Shell/tty Access via USB or Bluetooth?

Question

Overview

I am in the process of reverse engineering the software on my Infiniti Q50 head unit, and I am trying to figure out the best way to get shell access. I have pulled the image off of the microSD card and flashed it to another microSD that I am modifying, it runs a heavily modified version of Meego which was discontinued a while ago and I can't find docs for because it just goes to the Tizen website.

Background

• The head unit itself has diagnostic connectors board edge connectors that are not accessible while plugged in, so I want to get shell via Bluetooth or the attached USB-A ports
• The linux system partition was readonly with a separate home partition, but I enabled write access in the bootloader
• There are udev rules in place to automount USB drives (for infotainment system & updates)
• I have full root filesystem access and I can add/change any files on the system including adding scripts to systemd
• I do not have network access or shell access
• I can answer any other questions you may have about the system

Kernel Modules

Below is a GitHub gist of the /lib/2.6.37.6-35.1_DLK0041-android-intel-crossville_lapis-fastboot/kernel/ folder

Kernel Modules

Answer 1

Something like this has worked for me in the past in a similar situation:

• Check, if the directory of driver modules contains one or more modules for one of the popular USB-Serial adapter chips
  
• If not, you could compile one of them.
  Maybe you'll need to cross-compile on a different host architecture
• Find/Buy a USB-Serial adapter, that uses the correct chip for the driver module you found/compiled above.
• Modify the rootfs to start a getty on (what I assume will then be) /dev/ttyUSB0
• Connect all the hardware
• login via this serial connection.