I'm not sure that's necessarily completely true. I don't think you need to know the original MAC address.
I blindly issued the command in the above post WITH THE XX:XX:XX:XX:XX:XX left as 'X's. Obviously erroneous input to the set command, but what the heck, it was worth a shot since I didn't know my original MAC address. What did I have to lose by trying, I already had the .bk file.
If I now do a
calibrator get nvs_mac /system/etc/firmware/ti-connectivity/wl1271-nvs.bin
(note, that's a get not a set) I get a different MAC address than if I do a
calibrator get nvs_mac /system/etc/firmware/ti-connectivity/wl1271-nvs.bin.bk
(the backup file I made.)
It would appear to me, that if you don't assign a proper address (or per the help even leave out the MAC address completely), it might read the original MAC address from the network card. Or maybe it's just making one up - though I hope not. The help for the calibrator command indicates that the MAC address is an optional argument if I'm reading it correctly:
Usage: calibrator [options] command
--debug enable netlink debugging
--version show version (0.71)
set nvs_mac <nvs file> [<mac addr>]