DDC/CI command line tool.
Depends on loaded i2c-dev module (and the resulting /dev/i2c-? files to access the i2c bus you pass on the command line).
Does not depend on any smbus python modules or such.
Pretty raw at the moment. – Starting point for improving knowledge beyond the crappy spec: with real hardware reverse engineering.
I will try to get this working over DisplayPort. The DP AUX channel is definitively different to work with... and I can’t see the kernel code which does the legacy i2c mapping... maybe there is none. So I have to do it in the app.