[PATCH 5.14 004/849] Input: elantench - fix misreporting trackpoint coordinates

Greg Kroah-Hartman
2021-11-15T21:27:41Z

From: Phoenix Huang <phoenix@emc.com.tw>

commit be896bd3b72b44126c55768f14c22a8729b0992e upstream.

Some firmwares occasionally report bogus data from trackpoint, with X or Y
displacement being too large (outside of [-127, 127] range). Let's drop such
packets so that we do not generate jumps.

Signed-off-by: Phoenix Huang <phoenix@emc.com.tw>
Tested-by: Yufei Du <yufeidu@cs.unc.edu>
Link: https://lore.kernel.org/r/20210729010940.5752-1-phoenix@emc.com.tw
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/input/mouse/elantech.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

--- a/drivers/input/mouse/elantech.c
+++ b/drivers/input/mouse/elantech.c
@@ -517,6 +517,19 @@ static void elantech_report_trackpoint(s
case 0x16008020U:
case 0x26800010U:
case 0x36808000U:
+
+ /*
+ * This firmware misreport coordinates for trackpoint
+ * occasionally. Discard packets outside of [-127, 127] range
+ * to prevent cursor jumps.
+ */
+ if (packet[4] == 0x80 || packet[5] == 0x80 ||
+ packet[1] >> 7 == packet[4] >> 7 ||
+ packet[2] >> 7 == packet[5] >> 7) {
+ elantech_debug("discarding packet [%6ph]\n", packet);
+ break;
+
+ }
x = packet[4] - (int)((packet[1]^0x80) << 1);
y = (int)((packet[2]^0x80) << 1) - packet[5];