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 11:41:28 +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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George Dunlap writes ("Re: [Xen-devel] [PATCH V4 3/7] libxl: add pvusb API"):
> Ian / Ian / Wei / Jim:

Hi.

> 3. Have the libxl layer accept both busid and bus:addr.  Translate as
> necessary and store in the libxl_device_usb struct.
...
> The advantage of #3 internally is that the functions can do the
> translation once (if necessary), and can then pass around the public
> libxl_device_usb struct as-is without needing any extra parameters or
> a separate libxl_device_usb_internal.  The disadvantage, I think, is
> that from an interface perspective, it's fairly pointless to have
> both.  busid doesn't really give you any better or more control than
> the other, and it's not any more convenient for the user (in fact it's
> less convenient because it's more difficult to find).

Is the busid more stable in the face of plug/unplug ?  This is the
normal reason for a more path-like device specification.

If so then we must support it, even if it's not the usual way an
ordinary user would use it for a one-off.  Otherwise you have to write
something in your config files for the VMs on your VM host, which will
break when someone plugs a keyboard into the `wrong' USB port.

Ian.