On Mon, 23 Nov 2015, Patrick Shirkey wrote:
> >> Is there a method to determine if the system has multiple or single
> >> controllers available?
> >
> > lspci will tell you.
> >
> >> Do you or anyone else here have a link to the sysfs command to unbind
> >> the
> >> controller?
> >
> > If you provide the output from "lspci", I will tell you what command to
> > use.
> >
>
> Here's the USB info from lspci.
>
> # lspci
>
> 00:14.0 USB controller: Intel Corporation 8 Series/C220 Series Chipset
> Family USB xHCI (rev 05)
> 00:16.0 Communication controller: Intel Corporation 8 Series/C220 Series
> Chipset Family MEI Controller #1 (rev 04)
> 00:1a.0 USB controller: Intel Corporation 8 Series/C220 Series Chipset
> Family USB EHCI #2 (rev 05)
> 00:1d.0 USB controller: Intel Corporation 8 Series/C220 Series Chipset
> Family USB EHCI #1 (rev 05)
The first one is the xHCI controller and the last two are EHCI
controllers. The command to unbind the xhci-hcd driver from the
controller is this (as root):
echo 0000:00:14.0 >/sys/bus/pci/drivers/xhci_hcd/unbind
To rebind the driver back to the controller, you do:
echo 0000:00:14.0 >/sys/bus/pci/drivers/xhci_hcd/bind
> >> In regards to the last item can you provide some more details on why the
> >> software switch is only set if the kernel module is enable/disabled?
> >>
> >> I assume it has something to do with compiler flags and run time
> >> efficiency?
> >
> > No, it's simpler than that. If the kernel is built without support for
> > xHCI, it would be foolish to connect devices to the xHCI controller --
> > then the system wouldn't be able to communicate with them!
> >
> > Conversely, if the kernel does have support for xHCI, we assume that
> > the user will prefer xHCI over EHCI if the motherboard has xHCI.
> > Therefore the switch does get set to connect devices to the xHCI
> > controller.
> >
>
> Obviously the solution above should suffice for my purposes but out of
> interest is it viable to make the switch accessible to run time
> configuration?
I don't know. Mathias (the Linux xHCI maintainer) is the right person
to ask.
Alan Stern
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