touchpad: disable the pressure axes wherever the resolution is nonzero

The kernel/udev set the pressure resolution to nonzero to indicate the value
is in a known scale (units/g). We use that information to disable the
pressure axis on such devices - real pressure cannot be translated to
contact size.

For the kernel patch see:
https://www.spinics.net/lists/linux-input/msg71237.html

Fixes #569

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

meson.build

@@ -777,6 +777,7 @@ if get_option('tests')
 		'test/litest-device-dell-canvas-totem-touch.c',
 		'test/litest-device-elantech-touchpad.c',
 		'test/litest-device-elan-tablet.c',
+		'test/litest-device-generic-pressurepad.c',
 		'test/litest-device-generic-singletouch.c',
 		'test/litest-device-gpio-keys.c',
 		'test/litest-device-huion-pentablet.c',

src/evdev-mt-touchpad.c

@@ -3610,6 +3610,26 @@ out:
 	return rc;
 }
 
+static void
+tp_init_pressurepad(struct tp_dispatch *tp,
+		    struct evdev_device *device)
+{
+	/* On traditional touchpads, the pressure value equals contact
+	 * size. On PressurePads, pressure is a real physical axis for the
+	 * force down. So we disable it here because we don't do anything
+	 * with it anyway and using it for touch size messes things up.
+	 *
+	 * The kernel/udev set the resolution to non-zero on those devices
+	 * to indicate that the value is in a known axis space.
+	 *
+	 * See also #562
+	 */
+	if (libevdev_get_abs_resolution(device->evdev, ABS_MT_PRESSURE) != 0) {
+		libevdev_disable_event_code(device->evdev, EV_ABS, ABS_MT_PRESSURE);
+		libevdev_disable_event_code(device->evdev, EV_ABS, ABS_PRESSURE);
+	}
+}
+
 static int
 tp_init(struct tp_dispatch *tp,
 	struct evdev_device *device)
@@ -3625,10 +3645,12 @@ tp_init(struct tp_dispatch *tp,
 		return false;
 
 	tp_init_default_resolution(tp, device);
+	tp_init_pressurepad(tp, device);
 
 	if (!tp_init_slots(tp, device))
 		return false;
 
+
 	evdev_device_init_abs_range_warnings(device);
 	use_touch_size = tp_init_touch_size(tp, device);
 

test/litest-device-generic-pressurepad.c

@@ -0,0 +1,125 @@
+/*
+ * Copyright © 2021 Red Hat, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#include "config.h"
+
+#include "litest.h"
+#include "litest-int.h"
+
+/* This is the same device as the one from
+   https://gitlab.freedesktop.org/libinput/libinput/-/issues/562
+
+   Except this one has a different input_id and sets the pressure
+   resolution to test the generic pressure handling.
+ */
+
+static struct input_event down[] = {
+	{ .type = EV_ABS, .code = ABS_X, .value = LITEST_AUTO_ASSIGN  },
+	{ .type = EV_ABS, .code = ABS_Y, .value = LITEST_AUTO_ASSIGN },
+	{ .type = EV_ABS, .code = ABS_PRESSURE, .value = LITEST_AUTO_ASSIGN },
+	{ .type = EV_ABS, .code = ABS_MT_SLOT, .value = LITEST_AUTO_ASSIGN },
+	{ .type = EV_ABS, .code = ABS_MT_TRACKING_ID, .value = LITEST_AUTO_ASSIGN },
+	{ .type = EV_ABS, .code = ABS_MT_POSITION_X, .value = LITEST_AUTO_ASSIGN },
+	{ .type = EV_ABS, .code = ABS_MT_POSITION_Y, .value = LITEST_AUTO_ASSIGN },
+	{ .type = EV_SYN, .code = SYN_REPORT, .value = 0 },
+	{ .type = -1, .code = -1 },
+};
+
+static struct input_event move[] = {
+	{ .type = EV_ABS, .code = ABS_MT_SLOT, .value = LITEST_AUTO_ASSIGN },
+	{ .type = EV_ABS, .code = ABS_X, .value = LITEST_AUTO_ASSIGN  },
+	{ .type = EV_ABS, .code = ABS_Y, .value = LITEST_AUTO_ASSIGN },
+	{ .type = EV_ABS, .code = ABS_PRESSURE, .value = LITEST_AUTO_ASSIGN },
+	{ .type = EV_ABS, .code = ABS_MT_POSITION_X, .value = LITEST_AUTO_ASSIGN },
+	{ .type = EV_ABS, .code = ABS_MT_POSITION_Y, .value = LITEST_AUTO_ASSIGN },
+	{ .type = EV_SYN, .code = SYN_REPORT, .value = 0 },
+	{ .type = -1, .code = -1 },
+};
+
+
+static int
+get_axis_default(struct litest_device *d, unsigned int evcode, int32_t *value)
+{
+	switch (evcode) {
+	/* Always set pressure to zero. The real device sends pressure
+	 * values > 30 when the device is clicked but until this is a)
+	 * handled by libinput and b) integrated into this test suite
+	 * a zero value does the job.
+	 */
+	case ABS_PRESSURE:
+	case ABS_MT_PRESSURE:
+		*value = 0;
+		return 0;
+	}
+	return 1;
+}
+
+static struct litest_device_interface interface = {
+	.touch_down_events = down,
+	.touch_move_events = move,
+
+	.get_axis_default = get_axis_default,
+};
+
+static struct input_id input_id = {
+	.bustype = 0x18,
+	.vendor = 0x123,
+	.product = 0x4567,
+};
+
+static int events[] = {
+	EV_KEY, BTN_LEFT,
+	EV_KEY, BTN_TOOL_FINGER,
+	EV_KEY, BTN_TOUCH,
+	EV_KEY, BTN_TOOL_DOUBLETAP,
+	EV_KEY, BTN_TOOL_TRIPLETAP,
+	EV_KEY, BTN_TOOL_QUADTAP,
+	EV_KEY, BTN_TOOL_QUINTTAP,
+	INPUT_PROP_MAX, INPUT_PROP_POINTER,
+	INPUT_PROP_MAX, INPUT_PROP_BUTTONPAD,
+	-1, -1,
+};
+
+static struct input_absinfo absinfo[] = {
+	{ ABS_X, 0, 1224, 0, 0, 12 },
+	{ ABS_Y, 0, 756, 0, 0, 12 },
+	{ ABS_PRESSURE, 0, 255, 0, 0, 40 }, /* some random resolution */
+	{ ABS_MT_SLOT, 0, 4, 0, 0, 0 },
+	{ ABS_MT_POSITION_X, 0, 1224, 0, 0, 12 },
+	{ ABS_MT_POSITION_Y, 0, 756, 0, 0, 12 },
+	{ ABS_MT_TRACKING_ID, 0, 65535, 0, 0, 0 },
+	{ ABS_MT_PRESSURE, 0, 255, 0, 0, 40 }, /* some random resolution */
+	{ ABS_MT_TOOL_TYPE, 0, 2, 0, 0, 0 },
+	{ .value = -1 }
+};
+
+TEST_DEVICE("generic-pressurepad",
+	.type = LITEST_GENERIC_PRESSUREPAD,
+	.features = LITEST_TOUCHPAD | LITEST_CLICKPAD | LITEST_BUTTON,
+	.interface = &interface,
+
+	.name = "Some Generic Pressurepad Touchpad",
+	.id = &input_id,
+	.events = events,
+	.absinfo = absinfo,
+)

test/litest-device-synaptics-pressurepad.c

@@ -26,7 +26,12 @@
 #include "litest.h"
 #include "litest-int.h"
 
-/* Device from https://gitlab.freedesktop.org/libinput/libinput/-/issues/562 */
+/*
+ * Device from https://gitlab.freedesktop.org/libinput/libinput/-/issues/562
+ *
+ * This device relies on a quirk to disable the pressure axis, resolution is
+ * not set on ABS_PRESSURE.
+ */
 
 static struct input_event down[] = {
 	{ .type = EV_ABS, .code = ABS_X, .value = LITEST_AUTO_ASSIGN  },
@@ -98,12 +103,12 @@ static int events[] = {
 static struct input_absinfo absinfo[] = {
 	{ ABS_X, 0, 1224, 0, 0, 12 },
 	{ ABS_Y, 0, 756, 0, 0, 12 },
-	{ ABS_PRESSURE, 0, 255, 0, 0, 0 },
+	{ ABS_PRESSURE, 0, 255, 0, 0, 0 }, /* note: resolution zero */
 	{ ABS_MT_SLOT, 0, 4, 0, 0, 0 },
 	{ ABS_MT_POSITION_X, 0, 1224, 0, 0, 12 },
 	{ ABS_MT_POSITION_Y, 0, 756, 0, 0, 12 },
 	{ ABS_MT_TRACKING_ID, 0, 65535, 0, 0, 0 },
-	{ ABS_MT_PRESSURE, 0, 255, 0, 0, 0 },
+	{ ABS_MT_PRESSURE, 0, 255, 0, 0, 0 }, /* note: resolution zero */
 	{ ABS_MT_TOOL_TYPE, 0, 2, 0, 0, 0 },
 	{ .value = -1 }
 };

test/litest.h

@@ -308,6 +308,7 @@ enum litest_device_type {
 	LITEST_SONY_VAIO_KEYS,
 	LITEST_KEYBOARD_QUIRKED,
 	LITEST_SYNAPTICS_PRESSUREPAD,
+	LITEST_GENERIC_PRESSUREPAD,
 };
 
 #define LITEST_DEVICELESS	-2

test/test-touchpad-tap.c

@@ -3801,7 +3801,8 @@ touchpad_has_palm_pressure(struct litest_device *dev)
 		return false;
 
 	if (libevdev_has_event_code(evdev, EV_ABS, ABS_MT_PRESSURE))
-		return true;
+		return libevdev_get_abs_resolution(evdev,
+						   ABS_MT_PRESSURE) == 0;
 
 	return false;
 }

test/test-touchpad.c

@@ -1799,7 +1799,8 @@ touchpad_has_palm_pressure(struct litest_device *dev)
 		return false;
 
 	if (libevdev_has_event_code(evdev, EV_ABS, ABS_MT_PRESSURE))
-		return true;
+		return libevdev_get_abs_resolution(evdev,
+						   ABS_MT_PRESSURE) == 0;
 
 	return false;
 }
@@ -5920,7 +5921,8 @@ touchpad_has_pressure(struct litest_device *dev)
 		return false;
 
 	if (libevdev_has_event_code(evdev, EV_ABS, ABS_MT_PRESSURE))
-		return true;
+		return libevdev_get_abs_resolution(evdev,
+						   ABS_MT_PRESSURE) == 0;
 
 	if (libevdev_has_event_code(evdev, EV_ABS, ABS_PRESSURE) &&
 	    !libevdev_has_event_code(evdev, EV_ABS, ABS_MT_SLOT))