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Date:   Thu, 30 May 2019 10:22:19 +1000
From:   Peter Hutterer <peter.hutterer@...-t.net>
To:     Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc:     Sean O'Brien <seobrien@...omium.org>,
        Harry Cutts <hcutts@...omium.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        廖崇榮 <kt.liao@....com.tw>,
        Rob Herring <robh+dt@...nel.org>,
        Aaron Ma <aaron.ma@...onical.com>,
        Hans de Goede <hdegoede@...hat.com>,
        "open list:HID CORE LAYER" <linux-input@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 08/10] Input: elan_i2c - export true width/height

On Wed, May 29, 2019 at 09:16:38AM +0200, Benjamin Tissoires wrote:
> On Wed, May 29, 2019 at 2:12 AM Sean O'Brien <seobrien@...omium.org> wrote:
> >
> > We do still use a maxed out major axis as a signal for a palm in the touchscreen
> > logic, but I'm not too concerned because if that axis is maxed out, the contact
> > should probably be treated as a palm anyway...
> >
> > I'm more concerned with this affecting our gesture detection for
> > touchpad. It looks
> > like this change would cause all contacts to reported as some percentage bigger
> > than they are currently. Can you give me an idea of how big that percentage is?
> 
> On the P52, I currently have:
> [  +0.000009] max:    (3045,1731) drivers/input/mouse/elan_i2c_core.c:428
> [  +0.000003] traces: (24,14) drivers/input/mouse/elan_i2c_core.c:429
> 
> -> with the computation done in the kernel:
> width_ratio: 126
> height_ratio: 123
> 
> For my average finger, the reported traces are between 4 and 6:
> With the ETP_FWIDTH_REDUCE:
> Major between 144 to 216
> Minor between 132 to 198
> 
> Without:
> Major between 504 to 756
> Minor between 492 to 738
> 
> So a rough augmentation of 350%
> 
> For the Synaptics devices (over SMBus), they send the raw value of the
> traces, so you will get a major/minor between 2 to 5. Max on these
> axes is 15, so we should get the same percentage of value comparing to
> the range.
> Which is why libinput has a database of which device reports which
> pressure/major/minor ranges as otherwise the values are just
> impossible to understand.

yeah, I've given up on trying to guess finger/thumb/palm sizes.
git grep for these quirk names in libinput for the ranges:
    AttrTouchSizeRange
    AttrThumbSizeThreshold
    AttrPalmSizeThreshold

There are also matching s/Size/Pressure/ entries for touchpads without
major/minor. Looking at the database now, the palm size thresholds range
entries are 5 (Wacom) and a set of 800-1600 for apple touchpads. So yeah,
all this is really a bit random :) 

Feel free to steal those entries though and/or add to them where applicable.

Cheers,
   Peter
 
> 
> >
> > On Tue, May 28, 2019 at 11:13 AM Harry Cutts <hcutts@...omium.org> wrote:
> > >
> > > On Mon, 27 May 2019 at 18:21, Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:
> > > >
> > > > Hi Benjamin, KT,
> > > >
> > > > On Mon, May 27, 2019 at 11:55:01AM +0800, 廖崇榮 wrote:
> > > > > Hi
> > > > >
> > > > > -----Original Message-----
> > > > > From: Benjamin Tissoires [mailto:benjamin.tissoires@...hat.com]
> > > > > Sent: Friday, May 24, 2019 5:37 PM
> > > > > To: Dmitry Torokhov; KT Liao; Rob Herring; Aaron Ma; Hans de Goede
> > > > > Cc: open list:HID CORE LAYER; lkml; devicetree@...r.kernel.org
> > > > > Subject: Re: [PATCH v2 08/10] Input: elan_i2c - export true width/height
> > > > >
> > > > > On Tue, May 21, 2019 at 3:28 PM Benjamin Tissoires <benjamin.tissoires@...hat.com> wrote:
> > > > > >
> > > > > > The width/height is actually in the same unit than X and Y. So we
> > > > > > should not tamper the data, but just set the proper resolution, so
> > > > > > that userspace can correctly detect which touch is a palm or a finger.
> > > > > >
> > > > > > Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
> > > > > >
> > > > > > --
> > > > > >
> > > > > > new in v2
> > > > > > ---
> > > > > >  drivers/input/mouse/elan_i2c_core.c | 11 ++++-------
> > > > > >  1 file changed, 4 insertions(+), 7 deletions(-)
> > > > > >
> > > > > > diff --git a/drivers/input/mouse/elan_i2c_core.c
> > > > > > b/drivers/input/mouse/elan_i2c_core.c
> > > > > > index 7ff044c6cd11..6f4feedb7765 100644
> > > > > > --- a/drivers/input/mouse/elan_i2c_core.c
> > > > > > +++ b/drivers/input/mouse/elan_i2c_core.c
> > > > > > @@ -45,7 +45,6 @@
> > > > > >  #define DRIVER_NAME            "elan_i2c"
> > > > > >  #define ELAN_VENDOR_ID         0x04f3
> > > > > >  #define ETP_MAX_PRESSURE       255
> > > > > > -#define ETP_FWIDTH_REDUCE      90
> > > > > >  #define ETP_FINGER_WIDTH       15
> > > > > >  #define ETP_RETRY_COUNT                3
> > > > > >
> > > > > > @@ -915,12 +914,8 @@ static void elan_report_contact(struct elan_tp_data *data,
> > > > > >                         return;
> > > > > >                 }
> > > > > >
> > > > > > -               /*
> > > > > > -                * To avoid treating large finger as palm, let's reduce the
> > > > > > -                * width x and y per trace.
> > > > > > -                */
> > > > > > -               area_x = mk_x * (data->width_x - ETP_FWIDTH_REDUCE);
> > > > > > -               area_y = mk_y * (data->width_y - ETP_FWIDTH_REDUCE);
> > > > > > +               area_x = mk_x * data->width_x;
> > > > > > +               area_y = mk_y * data->width_y;
> > > > > >
> > > > > >                 major = max(area_x, area_y);
> > > > > >                 minor = min(area_x, area_y); @@ -1123,8 +1118,10 @@
> > > > > > static int elan_setup_input_device(struct elan_tp_data *data)
> > > > > >                              ETP_MAX_PRESSURE, 0, 0);
> > > > > >         input_set_abs_params(input, ABS_MT_TOUCH_MAJOR, 0,
> > > > > >                              ETP_FINGER_WIDTH * max_width, 0, 0);
> > > > > > +       input_abs_set_res(input, ABS_MT_TOUCH_MAJOR, data->x_res);
> > > > > >         input_set_abs_params(input, ABS_MT_TOUCH_MINOR, 0,
> > > > > >                              ETP_FINGER_WIDTH * min_width, 0, 0);
> > > > > > +       input_abs_set_res(input, ABS_MT_TOUCH_MINOR, data->y_res);
> > > > >
> > > > > I had a chat with Peter on Wednesday, and he mentioned that this is dangerous as Major/Minor are max/min of the width and height. And given that we might have 2 different resolutions, we would need to do some computation in the kernel to ensure the data is correct with respect to the resolution.
> > > > >
> > > > > TL;DR: I don't think we should export the resolution there :(
> > > > >
> > > > > KT, should I drop the patch entirely, or is there a strong argument for keeping the ETP_FWIDTH_REDUCE around?
> > > > > I suggest you apply the patch, I have no idea why ETP_FWIDTH_REDUCE existed.
> > > > > Our FW team know nothing about ETP_FWIDTH_REDUCE ether.
> > > > >
> > > > > The only side effect will happen on Chromebook because such computation have stayed in ChromeOS' kernel for four years.
> > > > > Chrome's finger/palm threshold may be different from other Linux distribution.
> > > > > We will discuss it with Google once the patch picked by chrome and cause something wrong.
> > > >
> > > > Chrome has logic that contact with maximum major/minor is treated as a
> > > > palm, so here the driver (which originally came from Chrome OS)
> > > > artificially reduces the contact size to ensure that palm rejection
> > > > logic does not trigger.
> > > >
> > > > I'm adding Harry to confirm whether we are still using this logic and to
> > > > see if we can adjust it to be something else.
> > >
> > > I'm not very familiar with our touchpad code, so adding Sean O'Brien, who is.

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