On Wed, Apr 22, 2015 at 11:45:09AM -0400, Benjamin Tissoires wrote:
> Synaptics PS/2 touchpad can send only 2 touches in a report. They can
> detect 4 or 5 and this information is valuable.
>
> In commit 63c4fda3c0bb ("Input: synaptics - allocate 3 slots to keep
> stability in image sensors"), we allocate 3 slots, but we still continue
> to report the 2 available fingers. That means that the client sees 2 used
> slots while there is a total of 3 fingers advertised by BTN_TOOL_TRIPLETAP.
>
> For old kernels this is not a problem because max_slots was 2 and libinput/
> xorg-synaptics knew how to deal with that. Now that max_slot is 3, the
> clients ignore BTN_TOOL_TRIPLETAP and count the actual used slots (so 2).
> It then gets confused when receiving the BTN_TOOL_TRIPLETAP and DOUBLETAP
> information, and goes wild.
>
> We can pin the 3 slots until we get a total number of fingers below 2.
>
> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1212230
Benjamin, I do not quite like it. It seems that original patch was not
quite right and we are adding more workarounds.
Synaptics can only track 2 contacts, correct? Why 2 slots to track them
is not enough?
>
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
> ---
> drivers/input/mouse/synaptics.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/drivers/input/mouse/synaptics.c b/drivers/input/mouse/synaptics.c
> index 630af73..c69b308 100644
> --- a/drivers/input/mouse/synaptics.c
> +++ b/drivers/input/mouse/synaptics.c
> @@ -935,6 +935,14 @@ static void synaptics_report_mt_data(struct psmouse *psmouse,
> input_report_abs(dev, ABS_MT_PRESSURE, hw[i]->z);
> }
>
> + /* keep (slot count <= num_fingers) by pinning all slots */
> + if (num_fingers >= 3) {
> + for (i = 0; i < 3; i++) {
> + input_mt_slot(dev, i);
> + input_mt_report_slot_state(dev, MT_TOOL_FINGER, true);
> + }
> + }
> +
> input_mt_drop_unused(dev);
>
> /* Don't use active slot count to generate BTN_TOOL events. */
> --
> 2.1.0
>
--
Dmitry
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