Re: [PATCH V4 3/7] libxl: add pvusb API

[George Dunlap <george.dunlap@eu.citrix.com>]

On 06/16/2015 02:06 PM, Juergen Gross wrote:
> On 06/16/2015 01:45 PM, Ian Jackson wrote:
>> Juergen Gross writes ("Re: [Xen-devel] [PATCH V4 3/7] libxl: add pvusb
>> API"):
>>> On 06/16/2015 01:10 PM, Ian Jackson wrote:
>>>> AIUI some devices have serial numbers, which means you can distinguish
>>>> them ?
>>>
>>> Yes, they have. The question is whether those are different on multiple
>>> instances? With "lsusb" I've found a device with serial number
>>> 0123456789ABCD. Do you really believe I'm just lucky owning the one with
>>> such a nice serial number? ;-)
>>
>> Heh.  I think, though, that this suggests that if the user has devices
>> whose serial numbers are actually different, they should be able to
>> specify a device by vid/pid/serial.
> 
> I think you are right.
> 
> The next question: should this be part of libxl or qemu? It should be
> possible to extend the qemu <vendorId>:<productId> syntax to
> <vendorId>:<productId>:<serial> without too much effort, as libusb
> includes some support to obtain the serial number.

It doesn't really matter what qemu or pvusb can do, as long as libxl can
convert what it has into something that they can use.  So if libxl is
given vid, pid, and serial (remember, this will be a struct, not a
string), it can look in sysfs and find the bus:addr (which is unique at
any given time) and hand it to qemu  (or the bus-port in the case of pvusb).

 -George