ACK: [PATCH 1/1][SRU][I/OEM-5.13/OEM-5.14] Input: elantench - fix misreporting trackpoint coordinates

[Kleber Souza]

On 02.12.21 09:35, Aaron Ma wrote:
> From: Phoenix Huang <phoenix at emc.com.tw>
>
> BugLink: https://bugs.launchpad.net/bugs/1936295
>
> 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 at emc.com.tw>
> Tested-by: Yufei Du <yufeidu at cs.unc.edu>
> Link: https://lore.kernel.org/r/20210729010940.5752-1-phoenix@emc.com.tw
> Cc: stable at vger.kernel.org
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov at gmail.com>
> (cherry picked from commit be896bd3b72b44126c55768f14c22a8729b0992e)
> Signed-off-by: Aaron Ma <aaron.ma at canonical.com>

Acked-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>

Thanks

> ---
>   drivers/input/mouse/elantech.c | 13 +++++++++++++
>   1 file changed, 13 insertions(+)
>
> diff --git a/drivers/input/mouse/elantech.c b/drivers/input/mouse/elantech.c
> index 2d0bc029619f..956d9cd34796 100644
> --- a/drivers/input/mouse/elantech.c
> +++ b/drivers/input/mouse/elantech.c
> @@ -517,6 +517,19 @@ static void elantech_report_trackpoint(struct psmouse *psmouse,
>   	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];
>