A strange one. In Linux 4.7-rc4, at least as build by the Ubuntu mainline ppa, gamma table updates via RandR don't work. No errors are reported and the X-Server thinks everything went well, but on Intel Ironlake and Ivybridge the updates don't have any visual effect.
The same problem doesn't happen with current drm-next, so something was fixed. Looking at the new code in intel_color.c i can't see anything obvious that would break it on 4.7-rc but make it work on drm-next? Are there some gamma fixes in drm-next that didn't make it into 4.7-rc yet? Thanks, -mario
