* [PATCH v1] Input: resistive-adc-touch - fix division by zero error on z1 == 0
@ 2021-10-07 9:57 Oleksij Rempel
2021-10-16 4:16 ` Dmitry Torokhov
0 siblings, 1 reply; 2+ messages in thread
From: Oleksij Rempel @ 2021-10-07 9:57 UTC (permalink / raw)
To: Dmitry Torokhov, Eugen Hristev
Cc: Oleksij Rempel, kernel, linux-kernel, linux-input, David Jander
For proper pressure calculation we need at least x and z1 to be non
zero. Even worse, in case z1 we may run in to division by zero
error.
Fixes: 60b7db914ddd ("Input: resistive-adc-touch - rework mapping of channels")
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
.../input/touchscreen/resistive-adc-touch.c | 29 ++++++++++---------
1 file changed, 16 insertions(+), 13 deletions(-)
diff --git a/drivers/input/touchscreen/resistive-adc-touch.c b/drivers/input/touchscreen/resistive-adc-touch.c
index 744544a723b7..6f754a8d30b1 100644
--- a/drivers/input/touchscreen/resistive-adc-touch.c
+++ b/drivers/input/touchscreen/resistive-adc-touch.c
@@ -71,19 +71,22 @@ static int grts_cb(const void *data, void *private)
unsigned int z2 = touch_info[st->ch_map[GRTS_CH_Z2]];
unsigned int Rt;
- Rt = z2;
- Rt -= z1;
- Rt *= st->x_plate_ohms;
- Rt = DIV_ROUND_CLOSEST(Rt, 16);
- Rt *= x;
- Rt /= z1;
- Rt = DIV_ROUND_CLOSEST(Rt, 256);
- /*
- * On increased pressure the resistance (Rt) is decreasing
- * so, convert values to make it looks as real pressure.
- */
- if (Rt < GRTS_DEFAULT_PRESSURE_MAX)
- press = GRTS_DEFAULT_PRESSURE_MAX - Rt;
+ if (likely(x && z1)) {
+ Rt = z2;
+ Rt -= z1;
+ Rt *= st->x_plate_ohms;
+ Rt = DIV_ROUND_CLOSEST(Rt, 16);
+ Rt *= x;
+ Rt /= z1;
+ Rt = DIV_ROUND_CLOSEST(Rt, 256);
+ /*
+ * On increased pressure the resistance (Rt) is
+ * decreasing so, convert values to make it looks as
+ * real pressure.
+ */
+ if (Rt < GRTS_DEFAULT_PRESSURE_MAX)
+ press = GRTS_DEFAULT_PRESSURE_MAX - Rt;
+ }
}
if ((!x && !y) || (st->pressure && (press < st->pressure_min))) {
--
2.30.2
^ permalink raw reply related [flat|nested] 2+ messages in thread* Re: [PATCH v1] Input: resistive-adc-touch - fix division by zero error on z1 == 0
2021-10-07 9:57 [PATCH v1] Input: resistive-adc-touch - fix division by zero error on z1 == 0 Oleksij Rempel
@ 2021-10-16 4:16 ` Dmitry Torokhov
0 siblings, 0 replies; 2+ messages in thread
From: Dmitry Torokhov @ 2021-10-16 4:16 UTC (permalink / raw)
To: Oleksij Rempel
Cc: Eugen Hristev, kernel, linux-kernel, linux-input, David Jander
On Thu, Oct 07, 2021 at 11:57:27AM +0200, Oleksij Rempel wrote:
> For proper pressure calculation we need at least x and z1 to be non
> zero. Even worse, in case z1 we may run in to division by zero
> error.
>
> Fixes: 60b7db914ddd ("Input: resistive-adc-touch - rework mapping of channels")
> Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Applied, thank you.
--
Dmitry
^ permalink raw reply [flat|nested] 2+ messages in thread
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