Re: [PATCH 1/2] usb: host: xhci: Allow non-Intel usb_link_tunnel_mode reporting

[Mika Westerberg <mika.westerberg@linux.intel.com>]

On Thu, May 07, 2026 at 02:53:22PM +0200, Konrad Dybcio wrote:
> On 5/7/26 2:48 PM, Mathias Nyman wrote:
> > On 5/7/26 13:40, Konrad Dybcio wrote:
> >> On 5/5/26 2:14 PM, Mika Westerberg wrote:
> >>> Hi,
> >>>
> >>> On Tue, May 05, 2026 at 10:55:04AM +0200, Konrad Dybcio wrote:
> >>>> From: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
> >>>>
> >>>> The Thunderbolt framework relies on the USB core to create device links
> >>>> for tunneled ports, so that the USB3 controller is only kept
> >>>> runtime-resumed for the duration of the tunneling.
> >>>>
> >>>> Currently, retrieving that information is only possibe on Intel XHCI
> >>>> hosts, through a vendor-specific capability. Extend xhci-plat to allow
> >>>> plumbing a custom one.
> >>>>
> >>>> Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
> >>>> ---
> >>>>   drivers/usb/host/xhci-hub.c  | 4 ++--
> >>>>   drivers/usb/host/xhci-plat.c | 2 ++
> >>>>   drivers/usb/host/xhci-plat.h | 1 +
> >>>>   drivers/usb/host/xhci.c      | 6 +++++-
> >>>>   drivers/usb/host/xhci.h      | 5 ++++-
> >>>>   5 files changed, 14 insertions(+), 4 deletions(-)
> >>>>
> >>>> diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
> >>>> index bacd0ddd0d09..09e5da912066 100644
> >>>> --- a/drivers/usb/host/xhci-hub.c
> >>>> +++ b/drivers/usb/host/xhci-hub.c
> >>>> @@ -750,7 +750,7 @@ static int xhci_exit_test_mode(struct xhci_hcd *xhci)
> >>>>   }
> >>>>     /**
> >>>> - * xhci_port_is_tunneled() - Check if USB3 connection is tunneled over USB4
> >>>> + * xhci_port_tunnel_mode() - Check if USB3 connection is tunneled over USB4
> >>>>    * @xhci: xhci host controller
> >>>>    * @port: USB3 port to be checked.
> >>>>    *
> >>>> @@ -764,7 +764,7 @@ static int xhci_exit_test_mode(struct xhci_hcd *xhci)
> >>>>    * detecting USB3 over USB4 tunnels. USB_LINK_NATIVE or USB_LINK_TUNNELED
> >>>>    * otherwise.
> >>>>    */
> >>>> -enum usb_link_tunnel_mode xhci_port_is_tunneled(struct xhci_hcd *xhci,
> >>>> +enum usb_link_tunnel_mode xhci_port_tunnel_mode(struct xhci_hcd *xhci,
> >>>>                           struct xhci_port *port)
> >>>
> >>> I'm wondering if this could be:
> >>>
> >>> bool xhci_port_is_tunneled()
> >>>
> >>> becase if I understand correctly that's the only information we need e.g is
> >>> it going over tunnel or not.
> >>
> >> It was originally introduced as a tristate enum in:
> >>
> >> f46a6e165197 ("usb: Add tunnel_mode parameter to usb device structure")
> >>
> >> but the usefulness of USB_LINK_UNKNOWN is limited to a dev_dbg() print..
> >> I don't really have strong opinions either way
> >>
> > 
> > Tunnel detection can be tried other ways if state is USB_LINK_UNKNOWN.
> > 
> > For example usb-acpi.c will try to create a tunnel if all the ACPI entries exists
> > that indicate a tunnel, but the current xHC doesn't support tunnel detection.
> 
> Fair, I didn't consider that!

Yeah, I missed it too. Thanks Mathias for explaining.