[dividuum]

> The configuration validity depends on the current state of the display controller.

Yep. At least now the Pi's implementation does cause kernel tracebacks or lockups any more. Was rough in the beginning :-}

Flipping is supported (but not 90/270 rotation) and I use that together with a recently added transpose feature in the Writeback connector to support mirroring the primary VC4's output to the minimal DRM implementation of the official 7" display.

I'm using the Writeback connector to support screenshots, but copying every plane's configuration would be too much sometimes, so I heuristically compose some framebuffers via GL and then only place the remaining framebuffers (including the GL one) on Writeback and HDMI.