From: Jason Gerecke <jason.gere...@wacom.com>

commit 69dbdfffef20c715df9f381b2cee4e9e0a4efd93 upstream.

The Bluetooth interface of the 2nd-gen Intuos Pro batches together four
independent "frames" of finger data into a single report. Each frame
is essentially equivalent to a single USB report, with the up-to-10
fingers worth of information being spread across two frames. At the
moment the driver only calls `input_sync` after processing all four
frames have been processed, which can result in the driver sending
multiple updates for a single slot within the same SYN_REPORT. This
can confuse userspace, so modify the driver to sync more often if
necessary (i.e., after reporting the state of all fingers).

Fixes: 4922cd26f03c ("HID: wacom: Support 2nd-gen Intuos Pro's Bluetooth 
classic interface")
Cc: <sta...@vger.kernel.org> # 4.11+
Signed-off-by: Jason Gerecke <jason.gere...@wacom.com>
Signed-off-by: Benjamin Tissoires <benjamin.tissoi...@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/hid/wacom_wac.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

--- a/drivers/hid/wacom_wac.c
+++ b/drivers/hid/wacom_wac.c
@@ -1328,11 +1328,17 @@ static void wacom_intuos_pro2_bt_touch(s
                if (wacom->num_contacts_left <= 0) {
                        wacom->num_contacts_left = 0;
                        wacom->shared->touch_down = 
wacom_wac_finger_count_touches(wacom);
+                       input_sync(touch_input);
                }
        }
 
-       input_report_switch(touch_input, SW_MUTE_DEVICE, !(data[281] >> 7));
-       input_sync(touch_input);
+       if (wacom->num_contacts_left == 0) {
+               // Be careful that we don't accidentally call input_sync with
+               // only a partial set of fingers of processed
+               input_report_switch(touch_input, SW_MUTE_DEVICE, !(data[281] >> 
7));
+               input_sync(touch_input);
+       }
+
 }
 
 static void wacom_intuos_pro2_bt_pad(struct wacom_wac *wacom)


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