和你一起终身学习,这里是程序员 Android
经典好文推荐,通过阅读本文,您将收获以下知识点:
一、Consumer端的FrameListener
二、消息队列MessageQueue
三、显示设备DispalyDevice
通过前面的简单介绍,我们对HWC合成有大致的了解。下面我们根据实际代码进行讲解。前面章节,我们已经说过,Layer的创建,和BufferQueue,那么Buffer进入到BufferQueue队列中后,怎么进行合成显示的呢?我们继续来看。
一、Consumer端的FrameListener
你还记得Producer的frameAvailableListener吗?Buffer放入队列BufferQueue后,是不是通过frameAvailableListener->onFrameAvailable
通知Consumer?大家可以再回望一下BufferQueueProducer::queueBuffer
。
frameAvailableListener是哪里来的?
我们先来看一下Consumer中Listener间的相互关系
image- BufferLayer有专门的Consumer,BufferLayerConsumer;BufferLayerConsumer继承ConsumerBase。ConsumerBase通过IGraphicBufferConsumer和BufferQueue进行通信的。
- BufferQueue中的frameAvailableListener,是一个IConsumerListener的接口,对应的Binder的Bn端实现为ProxyConsumerListener。
- BufferLayer实现了ContentsChangedListener,ContentsChangedListener继承FrameAvailableListener。BufferLayer的Listener实现,被传给了ConsumerBase。
- ConsumerBase实现ConsumerListener接口,构建ConsumerBase时,会创建ProxyConsumerListener,将ConsumerBase实现的Listener接口传给ProxyConsumerListener。
- BufferQueue中Listener回调时,会回调到ConsumerBase中。ConsumerBase中再通过BufferLayer实现的,传下来的Listener回调到BufferLayer中。
层层回调,别弄混淆了。
关键代码:
BufferQueueProducer中通过frameAvailableListener->onFrameAvailable
回调到ProxyConsumerListener中:
* frameworks/native/libs/gui/BufferQueue.cpp
void BufferQueue::ProxyConsumerListener::onFrameAvailable(
const BufferItem& item) {
sp<ConsumerListener> listener(mConsumerListener.promote());
if (listener != NULL) {
listener->onFrameAvailable(item);
}
}
ProxyConsumerListener中的mConsumerListener是ConsumerBase中的实现。这里的listener->onFrameAvailable
将回调到ConsumerBase中。
* frameworks/native/libs/gui/ConsumerBase.cpp
void ConsumerBase::onFrameAvailable(const BufferItem& item) {
CB_LOGV("onFrameAvailable");
sp<FrameAvailableListener> listener;
{ // scope for the lock
Mutex::Autolock lock(mFrameAvailableMutex);
listener = mFrameAvailableListener.promote();
}
if (listener != NULL) {
CB_LOGV("actually calling onFrameAvailable");
listener->onFrameAvailable(item);
}
}
ConsumerBase中的mFrameAvailableListener是BufferLayer中的实现:
* frameworks/native/services/surfaceflinger/BufferLayer.cpp
void BufferLayer::onFrameAvailable(const BufferItem& item) {
// Add this buffer from our internal queue tracker
{ // Autolock scope
Mutex::Autolock lock(mQueueItemLock);
mFlinger->mInterceptor.saveBufferUpdate(this, item.mGraphicBuffer->getWidth(),
item.mGraphicBuffer->getHeight(),
item.mFrameNumber);
// Reset the frame number tracker when we receive the first buffer after
// a frame number reset
if (item.mFrameNumber == 1) {
mLastFrameNumberReceived = 0;
}
// Ensure that callbacks are handled in order
while (item.mFrameNumber != mLastFrameNumberReceived + 1) {
status_t result = mQueueItemCondition.waitRelative(mQueueItemLock,
ms2ns(500));
if (result != NO_ERROR) {
ALOGE("[%s] Timed out waiting on callback", mName.string());
}
}
mQueueItems.push_back(item);
android_atomic_inc(&mQueuedFrames);
// Wake up any pending callbacks
mLastFrameNumberReceived = item.mFrameNumber;
mQueueItemCondition.broadcast();
}
mFlinger->signalLayerUpdate();
}
BufferLayer中调用onFrameAvailable,去通知SurfaceFlinger进行合成。
到这里,应用端(Producer)生产完Buffer这件事,就通知到了SurfaceFlinger中了。
SurfaceFlinger的signalLayerUpdate,是通过MessageQueue来处理的,我们先来看看MessageQueue。
二、消息队列MessageQueue
MessageQueue是SurfaceFlinger中的消息队列,为什么需要消息队列?我们应用有一个主线程,专门进行UI的处理。SurfaceFlinger同样的,也有一个主线程,SurfaceFlinger的主线程主要进行显示数据的处理,也就是合成。
SurfaceFlinger中,mEventQueue是MessageQueue的一个栈对象,采用mutable修饰。SurfaceFlinger在初次引用时,会对mEventQueue进行初始化。
* frameworks/native/services/surfaceflinger/MessageQueue.cpp
void MessageQueue::init(const sp<SurfaceFlinger>& flinger)
{
mFlinger = flinger;
mLooper = new Looper(true);
mHandler = new Handler(*this);
}
MessageQueue初始化时,创建了一个Looper和一个Handler。
此外,在SurfaceFlinger初始化时,创建了一个EventThread,并传给了MessageQueue。
void SurfaceFlinger::init() {
... ...
sp<VSyncSource> sfVsyncSrc =
new DispSyncSource(&mPrimaryDispSync, SurfaceFlinger::sfVsyncPhaseOffsetNs, true, "sf");
mSFEventThread = new EventThread(sfVsyncSrc, *this, true);
mEventQueue.setEventThread(mSFEventThread);
MessageQueue的setEventThread函数如下:
void MessageQueue::setEventThread(const sp<EventThread>& eventThread)
{
if (mEventThread == eventThread) {
return;
}
if (mEventTube.getFd() >= 0) {
mLooper->removeFd(mEventTube.getFd());
}
mEventThread = eventThread;
mEvents = eventThread->createEventConnection();
mEvents->stealReceiveChannel(&mEventTube);
mLooper->addFd(mEventTube.getFd(), 0, Looper::EVENT_INPUT,
MessageQueue::cb_eventReceiver, this);
}
MessageQueue在setEventThread时,主要做以下几件事:
-
创建一个BitTube对象mEventTube
-
创建一个EventConnection
sp<EventThread::Connection> EventThread::createEventConnection() const {
return new Connection(const_cast<EventThread*>(this));
}
Connection在第一次引用时,将会被注册到mEventThread中。
void EventThread::Connection::onFirstRef() {
// NOTE: mEventThread doesn't hold a strong reference on us
mEventThread->registerDisplayEventConnection(this);
}
在注册时,Connection将会被添加到mDisplayEventConnections 中。
status_t EventThread::registerDisplayEventConnection(
const sp<EventThread::Connection>& connection) {
Mutex::Autolock _l(mLock);
mDisplayEventConnections.add(connection);
mCondition.broadcast();
return NO_ERROR;
}
mDisplayEventConnections是一个已经注册的Connection的集合。
- 将mEventTube和EventConnection关联
status_t EventThread::Connection::stealReceiveChannel(gui::BitTube* outChannel) {
outChannel->setReceiveFd(mChannel.moveReceiveFd());
return NO_ERROR;
}
Connection创建时,将默认创建一个4k的BitTube,BitTube封装的是一对socket,一个发送,一个接收,可传输的Buffer大小为4K。
void BitTube::init(size_t rcvbuf, size_t sndbuf) {
int sockets[2];
if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, sockets) == 0) {
size_t size = DEFAULT_SOCKET_BUFFER_SIZE;
setsockopt(sockets[0], SOL_SOCKET, SO_RCVBUF, &rcvbuf, sizeof(rcvbuf));
setsockopt(sockets[1], SOL_SOCKET, SO_SNDBUF, &sndbuf, sizeof(sndbuf));
// since we don't use the "return channel", we keep it small...
setsockopt(sockets[0], SOL_SOCKET, SO_SNDBUF, &size, sizeof(size));
setsockopt(sockets[1], SOL_SOCKET, SO_RCVBUF, &size, sizeof(size));
fcntl(sockets[0], F_SETFL, O_NONBLOCK);
fcntl(sockets[1], F_SETFL, O_NONBLOCK);
mReceiveFd.reset(sockets[0]);
mSendFd.reset(sockets[1]);
} else {
mReceiveFd.reset();
ALOGE("BitTube: pipe creation failed (%s)", strerror(errno));
}
}
MessageQueue中的mEventTube,和mReceiveFd关联。
- addFd函数,将fd添加到MessageQueue的Looper中。
注意,Looper的callback为MessageQueue::cb_eventReceiver
,data为MessageQueue本身。
int MessageQueue::cb_eventReceiver(int fd, int events, void* data) {
MessageQueue* queue = reinterpret_cast<MessageQueue *>(data);
return queue->eventReceiver(fd, events);
}
回到SurfaceFlinger的signalLayerUpdate函数:
void SurfaceFlinger::signalLayerUpdate() {
mEventQueue.invalidate();
}
signalLayerUpdate中,调用MQ的invalidate。
void MessageQueue::invalidate() {
mEvents->requestNextVsync();
}
MQ的invalidate的函数,将请求下一个Vsync。Vsync是一种同步机制,垂直同步,我们可以理解为SurfaceFlinger的工作节拍。
void EventThread::requestNextVsync(
const sp<EventThread::Connection>& connection) {
Mutex::Autolock _l(mLock);
mFlinger.resyncWithRateLimit();
if (connection->count < 0) {
connection->count = 0;
mCondition.broadcast();
}
}
注意这里的count >= 0。
EventThread就是一个事件分发的线程,第一次引用时,线程启动。
void EventThread::onFirstRef() {
run("EventThread", PRIORITY_URGENT_DISPLAY + PRIORITY_MORE_FAVORABLE);
}
EventThread的threadLoop函数体如下:
bool EventThread::threadLoop() {
DisplayEventReceiver::Event event;
Vector< sp<EventThread::Connection> > signalConnections;
signalConnections = waitForEvent(&event);
// dispatch events to listeners...
const size_t count = signalConnections.size();
for (size_t i=0 ; i<count ; i++) {
const sp<Connection>& conn(signalConnections[i]);
// now see if we still need to report this event
status_t err = conn->postEvent(event);
if (err == -EAGAIN || err == -EWOULDBLOCK) {
... ...
ALOGW("EventThread: dropping event (%08x) for connection %p",
event.header.type, conn.get());
} else if (err < 0) {
removeDisplayEventConnection(signalConnections[i]);
}
}
return true;
}
waitForEvent,等待事件Event。看看哪些Connection是被触发的,对于被触发的Connection,signalConnections,通过postEvent将事件Event分发出去。
Event这边的控制逻辑,基本都在waitForEvent中。waitForEvent中,采用while循环,条件是signalConnections为空。EventThread中主要控制两事件,Vsync事件和显示屏的HotPlug热插拔事件
enum {
DISPLAY_EVENT_VSYNC = fourcc('v', 's', 'y', 'n'),
DISPLAY_EVENT_HOTPLUG = fourcc('p', 'l', 'u', 'g'),
};
我们分段来看:
Vector< sp<EventThread::Connection> > EventThread::waitForEvent(
DisplayEventReceiver::Event* event)
{
Mutex::Autolock _l(mLock);
Vector< sp<EventThread::Connection> > signalConnections;
do {
bool eventPending = false;
bool waitForVSync = false;
size_t vsyncCount = 0;
nsecs_t timestamp = 0;
for (int32_t i=0 ; i<DisplayDevice::NUM_BUILTIN_DISPLAY_TYPES ; i++) {
timestamp = mVSyncEvent[i].header.timestamp;
if (timestamp) {
// 有一个Vsync事件要分发
if (mInterceptVSyncs) {
mFlinger.mInterceptor.saveVSyncEvent(timestamp);
}
*event = mVSyncEvent[i];
mVSyncEvent[i].header.timestamp = 0;
vsyncCount = mVSyncEvent[i].vsync.count;
break;
}
}
看看有没有Vsync事件要分发,timestamp不为0,表示有Vync事件要分发。
if (!timestamp) {
// no vsync event, see if there are some other event
eventPending = !mPendingEvents.isEmpty();
if (eventPending) {
// we have some other event to dispatch
*event = mPendingEvents[0];
mPendingEvents.removeAt(0);
}
}
mPendingEvents,这里主要是是HotPlug事件。
找出在等待事件的Connection:
size_t count = mDisplayEventConnections.size();
for (size_t i=0 ; i<count ; ) {
sp<Connection> connection(mDisplayEventConnections[i].promote());
if (connection != NULL) {
bool added = false;
if (connection->count >= 0) {
// 需要Vsync,至少有一个Connection的count >= 0。
waitForVSync = true;
if (timestamp) {
// we consume the event only if it's time
// (ie: we received a vsync event)
if (connection->count == 0) {
// fired this time around
connection->count = -1;
signalConnections.add(connection);
added = true;
} else if (connection->count == 1 ||
(vsyncCount % connection->count) == 0) {
// continuous event, and time to report it
signalConnections.add(connection);
added = true;
}
}
}
if (eventPending && !timestamp && !added) {
// 没有Vsync事件要处理,但是有其他的事件要处理
signalConnections.add(connection);
}
++i;
} else {
// Connection不存在了
mDisplayEventConnections.removeAt(i);
--count;
}
}
Connection的count >= 0表示需要Vsync。eventPending && !timestamp && !added
表示没有Vsync事件要处理,但是有其他的事件要处理。
if (timestamp && !waitForVSync) {
disableVSyncLocked();
} else if (!timestamp && waitForVSync) {
enableVSyncLocked();
}
timestamp && !waitForVSync
如果有Vsync事件要分发,但是又没有Connection需要Vsync事件时,把Vsync给关掉。相反,如果有Connection需要Vsync,而此时又没有Vsync事件时,需要将Vsync打开。
if (!timestamp && !eventPending) {
if (waitForVSync) {
bool softwareSync = mUseSoftwareVSync;
nsecs_t timeout = softwareSync ? ms2ns(16) : ms2ns(1000);
if (mCondition.waitRelative(mLock, timeout) == TIMED_OUT) {
if (!softwareSync) {
ALOGW("Timed out waiting for hw vsync; faking it");
}
// FIXME: how do we decide which display id the fake
// vsync came from ?
mVSyncEvent[0].header.type = DisplayEventReceiver::DISPLAY_EVENT_VSYNC;
mVSyncEvent[0].header.id = DisplayDevice::DISPLAY_PRIMARY;
mVSyncEvent[0].header.timestamp = systemTime(SYSTEM_TIME_MONOTONIC);
mVSyncEvent[0].vsync.count++;
}
} else {
mCondition.wait(mLock);
}
}
} while (signalConnections.isEmpty());
return signalConnections;
}
如果此时没有Vsync事件,或其他的Event事件,那就处于等待中。如果是等待Vsync,那么通过mCondition.waitRelative
进行等待,如果是硬件Vsync还不能用或者出现问题时,设置一个超时时间,进行屏幕的唤醒。
如果Connection需要Vsync,那么就进程sleep。
Vsync事件到来时,将回调到onVSyncEvent:
void EventThread::onVSyncEvent(nsecs_t timestamp) {
Mutex::Autolock _l(mLock);
mVSyncEvent[0].header.type = DisplayEventReceiver::DISPLAY_EVENT_VSYNC;
mVSyncEvent[0].header.id = 0;
mVSyncEvent[0].header.timestamp = timestamp;
mVSyncEvent[0].vsync.count++;
mCondition.broadcast();
}
Hotplug事件到来时,将回调到onHotplugReceived:
void EventThread::onHotplugReceived(int type, bool connected) {
ALOGE_IF(type >= DisplayDevice::NUM_BUILTIN_DISPLAY_TYPES,
"received hotplug event for an invalid display (id=%d)", type);
Mutex::Autolock _l(mLock);
if (type < DisplayDevice::NUM_BUILTIN_DISPLAY_TYPES) {
DisplayEventReceiver::Event event;
event.header.type = DisplayEventReceiver::DISPLAY_EVENT_HOTPLUG;
event.header.id = type;
event.header.timestamp = systemTime();
event.hotplug.connected = connected;
mPendingEvents.add(event);
mCondition.broadcast();
}
}
注意,Event事件哪儿回调回来的我们先不管,我们先记住这里的逻辑。
Vsync事件是跟屏幕的刷新频率有关,比如60Hz的屏幕,两个Vsync事件间的时间为1/60s,也就是16.67ms左右。SurfaceFlinger每隔16.67ms进行一次合成,显示。
另外,需要注意的是,SurfaceFlinger和App的EventThread是分开的,不是同一个。
void SurfaceFlinger::init() {
... ...
// start the EventThread
sp<VSyncSource> vsyncSrc =
new DispSyncSource(&mPrimaryDispSync, SurfaceFlinger::vsyncPhaseOffsetNs, true, "app");
mEventThread = new EventThread(vsyncSrc, *this, false);
sp<VSyncSource> sfVsyncSrc =
new DispSyncSource(&mPrimaryDispSync, SurfaceFlinger::sfVsyncPhaseOffsetNs, true, "sf");
mSFEventThread = new EventThread(sfVsyncSrc, *this, true);
mEventQueue.setEventThread(mSFEventThread);
回到MessageQueue,Connection通过postEvent将Event抛出来后,通过sendEvents将事件发出去。
status_t EventThread::Connection::postEvent(
const DisplayEventReceiver::Event& event) {
ssize_t size = DisplayEventReceiver::sendEvents(&mChannel, &event, 1);
return size < 0 ? status_t(size) : status_t(NO_ERROR);
}
DisplayEventReceiver中是通过BitTube将事件发出去,sendObjects注意这里的参数。
ssize_t DisplayEventReceiver::sendEvents(gui::BitTube* dataChannel,
Event const* events, size_t count)
{
return gui::BitTube::sendObjects(dataChannel, events, count);
}
数据是什么地方接受的呢?回到SurfaceFlinger
SurfaceFlinger线程run时,启动一个死循环,循环等待事件。
void SurfaceFlinger::run() {
do {
waitForEvent();
} while (true);
}
waitForEvent中,调用MessageQueue的waitMessage函数:
void MessageQueue::waitMessage() {
do {
IPCThreadState::self()->flushCommands();
int32_t ret = mLooper->pollOnce(-1);
switch (ret) {
case Looper::POLL_WAKE:
case Looper::POLL_CALLBACK:
continue;
case Looper::POLL_ERROR:
ALOGE("Looper::POLL_ERROR");
continue;
case Looper::POLL_TIMEOUT:
// timeout (should not happen)
continue;
default:
// should not happen
ALOGE("Looper::pollOnce() returned unknown status %d", ret);
continue;
}
} while (true);
}
waitMessage,通过采用一个死循环,处理Looper的pollOnce。Looper内部的逻辑就不看了,主要是采用epoll_wait对fd进行监听,BitTube发送Event对象后,epoll_wait结束,调用callback,处理事件
int callbackResult = response.request.callback->handleEvent(fd, events, data);
MessageQueue对应的callback为cb_eventReceiver:
int MessageQueue::cb_eventReceiver(int fd, int events, void* data) {
MessageQueue* queue = reinterpret_cast<MessageQueue *>(data);
return queue->eventReceiver(fd, events);
}
eventReceiver,处理事件:
int MessageQueue::eventReceiver(int /*fd*/, int /*events*/) {
ssize_t n;
DisplayEventReceiver::Event buffer[8];
while ((n = DisplayEventReceiver::getEvents(&mEventTube, buffer, 8)) > 0) {
for (int i=0 ; i<n ; i++) {
if (buffer[i].header.type == DisplayEventReceiver::DISPLAY_EVENT_VSYNC) {
mHandler->dispatchInvalidate();
break;
}
}
}
return 1;
}
dispatchInvalidate,封装为MessageQueue::INVALIDATE
void MessageQueue::Handler::dispatchInvalidate() {
if ((android_atomic_or(eventMaskInvalidate, &mEventMask) & eventMaskInvalidate) == 0) {
mQueue.mLooper->sendMessage(this, Message(MessageQueue::INVALIDATE));
}
}
MessageQueue中,两种Message,INVALIDATE和REFRESH:
enum {
INVALIDATE = 0,
REFRESH = 1,
};
Message的分发略过,Handler对Message的处理如下:
void MessageQueue::Handler::handleMessage(const Message& message) {
switch (message.what) {
case INVALIDATE:
android_atomic_and(~eventMaskInvalidate, &mEventMask);
mQueue.mFlinger->onMessageReceived(message.what);
break;
case REFRESH:
android_atomic_and(~eventMaskRefresh, &mEventMask);
mQueue.mFlinger->onMessageReceived(message.what);
break;
}
}
收到消息后,再调回SurfaceFlinger在onMessageReceived中处理。
再看SurfaceFlinger的处理之前,我们先稍微整理一下MessageQueue,MessageQueue的类图如下:
image三、显示设备DispalyDevice
SurfaceFlinger中,每个显示屏我们用DisplayDevice进行描述,它除了描述了Display的信息,还包括很多和合成相关的逻辑。相比于native层,Display信息是在Android的Framework层管理的,提供了专门的服务DisplayManagerService(DMS),DMS后续再介绍。
3.1 Display接口服务
。从Android 8.0开始,Vsync和hotplug的接收接口IDisplayEventReceiver作为一个单独的库从SurfaceFlinger中独立出来,设计为3层模式,JAVA层,Native层和HAL层。编译为libdisplayservicehidl库,代码在如下位置:
frameworks/native/services/displayservice
Display 接口 Android.bp如下:
cc_library_shared {
name: "libdisplayservicehidl",
srcs: [
"DisplayService.cpp",
"DisplayEventReceiver.cpp",
],
shared_libs: [
"libbase",
"liblog",
"libgui",
"libhidlbase",
"libhidltransport",
"libutils",
"android.frameworks.displayservice@1.0",
],
export_include_dirs: ["include"],
export_shared_lib_headers: [
"android.frameworks.displayservice@1.0",
"libgui",
"libutils",
],
cflags: [
"-Werror",
"-Wall",
]
}
hal层也抽象出Display的单独模块displayservice。代码为在:
frameworks/hardware/interfaces/displayservice
displayservice的Android.bp如下:
hidl_interface {
name: "android.frameworks.displayservice@1.0",
root: "android.frameworks",
vndk: {
enabled: true,
},
srcs: [
"types.hal",
"IDisplayEventReceiver.hal",
"IDisplayService.hal",
"IEventCallback.hal",
],
interfaces: [
"android.hidl.base@1.0",
],
types: [
"Status",
],
gen_java: true,
}
displayservice还比较简单,没有太多接口:
- types中只定义了一个状态
* frameworks/hardware/interfaces/displayservice/1.0/types.hal
package android.frameworks.displayservice@1.0;
enum Status : uint32_t {
SUCCESS,
BAD_VALUE,
UNKNOWN,
};
- IDisplayEventReceiver.hal中定义了Receiver的接口
package android.frameworks.displayservice@1.0;
import IEventCallback;
interface IDisplayEventReceiver {
/**
* 添加callback,开始接收Events事件,热插拔是默认打开的,Vysnc需要通过setVsyncRate打开
*/
init(IEventCallback callback) generates (Status status);
/**
* 开始或停止发送callback
*/
setVsyncRate(int32_t count) generates (Status status);
/**
* 请求一个Vsync,如果setVsyncRate是0,这不起作用
*/
requestNextVsync() generates (Status status);
/**
* Server端丢弃所以的callback,停止发送
*/
close() generates (Status status);
};
- IDisplayService.hal
package android.frameworks.displayservice@1.0;
import IDisplayEventReceiver;
interface IDisplayService {
/**
* 创建新的receiver.
*/
getEventReceiver() generates(IDisplayEventReceiver receiver);
};
- IEventCallback.hal
package android.frameworks.displayservice@1.0;
interface IEventCallback {
/**
* Vsync事件
*/
oneway onVsync(uint64_t timestamp, uint32_t count);
/**
* hotplug事件
*/
oneway onHotplug(uint64_t timestamp, bool connected);
};
displayservice的接口,主要是提供给Vendor的HAL使用,让Vendor的HAL也能够接收Vsync数据。libdisplayservicehidl中也主要是DisplayEventReceiver。所以,这里的IDisplayEventReceiver接口 这么设计的 主要是提供给Vendor用。
3.2 显示屏的类型
显示屏幕什么时候创建?各类型的显示屏不一样,Android支持3中类型的显示屏:主显,外显,虚显。
* frameworks/native/services/surfaceflinger/DisplayDevice.h
enum DisplayType {
DISPLAY_ID_INVALID = -1,
DISPLAY_PRIMARY = HWC_DISPLAY_PRIMARY,
DISPLAY_EXTERNAL = HWC_DISPLAY_EXTERNAL,
DISPLAY_VIRTUAL = HWC_DISPLAY_VIRTUAL,
NUM_BUILTIN_DISPLAY_TYPES = HWC_NUM_PHYSICAL_DISPLAY_TYPES,
};
主显示屏幕和外显,都采用热插拔的形式,连接,断开时从底层驱动上报热插拔事件,这是在EventThread中处理的。
-
主显示屏 DISPLAY_PRIMARY
主显示屏幕默认是必现支持的,也就是说,开机时就应该上报 * 连接* 事件,知道屏幕关闭时,才断开。这里说的屏幕关闭是真正的关闭,休眠,锁屏等状态屏幕还是开着的。基本也就是关机的时候。 -
外显示屏 DISPLAY_EXTERNAL
外显示屏幕,一般是有线连接的屏幕,比如HDMI,MHL或者是其他连接标准连接的屏幕,外显一般经常进行热插拔。 -
虚拟显示屏 DISPLAY_VIRTUAL
虚拟显示屏,也就是说这个显示屏是不存在物理设备的,是个虚拟的。
我们先看看DisplayDevice相关类之间的关系:
image我们可以这么来理解:
- Android支持多个显示屏幕,每一个显示屏幕用DisplayDevice进行描述,SurfaceFlinger中有这些显示屏的信息即mDisplay
- 每个显示屏幕,都一个相关联的Buffer,这个Buffer用 DisplaySurface进行描述。
- 每种类型的显示屏,具体采用的Buffer不尽相同,主屏和外显采用FramebufferSurface,而虚拟显示屏采用VirtualDisplaySurface。
- DisplaySurface有自己的BufferQueue,都继承ConsumerBase,所以这里DisplaySurface比较特殊,都是消费者。VirtualDisplaySurface更猛,它还继承BnGraphicBufferProducer,也是生产者。
- RE_Surface是RE命名空间的Surface,和BufferQueue中的Surface同名,但是作用不一样。主要是给RenderEngine用,RenderEngine是一个抽象类,渲染引擎,用于Client端的合成,一般用OpenGL进程合成。
3.3 DisplayDevice的热插拔处理
SurfaceFlinger在初始化的时候,注册Callback接口后。显示屏幕插上和断开时,将通过HAL回调回来。HAL回调的过程先不关注,从SurfaceFlinger中开始看。
void SurfaceFlinger::onHotplugReceived(int32_t sequenceId,
hwc2_display_t display, HWC2::Connection connection,
bool primaryDisplay) {
ALOGV("onHotplugReceived(%d, %" PRIu64 ", %s, %s)",
sequenceId, display,
connection == HWC2::Connection::Connected ?
"connected" : "disconnected",
primaryDisplay ? "primary" : "external");
ConditionalLock lock(mStateLock,
std::this_thread::get_id() != mMainThreadId);
if (primaryDisplay) {
getBE().mHwc->onHotplug(display, connection);
if (!mBuiltinDisplays[DisplayDevice::DISPLAY_PRIMARY].get()) {
createBuiltinDisplayLocked(DisplayDevice::DISPLAY_PRIMARY);
}
createDefaultDisplayDevice();
} else {
if (sequenceId != getBE().mComposerSequenceId) {
return;
}
if (getBE().mHwc->isUsingVrComposer()) {
ALOGE("External displays are not supported by the vr hardware composer.");
return;
}
getBE().mHwc->onHotplug(display, connection);
auto type = DisplayDevice::DISPLAY_EXTERNAL;
if (connection == HWC2::Connection::Connected) {
createBuiltinDisplayLocked(type);
} else {
mCurrentState.displays.removeItem(mBuiltinDisplays[type]);
mBuiltinDisplays[type].clear();
}
setTransactionFlags(eDisplayTransactionNeeded);
}
}
接收到屏幕插拔事件后,主要做了如下的处理:
- 通知HWC onHotplug
通过onHotplug通知HWC;如果是连接,HWC将去获取新添加Display的config信息,如果是断开,将HWC中的Display同步断开。
-
创建Display的Token
createBuiltinDisplayLocked如果是连接状态,都将通过createBuiltinDisplayLocked创建Display的Token。添加到mBuiltinDisplays中,mBuiltinDisplays它只是Display的IBinder列表,我们也称之为Token列表。
sp<IBinder> mBuiltinDisplays[DisplayDevice::NUM_BUILTIN_DISPLAY_TYPES];
这个时候还没有创建DisplayDevice,只是创建了一个Token而已。Display的Token通知添加到mCurrentState的displays中。
- 创建主屏幕对应的DisplayDevice
如果是主屏,还会通过createDefaultDisplayDevice创建默认的DisplayDevice。
void SurfaceFlinger::createDefaultDisplayDevice() {
const DisplayDevice::DisplayType type = DisplayDevice::DISPLAY_PRIMARY;
wp<IBinder> token = mBuiltinDisplays[type];
// All non-virtual displays are currently considered secure.
const bool isSecure = true;
sp<IGraphicBufferProducer> producer;
sp<IGraphicBufferConsumer> consumer;
BufferQueue::createBufferQueue(&producer, &consumer);
sp<FramebufferSurface> fbs = new FramebufferSurface(*getBE().mHwc, type, consumer);
bool hasWideColorModes = false;
std::vector<android_color_mode_t> modes = getHwComposer().getColorModes(type);
for (android_color_mode_t colorMode : modes) {
switch (colorMode) {
case HAL_COLOR_MODE_DISPLAY_P3:
case HAL_COLOR_MODE_ADOBE_RGB:
case HAL_COLOR_MODE_DCI_P3:
hasWideColorModes = true;
break;
default:
break;
}
}
bool useWideColorMode = hasWideColorModes && hasWideColorDisplay && !mForceNativeColorMode;
sp<DisplayDevice> hw = new DisplayDevice(this, DisplayDevice::DISPLAY_PRIMARY, type, isSecure,
token, fbs, producer, useWideColorMode);
mDisplays.add(token, hw);
android_color_mode defaultColorMode = HAL_COLOR_MODE_NATIVE;
if (useWideColorMode) {
defaultColorMode = HAL_COLOR_MODE_SRGB;
}
setActiveColorModeInternal(hw, defaultColorMode);
hw->setCompositionDataSpace(HAL_DATASPACE_UNKNOWN);
// Add the primary display token to mDrawingState so we don't try to
// recreate the DisplayDevice for the primary display.
mDrawingState.displays.add(token, DisplayDeviceState(type, true));
// make the GLContext current so that we can create textures when creating
// Layers (which may happens before we render something)
hw->makeCurrent();
}
- 看到没有,主Display的BufferQueue是就是此时创建的。并且创建了前面所说的FramebufferSurface,这就是FBTarget。
- DisplayDevice对应的类型为DISPLAY_PRIMARY,创建了DisplayDevice后,添加到mDisplays中。而Display的Token被添加到mDrawingState的displays中,注意,是mDrawingState。
- 这里还有颜色模式Colormode和数据空间DataSpace的设置,这两个概念后续介绍。
- 最后,调用makeCurrent,表示该DisplayDevice进入可用状态
bool DisplayDevice::makeCurrent() const {
bool success = mFlinger->getRenderEngine().setCurrentSurface(mSurface);
setViewportAndProjection();
return success;
}
makeCurrent主要做了两件事:其一,设置RenderEngine的Surface,这个Surface封装了前面BufferQueue中创建的Producer,以及对应的NativeWindow;其二,设置Display的Viewport和Projection,做过OpengGL开发的,对这个应该没有什么难题,视窗大小和投影矩阵。也是设置到RenderEngine中,GPU合成用。
-
非主屏删除处理
非主屏时删除时,将Display的Token从mBuiltinDisplays中删掉,且Token也从mCurrentState中删掉。注意,这里的是mCurrentState。主屏一般只会添加一次,没有断开操纵,断开时系统已经关了。 -
Transaction处理
连接或断开显示屏,也算是一种Transaction。通过setTransactionFlags
,设置处理的flag eDisplayTransactionNeeded。
到此,连接时,主显的Token是添加到mDrawingState中的,已经创建对应的DisplayDevice,且没有断开处理。而非主显只创建了Display的Token,添加到这里的是mCurrentState中,还没有创建对应的DisplayDevice,断开的屏幕,Token从mCurrentState删除。简单点来说,mDrawingState中的Token都创建了DisplayDevice;在mCurrentState中的不再mDrawingState中的,都是添加的;在mDrawingState中的,不在mCurrentState中的都是断开的。
3.4 创建DisplayDevice
上面设置的setTransactionFlags什么时候处理?Vsync来的时候,Vsync来后,通过INVALIDATE消息,又回到SurfaceFlinger处理。中间的过程稍后介绍,我们直接看对这里设置的eDisplayTransactionNeeded的处理流程。
处理eDisplayTransactionNeeded时,其实就是同步 mDrawingState 和 mCurrentState 中displays。
-
屏幕断开时的处理
先处理删除的Display,屏幕的Token在mDrawingState中的,不在mCurrentState中的都是断开的。逻辑如下:
void SurfaceFlinger::handleTransactionLocked(uint32_t transactionFlags)
{
``` ```
if (transactionFlags & eDisplayTransactionNeeded) {
const KeyedVector< wp<IBinder>, DisplayDeviceState>& curr(mCurrentState.displays);
const KeyedVector< wp<IBinder>, DisplayDeviceState>& draw(mDrawingState.displays);
if (!curr.isIdenticalTo(draw)) {
mVisibleRegionsDirty = true;
const size_t cc = curr.size();
size_t dc = draw.size();
for (size_t i=0 ; i<dc ;) {
const ssize_t j = curr.indexOfKey(draw.keyAt(i));
if (j < 0) {
if (!draw[i].isMainDisplay()) {
const sp<const DisplayDevice> defaultDisplay(getDefaultDisplayDeviceLocked());
defaultDisplay->makeCurrent();
sp<DisplayDevice> hw(getDisplayDeviceLocked(draw.keyAt(i)));
if (hw != NULL)
hw->disconnect(getHwComposer());
if (draw[i].type < DisplayDevice::NUM_BUILTIN_DISPLAY_TYPES)
mEventThread->onHotplugReceived(draw[i].type, false);
mDisplays.removeItem(draw.keyAt(i));
} else {
ALOGW("trying to remove the main display");
}
} else {
// this display is in both lists. see if something changed.
const DisplayDeviceState& state(curr[j]);
const wp<IBinder>& display(curr.keyAt(j));
const sp<IBinder> state_binder = IInterface::asBinder(state.surface);
const sp<IBinder> draw_binder = IInterface::asBinder(draw[i].surface);
if (state_binder != draw_binder) {
sp<DisplayDevice> hw(getDisplayDeviceLocked(display));
if (hw != NULL)
hw->disconnect(getHwComposer());
mDisplays.removeItem(display);
mDrawingState.displays.removeItemsAt(i);
dc--;
// at this point we must loop to the next item
continue;
}
const sp<DisplayDevice> disp(getDisplayDeviceLocked(display));
if (disp != NULL) {
if (state.layerStack != draw[i].layerStack) {
disp->setLayerStack(state.layerStack);
}
if ((state.orientation != draw[i].orientation)
|| (state.viewport != draw[i].viewport)
|| (state.frame != draw[i].frame))
{
disp->setProjection(state.orientation,
state.viewport, state.frame);
}
if (state.width != draw[i].width || state.height != draw[i].height) {
disp->setDisplaySize(state.width, state.height);
}
}
}
++i;
}
如果Token在mDrawingState中,而没有在mCurrentState中,说明这个屏已经被断开了,需要删掉DisplayDevice。如果Token在两个状态中都存在,有修改,暂时将Token中mDrawingState删掉。注意两个状态啊,要不然理解不对。
断开时,调用DisplayDevice的disconnect,这其中将调用HWC中,HWC中创建的对应的Device也将被删除。同时将DisplayDevice从mDisplays中删除。
-
处理添加的Display
屏幕的Token在mCurrentState中的不再mDrawingState中的,都是添加的;处理逻辑如下。
void SurfaceFlinger::handleTransactionLocked(uint32_t transactionFlags)
{
``` ```
for (size_t i=0 ; i<cc ; i++) {
if (draw.indexOfKey(curr.keyAt(i)) < 0) {
const DisplayDeviceState& state(curr[i]);
sp<DisplaySurface> dispSurface;
sp<IGraphicBufferProducer> producer;
sp<IGraphicBufferProducer> bqProducer;
sp<IGraphicBufferConsumer> bqConsumer;
BufferQueue::createBufferQueue(&bqProducer, &bqConsumer);
int32_t hwcId = -1;
if (state.isVirtualDisplay()) {
// Virtual displays without a surface are dormant:
// they have external state (layer stack, projection,
// etc.) but no internal state (i.e. a DisplayDevice).
if (state.surface != NULL) {
// 虚拟显示用硬件
... ...
sp<VirtualDisplaySurface> vds =
new VirtualDisplaySurface(*getBE().mHwc,
hwcId, state.surface, bqProducer,
bqConsumer, state.displayName);
dispSurface = vds;
producer = vds;
}
} else {
ALOGE_IF(state.surface!=NULL,
"adding a supported display, but rendering "
"surface is provided (%p), ignoring it",
state.surface.get());
hwcId = state.type;
dispSurface = new FramebufferSurface(*getBE().mHwc, hwcId, bqConsumer);
producer = bqProducer;
}
const wp<IBinder>& display(curr.keyAt(i));
if (dispSurface != NULL) {
sp<DisplayDevice> hw =
new DisplayDevice(this, state.type, hwcId, state.isSecure, display,
dispSurface, producer, hasWideColorDisplay);
hw->setLayerStack(state.layerStack);
hw->setProjection(state.orientation,
state.viewport, state.frame);
hw->setDisplayName(state.displayName);
mDisplays.add(display, hw);
if (!state.isVirtualDisplay()) {
mEventThread->onHotplugReceived(state.type, true);
}
}
}
}
}
}
... ...
添加屏幕时,根据前面已经创建的BufferQueue,创建对应的DisplaySurface,外显和虚显的不一样。创建DisplaySurface后,再创建DisplayDevice;设置DisplayDevice的stack,投影矩阵Projection;将创建的DisplayDevice添加到mDisplays中;最后,对外显,调用EventThread的onHotplugReceived。
EventThread的onHotplugReceived函数中,将封装一个hotplug的Event事件DISPLAY_EVENT_HOTPLUG,EventThread再将事件分发出去。这里对hotplug感兴趣的主要就是框架层了,回调给DisplayManagerService。
3.5 hotplug的流程
这里主要将了Display相关的逻辑,主要是热插拔的处理。下面是整个Android系统添加屏幕时的处理流程。
imageDisplay相关的就介绍到这里,后续讲合成时,还会有很多相关的流程。
作者:夕月风
链接:https://www.jianshu.com/p/fa115146949f
至此,本篇已结束。转载网络的文章,小编觉得很优秀,欢迎点击阅读原文,支持原创作者,如有侵权,恳请联系小编删除,欢迎您的建议与指正。同时期待您的关注,感谢您的阅读,谢谢!
网友评论