Re: [PATCH v5] m68k: Fix atari mouse movement

[Michael Schmitz <schmitzmic@gmail.com>]

Hi Miro,

Am 21.10.2026 um 15:23 schrieb 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@gmail.com>
> Signed-off-by: Miro Kropacek <miro.kropacek@gmail.com>
> Cc: linux-input <linux-input@vger.kernel.org>
> ---
>
> 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.

Dmitry's reasoning makes sense to me, so we're back on v1 with no change 
in functionality.

Looks good to me, feel free to add my Reviewed-by if it helps get this 
merged.

Cheers,

	Michael


>
>  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);
>