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Date:	Mon, 05 Jan 2015 21:13:09 +0100
From:	Gabriele Mazzotta <gabriele.mzt@...il.com>
To:	Benjamin Tissoires <benjamin.tissoires@...il.com>
Cc:	Peter Hutterer <peter.hutterer@...-t.net>,
	Hans de Goede <hdegoede@...hat.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Henrik Rydberg <rydberg@...omail.se>,
	linux-input <linux-input@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Maxwell Anselm <silverhammermba@...il.com>
Subject: Re: [PATCH 1/2] input: synaptics - make image sensors report ABS_MT_TOUCH_MAJOR

On Monday 05 January 2015 14:24:30 Benjamin Tissoires wrote:
> Hi Gabriele,
> 
> [Adding Peter and Hans as this change will impact both
> xf86-input-synaptics and libinput]
> 
> On Sat, Dec 27, 2014 at 6:31 AM, Gabriele Mazzotta
> <gabriele.mzt@...il.com> wrote:
> > Despite claiming to be able to report ABS_TOOL_WIDTH, image sensors
> > were not doing it. Make them report widths and use ABS_MT_TOUCH_MAJOR
> > instead ABS_TOOL_WIDTH.
> 
> It looks like the current xorg-synaptics code already handles
> ABS_MT_TOUCH_MAJOR as finger_width. So I think we should be good in
> replacing the ABS_TOOL_WIDTH event. However, I'd prefer having Peter
> confirm this because xorg-synaptics still relies a lot on the single
> touch emulation.

Yes, xorg-synaptics handles ABS_MT_TOUCH_MAJOR, I sent the patch for it.
The width of the fingers is used only for the two fingers emulation and
the palm detection, both of which are broken on image sensors as the
width is never reported.

I'm normally using hid-rmi for my touchpad which never sends
ABS_TOOL_WIDTH and everything seems to work correctly. Same for
synaptics with this patch, although it seems that the pressure drops
drastically when there are more than one finger, so this must be taken
into account when defining the threshold values. I'll double check that
everything is correct for 'z'.

> >
> > Since the 'w' slot is used to report the finger count when two or more
> > fingers are on the touchpad, make sure that only meaningful values are
> > emitted, i.e. values greater than or equal to 4, and assign the correct
> > range to ABS_MT_TOUCH_MAJOR.
> >
> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=77161
> > Signed-off-by: Gabriele Mazzotta <gabriele.mzt@...il.com>
> > ---
> >  drivers/input/mouse/synaptics.c | 11 +++++++++--
> >  1 file changed, 9 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/input/mouse/synaptics.c b/drivers/input/mouse/synaptics.c
> > index f947292..ea0563e 100644
> > --- a/drivers/input/mouse/synaptics.c
> > +++ b/drivers/input/mouse/synaptics.c
> > @@ -814,6 +814,8 @@ static void synaptics_report_slot(struct input_dev *dev, int slot,
> 
> Just FYI, this does not apply anymore on top of Dmitry's tree.
> synaptics_report_slot() has been removed, and you should now report
> the slot state in synaptics_report_mt_data().
> 
> >         input_report_abs(dev, ABS_MT_POSITION_X, hw->x);
> >         input_report_abs(dev, ABS_MT_POSITION_Y, synaptics_invert_y(hw->y));
> >         input_report_abs(dev, ABS_MT_PRESSURE, hw->z);
> > +       if (hw->w >= 4)
> 
> That I don't like. IMO, at this point, .w should only contain the
> finger width, unconditionally.
> Also, with 2/2, .w is computed accurately for the second finger, but
> not for the first.
> 
> I tried to figure out a way to properly extract the actual width
> information from the sgm packet when the w is 0 or 1, and the only way
> I found was to do the fix in synaptics_image_sensor_process(). I would
> have preferred dealing with that in synaptics_parse_hw_state()
> directly, but I think the final code would be more and more ugly.
> Dealing with the true finger width in synaptics_image_sensor_process()
> is not a problem for cr48 sensors, because they will not have the
> ABS_MT_TOUCH_MAJOR event exported.
> 
> Anyway, something like that "should" work (sorry for the tab/space,
> gmail in use), of course, this is untested when I send the mail :) :
> 
> diff --git a/drivers/input/mouse/synaptics.c b/drivers/input/mouse/synaptics.c
> index 95c15451..caf7ccd 100644
> --- a/drivers/input/mouse/synaptics.c
> +++ b/drivers/input/mouse/synaptics.c
> @@ -852,6 +852,17 @@ static void synaptics_image_sensor_process(struct
> psmouse *psmouse,
>         else
>                 num_fingers = 4;
> 
> +       /* When multiple fingers are on the TouchPad, the width is encoded in
> +        * X, Y and Z */
> +       if (sgm->w == 0 || sgm->w == 1) {
> +               sgm->w = ((sgm->x & BIT(1)) >> 1) |
> +                         (sgm->y & BIT(1)) |
> +                        ((sgm->z & BIT(0)) << 1);
> +               sgm->x &= ~BIT(1);
> +               sgm->y &= ~BIT(1);
> +               sgm->z &= ~BIT(0);
> +       }
> +

It works perfectly with some adjustments:

	/* When multiple fingers are on the TouchPad, the width is encoded in
	 * X, Y and Z */
	if (sgm->w == 0 || sgm->w == 1) {
		sgm->w = (((sgm->x & BIT(1)) >> 1) |
			  (sgm->y & BIT(1)) |
			  ((sgm->z & BIT(0)) << 2)) + 8;
		sgm->x &= ~BIT(1);
		sgm->y &= ~BIT(1);
		sgm->z &= ~BIT(0);
	}

>         /* Send resulting input events to user space */
>         synaptics_report_mt_data(psmouse, sgm, num_fingers);
>  }
> 
> 
> > +               input_report_abs(dev, ABS_MT_TOUCH_MAJOR, hw->w);
> >  }
> >
> >  static void synaptics_report_mt_data(struct psmouse *psmouse,
> > @@ -1462,8 +1464,13 @@ static void set_input_params(struct psmouse *psmouse,
> >                                         INPUT_MT_TRACK : INPUT_MT_SEMI_MT));
> >         }
> >
> > -       if (SYN_CAP_PALMDETECT(priv->capabilities))
> > -               input_set_abs_params(dev, ABS_TOOL_WIDTH, 0, 15, 0, 0);
> > +       if (SYN_CAP_PALMDETECT(priv->capabilities)) {
> > +               if (SYN_CAP_IMAGE_SENSOR(priv->ext_cap_0c))
> > +                       input_set_abs_params(dev,
> > +                                            ABS_MT_TOUCH_MAJOR, 4, 15, 0, 0);
> > +               else
> > +                       input_set_abs_params(dev, ABS_TOOL_WIDTH, 0, 15, 0, 0);
> > +       }
> 
> Again, I'd prefer having Peter's point of view here.
> 
> If we really need both, we will need to change input-mt to also
> emulate ABS_TOOL_WIDTH from ABS_MT_TOUCH_MAJOR like we do between
> ABS_MT_POSITION_X|Y and ABS_X|Y.
> 
> Cheers,
> Benjamin
> 
> >
> >         __set_bit(BTN_TOUCH, dev->keybit);
> >         __set_bit(BTN_TOOL_FINGER, dev->keybit);
> > --
> > 2.1.4
> >
> > --
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