I do not have access to specific documents or header files. However, I can suggest some general resources and steps that may help you access the DP AUX channel.
Firstly, you can refer to the VESA DisplayPort specification available on their website. This specification defines the AUX channel and its use in DisplayPort devices. You can use this information to understand how to access the AUX channel.
Secondly, you can check if your device manufacturer provides any specific documentation or header files for accessing the AUX channel. You can reach out to their support team or check their website for any relevant information.
Finally, you can consult with the DisplayPort Alternate Mode adopters forum or other relevant forums to discuss and seek guidance from other developers who have worked on similar projects.
I hope this helps you.