- the factory flash tool needs the device to be plugged in _after_ it
   scans or starts
   - the scatter file it uses is basically just a list of mappings between
   filenames and partitions: or at least, it performs uploads if I treat
   it that way
   - using that approach I flashed the twrp but the phone does not boot
   when this is flashed. it could be because it's still locked.
   - the flashing baud rate is 921600 . this may be used to engage the
   ttyACM serial device the phone briefly exposes before boot.
   1328
   - I put the system images on a new partition but windows isn't
   recognising it. I ended up rebooting since kvm didnt seem to be
   working. noting the size of this partition would let me reformat it
   under windows.
   - in the twrp instructions it says "fastboot flashing unlock" , sounds
   important