Linux 5.3 To Enable HDR Metadata Support For AMDGPU Driver

When it comes to HDR display support on Linux we've seen a lot of infrastructure work being pursued by the developers at NVIDIA going back a few years while more recently Intel's open-source developers have been on it too with Icelake Gen11 graphics supporting HDR. We haven't seen much publicly on the AMD Linux front but with the upcoming 5.3 kernel cycle one of their HDR DC patches will be merged.

Buried within the drm-misc-next pull request today being sent to DRM-Next is HDR metadata support for the AMDGPU Direct Rendering Manager driver.

This AMDGPU display code work exposes the HDR output metadata for supported connectors as user-space needs to send the HDR meta-data to the display.

The property is attached to HDMI and DP connectors. Since the metadata isn't actually available when creating the connector this isn't a property we can dynamically support based on the extension block being available or not.

When the HDR metadata is changed a modeset will be forced for now. We need to switch from 8bpc to 10bpc in most cases anyway, and we want to fully exit HDR mode when userspace gives us a NULL metadata, so this isn't completely unnecessary.

The requirement can later be reduced to just entering and exiting HDR or switching max bpc.

The HDR display bits on the kernel-side are coming together but there still appears to be more work in user-space for preparing for the growing number of High Dynamic Range displays.