From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ian Jackson <Ian.Jackson@eu.citrix.com>
Subject: Re: [PATCH V4 3/7] libxl: add pvusb API
Date: Tue, 16 Jun 2015 17:32:14 +0100
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To: George Dunlap <George.Dunlap@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>
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I have just discovered that the value used in /dev/disk/by-path is not
from sysfs, or at least, not directly.

udev cobbles it together with a bunch of string mangling, from
information mostly from sysfs.  There is no corresponding thing for
usb devices.

So Linux, the kernel, does not actually provide a stable device name
string.  This is obviously absurd, but I think fixing it is out of
scope.

I suggest we provide a facility to allow a user to specify a fnmatch
glob pattern to be applied to the sysfs path.  That way when they see
their device is
  /devices/pci0000:00/0000:00:1d.7/usb1/1-1
they can write
  /devices/pci0000:00/0000:00:1d.7/usb*/*-1
which will match exactly and only the right thing.

Ian.