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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Peter Hutterer <peter.hutterer@who-t.net>,
        Benjamin Tissoires <benjamin.tissoires@redhat.com>,
        =?UTF-8?q?Aimo=20Mets=C3=A4l=C3=A4?= <aimetsal@outlook.com>
Subject: [PATCH 5.0 050/117] HID: logitech: Handle 0 scroll events for the m560
Date:   Mon, 15 Apr 2019 21:00:20 +0200
Message-Id: <20190415183747.522995530@linuxfoundation.org>
In-Reply-To: <20190415183744.887851196@linuxfoundation.org>
References: <20190415183744.887851196@linuxfoundation.org>
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From: Peter Hutterer <peter.hutterer@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: stable@vger.kernel.org # v5.0
Reported-and-tested-by: Aimo Metsälä <aimetsal@outlook.com>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@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);
 	}