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Re: [Xen-devel] [PATCH V4 3/7] libxl: add pvusb API
On 06/16/2015 03:19 PM, George Dunlap wrote:
On Tue, Jun 16, 2015 at 1:02 PM, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx> 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
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