Investigating the following gesture highlighted two slight implementation errors with choosing which slots to report in which slot when multiple contacts are present: Action SGM AGM (MTB slot:Contact) 1. Touch contact 0 (0:0) 2. Touch contact 1 (0:0, 1:1) 3. Lift contact 0 (1:1) 4. Touch contacts 2,3 (0:2, 1:3) In step 4, slot 1 was not being cleared first, which means the same tracking ID was being used for reporting both the old contact 1 and the new contact 3. This could result in "drumroll", where the old contact 1 would appear to suddenly jump to new finger 3 position. Similarly, if contacts 2 & 3 are not detected at the same sample, step 4 is split into two: Action SGM AGM (MTB slot:contact) 1. Touch contact 0 (0:0) 2. Touch contact 1 (0:0, 1:1) 3. Lift contact 0 (1:1) 4. Touch contact 2 (0:2, 1:1) 5. Touch contact 3 (0:2, 1:3) In this case, there was also a bug. In step 4, when contact 1 moves from SGM to AGM and contact 2 is first reported in SGM, slot 0 was actually empty. So slot 0 can be used to report the new SGM (contact 0), immediately. Since it was empty, contact 2 in slot 0 will get a new tracking ID. Signed-off-by: Daniel Kurtz <djkurtz@xxxxxxxxxxxx> --- drivers/input/mouse/synaptics.c | 30 +++++++++++++++++++++++++++--- 1 file changed, 27 insertions(+), 3 deletions(-) diff --git a/drivers/input/mouse/synaptics.c b/drivers/input/mouse/synaptics.c index b6c6838..47159d8 100644 --- a/drivers/input/mouse/synaptics.c +++ b/drivers/input/mouse/synaptics.c @@ -722,11 +722,13 @@ static void synaptics_report_mt_data(struct psmouse *psmouse, default: /* * If the finger slot contained in SGM is valid, and either - * hasn't changed, or is new, then report SGM in MTB slot 0. + * hasn't changed, or is new, or the old SGM has now moved to + * AGM, then report SGM in MTB slot 0. * Otherwise, empty MTB slot 0. */ if (mt_state->sgm != -1 && - (mt_state->sgm == old->sgm || old->sgm == -1)) + (mt_state->sgm == old->sgm || + old->sgm == -1 || mt_state->agm == old->sgm)) synaptics_report_slot(dev, 0, sgm); else synaptics_report_slot(dev, 0, NULL); @@ -735,9 +737,31 @@ static void synaptics_report_mt_data(struct psmouse *psmouse, * If the finger slot contained in AGM is valid, and either * hasn't changed, or is new, then report AGM in MTB slot 1. * Otherwise, empty MTB slot 1. + * + * However, in the case where the AGM is new, make sure that + * that it is either the same as the old SGM, or there was no + * SGM. + * + * Otherwise, if the SGM was just 1, and the new AGM is 2, then + * the new AGM will keep the old SGM's tracking ID, which can + * cause apparent drumroll. This happens if in the following + * valid finger sequence: + * + * Action SGM AGM (MTB slot:Contact) + * 1. Touch contact 0 (0:0) + * 2. Touch contact 1 (0:0, 1:1) + * 3. Lift contact 0 (1:1) + * 4. Touch contacts 2,3 (0:2, 1:3) + * + * In step 4, contact 3, in AGM must not be given the same + * tracking ID as contact 1 had in step 3. To avoid this, + * the first agm with contact 3 is dropped and slot 1 is + * invalidated (tracking ID = -1). */ if (mt_state->agm != -1 && - (mt_state->agm == old->agm || old->agm == -1)) + (mt_state->agm == old->agm || + (old->agm == -1 && + (old->sgm == -1 || mt_state->agm == old->sgm)))) synaptics_report_slot(dev, 1, agm); else synaptics_report_slot(dev, 1, NULL); -- 1.8.1 -- 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
