| Message ID | 20250129-fix_tsc_calculation_overflow-v1-1-3a6e388637c4@skidata.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | tsc2007: prevent overflow in pressure calculation | expand |
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@johanneskirchmair.de <mailinglist1@johanneskirchmair.de> > Gesendet: Mittwoch, 29. Jänner 2025 12:56 > An: Dmitry Torokhov <dmitry.torokhov@gmail.com> > Cc: linux-input@vger.kernel.org; Johannes Kirchmair - SKIDATA > <johannes.kirchmair@skidata.com> > 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@skidata.com> > > 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@skidata.com> > --- > 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@skidata.com>
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)