Re: [PATCH v2 08/10] Input: elan_i2c - export true width/height

From: Benjamin Tissoires
Date: Wed May 29 2019 - 03:20:19 EST

On Wed, May 29, 2019 at 2:12 AM Sean O'Brien <seobrien@xxxxxxxxxxxx> 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.

Cheers,
Benjamin



>
> On Tue, May 28, 2019 at 11:13 AM Harry Cutts <hcutts@xxxxxxxxxxxx> wrote:
> >
> > On Mon, 27 May 2019 at 18:21, Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx> wrote:
> > >
> > > Hi Benjamin, KT,
> > >
> > > On Mon, May 27, 2019 at 11:55:01AM +0800, ååæ wrote:
> > > > Hi
> > > >
> > > > -----Original Message-----
> > > > From: Benjamin Tissoires [mailto:benjamin.tissoires@xxxxxxxxxx]
> > > > 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@xxxxxxxxxxxxxxx
> > > > 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@xxxxxxxxxx> 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@xxxxxxxxxx>
> > > > >
> > > > > --
> > > > >
> > > > > 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.