[RFC usb-next v5 1/3] dt-bindings: usb: add the documentation for USB root-hub

[Alan Stern]

On Thu, 12 Oct 2017, Martin Blumenstingl wrote:

> Hi Alan,
> 
> On Thu, Oct 12, 2017 at 11:17 PM, Alan Stern <stern at rowland.harvard.edu> wrote:
> > On Thu, 12 Oct 2017, Martin Blumenstingl wrote:
> >
> >> I haven't tested the described use-case. however, this patch is not
> >> supposed to change the binding for actual devices.
> >> USB device numbering starts at 1, while 0 is reserved for the root-hub
> >> (at least from what I know).
> >
> > Actually 1 is reserved for the root hub.  External devices are numbered
> > starting from 2.  (We can't use 0 for the root hub because, as you
> > said, USB device numbering starts at 1!)
> I just had a look at lsusb again:
> $ lsusb -t
> /:  Bus 04.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/2p, 5000M
> 
> however, for the devicetree bindings the devices are supposed to use 1-31: [0]
> 
> Alan: just to make sure I understood you correctly: do you agree with
> this patch?

I have no idea.  I haven't read the patch and I'm not familiar with the
details of DeviceTree.  I was just trying to clear up your
misunderstanding of USB device numbering.

Alan Stern