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@vger.kernel.org Signed-off-by: msizanoen msizanoen@qtmlabs.xyz --- 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 */