Hi Clinton,
> input: appletouch: implement sensor data smoothing
>
> Use smoothed version of sensor array data to calculate movement and add weight
> to prior values when calculating average. This gives more granular and more
> predictable movement.
>
> Signed-off-by: Clinton Sprain <clintonsprain@xxxxxxxxx>
> ---
> drivers/input/mouse/appletouch.c | 72 ++++++++++++++++++++++++++++----------
> 1 file changed, 53 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/input/mouse/appletouch.c b/drivers/input/mouse/appletouch.c
> index 2745832..e00f126 100644
> --- a/drivers/input/mouse/appletouch.c
> +++ b/drivers/input/mouse/appletouch.c
> @@ -332,7 +332,11 @@ static void atp_reinit(struct work_struct *work)
> static int atp_calculate_abs(int *xy_sensors, int nb_sensors, int fact,
> int *z, int *fingers)
> {
> - int i;
> + int i, k;
> + int smooth[nb_sensors + 8];
> + int smooth_tmp[nb_sensors + 8];
> + int scale = 12;
> +
> /* values to calculate mean */
> int pcum = 0, psum = 0;
> int is_increasing = 0;
> @@ -344,9 +348,6 @@ static int atp_calculate_abs(int *xy_sensors, int nb_sensors, int fact,
> if (is_increasing)
> is_increasing = 0;
>
> - continue;
> - }
> -
> /*
> * Makes the finger detection more versatile. For example,
> * two fingers with no gap will be detected. Also, my
> @@ -361,27 +362,60 @@ static int atp_calculate_abs(int *xy_sensors, int nb_sensors, int fact,
> *
> * - Jason Parekh <jasonparekh@xxxxxxxxx>
> */
> - if (i < 1 ||
> +
> + } else if (i < 1 ||
> (!is_increasing && xy_sensors[i - 1] < xy_sensors[i])) {
> (*fingers)++;
> is_increasing = 1;
> } else if (i > 0 && (xy_sensors[i - 1] - xy_sensors[i] > threshold)) {
> is_increasing = 0;
> }
> + }
>
> - /*
> - * Subtracts threshold so a high sensor that just passes the
> - * threshold won't skew the calculated absolute coordinate.
> - * Fixes an issue where slowly moving the mouse would
> - * occasionally jump a number of pixels (slowly moving the
> - * finger makes this issue most apparent.)
> - */
> - pcum += (xy_sensors[i] - threshold) * i;
> - psum += (xy_sensors[i] - threshold);
> + /*
> + * Use a smoothed version of sensor data for movement calculations, to
> + * combat noise without needing to rely so heavily on a threshold.
> + * This improves tracking.
> + *
> + * The smoothed array is bigger than the original so that the smoothing
> + * doesn't result in edge values being truncated.
> + */
> +
> + for (i = 0; i < 4; i++)
> + smooth[i] = 0;
> + for (i = nb_sensors + 4; i < nb_sensors + 8; i++)
> + smooth[i] = 0;
> +
> + /* Pull base values, scaled up to help avoid truncation errors. */
> +
> + for (i = 0; i < nb_sensors; i++)
> + smooth[i + 4] = xy_sensors[i] << scale;
> +
> + for (k = 0; k < 4; k++) {
> +
> + /* Handle edge. */
> + smooth_tmp[0] = (smooth[0] + smooth[1]) >> 1;
> +
> + /* Average values with neighbors. */
> + for (i = 1; i < nb_sensors + 7; i++)
> + smooth_tmp[i] = (smooth[i - 1] + smooth[i] * 2 + smooth[i + 1]) >> 2;
> +
> + /* Handle other edge. */
> + smooth_tmp[nb_sensors + 7] = (smooth[nb_sensors + 7] + smooth[nb_sensors + 6]) >> 1;
> +
> + for (i = 0; i < nb_sensors + 8; i++)
> + smooth[i] = smooth_tmp[i];
> + }
> +
> + for (i = 0; i < nb_sensors + 8; i++) {
> + if ((smooth[i] >> scale) > 0) { /* Skip individual values if */
> + pcum += (smooth[i]) * i; /* they are small enough to */
> + psum += (smooth[i]); /* be truncated to 0 by our */
> + } /* scale; mostly just noise. */
> }
>
> if (psum > 0) {
> - *z = psum;
> + *z = psum >> scale; /* Scale down pressure output. */
> return pcum * fact / psum;
> }
>
> @@ -559,8 +593,8 @@ static void atp_complete_geyser_1_2(struct urb *urb)
>
> if (x && y) {
> if (dev->x_old != -1) {
> - x = (dev->x_old * 3 + x) >> 2;
> - y = (dev->y_old * 3 + y) >> 2;
> + x = (dev->x_old * 7 + x) >> 3;
> + y = (dev->y_old * 7 + y) >> 3;
> dev->x_old = x;
> dev->y_old = y;
>
> @@ -671,8 +705,8 @@ static void atp_complete_geyser_3_4(struct urb *urb)
>
> if (x && y) {
> if (dev->x_old != -1) {
> - x = (dev->x_old * 3 + x) >> 2;
> - y = (dev->y_old * 3 + y) >> 2;
> + x = (dev->x_old * 7 + x) >> 3;
> + y = (dev->y_old * 7 + y) >> 3;
> dev->x_old = x;
> dev->y_old = y;
>
>
Reviewed-by: Henrik Rydberg <rydberg@xxxxxxxxxxx>
Thanks,
Henrik
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