Android – How does Android schedule a device to wake from hibernation?

How does Android schedule a device to wake from hibernation?… here is a solution to the problem.

How does Android schedule a device to wake from hibernation?

When using AlarmManager, Android devices can wake up from sleep at some point.

How does Android schedule wakeups at the bottom level?

I tried using rtcwake

, but it failed rtcwake:/dev/rtc0 not enabled for wakeup events (if I force rtcwake to continue and do the necessary ioctl, I still don’t see the device being woken up on time).

What system calls does Android use to set up alerts and how do I set alerts myself from the console?

Solution

Android uses the /dev/alarm device to set an alarm that wakes the system from a suspended state.
It can access this device from JNI using ioctl. See the frameworks/base/services/jni/com_android_server_AlarmManagerService.cpp file.
Android has exclusive access to the device, and as far as I know, the interface is only available from Java that uses the AlarmManager service.
If you need to set these alerts at the Java level, you can access this service from native using getSystemservice(ALARM_SERVICE), which is a bit tricky and I’m currently having the same issue. I need to raise an alert in the native process, and I’m using a socket to communicate with the java service to schedule the alert. This may not be the answer you are looking for, but I would like to share my experience.

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