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Commit 33e60ca0 authored by msizanoen's avatar msizanoen Committed by Greg Kroah-Hartman
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Input: alps - fix compatibility with -funsigned-char 



commit 754ff5060daf5a1cf4474eff9b4edeb6c17ef7ab upstream.

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: f3f33c67 ("Input: alps - Rushmore and v7 resolution support")
Signed-off-by: default avatarmsizanoen <msizanoen@qtmlabs.xyz>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20230320045228.182259-1-msizanoen@qtmlabs.xyz


Signed-off-by: default avatarDmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 9f25e5cf

drivers/input/mouse/alps.c

+8 −8
Original line number Diff line number Diff line
@@ -855,8 +855,8 @@ static void alps_process_packet_v6(struct psmouse *psmouse) 
			x = y = z = 0;



		/* Divide 4 since trackpoint's speed is too fast */

		input_report_rel(dev2, REL_X, (char)x / 4);

		input_report_rel(dev2, REL_Y, -((char)y / 4));

		input_report_rel(dev2, REL_X, (s8)x / 4);

		input_report_rel(dev2, REL_Y, -((s8)y / 4));



		psmouse_report_standard_buttons(dev2, packet[3]);
@@ -1107,8 +1107,8 @@ static void alps_process_trackstick_packet_v7(struct psmouse *psmouse) 
	    ((packet[3] & 0x20) << 1);

	z = (packet[5] & 0x3f) | ((packet[3] & 0x80) >> 1);



	input_report_rel(dev2, REL_X, (char)x);

	input_report_rel(dev2, REL_Y, -((char)y));

	input_report_rel(dev2, REL_X, (s8)x);

	input_report_rel(dev2, REL_Y, -((s8)y));

	input_report_abs(dev2, ABS_PRESSURE, z);



	psmouse_report_standard_buttons(dev2, packet[1]);
@@ -2297,20 +2297,20 @@ 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 = (s8)(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 = (s8)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 = (s8)(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 = (s8)reg >> 4; /* sign extend upper 4 bits */

	y_electrode = 13 + y_electrode;



	x_phys = x_pitch * (x_electrode - 1); /* In 0.1 mm units */