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 @@ -435,6 +435,19 @@ 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];