Re: [PATCH 1/5] m68k: Fix atari mouse movement

Hi Michael,

CC linux-input

On Fri, 14 Aug 2026 at 05:17, Michael Schmitz [off-list ref] wrote:

From: Miro Kropacek <redacted>

Kernels are built with -funsigned-char since version 6.2, resulting
in signed mouse position deltas getting misinterpreted as unsigned.

Cast deltas passed in (unsigned) scancode buffer to correctly
interpret sign.

Fixes: 3bc753c06dd02a35 ("kbuild: treat char as always unsigned")
Link: https://lists.debian.org/debian-68k/2026/08/msg00000.html
Signed-off-by: Miro Kropacek <redacted>
Reviewed-by: Michael Schmitz <schmitzmic@gmail.com>

Since you're now in the path to upstream, you should add your SoB here
(applies to all patches).

Alternative, you could change/restore the function's signature to take a
"signed char *".

        atari_mouse_buttons = buttons;
 #endif

-       /* only relative events get here */
-       dx = buf[1];
-       dy = buf[2];
+       /* only relative events get here; the IKBD sends signed 8-bit
+        * deltas, and the kernel builds with -funsigned-char since 6.2,
+        * so an explicit signed cast is required
+        */
+       dx = (s8)buf[1];
+       dy = (s8)buf[2];

        input_report_rel(atamouse_dev, REL_X, dx);
        input_report_rel(atamouse_dev, REL_Y, dy);

Regardless:
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds