On Wed, May 30, 2012 at 5:08 PM, Jason Gerecke <killertofu@xxxxxxxxx> wrote:
> This changes how the touch packets for Intuos5 and 3rd-gen Bamboo
> are interpreted, so that proper values for the MAJOR and MINOR
> axes are reported. Instead of using the amplitude field (data[6]),
> we use the size field (data[5]) and do some calculation to
> transform it from a scaled-down area into axis lengths.
>
> Note that even though we assume a circular contact, both MAJOR and
> MINOR are reported since the resolution of the X and Y axes differ.
> ---
> Changes from v1:
> * Changed name from "Use touch size for ABS_MT_TOUCH_MAJOR"
>
> * Also populate ABS_MT_TOUCH_MINOR to avoid some userspace
> assumptions.
>
> * Experimentally determined the calculations necessary to produce
> proper values instead of simply using the raw value in data[5].
>
> drivers/input/tablet/wacom_wac.c | 28 ++++++++++++++++++++++++----
> 1 file changed, 24 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/input/tablet/wacom_wac.c b/drivers/input/tablet/wacom_wac.c
> index 004bc1b..940caf3 100644
> --- a/drivers/input/tablet/wacom_wac.c
> +++ b/drivers/input/tablet/wacom_wac.c
> @@ -25,6 +25,11 @@
> #define WACOM_INTUOS_RES 100
> #define WACOM_INTUOS3_RES 200
>
> +/* Scale factor relating reported contact size to logical contact area.
> + * 2^14/pi is a good approximation on Intuos5 and 3rd-gen Bamboo
> + */
> +#define WACOM_CONTACT_AREA_SCALE 5215
> +
> static int wacom_penpartner_irq(struct wacom_wac *wacom)
> {
> unsigned char *data = wacom->data;
> @@ -1036,11 +1041,21 @@ static void wacom_bpt3_touch_msg(struct wacom_wac *wacom, unsigned char *data)
> if (touch) {
> int x = (data[2] << 4) | (data[4] >> 4);
> int y = (data[3] << 4) | (data[4] & 0x0f);
> - int w = data[6];
> + int a = data[5];
> +
> + // "a" is a scaled-down area which we assume is roughly
> + // circular and which can be described as: a*C=(pi*r^2).
> + int x_res = input_abs_get_res(input, ABS_X);
> + int y_res = input_abs_get_res(input, ABS_Y);
> + int logical_diameter = 2 * int_sqrt(a * WACOM_CONTACT_AREA_SCALE);
> + int physical_diameter = logical_diameter / ((x_res + y_res) / 2);
> + int logical_width = physical_diameter * x_res;
> + int logical_height = physical_diameter * y_res;
>
> input_report_abs(input, ABS_MT_POSITION_X, x);
> input_report_abs(input, ABS_MT_POSITION_Y, y);
> - input_report_abs(input, ABS_MT_TOUCH_MAJOR, w);
> + input_report_abs(input, ABS_MT_TOUCH_MAJOR, logical_width);
> + input_report_abs(input, ABS_MT_TOUCH_MINOR, logical_height);
> }
> }
>
> @@ -1520,7 +1535,9 @@ int wacom_setup_input_capabilities(struct input_dev *input_dev,
> input_mt_init_slots(input_dev, features->touch_max);
>
> input_set_abs_params(input_dev, ABS_MT_TOUCH_MAJOR,
> - 0, 255, 0, 0);
> + 0, features->x_max, 0, 0);
> + input_set_abs_params(input_dev, ABS_MT_TOUCH_MINOR,
> + 0, features->y_max, 0, 0);
>
> input_set_abs_params(input_dev, ABS_MT_POSITION_X,
> 0, features->x_max,
> @@ -1625,7 +1642,10 @@ int wacom_setup_input_capabilities(struct input_dev *input_dev,
>
> input_set_abs_params(input_dev,
> ABS_MT_TOUCH_MAJOR,
> - 0, 255, 0, 0);
> + 0, features->x_max, 0, 0);
> + input_set_abs_params(input_dev,
> + ABS_MT_TOUCH_MINOR,
> + 0, features->y_max, 0, 0);
> }
>
> input_set_abs_params(input_dev, ABS_MT_POSITION_X,
> --
> 1.7.10.2
>
I just noticed this patch wasn't upstream yet. Anybody wanna go over
it and give a Reviewed-by?
Jason
---
When you're rife with devastation / There's a simple explanation:
You're a toymaker's creation / Trapped inside a crystal ball.
And whichever way he tilts it / Know that we must be resilient
We won't let them break our spirits / As we sing our silly song.
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