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From:   Benjamin Tissoires <benjamin.tissoires@redhat.com>
Date:   Fri, 24 May 2019 11:37:29 +0200
Message-ID: <CAO-hwJJXGTZq7zRVhcFNwh-kOo0rUhZOsNtFX1yA93Km=L+ynA@mail.gmail.com>
Subject: Re: [PATCH v2 08/10] Input: elan_i2c - export true width/height
To:     Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        KT Liao <kt.liao@emc.com.tw>, Rob Herring <robh+dt@kernel.org>,
        Aaron Ma <aaron.ma@canonical.com>,
        Hans de Goede <hdegoede@redhat.com>
Cc:     "open list:HID CORE LAYER" <linux-input@vger.kernel.org>,
        lkml <linux-kernel@vger.kernel.org>, devicetree@vger.kernel.org
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On Tue, May 21, 2019 at 3:28 PM Benjamin Tissoires
<benjamin.tissoires@redhat.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@redhat.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?

Cheers,
Benjamin


>
>         data->input = input;
>
> --
> 2.21.0
>