On Tue, 31 Mar 2020, John Donnelly wrote: > Hi , > > One more follow up question. > > How does a X86 kernel know where to look for USB buses/control > registers ? I am aware PowerPC has a device-tree that is passed by > reference from UBoot that contains known devices. Some of the information comes from ACPI tables in the BIOS. Other parts of it come from the components on the motherboard (for example, devices attached to a PCI bus can be discovered directly by the system). > For the BCM device : > > Bus 03.Port 1: Dev 1, Class=root_hub, Driver=uhci_hcd/2p, 12M > > Is there a corresponding register set I can examine ? Yes. For example, you can look at the files under /sys/kernel/debug/usb/uhci/. You can also use lspci and other related PCI utilities. Alan Stern
