Hi,
Did something wrong in this patch.
So please ignore it :-/
Will send v2 soon.
Sorry for the noise.
Best regards
Johannes
> -----Ursprüngliche Nachricht-----
> Von: mailinglist1@xxxxxxxxxxxxxxxxxxxx <mailinglist1@xxxxxxxxxxxxxxxxxxxx>
> Gesendet: Mittwoch, 29. Jänner 2025 12:56
> An: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
> Cc: linux-input@xxxxxxxxxxxxxxx; Johannes Kirchmair - SKIDATA
> <johannes.kirchmair@xxxxxxxxxxx>
> Betreff: [PATCH] tsc2007: prevent overflow in pressure calculation
>
> Caution: This is an external email, please take care when clicking links or
> opening attachments
>
> From: Johannes Kirchmair <johannes.kirchmair@xxxxxxxxxxx>
>
> The touch resistance calculation in the tsc2007 driver is prone to overflow
> if (z2 - z1) is large and also x is reasonably big. As an result the
> driver sometimes emit input events even with very little touch pressure
> applied. For those events the x and y coordinates can be substantially
> off. We fix the overflow problematic by calculating in a bigger int
> type.
>
> Signed-off-by: Johannes Kirchmair <johannes.kirchmair@xxxxxxxxxxx>
> ---
> drivers/input/touchscreen/tsc2007_core.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/input/touchscreen/tsc2007_core.c
> b/drivers/input/touchscreen/tsc2007_core.c
> index 8d832a372b89..80abbccd1feb 100644
> --- a/drivers/input/touchscreen/tsc2007_core.c
> +++ b/drivers/input/touchscreen/tsc2007_core.c
> @@ -68,11 +68,12 @@ static void tsc2007_read_values(struct tsc2007 *tsc,
> struct ts_event *tc)
>
> u32 tsc2007_calculate_resistance(struct tsc2007 *tsc, struct ts_event *tc)
> {
> - u32 rt = 0;
> + u64 rt = 0;
>
> /* range filtering */
> - if (tc->x == MAX_12BIT)
> + if (tc->x == MAX_12BIT) {
> tc->x = 0;
> + }
>
> if (likely(tc->x && tc->z1)) {
> /* compute touch resistance using equation #1 */
> @@ -83,7 +84,9 @@ u32 tsc2007_calculate_resistance(struct tsc2007 *tsc,
> struct ts_event *tc)
> rt = (rt + 2047) >> 12;
> }
>
> - return rt;
> + if (rt > U32_MAX)
> + return U32_MAX;
> + return (u32) rt;
> }
>
> bool tsc2007_is_pen_down(struct tsc2007 *ts)
>
> ---
> base-commit: 05dbaf8dd8bf537d4b4eb3115ab42a5fb40ff1f5
> change-id: 20250129-fix_tsc_calculation_overflow-90860d4e3492
>
> Best regards,
> --
> Johannes Kirchmair <johannes.kirchmair@xxxxxxxxxxx>
