On 23.02.2022 15:17, Alan Stern wrote: > On Wed, Feb 23, 2022 at 01:26:23PM +0100, Heiner Kallweit wrote: >> On 23.02.2022 03:10, Alan Stern wrote: >>> On Tue, Feb 22, 2022 at 10:13:09PM +0100, Heiner Kallweit wrote: >>>> >>>> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c >>>> index 83b5aff25..e3f40d1f4 100644 >>>> --- a/drivers/usb/core/hub.c >>>> +++ b/drivers/usb/core/hub.c >>>> @@ -1423,9 +1423,8 @@ static int hub_configure(struct usb_hub *hub, >>>> ret = -ENODEV; >>>> goto fail; >>>> } else if (hub->descriptor->bNbrPorts == 0) { >>>> - message = "hub doesn't have any ports!"; >>>> - ret = -ENODEV; >>>> - goto fail; >>>> + dev_info(hub_dev, "hub has no ports, exiting\n"); >>>> + return -ENODEV; >>>> } >>>> >>>> /* >>> >>> How about instead changing xhci-hcd so that it doesn't try to register >>> a USB-3 root hub if the controller doesn't have any USB-3 ports? I >>> think that would make more sense. >>> >> Right, this would be better. I checked and it seems to be a little bit >> bigger endeavor. If I let register_root_hub() fail, then this removes >> the USB3 bus/host (shared hcd), but also the USB2 bus/host. >> It took an additional change to xhci_plat_probe() to make it work on my >> system. Not sure what the impact could be on systems not using >> xhci_plat_probe(). Users may face the same issue like me, and having >> a USB3 hub with no ports may remove also the USB2 bus/host. > > Don't change register_root_hub(). Just change xhci_plat_probe(); make > it skip the second call to usb_add_hcd() if there are no USB-3 ports. > This works on my system. However a consequence is that xhci->shared_hcd is NULL. There are a few places like the following in xhci.c where this may result in a NPE. Not knowing the USB subsystem in detail I can't say whether these places are in any relevant path. static int xhci_run_finished(struct xhci_hcd *xhci) { if (xhci_start(xhci)) { xhci_halt(xhci); return -ENODEV; } xhci->shared_hcd->state = HC_STATE_RUNNING; > Alan Stern > >> What I can do: submit my patches as RFC, then there's a better basis >> for a discussion. >> >>> Alan Stern >> >> Heiner Heiner