Re: [Xen-devel] [PATCH V6 3/7] libxl: add pvusb API

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Most of what you say is right, I think, but:

Ian Campbell writes ("Re: [Xen-devel] [PATCH V6 3/7] libxl: add pvusb API"):
> On Fri, 2015-09-11 at 16:18 +0200, Juergen Gross wrote:
> >  In theory I think up to 7 cascaded
> > hubs are possible, but I don't think the resulting theoretical maximum
> > of about 1 trillion devices on a bus is to be considered. :-)
> 
> And this suggests that in principal a Linux hostbus could be 5*7 bits == 35
> bits, maybe. Or at least that any USB address can be encoded in that many
> bits.

No.  The total possible number of `buses' in that sense
per root is:
    1                   root
  + 31                  in theory a hub plugged into each of 31 ports
  + 31^2                in theory a hub plugged into each port
  ...
  + 31^6
You could plug hubs into the last layer but the maximum depth is 7 so
you wouldn't be able to plug any devices into that last hub.

And of course the number of root hubs is not really limited by
anything meaningful.

Ian.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel