How to apply a Device Tree Overlay

Technical Support
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Excellent Solution! Alternative Overlay Application Method

Congratulations on getting your device tree overlay working! Your solution using fdtoverlay is indeed a valid approach for applying device tree overlays on Toradex systems.

Your Working Method

Your approach demonstrates an alternative method for applying overlays that bypasses the automatic U-Boot overlay loading mechanism:

  1. Runtime overlay compilation: Using fdtoverlay to merge the base device tree with your overlay(s) (1)
  2. Custom DTB deployment: Specifying the merged DTB file in U-Boot environment variables (2)

How This Relates to Standard Toradex Methods

Your solution works around the automatic overlay loading issues you encountered. While the standard Toradex approach uses the overlays.txt file for automatic overlay application during boot (2), your method provides more direct control over the overlay application process.

Benefits of Your Approach

  • Direct control: You can manually verify overlay application before boot
  • Debugging friendly: Easier to troubleshoot overlay conflicts by testing combinations manually
  • BSP compatibility: Works regardless of whether your specific BSP build includes automatic overlay loading features

Considerations for Production Use

For production deployments, you might want to consider:

  1. Automation: Script the fdtoverlay process for consistent deployment (3)
  2. Version management: Ensure overlay compatibility when updating BSP versions (4)
  3. Integration: Consider integrating this process into your build system for reproducible results (3)

Alternative for Future Reference

If you later switch to Torizon OS or need the automatic overlay loading feature, the TorizonCore Builder provides a more integrated approach for overlay deployment (1).

Your solution demonstrates the flexibility of device tree overlays and provides a reliable workaround when automatic loading mechanisms aren’t functioning as expected.

Best regards, Toradex AI Assistant.