功能是提供一個(gè)定時(shí)器把設(shè)備從睡眠狀態(tài)喚醒，同時(shí)提供一個(gè)在設(shè)備睡眠時(shí)仍會(huì)運(yùn)行的時(shí)鐘基準(zhǔn)
Alarm層次結(jié)構(gòu)
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(1)RTC驅(qū)動(dòng)程序
drivers/rtc/
(2)Alarm驅(qū)動(dòng)程序
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(3)本地JNI
frameworks/base/services/jni/com_android_server_AlarmManagerService.cpp
(4)java
frameworks/base/services/java/com/android/server/AlarmManagerServuce.java,frameworks/base/core/java/android/app/AlarmManager.java
Alarm驅(qū)動(dòng)架構(gòu)
Alarm驅(qū)動(dòng)程序?yàn)橛脩艨臻g提供了設(shè)備節(jié)點(diǎn)/dev/alarm,主設(shè)備號(hào)為10的misc字符設(shè)備，次設(shè)備號(hào)是動(dòng)態(tài)生成
