[PATCH v3 05/12] PCI: Detect root port of internal USB4 devices by `usb4-host-interface`

[Mika Westerberg]

On Mon, Feb 14, 2022 at 01:11:05PM +0200, Mika Westerberg wrote:
> > > It is used to identify "tunneled" ports (whether PCIe, USB 3.x or
> > > DisplayPort). Tunnels are created by software (in Linux it is the
> > > Thunderbolt driver) and are dynamic in nature. The USB4 links go over
> > > USB Type-C cable which also is something user can plug/unplug freely.
> > > 
> > > I would say it is reasonable expectation that anything behind these
> > > ports can be assumed as "removable".
> > 
> > USB gadgets may be soldered to the mainboard.  Those cannot be
> > unplugged freely.  It is common practice to solder USB Ethernet
> > or USB FTDI serial ports and nothing's preventing a vendor to solder
> > USB4/Thunderbolt gadgets.
> 
> Right, that's why I say it is "reasonable expectation" that anything
> behind these ports can be assumed "removable" :) Of course they don't
> have to be but if we assume that in the driver where this actually
> matters we should be on the safe side, no?

Also the tunnels are not permanent anyway.