On Wed, Aug 13, 2014 at 5:30 PM, Peter Hutterer
<peter.hutte...@who-t.net> wrote:
> On Tue, Aug 12, 2014 at 11:49:37AM -0700, Jason Gerecke wrote:
>> On Tue, Aug 5, 2014 at 9:51 PM, Peter Hutterer <peter.hutte...@who-t.net>
>> wrote:
>> > On Thu, Jul 24, 2014 at 12:04:02PM -0700, Jason Gerecke wrote:
>> >> Currently pointer arbitration is taken care of through the use of
>> >> a 'wcomPenInProx' variable in the WacomCommonRec. If two devices
>> >> share a 'common' variable, the commonDispatchDevice function will
>> >> ensure that touches do not move the pointer while the pen is in
>> >> proximity.
>> >>
>> >> This patch adds support for cross-device pointer arbitration to
>> >> prevent other touches known to the driver from moving the pointer.
>> >> This is achieved with the introduction of a 'WACOM_DRIVER' structure
>> >> that is shared by all tools. Inside this structure is an 'active'
>> >> variable that keeps track of the last tool which was actively
>> >> controlling the pointer. When an event from any tool comes in, the
>> >> driver will attempt to determine if it should be filtered or not.
>> >> In some cases, the new device will be allowed to take control of
>> >> the pointer, and become the new active device.
>> >>
>> >> Note that arbitration occurs *after* we store the device state
>> >> to pChannel->valid.state. The code in wcmTouchFilter.c assumes
>> >> that states are not missing, and can become desynchronized from
>> >> reality if (for example) a finger were to go out of prox without
>> >> a corresponding state update.
>> >>
>> >> Signed-off-by: Jason Gerecke <killert...@gmail.com>
>> >> ---
>> >> src/wcmCommon.c | 69
>> >> ++++++++++++++++++++++++++++++++++++-----------------
>> >> src/xf86WacomDefs.h | 8 ++++++-
>> >> 2 files changed, 54 insertions(+), 23 deletions(-)
>> >>
>> >> diff --git a/src/wcmCommon.c b/src/wcmCommon.c
>> >> index 5bcd755..4e7098a 100644
>> >> --- a/src/wcmCommon.c
>> >> +++ b/src/wcmCommon.c
>> >> @@ -28,6 +28,11 @@
>> >> #include <xkbsrv.h>
>> >> #include <xf86_OSproc.h>
>> >>
>> >> +
>> >> +struct _WacomDriverRec WACOM_DRIVER = {
>> >> + .active = NULL,
>> >> +};
>> >
>> > just to make sure: you're intending to block events from other, unrelated
>> > devices if multiple tablets are connected? say, block touch from an I5
>> > while
>> > a pen is active on a cintiq.
>> >
>> That's correct. At the moment the X driver can only do arbitration if
>> the devices share the same USB ID. This isn't always sufficient, and
>> we rely on the kernel to work out the trickier cases. This isn't as
>> clever as the kernel's arbitration logic, but its brute-force approach
>> can actually work out well for tablet PC users... If an xorg.conf.d
>> rule is added to route all touchscreens to xf86-input-wacom,
>> arbitration will (finally) occur between the pen and touch even if
>> they're from different manufacturers. I'd like to know what your
>> thoughts are on that...
>
> for the X driver, there isn't much we can do without some extra amount of
> effort. I guess we could improve this with finer-grained arbitration based
> on device types, e.g. skip this arbitration if the two devices in question
> are two Intuos tablets.
>
> what does worry me though is that the driver has no idea of the use of the
> device. In the (quite rare) case of an MPX setup, you've now pretty much
> blocked the devices from working simultaneously but independently - which is
> rather the point of MPX, even though I'm not aware of a current setup that
> makes use of this. The same would be true if the device is set floating but
> that too is seen in the wild about as often as a yeti.
>
> I don't have a good solution here, short of another option that's going to
> be quite hard to work out properly. The tablet-pc case is more likely to
> happen than the MPX setup and we don't have a way in the driver to handle
> the latter anyway, so I'm giving this a i-wish-life-was-simpler
> Acked-by: Peter Hutterer <peter.hutte...@who-t.net>.
>
> Cheers,
> Peter
>
I considered adding a new option to the driver which would let the
user disable cross-device arbitration, but didn't believe it to be
worth the maintenance given how few MPX setups are out there . In
theory somebody could still probably use minor xorg.conf.d voodoo to
selectively route the touchscreen to a different driver, but that's
not exactly ideal either...
Jason
---
Now instead of four in the eights place /
you’ve got three, ‘Cause you added one /
(That is to say, eight) to the two, /
But you can’t take seven from three, /
So you look at the sixty-fours....
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