Add support for LIBINPUT_IGNORE_DEVICE

The recommended way to have libinput ignore specific devices so far was to
remove the ID_INPUT* properties from the device. That may also affect other
pieces of the stack that need access to this device.

For the niche case of a device that should only be ignored by libinput but
otherwise be treated normally by the system, we now support the
LIBINPUT_IGNORE_DEVICE property.

If the property is set to "0", it's equivalent to being unset. This gets
around some technical limitations in udev where unsetting a property is
impossible via a hwdb entry.

https://bugs.freedesktop.org/show_bug.cgi?id=102229

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

doc/device-configuration-via-udev.dox

@@ -32,6 +32,10 @@ Example values are:
 devices with the same property value are grouped into the same device group,
 the value itself is irrelevant otherwise.
 </dd>
+<dt>LIBINPUT_IGNORE_DEVICE</dt>
+<dd>If set to anything other than "0", the device is ignored by libinput.
+See @ref ignoring_devices for more details.
+</dd>
 <dt>ID_SEAT</dt>
 <dd>Assigns the physical @ref seats "seat" for this device. See
 libinput_seat_get_physical_name(). Defaults to "seat0".</dd>
@@ -105,6 +109,29 @@ ACTION=="add|change", KERNEL=="event[0-9]*", ENV{ID_VENDOR_ID}=="012a", \
 ENV{ID_MODEL_ID}=="034b", ENV{ID_INPUT_TOUCHPAD}="", ENV{ID_INPUT_TABLET}="1"
 @endcode
 
+
+@section ignoring_devices Ignoring specific devices
+
+If a device has the <b>LIBINPUT_IGNORE_DEVICE</b> udev property set to any
+value but "0", that device is not initialized by libinput. For a context
+created with libinput_udev_create_context(), the device is silently ignored
+and never shows up. If the device is added with libinput_path_add_device()
+to a context created with libinput_path_create_context(), adding the device
+will fail and return NULL (see that function's documentation for more
+information).
+
+If the property value is exactly "0", then the property is considered unset
+and libinput initializes the device normally.
+
+This property should be used for devices that are correctly detected as
+input devices (see @ref udev_device_type) but that should not be used by
+libinput. It is recommended that devices that should not be handled as input
+devices at all unset the <b>ID_INPUT</b> and related properties instead. The
+<b>LIBINPUT_IGNORE_DEVICE</b> property signals that only libinput should
+ignore this property but other parts of the stack (if any) should continue
+treating this device normally.
+
+
 @section model_specific_configuration Model-specific configuration
 
 libinput reserves the property prefixes <b>LIBINPUT_MODEL_</b> and

meson.build

@@ -541,6 +541,7 @@ if get_option('tests')
 		'test/litest-device-generic-singletouch.c',
 		'test/litest-device-gpio-keys.c',
 		'test/litest-device-huion-pentablet.c',
+		'test/litest-device-ignored-mouse.c',
 		'test/litest-device-keyboard.c',
 		'test/litest-device-keyboard-all-codes.c',
 		'test/litest-device-keyboard-razer-blackwidow.c',

src/evdev.c

@@ -3083,6 +3083,17 @@ libevdev_log_func(const struct libevdev *evdev,
 	log_msg_va(libinput, pri, fmt, args);
 }
 
+static bool
+udev_device_should_be_ignored(struct udev_device *udev_device)
+{
+	const char *value;
+
+	value = udev_device_get_property_value(udev_device,
+					       "LIBINPUT_IGNORE_DEVICE");
+
+	return value && !streq(value, "0");
+}
+
 struct evdev_device *
 evdev_device_create(struct libinput_seat *seat,
 		    struct udev_device *udev_device)
@@ -3095,6 +3106,11 @@ evdev_device_create(struct libinput_seat *seat,
 	const char *devnode = udev_device_get_devnode(udev_device);
 	const char *sysname = udev_device_get_sysname(udev_device);
 
+	if (udev_device_should_be_ignored(udev_device)) {
+		log_debug(libinput, "%s: device is ignored\n", sysname);
+		return NULL;
+	}
+
 	/* Use non-blocking mode so that we can loop on read on
 	 * evdev_device_data() until all events on the fd are
 	 * read.  mtdev_get() also expects this. */

test/litest-device-ignored-mouse.c

@@ -0,0 +1,73 @@
+/*
+ * Copyright © 2017 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"
+
+static void litest_mouse_setup(void)
+{
+	struct litest_device *d = litest_create_device(LITEST_IGNORED_MOUSE);
+	litest_set_current_device(d);
+}
+
+static struct input_id input_id = {
+	.bustype = 0x3,
+	.vendor = 0x17ef,
+	.product = 0x6019,
+};
+
+static int events[] = {
+	EV_KEY, BTN_LEFT,
+	EV_KEY, BTN_RIGHT,
+	EV_KEY, BTN_MIDDLE,
+	EV_REL, REL_X,
+	EV_REL, REL_Y,
+	EV_REL, REL_WHEEL,
+	-1 , -1,
+};
+
+static const char udev_rule[] =
+"ACTION==\"remove\", GOTO=\"mouse_end\"\n"
+"KERNEL!=\"event*\", GOTO=\"mouse_end\"\n"
+"ENV{ID_INPUT_MOUSE}==\"\", GOTO=\"mouse_end\"\n"
+"\n"
+"ATTRS{name}==\"litest Ignored Mouse*\",\\\n"
+"    ENV{LIBINPUT_IGNORE_DEVICE}=\"1\"\n"
+"\n"
+"LABEL=\"mouse_end\"";
+
+struct litest_test_device litest_ignored_mouse_device = {
+	.type = LITEST_IGNORED_MOUSE,
+	.features = LITEST_IGNORED | LITEST_BUTTON | LITEST_RELATIVE,
+	.shortname = "ignored-mouse",
+	.setup = litest_mouse_setup,
+	.interface = NULL,
+
+	.name = "Ignored Mouse",
+	.id = &input_id,
+	.absinfo = NULL,
+	.events = events,
+	.udev_rule = udev_rule,
+};

test/litest.c

@@ -415,6 +415,7 @@ extern struct litest_test_device litest_lid_switch_device;
 extern struct litest_test_device litest_lid_switch_surface3_device;
 extern struct litest_test_device litest_appletouch_device;
 extern struct litest_test_device litest_gpio_keys_device;
+extern struct litest_test_device litest_ignored_mouse_device;
 
 struct litest_test_device* devices[] = {
 	&litest_synaptics_clickpad_device,
@@ -481,6 +482,7 @@ struct litest_test_device* devices[] = {
 	&litest_lid_switch_surface3_device,
 	&litest_appletouch_device,
 	&litest_gpio_keys_device,
+	&litest_ignored_mouse_device,
 	NULL,
 };
 
@@ -610,6 +612,9 @@ litest_add_tcase(const char *suite_name,
 		added = true;
 	} else if (required != LITEST_ANY || excluded != LITEST_ANY) {
 		for (; *dev; dev++) {
+			if ((*dev)->features & LITEST_IGNORED)
+				continue;
+
 			if (filter_device &&
 			    fnmatch(filter_device, (*dev)->shortname, 0) != 0)
 				continue;
@@ -626,6 +631,9 @@ litest_add_tcase(const char *suite_name,
 		}
 	} else {
 		for (; *dev; dev++) {
+			if ((*dev)->features & LITEST_IGNORED)
+				continue;
+
 			if (filter_device &&
 			    fnmatch(filter_device, (*dev)->shortname, 0) != 0)
 				continue;

test/litest.h

@@ -235,6 +235,7 @@ enum litest_device_type {
 	LITEST_LID_SWITCH_SURFACE3,
 	LITEST_APPLETOUCH,
 	LITEST_GPIO_KEYS,
+	LITEST_IGNORED_MOUSE,
 };
 
 enum litest_device_feature {
@@ -267,6 +268,7 @@ enum litest_device_feature {
 	LITEST_TRACKBALL = 1 << 24,
 	LITEST_LEDS = 1 << 25,
 	LITEST_SWITCH = 1 << 26,
+	LITEST_IGNORED = 1 << 27,
 };
 
 /* this is a semi-mt device, so we keep track of the touches that the tests

test/test-path.c

@@ -961,6 +961,26 @@ START_TEST(path_udev_assign_seat)
 }
 END_TEST
 
+START_TEST(path_ignore_device)
+{
+	struct litest_device *dev;
+	struct libinput *li;
+	struct libinput_device *device;
+	const char *path;
+
+	dev = litest_create(LITEST_IGNORED_MOUSE, NULL, NULL, NULL, NULL);
+	path = libevdev_uinput_get_devnode(dev->uinput);
+	ck_assert_notnull(path);
+
+	li = litest_create_context();
+	device = libinput_path_add_device(li, path);
+	ck_assert(device == NULL);
+
+	libinput_unref(li);
+	litest_delete_device(dev);
+}
+END_TEST
+
 void
 litest_setup_tests_path(void)
 {
@@ -987,4 +1007,6 @@ litest_setup_tests_path(void)
 	litest_add_for_device("path:device events", path_double_remove_device, LITEST_SYNAPTICS_CLICKPAD_X220);
 	litest_add_no_device("path:seat", path_seat_recycle);
 	litest_add_for_device("path:udev", path_udev_assign_seat, LITEST_SYNAPTICS_CLICKPAD_X220);
+
+	litest_add_no_device("path:ignore", path_ignore_device);
 }

test/test-udev.c

@@ -560,6 +560,51 @@ START_TEST(udev_path_remove_device)
 }
 END_TEST
 
+START_TEST(udev_ignore_device)
+{
+	struct udev *udev;
+	struct libinput *li;
+	struct libinput_device *device;
+	struct libinput_event *event;
+	struct litest_device *dev;
+	const char *devname;
+
+	dev = litest_create(LITEST_IGNORED_MOUSE, NULL, NULL, NULL, NULL);
+	devname = libevdev_get_name(dev->evdev);
+
+	udev = udev_new();
+	ck_assert(udev != NULL);
+
+	li = libinput_udev_create_context(&simple_interface, NULL, udev);
+	ck_assert(li != NULL);
+	litest_restore_log_handler(li);
+
+	ck_assert_int_eq(libinput_udev_assign_seat(li, "seat0"), 0);
+	libinput_dispatch(li);
+
+	event = libinput_get_event(li);
+	ck_assert(event != NULL);
+	while (event) {
+		if (libinput_event_get_type(event) ==
+		    LIBINPUT_EVENT_DEVICE_ADDED) {
+			const char *name;
+
+			device = libinput_event_get_device(event);
+			name = libinput_device_get_name(device);
+			ck_assert_str_ne(devname, name);
+		}
+		libinput_event_destroy(event);
+		libinput_dispatch(li);
+		event = libinput_get_event(li);
+	}
+
+	libinput_unref(li);
+	udev_unref(udev);
+
+	litest_delete_device(dev);
+}
+END_TEST
+
 void
 litest_setup_tests_udev(void)
 {
@@ -579,4 +624,6 @@ litest_setup_tests_udev(void)
 
 	litest_add_no_device("udev:path", udev_path_add_device);
 	litest_add_for_device("udev:path", udev_path_remove_device, LITEST_SYNAPTICS_CLICKPAD_X220);
+
+	litest_add_no_device("udev:ignore", udev_ignore_device);
 }