
             mSlots[found].mFence = Fence::NO_FENCE;
             mCore->mBufferAge = 0;
+            mCore->mIsAllocating = true;
 
             returnFlags |= BUFFER_NEEDS_REALLOCATION;
         } else {
@@ -405,21 +422,26 @@ status_t BufferQueueProducer::dequeueBuffer(int *outSlot,
         BQ_LOGV("dequeueBuffer: allocating a new buffer for slot %d", *outSlot);
         sp<GraphicBuffer> graphicBuffer(mCore->mAllocator->createGraphicBuffer(
                 width, height, format, usage, &error));
-        if (graphicBuffer == NULL) {
-            BQ_LOGE("dequeueBuffer: createGraphicBuffer failed");
-            return error;
-        }
-
         { // Autolock scope
             Mutex::Autolock lock(mCore->mMutex);
 
+            if (graphicBuffer != NULL && !mCore->mIsAbandoned) {
+                graphicBuffer->setGenerationNumber(mCore->mGenerationNumber);
+                mSlots[*outSlot].mGraphicBuffer = graphicBuffer;
+            }
+
+            mCore->mIsAllocating = false;
+            mCore->mIsAllocatingCondition.broadcast();
+
+            if (graphicBuffer == NULL) {
+                BQ_LOGE("dequeueBuffer: createGraphicBuffer failed");
+                return error;
+            }
+
             if (mCore->mIsAbandoned) {
                 BQ_LOGE("dequeueBuffer: BufferQueue has been abandoned");
                 return NO_INIT;
             }
-
-            graphicBuffer->setGenerationNumber(mCore->mGenerationNumber);
-            mSlots[*outSlot].mGraphicBuffer = graphicBuffer;
         } // Autolock scope
     }
 
@@ -453,33 +475,40 @@ status_t BufferQueueProducer::dequeueBuffer(int *outSlot,
 status_t BufferQueueProducer::detachBuffer(int slot) {
     ATRACE_CALL();
     ATRACE_BUFFER_INDEX(slot);
-    BQ_LOGV("detachBuffer(P): slot %d", slot);
+    BQ_LOGV("detachBuffer: slot %d", slot);
     Mutex::Autolock lock(mCore->mMutex);
 
     if (mCore->mIsAbandoned) {
-        BQ_LOGE("detachBuffer(P): BufferQueue has been abandoned");
+        BQ_LOGE("detachBuffer: BufferQueue has been abandoned");
         return NO_INIT;
     }
 
     if (mCore->mConnectedApi == BufferQueueCore::NO_CONNECTED_API) {
-        BQ_LOGE("detachBuffer(P): BufferQueue has no connected producer");
+        BQ_LOGE("detachBuffer: BufferQueue has no connected producer");
         return NO_INIT;
     }
 
+    if (mCore->mSingleBufferMode) {
+        BQ_LOGE("detachBuffer: cannot detach a buffer in single buffer"
+                "mode");
+        return BAD_VALUE;
+    }
+
     if (slot < 0 || slot >= BufferQueueDefs::NUM_BUFFER_SLOTS) {
-        BQ_LOGE("detachBuffer(P): slot index %d out of range [0, %d)",
+        BQ_LOGE("detachBuffer: slot index %d out of range [0, %d)",
                 slot, BufferQueueDefs::NUM_BUFFER_SLOTS);
         return BAD_VALUE;
-    } else if (mSlots[slot].mBufferState != BufferSlot::DEQUEUED) {
-        BQ_LOGE("detachBuffer(P): slot %d is not owned by the producer "
-                "(state = %d)", slot, mSlots[slot].mBufferState);
+    } else if (!mSlots[slot].mBufferState.isDequeued()) {
+        BQ_LOGE("detachBuffer: slot %d is not owned by the producer "
+                "(state = %s)", slot, mSlots[slot].mBufferState.string());
         return BAD_VALUE;
     } else if (!mSlots[slot].mRequestBufferCalled) {
-        BQ_LOGE("detachBuffer(P): buffer in slot %d has not been requested",
+        BQ_LOGE("detachBuffer: buffer in slot %d has not been requested",
                 slot);
         return BAD_VALUE;
     }
 
+    mSlots[slot].mBufferState.detachProducer();
     mCore->freeBufferLocked(slot);
     mCore->mDequeueCondition.broadcast();
     mCore->validateConsistencyLocked();
@@ -511,6 +540,12 @@ status_t BufferQueueProducer::detachNextBuffer(sp<GraphicBuffer>* outBuffer,
         return NO_INIT;
     }
 
+    if (mCore->mSingleBufferMode) {
+        BQ_LOGE("detachNextBuffer: cannot detach a buffer in single buffer"
+                "mode");
+        return BAD_VALUE;
+    }
+
     mCore->waitWhileAllocatingLocked();
 
     if (mCore->mFreeBuffers.empty()) {
@@ -535,25 +570,30 @@ status_t BufferQueueProducer::attachBuffer(int* outSlot,
     ATRACE_CALL();
 
     if (outSlot == NULL) {
-        BQ_LOGE("attachBuffer(P): outSlot must not be NULL");
+        BQ_LOGE("attachBuffer: outSlot must not be NULL");
         return BAD_VALUE;
     } else if (buffer == NULL) {
-        BQ_LOGE("attachBuffer(P): cannot attach NULL buffer");
+        BQ_LOGE("attachBuffer: cannot attach NULL buffer");
         return BAD_VALUE;
     }
 
     Mutex::Autolock lock(mCore->mMutex);
 
     if (mCore->mIsAbandoned) {
-        BQ_LOGE("attachBuffer(P): BufferQueue has been abandoned");
+        BQ_LOGE("attachBuffer: BufferQueue has been abandoned");
         return NO_INIT;
     }
 
     if (mCore->mConnectedApi == BufferQueueCore::NO_CONNECTED_API) {
-        BQ_LOGE("attachBuffer(P): BufferQueue has no connected producer");
+        BQ_LOGE("attachBuffer: BufferQueue has no connected producer");
         return NO_INIT;
     }
 
+    if (mCore->mSingleBufferMode) {
+        BQ_LOGE("attachBuffer: cannot atach a buffer in single buffer mode");
+        return BAD_VALUE;
+    }
+
     if (buffer->getGenerationNumber() != mCore->mGenerationNumber) {
         BQ_LOGE("attachBuffer: generation number mismatch [buffer %u] "
                 "[queue %u]", buffer->getGenerationNumber(),
@@ -565,7 +605,7 @@ status_t BufferQueueProducer::attachBuffer(int* outSlot,
 
     status_t returnFlags = NO_ERROR;
     int found;
-    status_t status = waitForFreeSlotThenRelock("attachBuffer(P)", &found,
+    status_t status = waitForFreeSlotThenRelock("attachBuffer", &found,
             &returnFlags);
     if (status != NO_ERROR) {
         return status;
@@ -573,17 +613,17 @@ status_t BufferQueueProducer::attachBuffer(int* outSlot,
 
     // This should not happen
     if (found == BufferQueueCore::INVALID_BUFFER_SLOT) {
-        BQ_LOGE("attachBuffer(P): no available buffer slots");
+        BQ_LOGE("attachBuffer: no available buffer slots");
         return -EBUSY;
     }
 
     *outSlot = found;
     ATRACE_BUFFER_INDEX(*outSlot);
-    BQ_LOGV("attachBuffer(P): returning slot %d flags=%#x",
+    BQ_LOGV("attachBuffer: returning slot %d flags=%#x",
             *outSlot, returnFlags);
 
     mSlots[*outSlot].mGraphicBuffer = buffer;
-    mSlots[*outSlot].mBufferState = BufferSlot::DEQUEUED;
+    mSlots[*outSlot].mBufferState.attachProducer();
     mSlots[*outSlot].mEglFence = EGL_NO_SYNC_KHR;
     mSlots[*outSlot].mFence = Fence::NO_FENCE;
     mSlots[*outSlot].mRequestBufferCalled = true;
@@ -649,9 +689,9 @@ status_t BufferQueueProducer::queueBuffer(int slot,
             BQ_LOGE("queueBuffer: slot index %d out of range [0, %d)",
                     slot, maxBufferCount);
             return BAD_VALUE;
-        } else if (mSlots[slot].mBufferState != BufferSlot::DEQUEUED) {
+        } else if (!mSlots[slot].mBufferState.isDequeued()) {
             BQ_LOGE("queueBuffer: slot %d is not owned by the producer "
-                    "(state = %d)", slot, mSlots[slot].mBufferState);
+                    "(state = %s)", slot, mSlots[slot].mBufferState.string());
             return BAD_VALUE;
         } else if (!mSlots[slot].mRequestBufferCalled) {
             BQ_LOGE("queueBuffer: slot %d was queued without requesting "
@@ -681,7 +721,8 @@ status_t BufferQueueProducer::queueBuffer(int slot,
         }
 
         mSlots[slot].mFence = fence;
-        mSlots[slot].mBufferState = BufferSlot::QUEUED;
+        mSlots[slot].mBufferState.queue();
+
         ++mCore->mFrameCounter;
         mSlots[slot].mFrameNumber = mCore->mFrameCounter;
 
@@ -700,11 +741,21 @@ status_t BufferQueueProducer::queueBuffer(int slot,
         item.mSlot = slot;
         item.mFence = fence;
         item.mIsDroppable = mCore->mAsyncMode ||
-                mCore->mDequeueBufferCannotBlock;
+                mCore->mDequeueBufferCannotBlock ||
+                (mCore->mSingleBufferMode && mCore->mSingleBufferSlot == slot);
         item.mSurfaceDamage = surfaceDamage;
 
         mStickyTransform = stickyTransform;
 
+        // Cache the shared buffer data so that the BufferItem can be recreated.
+        if (mCore->mSingleBufferMode) {
+            mCore->mSingleBufferCache.crop = crop;
+            mCore->mSingleBufferCache.transform = transform;
+            mCore->mSingleBufferCache.scalingMode = static_cast<uint32_t>(
+                    scalingMode);
+            mCore->mSingleBufferCache.dataspace = dataSpace;
+        }
+
         if (mCore->mQueue.empty()) {
             // When the queue is empty, we can ignore mDequeueBufferCannotBlock
             // and simply queue this buffer
@@ -718,8 +769,19 @@ status_t BufferQueueProducer::queueBuffer(int slot,
                 // If the front queued buffer is still being tracked, we first
                 // mark it as freed
                 if (mCore->stillTracking(front)) {
-                    mSlots[front->mSlot].mBufferState = BufferSlot::FREE;
-                    mCore->mFreeBuffers.push_front(front->mSlot);
+                    mSlots[front->mSlot].mBufferState.freeQueued();
+
+                    // After leaving single buffer mode, the shared buffer will
+                    // still be around. Mark it as no longer shared if this
+                    // operation causes it to be free.
+                    if (!mCore->mSingleBufferMode &&
+                            mSlots[front->mSlot].mBufferState.isFree()) {
+                        mSlots[front->mSlot].mBufferState.mShared = false;
+                    }
+                    // Don't put the shared buffer on the free list.
+                    if (!mSlots[front->mSlot].mBufferState.isShared()) {
+                        mCore->mFreeBuffers.push_front(front->mSlot);
+                    }
                 }
                 // Overwrite the droppable buffer with the incoming one
                 *front = item;
@@ -795,21 +857,36 @@ status_t BufferQueueProducer::cancelBuffer(int slot, const sp<Fence>& fence) {
         return NO_INIT;
     }
 
+    if (mCore->mSingleBufferMode) {
+        BQ_LOGE("cancelBuffer: cannot cancel a buffer in single buffer mode");
+        return BAD_VALUE;
+    }
+
     if (slot < 0 || slot >= BufferQueueDefs::NUM_BUFFER_SLOTS) {
         BQ_LOGE("cancelBuffer: slot index %d out of range [0, %d)",
                 slot, BufferQueueDefs::NUM_BUFFER_SLOTS);
         return BAD_VALUE;
-    } else if (mSlots[slot].mBufferState != BufferSlot::DEQUEUED) {
+    } else if (!mSlots[slot].mBufferState.isDequeued()) {
         BQ_LOGE("cancelBuffer: slot %d is not owned by the producer "
-                "(state = %d)", slot, mSlots[slot].mBufferState);
+                "(state = %s)", slot, mSlots[slot].mBufferState.string());
         return BAD_VALUE;
     } else if (fence == NULL) {
         BQ_LOGE("cancelBuffer: fence is NULL");
         return BAD_VALUE;
     }
 
-    mCore->mFreeBuffers.push_front(slot);
-    mSlots[slot].mBufferState = BufferSlot::FREE;
+    mSlots[slot].mBufferState.cancel();
+
+    // After leaving single buffer mode, the shared buffer will still be around.
+    // Mark it as no longer shared if this operation causes it to be free.
+    if (!mCore->mSingleBufferMode && mSlots[slot].mBufferState.isFree()) {
+        mSlots[slot].mBufferState.mShared = false;
+    }
+
+    // Don't put the shared buffer on the free list.
+    if (!mSlots[slot].mBufferState.isShared()) {
+        mCore->mFreeBuffers.push_front(slot);
+    }
     mSlots[slot].mFence = fence;
     mCore->mDequeueCondition.broadcast();
     mCore->validateConsistencyLocked();
@@ -878,26 +955,26 @@ status_t BufferQueueProducer::connect(const sp<IProducerListener>& listener,
     ATRACE_CALL();
     Mutex::Autolock lock(mCore->mMutex);
     mConsumerName = mCore->mConsumerName;
-    BQ_LOGV("connect(P): api=%d producerControlledByApp=%s", api,
+    BQ_LOGV("connect: api=%d producerControlledByApp=%s", api,
             producerControlledByApp ? "true" : "false");
 
     if (mCore->mIsAbandoned) {
-        BQ_LOGE("connect(P): BufferQueue has been abandoned");
+        BQ_LOGE("connect: BufferQueue has been abandoned");
         return NO_INIT;
     }
 
     if (mCore->mConsumerListener == NULL) {
-        BQ_LOGE("connect(P): BufferQueue has no consumer");
+        BQ_LOGE("connect: BufferQueue has no consumer");
         return NO_INIT;
     }
 
     if (output == NULL) {
-        BQ_LOGE("connect(P): output was NULL");
+        BQ_LOGE("connect: output was NULL");
         return BAD_VALUE;
     }
 
     if (mCore->mConnectedApi != BufferQueueCore::NO_CONNECTED_API) {
-        BQ_LOGE("connect(P): already connected (cur=%d req=%d)",
+        BQ_LOGE("connect: already connected (cur=%d req=%d)",
                 mCore->mConnectedApi, api);
         return BAD_VALUE;
     }
@@ -920,14 +997,14 @@ status_t BufferQueueProducer::connect(const sp<IProducerListener>& listener,
                 status = IInterface::asBinder(listener)->linkToDeath(
                         static_cast<IBinder::DeathRecipient*>(this));
                 if (status != NO_ERROR) {
-                    BQ_LOGE("connect(P): linkToDeath failed: %s (%d)",
+                    BQ_LOGE("connect: linkToDeath failed: %s (%d)",
                             strerror(-status), status);
                 }
             }
             mCore->mConnectedProducerListener = listener;
             break;
         default:
-            BQ_LOGE("connect(P): unknown API %d", api);
+            BQ_LOGE("connect: unknown API %d", api);
             status = BAD_VALUE;
             break;
     }
@@ -942,7 +1019,7 @@ status_t BufferQueueProducer::connect(const sp<IProducerListener>& listener,
 
 status_t BufferQueueProducer::disconnect(int api) {
     ATRACE_CALL();
-    BQ_LOGV("disconnect(P): api %d", api);
+    BQ_LOGV("disconnect: api %d", api);
 
     int status = NO_ERROR;
     sp<IConsumerListener> listener;
@@ -979,13 +1056,13 @@ status_t BufferQueueProducer::disconnect(int api) {
                     mCore->mDequeueCondition.broadcast();
                     listener = mCore->mConsumerListener;
                 } else if (mCore->mConnectedApi != BufferQueueCore::NO_CONNECTED_API) {
-                    BQ_LOGE("disconnect(P): still connected to another API "
+                    BQ_LOGE("disconnect: still connected to another API "
                             "(cur=%d req=%d)", mCore->mConnectedApi, api);
                     status = BAD_VALUE;
                 }
                 break;
             default:
-                BQ_LOGE("disconnect(P): unknown API %d", api);
+                BQ_LOGE("disconnect: unknown API %d", api);
                 status = BAD_VALUE;
                 break;
         }
@@ -1038,7 +1115,7 @@ void BufferQueueProducer::allocateBuffers(uint32_t width, uint32_t height,
                 if (mSlots[slot].mGraphicBuffer != NULL) {
                     ++currentBufferCount;
                 } else {
-                    if (mSlots[slot].mBufferState != BufferSlot::FREE) {
+                    if (!mSlots[slot].mBufferState.isFree()) {
                         BQ_LOGE("allocateBuffers: slot %d without buffer is not FREE",
                                 slot);
                         continue;
@@ -1101,7 +1178,7 @@ void BufferQueueProducer::allocateBuffers(uint32_t width, uint32_t height,
 
             for (size_t i = 0; i < newBufferCount; ++i) {
                 int slot = freeSlots[i];
-                if (mSlots[slot].mBufferState != BufferSlot::FREE) {
+                if (!mSlots[slot].mBufferState.isFree()) {
                     // A consumer allocated the FREE slot with attachBuffer. Discard the buffer we
                     // allocated.
                     BQ_LOGV("allocateBuffers: slot %d was acquired while allocating. "
@@ -1159,6 +1236,19 @@ uint64_t BufferQueueProducer::getNextFrameNumber() const {
     return nextFrameNumber;
 }
 
+status_t BufferQueueProducer::setSingleBufferMode(bool singleBufferMode) {
+    ATRACE_CALL();
+    BQ_LOGV("setSingleBufferMode: %d", singleBufferMode);
+
+    Mutex::Autolock lock(mCore->mMutex);
+    if (!singleBufferMode) {
+        mCore->mSingleBufferSlot = BufferQueueCore::INVALID_BUFFER_SLOT;
+    }
+    mCore->mSingleBufferMode = singleBufferMode;
+
+    return NO_ERROR;
+}
+
 void BufferQueueProducer::binderDied(const wp<android::IBinder>& /* who */) {
     // If we're here, it means that a producer we were connected to died.
     // We're guaranteed that we are still connected to it because we remove