Hi Clinton,
> 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 | 60 ++++++++++++++++++++++++++------------
> 1 file changed, 42 insertions(+), 18 deletions(-)
I like this patch, but there are some technical glitches, comments below.
> diff --git a/drivers/input/mouse/appletouch.c b/drivers/input/mouse/appletouch.c
> index d48181b..edbdd95 100644
> --- a/drivers/input/mouse/appletouch.c
> +++ b/drivers/input/mouse/appletouch.c
> @@ -338,21 +338,51 @@ 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 + 2];
> + int smooth_tmp[nb_sensors + 2];
> +
> /* values to calculate mean */
> int pcum = 0, psum = 0;
> int is_increasing = 0;
>
> *fingers = 0;
>
> + /*
> + * Use a smoothed version of sensor data for movement calculations, to
> + * combat noise without needing to toss out values based on a threshold.
> + * This improves tracking. Finger count is calculated separately based
> + * on raw data.
> + */
> +
> + for (i = 0; i < nb_sensors; i++) { /* Scale up to minimize */
> + smooth[i] = xy_sensors[i] << 12; /* rounding/truncation. */
> + }
> +
> + /* Mitigate some of the data loss from smoothing on the edge sensors. */
> + smooth[-1] = smooth[0] >> 2;
> + smooth[nb_sensors] = smooth[nb_sensors - 1] >> 2;
Out of bounds array... also, the boundary condition seems odd. If you want to
extrapolate the edge velocity, and assuming smooth[0] is the first sensor, you
would get something like (N = nb_sensors)
smooth_tmp[0] = 2 * smooth[1] - smooth[2];
smooth_tmp[N-1] = 2 * smooth[N-2] - smooth[N-3];
> + for (k = 0; k < 4; k++) {
> + for (i = 0; i < nb_sensors; i++) { /* Blend with neighbors. */
And here would be for (i = 1; i < nb_sensors - 1; i++)
> + smooth_tmp[i] = (smooth[i - 1] + smooth[i] * 2 + smooth[i + 1]) >> 2;
> + }
> +
> + for (i = 0; i < nb_sensors; i++) {
> + smooth[i] = smooth_tmp[i];
> + if (k == 3) /* Last go-round, so scale back down. */
> + smooth[i] = smooth[i] >> 12;
The scale-up is done separately, so why not make the scale-down separately too?
> + }
> +
> + smooth[-1] = smooth[0] >> 2;
> + smooth[nb_sensors] = smooth[nb_sensors - 1] >> 2;
And these would be dropped.
> + }
> +
> for (i = 0; i < nb_sensors; i++) {
> if (xy_sensors[i] < threshold) {
> 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
> @@ -367,7 +397,8 @@ 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;
> @@ -375,15 +406,8 @@ static int atp_calculate_abs(int *xy_sensors, int nb_sensors, int fact,
> 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);
> + pcum += (smooth[i]) * i;
> + psum += (smooth[i]);
Great, this makes so much more sense.
> }
>
> if (psum > 0) {
> @@ -565,8 +589,8 @@ 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;
>
> @@ -677,8 +701,8 @@ 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;
Would you say that the cursor slow-down here is noticeable, or are there enough
samples per second that it does not matter?
Thanks,
Henrik
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