Just to update you guys,
What happened?
Several of the guys who flashed the MG4 firmware had their EFS partition modified. Which means that MG4 ROMs work only with MG4 modems at this moment.
Which ROM?
[Stock Official Firmwares] I9300XXEMG4 (4.1.2) - United Kingdom (BTU)
What does it mean to us?
So in case if you have to go back to earlier firmware you will have problems with IMEI. You have to then,
(1) Restore EFS (that is backed up before this change) or
(2) Flash MG4 modem which can still read the modified EFS.
Edit: Update from User: JustArchi
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1. Problem is caused by a modem. On the first boot with XXEMG4 modem it changes /efs folder/partition into some kind of new format.
2. This problem isn't caused by RIL or Samsung ROM. It's caused by a modem. That means it also affects CM/AOSP/AOKP/Other, tested on ArchiDroid 2.X.
3. If we use old modem with already changed /efs we won't be able to connect to the network and our IMEI will change to unknown, starting from numbers 0079.
4. If you don't want to mess with /efs folder anymore or don't have a backup of your old /efs you can temporarily use my emergency zip, which changes modem into XXEMG4, not touching RIL or any other stuff, so it's also compatible with CM/AOSP/AOKP/Other variants.
Most important thing - XXEMG4 doesn't corrupt your /EFS, it changes it into a new format.
For now I strongly recommend to not touch anything linked to XXEMG4 and if you did that already I recommend immediately creating a backup of current already changed /efs partition and using my zip to stay on XXEMG4 modem unless we'll have more info.
Source: Original Post here
----------------------------------------------------------------------------------------------------
Thanks: JustArchi, Peter (User:whiskerp) and User:SignetSphere
Also look at discussions: here
What happened?
Several of the guys who flashed the MG4 firmware had their EFS partition modified. Which means that MG4 ROMs work only with MG4 modems at this moment.
Which ROM?
[Stock Official Firmwares] I9300XXEMG4 (4.1.2) - United Kingdom (BTU)
What does it mean to us?
So in case if you have to go back to earlier firmware you will have problems with IMEI. You have to then,
(1) Restore EFS (that is backed up before this change) or
(2) Flash MG4 modem which can still read the modified EFS.
Edit: Update from User: JustArchi
----------------------------------------------------------------------------------------------------
1. Problem is caused by a modem. On the first boot with XXEMG4 modem it changes /efs folder/partition into some kind of new format.
2. This problem isn't caused by RIL or Samsung ROM. It's caused by a modem. That means it also affects CM/AOSP/AOKP/Other, tested on ArchiDroid 2.X.
3. If we use old modem with already changed /efs we won't be able to connect to the network and our IMEI will change to unknown, starting from numbers 0079.
4. If you don't want to mess with /efs folder anymore or don't have a backup of your old /efs you can temporarily use my emergency zip, which changes modem into XXEMG4, not touching RIL or any other stuff, so it's also compatible with CM/AOSP/AOKP/Other variants.
Most important thing - XXEMG4 doesn't corrupt your /EFS, it changes it into a new format.
For now I strongly recommend to not touch anything linked to XXEMG4 and if you did that already I recommend immediately creating a backup of current already changed /efs partition and using my zip to stay on XXEMG4 modem unless we'll have more info.
Source: Original Post here
----------------------------------------------------------------------------------------------------
Thanks: JustArchi, Peter (User:whiskerp) and User:SignetSphere
Also look at discussions: here