Aspect Ratio Support Within The Linux Kernel's DRM Code Revised

Intel open-source developer Ankit Nautiyal has restarted work on adding picture aspect ratio support to the Linux kernel's Direct Rendering Manager (DRM) layer.

Previous work on adding aspect ratio handling to the DRM subsystem's mode-setting paths and exposing that to user-space had failed and been reverted since it didn't properly deal with user-space applications not supporting the aspect ratio information attached to modes. With these new patches, the new aspect ratio support is hidden behind a capability flag as to not cause problems for existing software.

The benefit though of this code is with the proper aspect ratio support, the Linux DRM code is now able to pass some more HDMI compliance tests. The last of these patches also add support for HDMI 2.0's new 64:27 and 256:135 aspect ratios.

Intel GPU Tools has already been modified to support mode-setting with only aspect ratio modes. There is also a patch for Wayland/Weston's DRM compositor code to add aspect ratio parsing support too as a real-world user.

More details on this revised DRM aspect ratio handling code via this patch series.