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

[Juergen Gross <jgross@xxxxxxxx>]

On 06/16/2015 01:10 PM, Ian Jackson wrote:
> Jürgen Groß writes ("Re: [Xen-devel] [PATCH V4 3/7] libxl: add pvusb API"):
> > On 06/16/2015 12:41 PM, Ian Jackson wrote:
> > > Is the busid more stable in the face of plug/unplug ?  This is the
> > > normal reason for a more path-like device specification.
> ...
> > Unfortunately the busid isn't stable at least across reboots.
> I see.
>
> Presumably the busdev isn't either.  We need to be let users specify
> something that _is_ stable, obviously.
>
> On my netbook I have this kind of thing in /etc/fstab:
>
> /dev/disk/by-path/pci-0000:00:1d.7-usb-0:1:1.0-scsi-0:0:0:0-part1 /media/usb1 
> auto rw,user,noauto 0 0
>
> Is a similar specification possible ?
>
> > qemu does support specifying a USB device via <vendorId>:<productId>,
> > which is stable even across reboots, but unfortunately it isn't
> > guaranteed to be unique (you can have plugged in two devices of the
> > same type).
> Indeed.  That would also be a thing we should allow people to do.
>
> 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? ;-)

Juergen

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