Function gpu_bring_up 

pub(crate) fn gpu_bring_up(
    device_path: &Path,
    width: u32,
    height: u32,
) -> Result<GpuBringUp, String>

The GL renderer on device_path, the dmabuf formats it imports, and its offscreen render target at width by height. It touches no Wayland global: the caller advertises the GPU only once this succeeded, since a dmabuf global left behind by a failed start (a render node whose EGL comes up but whose allocator refuses the target, as on a virtual GPU) offered the GL renderer’s formats to a compositor rendering in Pixman, which refused every buffer, and a nested kwin_wayland died of the protocol error.