On 24.02.2022 21:06, Jack Pham wrote: > On Wed, Feb 23, 2022 at 05:13:03PM -0500, Alan Stern wrote: >> On Wed, Feb 23, 2022 at 09:58:56PM +0100, Heiner Kallweit wrote: >>> On 23.02.2022 15:17, Alan Stern wrote: >>>> 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. > > I believe this had been attempted in the past, but it does not appear > that patch was ever accepted: > > https://lore.kernel.org/linux-usb/1517221474-19627-1-git-send-email-tqnguyen@xxxxxxx/ > I also found that xhci at several places relies on a proper shared_hcd, even if there are no USB3 ports. Therefore maybe go with the less invasive original version of my patch? https://www.spinics.net/lists/linux-usb/msg222998.html > Jack > >>> This works on my system. However a consequence is that xhci->shared_hcd >>> is NULL. >> >> Why is that? xhci->shared_hcd doesn't get set in usb_add_hcd(), so >> skipping that call shouldn't cause it to be NULL. >> >> Note: If you skip calling usb_add_hcd(), you will also have to skip the >> corresponding call to usb_remove_hcd(). There may be a few more >> subtleties involved as well; like I said before, I'm not an expert on >> this driver. You should ask the xhci-hcd maintainer for advice. >> >> Alan Stern >> >>> 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
