Raspbian Likely To Use Firmware-Based KMS For Raspberry Pi As Temporary Measure

Eric Anholt has been working at Broadcom for more than two years to develop the "VC4" open-source Linux graphics driver stack consisting of the DRM/KMS kernel driver and VC4 Gallium3D driver in user-space. While there's been 2+ years of work and tons of progress made, it's still not feature-complete compared to the older proprietary driver and as an interim solution Eric has hacked up a firmware-based KMS path.

Among the KMS work left still to be accomplished for the clean VC4 DRM/KMS driver is HDMI audio, DSI power management, SDTV support, and other functionality. It will still be a "long time" before it's regression-free and at parity to the original Broadcom driver originally baked for the Raspberry Pi.

As a stop-gap measure for being able to use the Gallium3D code but without the newer KMS code-paths, Eric developed a quick branch to expose the Pi's firmware display stack as the KMS pipeline.

Eric commented in his weekly VC4 driver status update, "I put together a quick branch to expose the firmware's display stack as the KMS display pipeline. It's a filthy hack, and loses us a lot of the important new features that the open stack was going to bring (changing video modes in X, vblank timestamping, power management), but it gets us much closer to the featureset of the previous stack. Hopefully [the Raspberry Pi Foundation will] be switching to it as the default in new installs soon."