[PATCH v5] m68k: Fix atari mouse movement

[Miro Kropacek]

Kernels are built with -funsigned-char since version 6.2, resulting in
the signed 8-bit position deltas reported by the IKBD being
misinterpreted as unsigned.

The hook is handed a raw IKBD packet, so take it as a byte stream and
apply the sign to the two displacement values alone.

Fixes: 3bc753c06dd02a35 ("kbuild: treat char as always unsigned")
Link: https://lists.debian.org/debian-68k/2026/08/msg00000.html
Suggested-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
Signed-off-by: Miro Kropacek <miro.kropacek@xxxxxxxxx>
Cc: linux-input <linux-input@xxxxxxxxxxxxxxx>
---

Changes in v5:

- take the packet as u8 * and cast only the two displacement values,
  as suggested; this drops the call-site cast v4 needed, and with it
  the -Wpointer-sign warning
- add the types include atarikb.h now relies on

The same cast of the two displacement values was tested on an Atari
Falcon030 with CT60 in v1 of this patch; v5 differs from it only in the
type of the hook argument.

Michael's Reviewed-by from v3 is dropped, as the approach has changed
twice since.

 arch/m68k/atari/atakeyb.c        | 2 +-
 arch/m68k/include/asm/atarikb.h  | 4 +++-
 drivers/input/mouse/atarimouse.c | 6 +++---
 3 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/arch/m68k/atari/atakeyb.c b/arch/m68k/atari/atakeyb.c
index 49a9a459bdf4..b715e2b8351c 100644
--- a/arch/m68k/atari/atakeyb.c
+++ b/arch/m68k/atari/atakeyb.c
@@ -39,7 +39,7 @@ void (*atari_MIDI_interrupt_hook) (void);
 /* Hook for keyboard inputdev  driver */
 void (*atari_input_keyboard_interrupt_hook) (unsigned char, char);
 /* Hook for mouse inputdev  driver */
-void (*atari_input_mouse_interrupt_hook) (char *);
+void (*atari_input_mouse_interrupt_hook)(u8 *buf);
 EXPORT_SYMBOL(atari_input_keyboard_interrupt_hook);
 EXPORT_SYMBOL(atari_input_mouse_interrupt_hook);
 
diff --git a/arch/m68k/include/asm/atarikb.h b/arch/m68k/include/asm/atarikb.h
index 68f3622bf591..bdf67bff1472 100644
--- a/arch/m68k/include/asm/atarikb.h
+++ b/arch/m68k/include/asm/atarikb.h
@@ -15,6 +15,8 @@
 #ifndef _LINUX_ATARIKB_H
 #define _LINUX_ATARIKB_H
 
+#include <linux/types.h>
+
 void ikbd_write(const char *, int);
 void ikbd_mouse_button_action(int mode);
 void ikbd_mouse_rel_pos(void);
@@ -37,7 +39,7 @@ extern void (*atari_MIDI_interrupt_hook) (void);
 /* Hook for keyboard inputdev  driver */
 extern void (*atari_input_keyboard_interrupt_hook) (unsigned char, char);
 /* Hook for mouse inputdev  driver */
-extern void (*atari_input_mouse_interrupt_hook) (char *);
+extern void (*atari_input_mouse_interrupt_hook)(u8 *buf);
 
 int atari_keyb_init(void);
 
diff --git a/drivers/input/mouse/atarimouse.c b/drivers/input/mouse/atarimouse.c
index b1219cc4d9a2..c5b794262e85 100644
--- a/drivers/input/mouse/atarimouse.c
+++ b/drivers/input/mouse/atarimouse.c
@@ -60,7 +60,7 @@ extern int atari_mouse_buttons;
 
 static struct input_dev *atamouse_dev;
 
-static void atamouse_interrupt(char *buf)
+static void atamouse_interrupt(u8 *buf)
 {
 	int buttons, dx, dy;
 
@@ -71,8 +71,8 @@ static void atamouse_interrupt(char *buf)
 #endif
 
 	/* only relative events get here */
-	dx = buf[1];
-	dy = buf[2];
+	dx = (s8)buf[1];
+	dy = (s8)buf[2];
 
 	input_report_rel(atamouse_dev, REL_X, dx);
 	input_report_rel(atamouse_dev, REL_Y, dy);
-- 
2.43.0