[PATCH 3/3] Input: synaptics - remove touches over button click area

[Chris Bagwell]

On Mon, Oct 11, 2010 at 12:10 PM, Takashi Iwai <tiwai at suse.de> wrote:
> At Mon, 11 Oct 2010 11:24:04 -0500,
> Chris Bagwell wrote:
>>
>> On Fri, Oct 8, 2010 at 9:58 AM, Chase Douglas
>> <chase.douglas at canonical.com> wrote:
>> > Now that we have proper multitouch support, we can handle integrated
>> > buttons better. If we know the top of the buttons on the touchpad, we
>> > can ignore any touches that occur within the touchpad area while a
>> > button is clicked. It may be possible to get the button area by querying
>> > the device, but for now allow the user to manually set it.
>> >
>> > A note on why this works: the Synaptics touchpads have pseudo touch
>> > tracking. When two touches are on the touchpad, an MT touch packet with
>> > just the X, Y, and pressure values is sent before a normal Synaptics
>> > touch packet. When one touch is obviously in motion and the other is
>> > stationary, the touchpad controller sends the touch in motion in the
>> > normal packet and the stationary touch in the MT packet. Single touch
>> > emulation is provided by the normal packet, so an action like clicking
>> > a button and dragging with another finger still works as expected.
>> >
>> > Tested on a Dell Mini 1012 with synaptics_multitouch=1 and
>> > synaptics_button_thresh=4100.
>> >
>> > Signed-off-by: Chase Douglas <chase.douglas at canonical.com>
>> > ---
>> >  drivers/input/mouse/synaptics.c |   16 +++++++++++++++-
>> >  1 files changed, 15 insertions(+), 1 deletions(-)
>> >
>> > diff --git a/drivers/input/mouse/synaptics.c b/drivers/input/mouse/synaptics.c
>> > index 7289d88..e67778d 100644
>> > --- a/drivers/input/mouse/synaptics.c
>> > +++ b/drivers/input/mouse/synaptics.c
>> > @@ -49,6 +49,12 @@ module_param(synaptics_multitouch, bool, 0644);
>> >  MODULE_PARM_DESC(synaptics_multitouch,
>> >                 "Enable multitouch mode on Synaptics devices");
>> >
>> > +static int synaptics_button_thresh = YMIN_NOMINAL + YMAX_NOMINAL;
>> > +module_param(synaptics_button_thresh, int, 0644);
>> > +MODULE_PARM_DESC(synaptics_button_thres,
>> > +                "Y coordinate threshold of integrated buttons on Synaptics "
>> > +                "devices");
>> > +
>> >  /*****************************************************************************
>> >  *     Stuff we need even when we do not want native Synaptics support
>> >  ****************************************************************************/
>> > @@ -463,6 +469,10 @@ static void synaptics_parse_hw_state(unsigned char buf[], struct synaptics_data
>> >        }
>> >  }
>> >
>> > +#define TOUCH_OVER_BUTTON(hw) (((hw).left || (hw).middle || (hw).right) && \
>> > +                              (YMAX_NOMINAL + YMIN_NOMINAL - (hw).y > \
>> > +                               synaptics_button_thresh))
>> > +
>> >  /*
>> >  *  called for each full received packet from the touchpad
>> >  */
>> > @@ -477,7 +487,7 @@ static void synaptics_process_packet(struct psmouse *psmouse)
>> >        synaptics_parse_hw_state(psmouse->packet, priv, &hw);
>> >
>> >        if (SYN_MULTITOUCH(priv, &hw)) {
>> > -               if (hw.z > 0) {
>> > +               if (hw.z > 0 && !TOUCH_OVER_BUTTON(hw)) {
>> >                        input_report_abs(dev, ABS_MT_POSITION_X, hw.x);
>> >                        input_report_abs(dev, ABS_MT_POSITION_Y,
>> >                                         YMAX_NOMINAL + YMIN_NOMINAL - hw.y);
>> > @@ -509,6 +519,10 @@ static void synaptics_process_packet(struct psmouse *psmouse)
>> >                return;
>> >        }
>> >
>> > +       /* If touch occurs over depressed button, ignore it */
>> > +       if (TOUCH_OVER_BUTTON(hw))
>> > +               hw.z = 0;
>> > +
>> >        if (hw.z > 0) {
>> >                priv->num_fingers++;
>> >                finger_width = 5;
>> > --
>> > 1.7.1
>> >
>> >
>>
>> I'm convinced now that clickpad style touchpads can't work without
>> multi-touch and something like logic in xf86-input-multitouch.
>
> Actually Clickpad works without multi-touch patch.  With my patches to
> synaptics, it worked in some level.  There are many restrictions (e.g.
> pushing the button first then drag), though.
>

True, but if I understand synaptic hardware MT behavior (sends
actively moving finger in higher resolution packet regardless of
original finger touch) then your patch will result in jumpy cursor on
X side and that side would need patches to attempt to guess invalid
data and discard.  I've worked on a few similar patches to various
xf86-input-* and generally they've failed to detect difference between
invalid packets vs. fast user movements.

The main point of my 3 options was to address jumpy cursor in
xf86-input-* that are not MT aware.  I think ABS_X/ABS_Y should only
allow its meaning to change at detectable time periods so user can
account for it and, specifically, that time period is best at
transition of BTN_TOOL_DOUBLETAP.

Assuming its easy enough to support exact rules for ABS_X/ABS_Y
changing meanings on kernel side (which I think it probably is pretty
easy), I think we should do it so that applications don't have to
become MT-aware as the official solution for jumpy cursors.

Chris