Re: [PATCH V7 6/7] xl: add usb-assignable-list command

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

On 07/10/15 12:25, Juergen Gross wrote:
> On 10/07/2015 01:20 PM, George Dunlap wrote:
>> On 07/10/15 12:09, Ian Campbell wrote:
>>> On Wed, 2015-10-07 at 11:10 +0100, George Dunlap wrote:
>>>
>>>>> So IMHO xl usb-assignable-list should behave like
>>>>> pci-assignable-list by
>>>>> default.
>>>>
>>>> I don't think that's really suitable.
>>>
>>> Then I'm terribly confused because I thought that is what you were
>>> initially advocating.
>>
>> I think in v3 I was trying to come up with a different name
>> (usb-available-list or something); but my main point was that it
>> *shouldn't* be named similarly but have different functionality.
>>
>> As I said, for this am I was ready to just let it slide; I just wanted
>> to make sure other people knew what was being let slide. :-)
>>
>>>
>>> [...]
>>>
>>>> For USB, there is no "assignable" stage -- "usb-attach" will take it
>>>> all the way from being assigned to a driver to being assigned to the
>>>> guest.  (You can think of this as pci-attach with "seize=1" always.)
>>>> So making "usb-assignable-list" act like "pci-assignable-list" doesn't
>>>> actually make any sense.
>>>
>>> Thanks. Jeurgen has also explained this.
>>>
>>> Do you agree that adding a dummy usbback driver just for the purposes of
>>> adding this extra "assignable" state doesn't make sense?
>>
>> Yes, I agree.
>>
>>>>> Now, maybe it should also support some sort of --all or --full or
>>>>> --host
>>>>> option which lists everything, ideally with some indication as to
>>>>> whether
>>>>> they are attached to usbback or not and using syntax which can just
>>>>> be cut
>>>>> -and-pasted into a cfg file (without at least one of those it's just a
>>>>> pointless reimplementation of lsusb).
>>>>>
>>>>> However I think --all/full/host is an optional extra.
>>>>
>>>> Juergen suggested having "usb-list" have an --all option in the v3
>>>> discussion.  If like me you're concerned about confusing people, then
>>>> having --all and --host is probably the best option.
>>>>
>>>> Thoughts?
>>>
>>> If there is no assignable state in usb then I guess I don't really
>>> understand what usb-list-assignable would even be for, so I don't really
>>> understand why anyone is arguing what semantics it should have (my
>>> initial
>>> reply was predicated on this state existing and it therefore being
>>> useful
>>> to discuss how the command should behave).
>>>
>>> Given that doing something with usb-list seems most plausible _if_ we
>>> need
>>> some sort of thing like that at all.
>>>
>>> What would "usb-list --all" add over and above using lsusb?
>>>
>>> I take it that as things stand in patch #5:
>>>      # xl usb-list <vm>
>>> will list the usb devices attached to <vm> and that:
>>>      # xl usb-list
>>> will list the usb devices attached to every vm, is that
>>> correct?
>>>
>>> So the idea would then be to add some way of listing the devices not
>>> included in "xl usb-list", which are notionally attached to dom0, but
>>> via physical USB and not PV usb.
>>
>> The "usb-assignable-list" that Chunyan has submitted will give you a
>> list of all dom0 USB devices that have not yet been assigned to a guest.
>>   It should be basically equivalent to "lsusb", except that it filters
>> out devices which have already been assigned to VMs.
>>
>> In the e-mail you respond to, I was suggesting that
>>
>> # xl usb-list --all
>>
>> would show you usb devices attached to every VM, and also USB devices
>> attached to no VM, and that
>>
>> # xl usb-list --host
>>
>> would show you only host usb devices not attached to any VM.
>>
>> I think it's the second bit if functionality which Juergen is keen be
>> available in some form or other.
> 
> Exactly.
> 
> BTW: I've explained that in another reply, but my mail client has chosen
> to send it via another account - I've no idea how that happened. So now
> my wife has some xen-devel history as well. ;-)

Oh, right -- I wondered where "Christiane" came from.  I just figured it
was an alternate name you used sometimes (like maybe Juergen was your
middle name but the one you normally went by). :-)

 -George