Hi Chung-yih Wang,
> The single touch path imposes a minimum z value (with hysterisis) before
> registering BTN_TOUCH. Apply the same (hard coded) threshold when
> deciding how many fingers to report in the semi-mt path.
>
> This patch improves performance of the Google Cr-48 chromebook's
> extremely sensitive Synaptics profile sensor touchpad by filtering out
> touch events for hovering fingers.
>
> Note: We continue to use the same hard coded threshold value used in the
> single touch case as it appears this works just as well on these
> multitouch profile sensor pads as on whatever pads it was originally
> discovered.
>
> Signed-off-by: Chung-Yih Wang <cywang@xxxxxxxxxxxx>
> ---
The idea is sound and has worked well in practise for a long
time. However, please see the comments inline.
> drivers/input/mouse/synaptics.c | 15 +++++++++++----
> 1 files changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/input/mouse/synaptics.c b/drivers/input/mouse/synaptics.c
> index 8081a0a..746dbcc 100644
> --- a/drivers/input/mouse/synaptics.c
> +++ b/drivers/input/mouse/synaptics.c
> @@ -568,17 +568,22 @@ static void synaptics_report_semi_mt_slot(struct input_dev *dev, int slot,
> }
> }
>
> +static bool finger_touched(const struct synaptics_hw_state *hw)
> +{
> + return (hw->z > 30);
> +}
> +
> static void synaptics_report_semi_mt_data(struct input_dev *dev,
> const struct synaptics_hw_state *a,
> const struct synaptics_hw_state *b,
> int num_fingers)
> {
> - if (num_fingers >= 2) {
> + if ((num_fingers >= 2) && finger_touched(a) && finger_touched(b)) {
> synaptics_report_semi_mt_slot(dev, 0, true, min(a->x, b->x),
> min(a->y, b->y));
> synaptics_report_semi_mt_slot(dev, 1, true, max(a->x, b->x),
> max(a->y, b->y));
> - } else if (num_fingers == 1) {
> + } else if ((num_fingers == 1) && finger_touched(a)) {
> synaptics_report_semi_mt_slot(dev, 0, true, a->x, a->y);
> synaptics_report_semi_mt_slot(dev, 1, false, 0, 0);
> } else {
So if num_fingers == 2 and only one of a and b returns
finger_touched() == true, we fall back to zero fingers?
> @@ -1040,8 +1045,10 @@ static void synaptics_process_packet(struct psmouse *psmouse)
> * BTN_TOUCH has to be first as mousedev relies on it when doing
> * absolute -> relative conversion
> */
> - if (hw.z > 30) input_report_key(dev, BTN_TOUCH, 1);
> - if (hw.z < 25) input_report_key(dev, BTN_TOUCH, 0);
> + if (finger_touched(&hw))
> + input_report_key(dev, BTN_TOUCH, 1);
> + if (hw.z < 25)
> + input_report_key(dev, BTN_TOUCH, 0);
>
> if (num_fingers > 0) {
> input_report_abs(dev, ABS_X, hw.x);
Why not introduce hysteresis for all fingers here? There is an example
implementation in bcm5974.c in the same directory.
Thanks,
Henrik
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