Re: [PATCH] CHROMIUM: Input: synaptics - filter out the events with low z values
From: Henrik Rydberg <hidden>
Date: 2012-02-22 08:38:54
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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 <redacted> ---
The idea is sound and has worked well in practise for a long time. However, please see the comments inline.
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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?
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@@ -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