From mboxrd@z Thu Jan  1 00:00:00 1970
From: Juergen Gross <jgross@suse.com>
Subject: Re: [PATCH V4 3/7] libxl: add pvusb API
Date: Tue, 16 Jun 2015 15:32:58 +0200
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To: George Dunlap <George.Dunlap@eu.citrix.com>, Ian Jackson <Ian.Jackson@eu.citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>, Ian Campbell <ian.campbell@citrix.com>, Chunyan Liu <cyliu@suse.com>, "xen-devel@lists.xen.org" <xen-devel@lists.xen.org>, Jim Fehlig <jfehlig@suse.com>, Simon Cao <caobosimon@gmail.com>
List-Id: xen-devel@lists.xenproject.org

On 06/16/2015 03:19 PM, George Dunlap wrote:
> On Tue, Jun 16, 2015 at 1:02 PM, Ian Jackson <Ian.Jackson@eu.citrix.com> wrote:
>> George Dunlap writes ("Re: [Xen-devel] [PATCH V4 3/7] libxl: add pvusb API"):
>>> So it sounds like we're converging on "Allow multiple ways to specify
>>> the interface", with at least the following fields:
>>> - bus (int - 1,2,3, &c)
>>> - port (string - 2.1.3, &c)
>>> - address/devnum (int)
>>> - vendorid (uint16_t)
>>> - deviceid (uint16_t)
>>
>> You're missing the full device path from that list.  Typically that
>> will include at least one pci bus address.
>
> I'm not sure what constitutes a "full device path".  Is that defined somewhere?
>
> Remember that the path you gave in your previous e-mail isn't the path
> for the *usb device*, it's the path for the *block device*.  It
> contains a PCI address, but it looks like it also contains part of the
> USB topology.  Are you sure that's actually a stable interface, or
> does it just happen that on your hardware the discovery always happens
> in the same order?
>
> On my system /sys/bus/usb/devices/2-3.3 is a link to
> /sys/devices/pci0000:00/0000:00:1d.7/usb2/2-3/2-3.3/.  This contains
> the pci bus address, but it also contains the bus number, which we've
> just said may be unstable across reboots.
>
> I suppose it might be possible to specify <buspci,port> -- the pci
> address of the root bus, and the topology from there.  In theory I
> guess that should be stable?

Hmm, perhaps. On my system I've got:

/sys/devices/pci0000:00/0000:00:14.0/usb3/
/sys/devices/pci0000:00/0000:00:14.0/usb4/

So two busses on one pci bus address. Are usb3 and usb4 always in this
order or are they sometimes just numbered the other way round?


Juergen