I started implementing the xHCI driver. The first obstacle was to overcome a weird lack of configuration of the card (it’s a PCIe device) by coreboot. First I suspected that something went wrong because it uses a 64bit memory BAR, but then it was just a disabled PCIe bus in the devicetree.cb.
Thanks to Stefan for working out that issue.
However, the last days weren’t wasted, as I read the xHCI spec again and again, to build a mental image of how things interact in that standard.
Now I’m chugging along with implementing the data structures in C that xHCI requires (many more than in the older USB HCI specs)