On Mon, Jan 19, 2015 at 3:53 PM, Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx> wrote: > When tapping a clickpad with two fingers, there is a chance that the sensor > sees first only one finger, and at the next scan only the second one. > In this case, the sensors says that there has been only one finger > on the clickpad, which moved really fast between two scans. > > We can try to counter this by adding a limit to what an actual finger > can move between 2 scans. > We can try to provide a reasonable distance of 1cm between two scans for > one finger. This is what is used in the synaptcs.c portion of the patch. > > However, this is not really accurate because the resolution in X and in Y > differs. But heh, that's how the in-kernel tracking works right now, and > its job is quite good even with this approximation. > > Once a driver has set the maximum distance for a jump of a finger between > two scans, we can tell the in-kernel tracking to dissociate the slots > and the touch with input_mt_check_slots(). > > In order not to penalize better sensors, this parameter is not > automatically enabled, but each driver has to manually set it to a > reasonable value. > > Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=76722 > > Signed-off-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx> > --- > drivers/input/input-mt.c | 67 +++++++++++++++++++++++++++++++++++++++-- > drivers/input/mouse/synaptics.c | 3 +- > include/linux/input/mt.h | 4 +++ > 3 files changed, 71 insertions(+), 3 deletions(-) > > diff --git a/drivers/input/input-mt.c b/drivers/input/input-mt.c > index c7b3752..d326262 100644 > --- a/drivers/input/input-mt.c > +++ b/drivers/input/input-mt.c > @@ -403,9 +403,51 @@ static int input_mt_set_matrix(struct input_mt *mt, > } > > /** > + * input_mt_check_slots() - validate the slot assignments > + * @mt: the input_mt handle of the current device > + * @pos: the position array to match > + * @slots: the slot assignment to be filled > + * @num_pos: number of positions > + * > + * For each assigned touch in pos, check if the distance between this touch > + * and the previously reported position is not too big. > + * If it is too big, break the assignment by resetting the slot value to -1. > + * While syncing the frame, the previously matched slot will be freed, and > + * a new one will be assigned in input_mt_set_slots(). > + * > + * The "too big" parameter is stored in mt->dmax2. > + */ > +static void input_mt_check_slots(struct input_mt *mt, > + const struct input_mt_pos *pos, int *slots, > + int num_pos) > +{ > + struct input_mt_slot *s; > + int *p; > + int i, x, y, d2, dx, dy; > + struct input_mt_pos *mt_pos; Grmbl... checkpatch.pl complained about a missing line between the declarations and the actual code (I first declared mt_pos within the for loop). So I re-scrambled the things, and of course I forget to re-add the "const" qualifer. So this line shows a pretty warning which will be fixed in v2 :( Cheers, Benjamin > + > + if (!mt->dmax2) > + return; > + > + for (i = 0; i < num_pos; i++) { > + mt_pos = pos + i; > + p = slots + i; > + s = mt->slots + *p; > + x = input_mt_get_value(s, ABS_MT_POSITION_X); > + y = input_mt_get_value(s, ABS_MT_POSITION_Y); > + dx = x - mt_pos->x; > + dy = y - mt_pos->y; > + d2 = dx * dx + dy * dy; > + if (d2 >= mt->dmax2) > + *p = -1; > + } > +} > + > +/** > * input_mt_set_slots() - assign slots to the list of pos thanks to the reduced > * cost matrix > * @mt: the input_mt handle of the current device > + * @pos: the position array to match > * @slots: the slot assignment to be filled > * @num_pos: number of positions > * > @@ -414,7 +456,8 @@ static int input_mt_set_matrix(struct input_mt *mt, > * sent slots. > */ > static void input_mt_set_slots(struct input_mt *mt, > - int *slots, int num_pos) > + const struct input_mt_pos *pos, int *slots, > + int num_pos) > { > struct input_mt_slot *s; > int *red_cost_matrix = mt->red; > @@ -436,6 +479,8 @@ static void input_mt_set_slots(struct input_mt *mt, > *p = s - mt->slots; > } > > + input_mt_check_slots(mt, pos, slots, num_pos); > + > /* for each unassigned touch in pos, assign a new slot for it */ > for (s = mt->slots; s != mt->slots + mt->num_slots; s++) { > if (input_mt_is_active(s)) > @@ -478,13 +523,31 @@ int input_mt_assign_slots(struct input_dev *dev, int *slots, > n_rows = n_elems / num_pos; > n_columns = num_pos; > find_reduced_matrix(mt->red, n_columns, n_rows, n_elems); > - input_mt_set_slots(mt, slots, num_pos); > + input_mt_set_slots(mt, pos, slots, num_pos); > > return 0; > } > EXPORT_SYMBOL(input_mt_assign_slots); > > /** > + * input_mt_set_dmax_tracking() - enhance tracking > + * @dev: input device with allocated MT slots > + * @dmax: the max distance between two touches to be considered as the same > + * > + * Enhance the in-kernel tracking by providing a maximum distance between > + * 2 touches to be considered as the same slot. > + * The stored value is the square of the provided distance to ease the tests > + * later on. The input distance has to be given in the device coordinate system. > + */ > +void input_mt_set_dmax_tracking(struct input_dev *dev, int dmax) > +{ > + struct input_mt *mt = dev->mt; > + > + mt->dmax2 = dmax * dmax; > +} > +EXPORT_SYMBOL(input_mt_set_dmax_tracking); > + > +/** > * input_mt_get_slot_by_key() - return slot matching key > * @dev: input device with allocated MT slots > * @key: the key of the sought slot > diff --git a/drivers/input/mouse/synaptics.c b/drivers/input/mouse/synaptics.c > index f89de89..95c15451 100644 > --- a/drivers/input/mouse/synaptics.c > +++ b/drivers/input/mouse/synaptics.c > @@ -1077,7 +1077,8 @@ static void set_input_params(struct psmouse *psmouse, > ABS_MT_POSITION_Y); > /* Image sensors can report per-contact pressure */ > input_set_abs_params(dev, ABS_MT_PRESSURE, 0, 255, 0, 0); > - input_mt_init_slots(dev, 2, INPUT_MT_POINTER | INPUT_MT_TRACK); > + input_mt_init_slots(dev, 4, INPUT_MT_POINTER | INPUT_MT_TRACK); > + input_mt_set_dmax_tracking(dev, 10 * priv->x_res); > > /* Image sensors can signal 4 and 5 finger clicks */ > __set_bit(BTN_TOOL_QUADTAP, dev->keybit); > diff --git a/include/linux/input/mt.h b/include/linux/input/mt.h > index f583ff6..c4b35c4 100644 > --- a/include/linux/input/mt.h > +++ b/include/linux/input/mt.h > @@ -41,6 +41,7 @@ struct input_mt_slot { > * @flags: input_mt operation flags > * @frame: increases every time input_mt_sync_frame() is called > * @red: reduced cost matrix for in-kernel tracking > + * @dmax2: max (squared) distance between 2 points when using in-kernel tracking > * @slots: array of slots holding current values of tracked contacts > */ > struct input_mt { > @@ -50,6 +51,7 @@ struct input_mt { > unsigned int flags; > unsigned int frame; > int *red; > + int dmax2; > struct input_mt_slot slots[]; > }; > > @@ -100,6 +102,8 @@ static inline bool input_is_mt_axis(int axis) > return axis == ABS_MT_SLOT || input_is_mt_value(axis); > } > > +void input_mt_set_dmax_tracking(struct input_dev *dev, int dmax); > + > void input_mt_report_slot_state(struct input_dev *dev, > unsigned int tool_type, bool active); > > -- > 2.1.0 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
