So with the recent dropping of Generic-Legacy (X11) I moved a system to Generic (GBM) and found it produces a rainbow looking picture. This likely is a bug in Mesa's Crocus driver. Kodi currently is looking and using the reported modifiers, and Crocus is reporting the modifier INTEL_X_TILED which seems to be invalid for the Ironlake GPUs (yes I know it is an ancient system).
I know this GPU had worked with GBM a long time back. Looking back through the Kodi history, at one point the modifiers were just defaults but became dynamic with this pull https://github.com/xbmc/xbmc/pull/18570/commits
I've tried various environment variables that claim to disable Mesa's reporting of tiling, however the planes still report INTEL_X_TILED.
The question then is, in order to confirm the issue is with Crocus, is there any way to force Kodi (from Kodi side, not Mesa) to use Linear without having to patch the code?