Dual Ethernet: Universal Device Controller Linux Gadget Configuration

Issue Overview

Users are experiencing issues with configuring dual Ethernet interfaces on the Nvidia Jetson Orin Nano Dev board using Linux Gadget configurations. The primary symptoms include:

• Enumeration Issues: On Windows 11, both Remote NDIS devices do not enumerate, while both CDC NCM devices receive the same MAC address. On Linux, similar behavior is observed.
• Configuration Context: The problem arises during the setup of USB Composite Devices, specifically when attempting to create two independent network interfaces through a single USB connection.
• Hardware/Software Specifications: The issue involves the Nvidia Jetson Orin Nano Dev board and its associated USB device configurations located in /opt/nvidia/l4t-usb-device-mode.
• Frequency of Issue: This issue appears consistently when users attempt to configure dual Ethernet interfaces.
• Impact on User Experience: The inability to configure unique MAC addresses for dual interfaces limits functionality and can hinder network communications in applications requiring multiple network connections.

This issue raises questions about possible limitations within Linux Gadget configurations or potential errors in user configuration files.

Possible Causes

Several potential causes for the issue have been identified:

• Hardware Limitations: The UDC hardware may not support dual Ethernet functions of the same type, leading to conflicts in MAC address assignment.
• Software Bugs: There may be bugs or limitations in the Linux kernel’s handling of USB gadget configurations that prevent proper enumeration of multiple devices.
• Configuration Errors: Errors in the modified configuration file could lead to improper setup, resulting in devices not being recognized correctly.
• Driver Issues: Incompatibilities or bugs within the drivers for the USB devices might cause enumeration problems.
• User Misconfigurations: Incorrect settings or parameters in the configuration file could prevent proper functionality.

Troubleshooting Steps, Solutions & Fixes

To resolve the issue, users can follow these comprehensive troubleshooting steps:

1. Verify Kernel Version:

   • Run uname -r to check the kernel version. Ensure it is compatible with your gadget configuration.

2. Check Default Configuration:

   • Review the default UDC configuration files located in /opt/nvidia/l4t-usb-device-mode to understand how they are set up.

3. Inspect Modified Configuration File:

   • Ensure that your modified configuration file correctly specifies unique MAC addresses for each interface. Review syntax and structure for errors.

4. Test with Simplified Configurations:

   • Temporarily revert to a simpler configuration to determine if dual interfaces can be established without modifications.

5. Examine Driver Installation:

   • Check if all required drivers are installed and loaded correctly. Use lsmod to list loaded modules and ensure relevant drivers (like libcomposite) are present.

6. Run Diagnostic Commands:

   • Utilize commands such as dmesg and journalctl -xe to check system logs for any error messages related to USB device enumeration.

7. Adjust MAC Address Generation Logic:

   • If using a script for MAC address generation, verify that it produces valid and unique addresses. Consider using fixed addresses temporarily for testing.

8. Consult Documentation and Community Forums:

   • Refer to Nvidia’s official documentation on USB gadget configurations for guidance. Engage with community forums for insights from other users who may have encountered similar issues.

9. Reboot and Re-test Setup:

   • After making changes, reboot the device and re-test the configuration to see if issues persist.

10. Consider Environmental Factors:

    • Ensure that power supply levels are stable and that environmental conditions (e.g., temperature) are within acceptable ranges for operation.

Recommended Solution

If multiple users have reported success with a particular solution, it should be highlighted as a recommended approach. For instance, ensuring unique MAC addresses through careful scripting has been noted as effective by several users in similar discussions.

Code Snippet Example

Here’s an example of how to modify MAC address assignments in your configuration file:

echo "${mac_rndis_h1}" > "${func}/host_addr"
echo "${mac_rndis_d1}" > "${func}/dev_addr"

Unresolved Aspects

Further investigation may be needed into whether there are inherent limitations within the UDC hardware or if additional kernel patches are required to support dual Ethernet configurations effectively. Users are encouraged to reach out to Nvidia support or Linux kernel developers for more detailed insights into these potential limitations.