Input子系統(tǒng)架構(gòu)包括內(nèi)核層與框架層詳解

1、第1章 android input子系統(tǒng)架構(gòu)1.1 input服務(wù)的啟動(dòng)在android的開機(jī)過(guò)程中，系統(tǒng)中的服務(wù)很多都是由systemserver中啟動(dòng)的。systemserver的代碼中有這么一句話。framework/base/services/java/com/android/server/systemserver.javaslog.i(tag, window manager); wm = windowmanagerservice.main(context, power, factorytest != systemserver.factory_test_low_level,!first

2、boot);在這里new了一個(gè)windowmanagerservice的類，我們找到這個(gè)類的構(gòu)造函數(shù)。framework/base/services/java/com/android/server/wm/windowmanagerserver.javaprivate windowmanagerservice(context context, powermanagerservice pm, boolean haveinputmethods, boolean showbootmsgs) minputmanager = new inputmanager(context, this);minputma

3、nager.start();在windowmanagerservice的構(gòu)造函數(shù)中又new了一個(gè)inputmanager類。inputmanager類是整個(gè)android的input的上層代碼最重要的類，就是通過(guò)這個(gè)類繁衍出了整個(gè)復(fù)雜的android的input子系統(tǒng)。作用就好像zygote的孕育著android的各個(gè)服務(wù)，而inputmanager就是負(fù)責(zé)將整個(gè)android的input子系統(tǒng)。framework/base/services/java/com/android/server/wm/windowmanagerserver.javapublic inputmanager(conte

4、xt context, windowmanagerservice windowmanagerservice) looper looper = windowmanagerservice.mh.getlooper();nativeinit(mcontext, mcallbacks, looper.getqueue();在inputmanger的構(gòu)造函數(shù)中，調(diào)用了nativeinit這個(gè)方式，看到native開頭或者結(jié)尾的函數(shù)，一般都是jni。在inputmanager的jni可以找到這個(gè)函數(shù)的實(shí)現(xiàn)。framework/base/services/jni/com_android_server_inp

5、utmanager.javastatic jninativemethod ginputmanagermethods = nativeinit, (landroid/content/context;lcom/android/server/wm/inputmanager$callbacks;landroid/os/messagequeue;)v, (void*) android_server_inputmanager_nativeinit ,簡(jiǎn)單介紹下jni的代碼風(fēng)格，第一個(gè)引號(hào)括起來(lái)的函數(shù)就是我們java代碼的函數(shù)原型，中間的引號(hào)中的就是代表java原型函數(shù)的參數(shù)。而最后的那個(gè)函數(shù)就是在對(duì)應(yīng)的函

6、數(shù)。一般都是c+代碼。framework/base/services/jni/com_android_server_inputmanager.javastatic void android_server_inputmanager_nativeinit(jnienv* env, jclass clazz, jobject contextobj, jobject callbacksobj, jobject messagequeueobj) gnativeinputmanager = new nativeinputmanager(contextobj, callbacksobj, looper);在

7、jni的代碼中，又構(gòu)造了一個(gè)重要的nativeinputmanager類，這是個(gè)c+的本地類。已經(jīng)不在是之前了那個(gè)java的inputmanager類。接下來(lái)看看nativeinputmanager的構(gòu)造函數(shù)。framework/base/services/jni/com_android_server_inputmanager.javanativeinputmanager:nativeinputmanager(jobject contextobj, jobject callbacksobj, const sp& looper) :mlooper(looper) sp eventhub = ne

8、w eventhub(); minputmanager = new inputmanager(eventhub, this, this);這里new了兩個(gè)類，eventhub和inputmanager類。eventhub就是input子系統(tǒng)的hal層了，負(fù)責(zé)將linux的所有的input設(shè)備打開并負(fù)責(zé)輪詢讀取他們的上報(bào)的數(shù)據(jù)，后面會(huì)詳細(xì)介紹，這里先簡(jiǎn)單介紹一下。inputmanager類主要是負(fù)責(zé)管理input event，有inputreader從eventhub讀取事件，然后交給inputdispatcher進(jìn)行分發(fā)。framework/base/services/input/inputm

9、anager.cppinputmanager:inputmanager( const sp& reader, const sp& dispatcher) : mreader(reader), mdispatcher(dispatcher) initialize();void inputmanager:initialize() mreaderthread = new inputreaderthread(mreader); mdispatcherthread = new inputdispatcherthread(mdispatcher);在inputmanager中的initialize的初始化

10、了兩個(gè)線程。一個(gè)是inputreaderthread，負(fù)責(zé)從eventhub中讀取事件，另外一個(gè)是inputdispatcherthread線程，主要負(fù)責(zé)分發(fā)讀取的事件去處理。framework/base/services/java/com/android/server/wm/windowmanagerserver.javaprivate windowmanagerservice(context context, powermanagerservice pm, boolean haveinputmethods, boolean showbootmsgs) minputmanager.start

11、();在開始的時(shí)候，new了一個(gè)inputmanager，然后在繼續(xù)調(diào)用其start方法。framework/base/services/java/com/android/server/wm/windowmanagerserver.javapublic void start() slog.i(tag, starting input manager); nativestart(); registerpointerspeedsettingobserver(); registershowtouchessettingobserver(); updatepointerspeedfromsettings(

12、); updateshowtouchesfromsettings(); nativestart()跑到j(luò)ni的代碼中去了，跟上面的方式一樣。framework/base/services/jni/com_android_server_inputmanager.javastatic jninativemethod ginputmanagermethods = nativestart, ()v, (void*) android_server_inputmanager_nativestart ,static void android_server_inputmanager_nativestart(j

13、nienv* env, jclass clazz) status_t result = gnativeinputmanager-getinputmanager()-start();在java代碼中用了nativestart()，然后jni中又調(diào)用了nativeinputmanager的start方法。在native的inputmanager中找到start的實(shí)現(xiàn)。framework/base/services/input/inputmanager.cppstatus_t inputmanager:start() status_t result = mdispatcherthread-run(i

14、nputdispatcher, priority_urgent_display);result = mreaderthread-run(inputreader, priority_urgent_display);這個(gè)方法就是在前面inputmanager中的構(gòu)造函數(shù)initialize中的兩個(gè)線程運(yùn)行起來(lái)。先看inputdispatcher線程運(yùn)行的情況，然后就是inputreader線程。framework/base/services/input/inputdispatcher.cppbool inputdispatcherthread:threadloop() mdispatcher-di

15、spatchonce(); return true;inputdispatcher線程調(diào)用了dispatcher的dispatchonce的方法。同樣的inputreader線程也會(huì)調(diào)用reader的readeronce的方法。framework/base/services/input/inputdispatcher.cppvoid inputdispatcher:dispatchonce() dispatchonceinnerlocked(&nextwakeuptime); int timeoutmillis = tomillisecondtimeoutdelay(currenttime,

16、nextwakeuptime); mlooper-pollonce(timeoutmillis);dispatchonceinnerlocked是處理input輸入消息，mlooper-pollonce(timeoutmillis)是等待下次輸入消息的事件。先看下消息在dispatchonceinnerlocked函數(shù)中是如何處理的。framework/base/services/input/inputdispatcher.cppvoid inputdispatcher:dispatchonceinnerlocked(nsecs_t* nextwakeuptime) case eventent

17、ry:type_keydone = dispatchkeylocked(currenttime, typedentry, &dropreason, nextwakeuptime);case evententry:type_motion: done = dispatchmotionlocked(currenttime, typedentry, &dropreason, nextwakeuptime);這個(gè)函數(shù)比較長(zhǎng)，input事件在android的上層通過(guò)兩個(gè)隊(duì)列來(lái)保存，分別是inboundqueue和outboundqueue。當(dāng)有input事件產(chǎn)生時(shí)候，會(huì)判斷inboundqueue是否為空

18、，如果事件不為空的話，就從隊(duì)列中取出這個(gè)input事件，然后根據(jù)input事件的類型來(lái)分發(fā)事件給不同的處理函數(shù)，比較常見(jiàn)的是key和motion事件。不管是key事件也好還是motion事件都會(huì)調(diào)用dispatcheventtocurrentinputtargetslocked(currenttime, entry, false);這個(gè)函數(shù)來(lái)繼續(xù)處理。framework/base/services/input/inputdispatcher.cppvoid inputdispatcher:dispatcheventtocurrentinputtargetslocked(nsecs_t curr

19、enttime, evententry* evententry, bool resumewithappendedmotionsample) preparedispatchcyclelocked(currenttime, connection, evententry, & inputtarget, resumewithappendedmotionsample);在這個(gè)函數(shù)中會(huì)繼續(xù)調(diào)用preparedispatchcyclelocked方法來(lái)繼續(xù)處理。而在preparedispatchcyclelocked中又會(huì)繼續(xù)調(diào)用startdispatchcyclelocked(currenttime, c

20、onnection)來(lái)進(jìn)一步處理。framework/base/services/input/inputdispatcher.cppvoid inputdispatcher:startdispatchcyclelocked(nsecs_t currenttime, const sp& connection) switch (evententry-type) case evententry:type_key: status = connection-inputpublisher.publishkeyeventcase evententry:type_motion: status = connec

21、tion-inputpublisher.publishmotioneventstatus = connection-inputpublisher.senddispatchsignal();這個(gè)函數(shù)主要是根據(jù)input事件的類型來(lái)分發(fā)給不同的函數(shù)去處理，如果是key類型的事件就調(diào)用inputpublisher類的publishkeyevent,如果是motion類的事件就會(huì)調(diào)用inputpublisher類的publishmotionevent方法。并在最后發(fā)一個(gè)senddispatchsignal。framework/base/libs/ui/inputtransport.cppstatus_

22、t inputpublisher:publishinputevent(int ashmemfd = mchannel-getashmemfd();int result = ashmem_pin_region(ashmemfd, 0, 0);msemaphoreinitialized = true; msharedmessage-consumed = false; msharedmessage-type = type; msharedmessage-deviceid = deviceid;msharedmessage-source = source;利用publisher中的publishinp

23、utevent將input event寫入共享內(nèi)存。這邊產(chǎn)生了事件，另外一邊必然會(huì)有個(gè)地方回去消費(fèi)這個(gè)事件。注意到上面的代碼中，最后發(fā)送了一個(gè)senddispatchsignal。framework/base/libs/ui/inputtransport.cppstatus_t inputpublisher:senddispatchsignal() return mchannel-sendsignal(input_signal_dispatch);這個(gè)函數(shù)直接調(diào)用了inputchannel的sendsignal方法。繼續(xù)找到inputchannel的sendsignal實(shí)現(xiàn)。framework

24、/base/libs/ui/inputtransport.cppstatus_t inputchannel:sendsignal(char signal) do nwrite = :write(msendpipefd, & signal, 1); while (nwrite = -1 & errno = eintr);而在注冊(cè)inputchannel的時(shí)候就曾經(jīng)注冊(cè)了當(dāng)looper接收到了信號(hào)的一個(gè)回調(diào)函數(shù)。framework/base/services/input/inputdispatcher.cppstatus_t inputdispatcher:registerinputchannel

25、(const sp& inputchannel, const sp& inputwindowhandle, bool monitor) mlooper-addfd(receivefd, 0, alooper_event_input, handlereceivecallback, this);在handlereceivecallback中，作為回調(diào)函數(shù)然后調(diào)用inputconsumer的consume函數(shù)來(lái)消費(fèi)從inputreader中讀取過(guò)來(lái)的inputevent。framework/base/core/jni/android_view_inputqueue.cppint nativeinpu

26、tqueue:handlereceivecallback(int receivefd, int events, void* data) status = connection-inputconsumer.consume(& connection-inputeventfactory, & inputevent);回過(guò)頭來(lái)看之前的inputreader線程，在inputmanager的start方法被調(diào)用了，input的線程也就開始運(yùn)行了。framework/base/services/input/inputreader.cppbool inputreaderthread:threadloop()

27、 mreader-looponce(); return true;在inputreader的looponce中會(huì)調(diào)用eventhub的getevents方法。這個(gè)方法會(huì)和linux內(nèi)核的input子系統(tǒng)打交道。framework/base/services/input/inputreader.cppvoid inputreader:looponce() size_t count = meventhub-getevents(timeoutmillis, meventbuffer, event_buffer_size);if (count) processeventslocked(meventbu

28、ffer, count); 這個(gè)函數(shù)主要通過(guò)eventhub的getevents來(lái)獲取input事件。framework/base/services/input/eventhub.cppsize_t eventhub:getevents(int timeoutmillis, rawevent* buffer, size_t buffersize) struct input_event readbufferbuffersize;for (;) if (mneedtoscandevices) mneedtoscandevices = false; scandeviceslocked(); mnee

29、dtosendfinisheddevicescan = true; 在eventhub初始化的時(shí)候mneedtoscandevices的值是ture的，所以會(huì)直接進(jìn)入到scandeviceslocked。而在內(nèi)核里面所有的input device在注冊(cè)的時(shí)候都會(huì)在linux的文件系統(tǒng)下的/dev/input 下面，所以按照一般的hal的思想，如果要去操作這個(gè)設(shè)備，首先還是要打開這個(gè)設(shè)備節(jié)點(diǎn)的。framework/base/services/input/eventhub.cppvoid eventhub:scandeviceslocked() status_t res = scandirlock

30、ed(device_path); if(res 0) loge(scan dir failed for %sn, device_path); status_t eventhub:scandirlocked(const char *dirname)opendevicelocked(devname);代碼中的while循環(huán)會(huì)對(duì)device_path(/dev/input)下的所有的設(shè)備節(jié)點(diǎn)調(diào)用opendevicelocked方法。framework/base/services/input/eventhub.cppstatus_t eventhub:opendevicelocked(const ch

31、ar *devicepath) int fd = open(devicepath, o_rdwr);inputdeviceidentifier identifier;if(ioctl(fd, eviocgname(sizeof(buffer) - 1), &buffer) next = mopeningdevices; mopeningdevices = device;return 0;首先通過(guò)open系統(tǒng)調(diào)用得到設(shè)備節(jié)點(diǎn)的文件描述符，然后新構(gòu)造一個(gè)叫inputdeviceidentifier類。接著通過(guò)對(duì)剛才得到的設(shè)備節(jié)點(diǎn)描述下ioctl的命令獲取設(shè)備的一些簡(jiǎn)單信息，譬如：設(shè)備的名字，設(shè)備驅(qū)

32、動(dòng)的版本號(hào)，設(shè)備的唯一id，和描述符輪詢的方式。得到的這些信息保存在inputdeviceidentifier類里面。最后又構(gòu)造了一個(gè)device類，其中設(shè)備描述符和剛才的構(gòu)造inputdeviceidentifier類作為參數(shù)重新構(gòu)造了device類。然后在構(gòu)造成功了device類又會(huì)通過(guò)ioctl系統(tǒng)調(diào)用獲取input設(shè)備的一些比較重要的參數(shù)。比如：設(shè)備上報(bào)事件的類型是相對(duì)事件還是絕對(duì)事件，相對(duì)事件一般是指像鼠標(biāo)滑動(dòng)，絕對(duì)事件就好比觸摸屏上報(bào)的坐標(biāo)，設(shè)備所屬的class等一些比較重要的信息。舉一些例子：input_device_class_keyboard(按鍵類型)，input_devi

33、ce_class_cursor(帶游標(biāo)類型：鼠標(biāo)和軌跡球等)，input_device_class_touch(觸摸類型：?jiǎn)吸c(diǎn)觸摸或多點(diǎn)觸摸)，input_device_class_touch_mt(這個(gè)類型特指多點(diǎn)觸摸)等。如果一個(gè)設(shè)備的驅(qū)動(dòng)沒(méi)有指明設(shè)備的類型的話，那么他在android中上報(bào)的數(shù)據(jù)時(shí)不會(huì)被處理的。這個(gè)函數(shù)的最后是將input設(shè)備的文件描述符加入到輪詢的集合中去，如果接收到事件就會(huì)去處理。framework/base/services/input/inputreader.cppvoid inputreader:looponce() size_t count = meventh

34、ub-getevents(timeoutmillis, meventbuffer, event_buffer_size);if (count) processeventslocked(meventbuffer, count); 回到之前的inputreader的線程中，通過(guò)eventhub的getevents方法得到了input事件。函數(shù)返回的是獲取的事件數(shù)目。如果事件不為零或者負(fù)數(shù)就會(huì)調(diào)用processeventlocked來(lái)處理。framework/base/services/input/inputreader.cppvoid inputreader:processeventslocked

35、(const rawevent* rawevents, size_t count) processeventsfordevicelocked(deviceid, rawevent, batchsize);case eventhubinterface:device_added: adddevicelocked(rawevent-when, rawevent-deviceid);case eventhubinterface:device_removed: removedevicelocked(rawevent-when, rawevent-deviceid);case eventhubinterf

36、ace:finished_device_scan: handleconfigurationchangedlocked(rawevent-when);在處理input的事件時(shí)候，如果不是設(shè)備的添加，刪除和完成掃描的時(shí)候。就會(huì)調(diào)用processeventsfordevicelocked來(lái)處理。framework/base/services/input/inputreader.cppvoid inputreader:processeventsfordevicelocked(int32_t deviceid, const rawevent* rawevents, size_t count) devic

37、e-process(rawevents, count);這個(gè)函數(shù)也很簡(jiǎn)單直接回調(diào)了device的process方法來(lái)進(jìn)行處理，這個(gè)device就是在之前的eventhub打開設(shè)備時(shí)候構(gòu)造了一個(gè)device類。下面來(lái)具體看看device的process是如何進(jìn)行處理的。framework/base/services/input/inputreader.cppvoid inputdevice:process(const rawevent* rawevents, size_t count) for (size_t i = 0; i process(rawevent); 這里直接調(diào)用了mapper的p

38、rocess。那inputmapper是什么時(shí)候初始化的呢？前面提到如果設(shè)備不是設(shè)備的添加或刪除的時(shí)候就調(diào)用processeventsfordevicelocked來(lái)處理。也就是說(shuō)當(dāng)設(shè)備第一次添加的時(shí)候，就會(huì)調(diào)用adddevicelocked。inputmapper就是從這個(gè)地方注冊(cè)過(guò)來(lái)的。具體看下面的代碼：framework/base/services/input/inputreader.cppvoid inputreader:adddevicelocked(nsecs_t when, int32_t deviceid) inputdevice* device = createdevicel

39、ocked(deviceid, name, classes);inputdevice* inputreader:createdevicelocked(int32_t deviceid,const string8& name, uint32_t classes) inputdevice* device = new inputdevice(&mcontext, deviceid, name, classes);if (classes & input_device_class_switch) device-addmapper(new switchinputmapper(device);if (cla

40、sses & input_device_class_cursor) device-addmapper(new cursorinputmapper(device);if (classes & input_device_class_touch_mt) device-addmapper(new multitouchinputmapper(device); else if (classes & input_device_class_touch) device-addmapper(new singletouchinputmapper(device);if (classes & input_device_

41、class_joystick) device-addmapper(new joystickinputmapper(device);return device;從上面的代碼可以非常明顯的看出，inputmapper是根據(jù)inputdevice的class來(lái)構(gòu)造的這么一個(gè)類。也就是說(shuō)如果我們的設(shè)備是switch類就為這個(gè)設(shè)備構(gòu)造一個(gè)switchinputmapper類，我們假設(shè)我們現(xiàn)在的事件是由觸摸屏上報(bào)的事件處理流程。在前面處理的過(guò)程中我們就會(huì)調(diào)用multitouchinputmapper的process來(lái)繼續(xù)處理。也就是說(shuō)當(dāng)處理到mapper-process的時(shí)候，代碼就會(huì)根據(jù)具體的設(shè)備cla

42、ss類型來(lái)處理相應(yīng)的事件。這么多inputmapper，我們就以multitouchinputmapper的流程繼續(xù)來(lái)分析事件的處理流程。framework/base/services/input/inputreader.cppvoid multitouchinputmapper:process(const rawevent* rawevent) touchinputmapper:process(rawevent); mmultitouchmotionacess(rawevent);void multitouchmotionaccumulator:process(c

43、onst rawevent* rawevent) switch (rawevent-scancode) case abs_mt_position_x: slot-minuse = true; slot-mabsmtpositionx = rawevent-value;case abs_mt_position_y: slot-minuse = true; slot-mabsmtpositiony = rawevent-value;case abs_mt_touch_major: slot-minuse = true; slot-mabsmttouchmajor = rawevent-value;

44、 break;case abs_mt_touch_minor: slot-minuse = true; slot-mabsmttouchminor = rawevent-value; slot-mhaveabsmttouchminor = true;在這個(gè)處理過(guò)程中將上報(bào)的原始事件的一些重要參數(shù)都賦值給了一個(gè)叫slot的結(jié)構(gòu)的成員。我們知道多點(diǎn)觸摸上報(bào)的一些參數(shù)主要包括：x軸和y軸的坐標(biāo)點(diǎn)，abs_mt_touch_major代表手指和觸摸屏接觸面的長(zhǎng)軸(如果假定人手指和觸摸屏接觸面一般都是橢圓)，abs_mt_touch_minor代表手指和屏幕接觸面的短軸等等一些重要的參數(shù)都對(duì)號(hào)入座的賦值

45、給了一個(gè)叫slot的結(jié)構(gòu)體成員，具體更多的參數(shù)代表什么意思我就不多說(shuō)了(大家可以參照l(shuí)inux內(nèi)核文檔，多點(diǎn)觸摸協(xié)議)。multitouchinputmapper的process處理分了兩部分，首先是調(diào)用了touchinputmapper的process方法，然后調(diào)用了mmultitouchmotionacess來(lái)進(jìn)行處理。先看touchinputmapper的處理流程。framework/base/services/input/inputreader.cppvoid touchinputmapper:process(const rawevent* rawevent

46、) if (rawevent-type = ev_syn & rawevent-scancode = syn_report) sync(rawevent-when); 在linux內(nèi)核往上層上報(bào)input event的時(shí)候是由順序的，以觸摸屏為例，input_report_abs會(huì)被用來(lái)上報(bào)一些絕對(duì)事件(如：接觸面積半徑，x和y軸的坐標(biāo)點(diǎn))，但是在每一次上報(bào)完成后都會(huì)調(diào)用input_sync(input_dev);來(lái)表示一次完整的事件上報(bào)，換句話說(shuō)這個(gè)rawevent-type為ev_syn的事件就是許多input event的分隔符。framework/base/services/input

47、/inputreader.cppvoid touchinputmapper:sync(nsecs_t when) bool havepointerids = true; mcurrentrawpointerdata.clear();synctouch(when, &havepointerids);cookpointerdata();dispatchhoverexit(when, policyflags);dispatchtouches(when, policyflags);dispatchhoverenterandmove(when, policyflags);通過(guò)同步觸摸事件，然后調(diào)用coo

48、kpointerdata來(lái)計(jì)算x和y的坐標(biāo)，前后兩次上報(bào)數(shù)據(jù)的距離，和根據(jù)縮放的大小及方向來(lái)判斷是不是需要旋轉(zhuǎn)屏幕。然后dispatchtouches中又調(diào)用了disaptchmotion方法。framework/base/services/input/inputreader.cppvoid touchinputmapper:dispatchmotion(nsecs_t when, uint32_t policyflags, uint32_t source,) getlistener()-notifymotion(&args);通過(guò)getlister的方法得到inputlistener并調(diào)用其

49、notifymotion。void queuedinputlistener:notifymotion(const notifymotionargs* args) margsqueue.push(new notifymotionargs(*args);在構(gòu)造了一個(gè)notifymotionargs類之后，我們回到之前的inputreader的looponce方法中，在最后調(diào)用了mqueuedlistener-flush();flush函數(shù)就是要把margsqueue中的所有notifyargs進(jìn)行處理。為描述方便，先看看其代碼：framework/base/services/input/input

50、lisenter.cppvoid queuedinputlistener:flush() size_t count = margsqueue.size(); for (size_t i = 0; i notify(minnerlistener); delete args; margsqueue.clear();繼續(xù)在notifyargs中調(diào)用了其notify的方法。還是在這個(gè)文件中可以看看我們notifymotionargs的notify方法。framework/base/services/input/inputlisenter.cppvoid notifymotionargs:notify(const sp& listener) const listener-notifymotion(this);在inputdispatcher.h中inputdispatcherinterface是繼承inputlistenerinterface，父類調(diào)用了子類的虛函數(shù)notifymotion的實(shí)例化。在inputdispacher的notifymotion中繼續(xù)，這就重新回到了我們上面分析的inputdispatch線程的代碼。正好完成了一邊生產(chǎn)事件而在另一邊消費(fèi)事件。