Input: focaltech - use explicitly signed char type

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 explicitly
signed, to take into account negative offsets.

Fixes: 3bc753c06dd0 ("kbuild: treat char as always unsigned")
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Cc: stable@vger.kernel.org
Link: https://bugzilla.kernel.org/show_bug.cgi?id=217211
Link: https://lore.kernel.org/r/20230318133010.1285202-1-Jason@zx2c4.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

diff --git a/drivers/input/mouse/focaltech.c b/drivers/input/mouse/focaltech.c
index 6fd5fff0cbfffd752748d995bab8256c12c9e258..c74b99077d16a35637c1d0c015a772cea687c13b 100644 (file)
--- 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 += (s8)packet[1];
+               state->fingers[finger1].y += (s8)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 += (s8)packet[4];
+               state->fingers[finger2].y += (s8)packet[5];
        }
 }