USB Gadget Multi-Function Networking

One of the most powerful features of Linux on the MSM8916 is the Linux USB Gadget Subsystem (ConfigFS).

Because the USB controller is natively dual-role (OTG), the dongle does not simply act as a consumer device—it can emulate multiple USB peripheral devices simultaneously to your host computer.

What Can USB Gadget Emulate?

                    ┌─────────────────────────┐
                    │   MSM8916 OpenStick     │
                    └───────────┬─────────────┘
                                │ (Single USB-A Plug)
             ┌──────────────────┼──────────────────┐
             ▼                  ▼                  ▼
    Virtual Ethernet    Virtual Serial Port   Mass Storage
       (RNDIS/ECM)           (CDC-ACM)            (LUN)
    192.168.68.1 / SSH   /dev/ttyACM0 debug    Mounted Drive

Virtual Ethernet (RNDIS / CDC-ECM / CDC-NCM):
- Appears as a high-speed network adapter.
- Provides instant IP communication (192.168.68.1) and SSH access without needing Wi-Fi.
Serial Console (CDC-ACM):
- Appears as a COM port (Windows) or /dev/ttyACM0 (Linux/macOS).
- Allows direct terminal login even if the network stack fails or IP changes.
Mass Storage (USB Drive):
- Presents a portion of the eMMC or a loopback .img file as a plug-and-play USB thumb drive to your PC.

Managing Gadget Functions via ConfigFS

On OpenStick Debian, gadget configuration is automated via /usr/sbin/gadget or systemd scripts located in /etc/init.d/usb-gadget.

Changing the Gadget IP Address

If 192.168.68.1 conflicts with your local home network:

# Edit the DHCP / DNS daemon config
sudo nano /etc/dnsmasq.d/usb.conf

# Change interface address:
# address=/openstick/192.168.70.1
# dhcp-range=192.168.70.10,192.168.70.50,12h

# Update the network interface config
sudo nano /etc/network/interfaces.d/usb0

# Restart networking
sudo systemctl restart networking
sudo systemctl restart dnsmasq

Connecting via USB Serial Console

If your computer fails to acquire an IP over USB Ethernet:

Open your terminal or PuTTY / Serial client.
Select device /dev/ttyACM0 (or COMx on Windows).
Set baud rate to 115200.

Press Enter to see the login prompt:

Debian GNU/Linux 11 openstick ttyGS0

openstick login:

This provides a 100% reliable rescue channel regardless of firewall or network configuration!