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

[Jean Guyader <jean.guyader@xxxxxxxxx>]

2009/10/12 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)
>

Yes.

> * 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 :)
>

Yep it does work, that is wrong in our code.
I didn't know about this xenstore protocol when I hacked it up.

Here is the nasty patch:
http://git/git/xenclient/ioemu-pq.git/tree/master/fix-imobile-mouse

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

Yep, I belive there is a bug somewhere.

> What now?  Could XCI upgrade to absolute?  If not, could it at least
> stop offering feature-abs-pointer?
>
I'll fix that inside our code.

I don't really thing we could use absolute because we do graphic
device pass through with PV guest and the resolution we have on the
screen is completely decouple with the fb resolution.

Jean

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