Android suspend/resume flow (Part 1: User Mode)

When the user presses the power button:

0) Android/frameworks/base/services/Java/COM/Android/Server/windowmanagerservice. Java
Boolean screenisoff =! Mpowermanager. isscreenon ();
Boolean screenisdim =! Mpowermanager. isscreenbright ();
Int actions = mpolicy. interceptkeytq (event ,! Screenisoff); ==> Step 1
If (Actions & windowmanagerpolicy. action_go_to_sleep )! = 0 ){
Mpowermanager. Gotosleep (event. When); ==> Step 2
}

 

1) Android/frameworks/policies/base/phone/COM/Android/Internal/policy/impl/phonewindowmanager. Java

Interceptkeytq Function

 

If (type = rawinputevent. ev_key ){
If (code = keyevent. keycode_endcall
| Code = keyevent. keycode_power ){

If (down ){

...................

// Only try to turn off the screen if we didn't already hang up
Mshouldturnoffonkeyup = true;
Mhandler. postdelayed (mpowerlongpress,
Viewconfiguration. getglobalactionkeytimeout (); ==> over Ms pop-up dialog box
Result & = ~ Action_pass_to_user;

}

Else {

Log. D (TAG, "power button up/R/N ");
Mhandler. removecallbacks (mpowerlongpress); ==> if the power up key exists within ms, cancel the dialog box

.................

Result | = action_go_to_sleep;
}

 

2) Android/framework/base/services/Java/COM/Android/Server/powermanagerservice. Java
Public void Gotosleep (long time)
{
Gotosleepwithreason (time, windowmanagerpolicy. off_because_of_user );
}

3) Jave Native Interface:
Android/frameworks/base/CORE/JNI/android_ OS _power.cpp

Static int
Setscreenstate (jnienv * ENV, jobject clazz, jboolean on)
{
Return set_screen_state (on );
}

4) Android/hardware/libhardware_legacy/power. c
Int
Set_screen_state (INT on)
{
Qemu_fallback (set_screen_state (on ));

Initialize_fds () ;==> open ("/sys/power/State", o_rdwr );

If (g_error) return g_error;

Char Buf [32];
Int Len;
If (on)
Len = sprintf (BUF, on_state );
Else
Len = sprintf (BUF, off_state );
Len = write (g_fds [request_state], Buf, Len) ;==> echo mem>/sys/power/State
If (LEN <0 ){
LogE ("failed setting last user activity: g_error = % d/N", g_error );
}
Return 0;
}

5) system will enter suspend mode and it will start normal Linux suspend Flow