From: Phoenix Huang <phoenix@xxxxxxxxxx> 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@xxxxxxxxxx> Tested-by: Yufei Du <yufeidu@xxxxxxxxxx> Link: https://lore.kernel.org/r/20210729010940.5752-1-phoenix@xxxxxxxxxx Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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];
