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Re: [Xen-devel] Re: [patch] pvfb: Split mouse and keyboard into separate devices.

Daniel P. Berrange wrote:
> Is there some way we can keep the original device supplying both keyboard
> and mouse events as before, and just have this second device as an opt-in
> 'absolute pointer' event device. That way existing Xorg setups will still
> work correctly without needing any config changes, while providing the 
> ability to opt-in to getting absolute events by adding the extra config.

Should be possible.  Some linux input layer background:

You'll get one /dev/input/event<nr> file per input device.

Applications can open it, they can ask for exclusive access to it (what
usually is a good idea), and if they do so nobody else gets events from
that device.

Input events which are not grabbed that way go the usual route through
the linux input layer and end up as normal key presses in the keyboard
driver or as mouse events in the ps/2 mouse emulation (aka /dev/input/mice).

Splitting keyboard and mouse into two devices makes it possible to
handle the mouse events via /dev/input/event<nr> and let the keyboard
events still go the usual route.

> Ideally Xorg hardware probing could then be modified, so that future Xorg
> releases would automatically utilize the extra device (if present) for 
> absolute co-ords without needing the extra config at all.

Xorg 7.2 comes with a manpage for evdev ;)

Have played only with sles10 guests so far, which unfortunaly has an
older Xorg version, where the evdev driver has much less features, thus
the stuff below is untested ...

Xorg 7.2 evdev can match input devices by name and by id, so you can add
a sections like this:

  Section "InputDevice"
    Driver       "evdev"
    Identifier   "Mouse[1]"
    Option       "Name" "Xen Virtual Pointer"

and be done with it.  The /dev/input/mice section can stay.  It doesn't
hurt, there are no mouse events coming due to evdev asking for exclusive


Gerd Hoffmann <kraxel@xxxxxxx>

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