How to check the highest speed and supported alt-mode for a usb-host?

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

Hi,

With more and more usb-c hosts (and their alt-modes) found in 
laptops/pcs, I'm wondering what's the most accurate way inside linux to 
check the highest speed and hopefully alt modes.

There is `lsusb -tv`, but the speed only shows upto 10Gbps, meanwhile my 
usb host supports USB4, thus I think it should be much higher:

/:  Bus 006.Port 001: Dev 001, Class=root_hub, Driver=xhci_hcd/1p, 
10000M <<<
     ID 1d6b:0003 Linux Foundation 3.0 root hub
     |__ Port 001: Dev 002, If 0, Class=Imaging, Driver=[none], 5000M
         ID 18d1:4ee1 Google Inc. Nexus/Pixel Device (MTP)



Another thing is related to alt-mode, which I understand is very hard to 
check because the controller may support alt-mode but has no DP input 
connected etc.

But if there is some interface reporting the supported alt-modes of a 
host controller, it will be very helpful.

Thanks,
Qu