HID: wacom: Interpret tilt data from Intuos Pro BT as signed values

JIRA: https://issues.redhat.com/browse/RHEL-102058
Upstream Status: since v6.13

commit 49a397a
Author: Jason Gerecke <jason.gerecke@wacom.com>
Date:   Mon Oct 28 10:39:14 2024 -0700

    HID: wacom: Interpret tilt data from Intuos Pro BT as signed values

    The tilt data contained in the Bluetooth packets of an Intuos Pro are
    supposed to be interpreted as signed values. Simply casting the values
    to type `char` is not guaranteed to work since it is implementation-
    defined whether it is signed or unsigned. At least one user has noticed
    the data being reported incorrectly on their system. To ensure that the
    data is interpreted properly, we specifically cast to `signed char`
    instead.

    Link: linuxwacom/input-wacom#445
    Fixes: 4922cd2 ("HID: wacom: Support 2nd-gen Intuos Pro's Bluetooth classic interface")
    CC: stable@vger.kernel.org # 4.11+
    Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
    Signed-off-by: Jiri Kosina <jkosina@suse.com>

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

Author: bentiss

drivers/hid/wacom_wac.c

@@ -1353,9 +1353,9 @@ static void wacom_intuos_pro2_bt_pen(struct wacom_wac *wacom)
 					rotation -= 1800;
 
 				input_report_abs(pen_input, ABS_TILT_X,
-						 (char)frame[7]);
+						 (signed char)frame[7]);
 				input_report_abs(pen_input, ABS_TILT_Y,
-						 (char)frame[8]);
+						 (signed char)frame[8]);
 				input_report_abs(pen_input, ABS_Z, rotation);
 				input_report_abs(pen_input, ABS_WHEEL,
 						 get_unaligned_le16(&frame[11]));