On Mon, Jan 06, 2014 at 04:44:51PM -0500, Alan Stern wrote: > Finally, blacklisting xhci-hcd won't solve the problem at hand, because > the ports get switched from EHCI to xHCI during early PCI processing, > before xhci-hcd is loaded. The only check is for whether > CONFIG_USB_XHCI_HCD is enabled, which isn't affected by blacklisting. > > As far as I can see, the code that switches the ports back to EHCI gets > run only when the computer is turned off (and then only for some types > of machines). I think in my case quirk_usb_handoff_xhci is called during boot that will switch the ports to the XHCI. The question is about defaults. My RFC patch proposed to route the ports to the EHCI until the XHCI module is loaded. I had modified a comment to highlight a potential issue with this approach. The comment mentioned that the code tries to avoid taking away an already enumerated device (e.g. usb storage already mounted) from the EHCI. In my case this did not happen. ehci-hcd starts after xhci-hcd but this might be sheer luck. The question is if this can be made deterministic or not. > The best way to solve this problem would be a boot command-line option. Do you have a proposal for a name? -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
