Intel Pulls In ShadowFB Support For KMS
Adding back UMS support to the xf86-video-intel driver would add around 50,000 lines of code back to the DDX driver and it would likely receive little in the way of new development and testing, so a much less invasive solution was devised by Intel's Chris Wilson. This new workaround, which we talked about recently, was adding shadow frame-buffer support to Intel KMS. In other words, kernel mode-setting still could be used by i8xx owners, but a ShadowFB-like method would be used for acceleration, which basically means no GPU acceleration at all.
The few hundred line commit adding shadow frame-buffer support to the Intel driver was merged to master early this morning. When the Shadow option is enabled from the xorg.conf, no GPU acceleration will be used but rather it will be leveraged on the CPU and system memory. No X-Video or 3D acceleration can be used with this driver, but now at least there is X-Video still possible via the hardware overlay. But because GEM isn't being tapped, the incoherency bugs for i8xx should be worked around thereby giving you a stable system.
The commit showing this shadow support being merged into the mainline xf86-video-intel driver can be found on Git. This support will be found in the xf86-video-intel 2.13 driver, which should be released in a few weeks.