Re: [Xen-devel] RFC: drop frontend support for relative pointer

[Markus Armbruster <armbru@xxxxxxxxxx>]

Jean Guyader <jean.guyader@xxxxxxxxx> writes:

> 2009/10/12 Jean Guyader <jean.guyader@xxxxxxxxx>:
>> 2009/10/8 Markus Armbruster <armbru@xxxxxxxxxx>:
>>> Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx> writes:
>>>
>>>> On Wed, 7 Oct 2009, Daniel P. Berrange wrote:
>>>>> That's good to know - stubdom was one area I was concerned about. To the
>>>>> best of my knowledge the only backend that ever sent relative mouse events
>>>>> was the old PVFB we had in Fedora 6 which was the original code before
>>>>> the eventual merge into official xen-devel trees. So official repos have
>>>>> always defaulted to absolute mode.  Hopefully no one out there has gone
>>>>> and re-implemented the PVFB backend in any other fork of Xen and dropped
>>>>> ABS mode or made REL the default ???
>>>>>
>>>>> IMHO if ABS mode is able to work correctly, then there's absolutely no
>>>>> benefit in having a REL mode at all, so its best deleted / removed.
>>>>
>>>> I guess keeping around unused code doesn't make much sense but I was just
>>>> being cautious, given that for example XCI is currently using relative
>>>> coordinates so they are not dead just yet.
>>>
>>> Just to avoid misunderstandings:
>>>
>>> * Does XCI set feature-abs-pointer in xenstore?
>>>
>>> * If it does, does it read request-abs-pointer from xenstore?
>>>
>>> * Under what circumstances (if any) does it send XENKBD_TYPE_MOTION, and
>>>  under what circumstances (if any) does it send XENKBD_TYPE_POS?
>>>
>>
>> Hi,
>>
>> I just checked and we have feature-abs-pointer and request-abs-pointer
>> set to 1 xenstore.
>> The function we use to inject mouse/keyboard event in the guess is
>> kbd_mouse_event and it works with xenkbd.
>>
>
> I checked into the code and we force xenkb to use relative coordinates.
> We use that because in XCI the hardware mouse on the host is generally
> setup to send relative coordinates, and we do a 1 to 1 map for the
> mouse/keyboard
> event.

Thanks for your help.  To sum up:

* The XCI backend advertizes absolute pointers (feature-abs-pointer set
  in xenstore)

* The frontend asks for it (request-abs-pointer set in xenstore)

* Regardless, the XCI backend sends only relative coordinates (event
  type XENKBD_TYPE_POS).

Correct?

If yes, then this works more by accident than by design :)

By setting feature-abs-pointer, the backend offers absolute events.
Reneging on this offer after the frontend accepted it is a bug.

What now?  Could XCI upgrade to absolute?  If not, could it at least
stop offering feature-abs-pointer?

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