linux-kernel - [PATCH] HID: logitech: Handle 0 scroll events for the m560

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Date:   Wed, 20 Mar 2019 08:48:23 +1000
From:   Peter Hutterer <peter.hutterer@...-t.net>
To:     linux-input@...r.kernel.org
Cc:     Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Aimo Metsälä <aimetsal@...look.com>,
        nlopezcasad@...itech.com, Jiri Kosina <jikos@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] HID: logitech: Handle 0 scroll events for the m560

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.

Reported-and-tested-by: Aimo Metsälä <aimetsal@...look.com>
Signed-off-by: Peter Hutterer <peter.hutterer@...-t.net>
---
 drivers/hid/hid-logitech-hidpp.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
index 15ed6177a7a3..f040c8a7f9a9 100644
--- 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_device *hdev, u8 *data, int size)
 		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);
 	}
-- 
2.20.1