onyon.net - Samsung Galaxy S3 LTE (i9305), Proximity sensor fix

The problem with proximity sensor is described better in these threads on XDA: first and second. Basically, phone's screen stays off during calls, no matter whether it's on the ear or in your hand.

I found that there are differences between my phone and the others: If I tried to count correct value to write to /efs/prox_cal I always got 0. That value changed nothing. Then I tried value from the first thread which is 45 in hex and that worked. But somehow the value wouldn't persist through reboots. So I rolled my own solution which is to write custom init script. I'm running AMCHA Rom 9.0 (based on stock) if it matters.

You need root shell on the phone
Make the system partition writable:
```
mount -o remount,rw /system
```
```
cd /etc/init.d
```
```
vi 20fixproximity
```

#!/system/bin/sh

echo -en $'\x45' > /efs/prox_cal
chown system:system /efs/prox_cal
chmod 644 /efs/prox_cal

Change ownership and permissions on 20fixproximity file to match other init files in the directory
reboot