diff mbox series

Input: focaltech - use explicitly signed char type

Message ID 20230318133010.1285202-1-Jason@zx2c4.com
State New
Headers show
Series Input: focaltech - use explicitly signed char type | expand

Commit Message

Jason A. Donenfeld March 18, 2023, 1:30 p.m. UTC 
The recent change of -funsigned-char causes additions of negative
numbers to become additions of large positive numbers, leading to wrong
calculations of mouse movement. Change these casts to be explictly
signed, to take into account negative offsets.

Fixes: 3bc753c06dd0 ("kbuild: treat char as always unsigned")
Cc: stable@vger.kernel.org
Cc: regressions@leemhuis.info
Cc: barry@messagefor.me.uk
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
Wrote this patch from my phone, untested, so it would be nice if
somebody with hardware could confirm it works.

 drivers/input/mouse/focaltech.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)
diff mbox series

Patch

diff --git a/drivers/input/mouse/focaltech.c b/drivers/input/mouse/focaltech.c
index 6fd5fff0cbff..3dbad0d8e8c9 100644
--- a/drivers/input/mouse/focaltech.c
+++ b/drivers/input/mouse/focaltech.c
@@ -202,8 +202,8 @@  static void focaltech_process_rel_packet(struct psmouse *psmouse,
 	state->pressed = packet[0] >> 7;
 	finger1 = ((packet[0] >> 4) & 0x7) - 1;
 	if (finger1 < FOC_MAX_FINGERS) {
-		state->fingers[finger1].x += (char)packet[1];
-		state->fingers[finger1].y += (char)packet[2];
+		state->fingers[finger1].x += (signed char)packet[1];
+		state->fingers[finger1].y += (signed char)packet[2];
 	} else {
 		psmouse_err(psmouse, "First finger in rel packet invalid: %d\n",
 			    finger1);
@@ -218,8 +218,8 @@  static void focaltech_process_rel_packet(struct psmouse *psmouse,
 	 */
 	finger2 = ((packet[3] >> 4) & 0x7) - 1;
 	if (finger2 < FOC_MAX_FINGERS) {
-		state->fingers[finger2].x += (char)packet[4];
-		state->fingers[finger2].y += (char)packet[5];
+		state->fingers[finger2].x += (signed char)packet[4];
+		state->fingers[finger2].y += (signed char)packet[5];
 	}
 }