[android-porting] Correct way of adding a daemon to AOSP

[Rohit Mohan]

Hi ,
I needed to add a daemon written in C to AOSP start up. Basically it needs
to read and write to some sysfs files and also enable/disable airplane mode
based on a button press. I get button events from linux input key events(
/dev/input/event1 ) and enable airplane mode using the command "settings
put global airplane_mode_on 1" in my C code. The code is in "external"
directory and I have added below snippet in
device/qcom/msm8996/init.target.rc.

service myapp /system/bin/myapp
class main
user root
group system wakelock

on property:sys.boot_completed=1
start hotswapd

I am a linux kernel guy and not much into AOSP customization. I am
struggling with sepolicy issues. If anyone could answer below queries, I
would greatly appreciate it.

1. Is this the right way to add a daemon?
2. What are the exact steps to get this daemon to run with all required
permissions at start up?
3. What happens if this daemon is killed? Will it be restarted by android?
4. Am I enabling airplane mode in the right way? Is there a better/cleaner
way of doing it?

Thanks

Rohith