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Re: [Xen-devel] [PATCH V4 3/7] libxl: add pvusb API
On 06/16/2015 03:09 PM, George Dunlap wrote:
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).
Hmm, I'd rather have it all in one place. Putting it in qemu would
enable us to handle hotplug as well. A USB device assigned via it's
serial to a domU could be automatically passed through by qemu when
showing up. This isn't possible today, but we wouldn't have to change
libxl again for supporting it, only qemu would have to be adapted.
Juergen
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