[libvirt] [PATCH 04/17] Add a test for long USB port paths

[Gerd Hoffmann]

On Di, 2016-06-21 at 18:19 +0200, Ján Tomko wrote:
> On Mon, Jun 20, 2016 at 08:50:31AM +0200, Gerd Hoffmann wrote:
> >On Fr, 2016-06-17 at 20:07 +0200, Ján Tomko wrote:
> >> For some reason, we support up to four levels of nested USB devices
> >> in the guest.
> >
> >FYI: The reason is simply that usb is specified that way.  You can't
> >chain usb hubs endlessly.
> >
> 
> I was under the impression that 7 is the maximum depth.

5 hubs IIRC (not fully sure whenever that includes the root hub or not).
So, yes, we can do more than 4.  The only use case for that I've seen so
far is QA trying to go to the limits.  For all practical purposes I'd
expect 4 levels is *way* more than you'll ever need.  Especially as the
qemu usb hub supports usb 1.1 only.

cheers,
  Gerd