1 /* 2 * Copyright (C) 2017 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #pragma once 18 19 #include <cstdint> 20 #include <vector> 21 22 #include <gui/BufferQueue.h> 23 #include <utils/StrongPointer.h> 24 25 namespace android { 26 27 class GraphicBuffer; 28 29 namespace compositionengine::impl { 30 31 // With HIDLized hwcomposer HAL, the HAL can maintain a buffer cache for each 32 // HWC display and layer. When updating a display target or a layer buffer, 33 // we have the option to send the buffer handle over or to request the HAL to 34 // retrieve it from its cache. The latter is cheaper since it eliminates the 35 // overhead to transfer the handle over the trasport layer, and the overhead 36 // for the HAL to clone and retain the handle. 37 // 38 // To be able to find out whether a buffer is already in the HAL's cache, we 39 // use HWComposerBufferCache to mirror the cache in SF. 40 class HwcBufferCache { 41 public: 42 HwcBufferCache(); 43 // Given a buffer, return the HWC cache slot and 44 // buffer to be sent to HWC. 45 // 46 // outBuffer is set to buffer when buffer is not in the HWC cache; 47 // otherwise, outBuffer is set to nullptr. 48 void getHwcBuffer(int slot, const sp<GraphicBuffer>& buffer, uint32_t* outSlot, 49 sp<GraphicBuffer>* outBuffer); 50 51 private: 52 // an array where the index corresponds to a slot and the value corresponds to a (counter, 53 // buffer) pair. "counter" is a unique value that indicates the last time this slot was updated 54 // or used and allows us to keep track of the least-recently used buffer. 55 wp<GraphicBuffer> mBuffers[BufferQueue::NUM_BUFFER_SLOTS]; 56 }; 57 58 } // namespace compositionengine::impl 59 } // namespace android 60
