From: Peter Hutterer <peter.hutte...@who-t.net>

commit fd35759ce32b60d3eb52436894bab996dbf8cffa upstream.

hidpp_scroll_counter_handle_scroll() doesn't expect a 0-value scroll event, it
gets interpreted as a negative scroll direction event. This can cause scroll
direction resets and thus broken scrolling.

Fixes: 4435ff2f09a2fc ("HID: logitech: Enable high-resolution scrolling on 
Logitech mice")
Cc: sta...@vger.kernel.org # v5.0
Reported-and-tested-by: Aimo Metsälä <aimet...@outlook.com>
Signed-off-by: Peter Hutterer <peter.hutte...@who-t.net>
Signed-off-by: Benjamin Tissoires <benjamin.tissoi...@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/hid/hid-logitech-hidpp.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/hid/hid-logitech-hidpp.c
+++ b/drivers/hid/hid-logitech-hidpp.c
@@ -2608,8 +2608,9 @@ static int m560_raw_event(struct hid_dev
                input_report_rel(mydata->input, REL_Y, v);
 
                v = hid_snto32(data[6], 8);
-               hidpp_scroll_counter_handle_scroll(
-                               &hidpp->vertical_wheel_counter, v);
+               if (v != 0)
+                       hidpp_scroll_counter_handle_scroll(
+                                       &hidpp->vertical_wheel_counter, v);
 
                input_sync(mydata->input);
        }


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