Hi,
On 3/18/23 15:42, msizanoen wrote:
> The AlpsPS/2 code previously relied on the assumption that `char` is a
> signed type, which was true on x86 platforms (the only place where this
> driver is used) before kernel 6.2. However, on 6.2 and later, this
> assumption is broken due to the introduction of -funsigned-char as a new
> global compiler flag.
>
> Fix this by explicitly specifying the signedness of `char` when sign
> extending the values received from the device.
>
> Fixes: f3f33c677699 ("Input: alps - Rushmore and v7 resolution support")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: msizanoen <msizanoen@xxxxxxxxxxx>
Thanks, patch looks good to me:
Reviewed-by: Hans de Goede <hdegoede@xxxxxxxxxx>
Regards,
Hans
> ---
> drivers/input/mouse/alps.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/input/mouse/alps.c b/drivers/input/mouse/alps.c
> index 989228b5a0a4..1c570d373b30 100644
> --- a/drivers/input/mouse/alps.c
> +++ b/drivers/input/mouse/alps.c
> @@ -2294,20 +2294,20 @@ static int alps_get_v3_v7_resolution(struct psmouse *psmouse, int reg_pitch)
> if (reg < 0)
> return reg;
>
> - x_pitch = (char)(reg << 4) >> 4; /* sign extend lower 4 bits */
> + x_pitch = (signed char)(reg << 4) >> 4; /* sign extend lower 4 bits */
> x_pitch = 50 + 2 * x_pitch; /* In 0.1 mm units */
>
> - y_pitch = (char)reg >> 4; /* sign extend upper 4 bits */
> + y_pitch = (signed char)reg >> 4; /* sign extend upper 4 bits */
> y_pitch = 36 + 2 * y_pitch; /* In 0.1 mm units */
>
> reg = alps_command_mode_read_reg(psmouse, reg_pitch + 1);
> if (reg < 0)
> return reg;
>
> - x_electrode = (char)(reg << 4) >> 4; /* sign extend lower 4 bits */
> + x_electrode = (signed char)(reg << 4) >> 4; /* sign extend lower 4 bits */
> x_electrode = 17 + x_electrode;
>
> - y_electrode = (char)reg >> 4; /* sign extend upper 4 bits */
> + y_electrode = (signed char)reg >> 4; /* sign extend upper 4 bits */
> y_electrode = 13 + y_electrode;
>
> x_phys = x_pitch * (x_electrode - 1); /* In 0.1 mm units */
