evdev: detect virtual devices

The quirk AttrIsVirtual takes precedence, if present. If not, use the
syspath of the event device to detect if it is virtual, as long as we
aren't running the test suite. (Test suite devices are all virtual, but
we should test them as if they aren't.)

Part-of: <https://gitlab.freedesktop.org/libinput/libinput/-/merge_requests/1213>

src/evdev.c

@@ -44,6 +44,7 @@
 #include "libinput-private.h"
 #include "quirks.h"
 #include "util-input-event.h"
+#include "util-udev.h"
 
 #if HAVE_LIBWACOM
 #include <libwacom/libwacom.h>
@@ -2256,6 +2257,7 @@ evdev_pre_configure_model_quirks(struct evdev_device *device)
 	struct quirks *q;
 	const struct quirk_tuples *t;
 	char *prop;
+	bool is_virtual;
 
 	/* Touchpad claims to have 4 slots but only ever sends 2
 	 * https://bugs.freedesktop.org/show_bug.cgi?id=98100 */
@@ -2334,6 +2336,13 @@ evdev_pre_configure_model_quirks(struct evdev_device *device)
 		}
 	}
 
+	if (!quirks_get_bool(q, QUIRK_ATTR_IS_VIRTUAL, &is_virtual)) {
+		is_virtual = !getenv("LIBINPUT_RUNNING_TEST_SUITE") &&
+			udev_device_is_virtual(device->udev_device);
+	}
+	if (is_virtual)
+		device->tags |= EVDEV_TAG_VIRTUAL;
+
 	quirks_unref(q);
 }
 

src/quirks.c

@@ -292,6 +292,7 @@ quirk_get_name(enum quirk q)
 	case QUIRK_ATTR_MSC_TIMESTAMP:			return "AttrMscTimestamp";
 	case QUIRK_ATTR_EVENT_CODE:			return "AttrEventCode";
 	case QUIRK_ATTR_INPUT_PROP:			return "AttrInputProp";
+	case QUIRK_ATTR_IS_VIRTUAL:			return "AttrIsVirtual";
 	default:
 		abort();
 	}
@@ -878,6 +879,13 @@ parse_attr(struct quirks_context *ctx,
 		p->value.tuples.ntuples = nprops;
 		p->type = PT_TUPLES;
 
+		rc = true;
+	} else if (streq(key, quirk_get_name(QUIRK_ATTR_IS_VIRTUAL))) {
+		p->id = QUIRK_ATTR_IS_VIRTUAL;
+		if (!parse_boolean_property(value, &b))
+			goto out;
+		p->type = PT_BOOL;
+		p->value.b = b;
 		rc = true;
 	} else {
 		qlog_error(ctx, "Unknown key %s in %s\n", key, s->name);

src/quirks.h

@@ -111,6 +111,7 @@ enum quirk {
 	QUIRK_ATTR_MSC_TIMESTAMP,
 	QUIRK_ATTR_EVENT_CODE,
 	QUIRK_ATTR_INPUT_PROP,
+	QUIRK_ATTR_IS_VIRTUAL,
 
 	_QUIRK_LAST_ATTR_QUIRK_, /* Guard: do not modify */
 };

src/util-udev.h

@@ -0,0 +1,41 @@
+/*
+ * Copyright © 2025 Ryan Hendrickson
+ *
+ * 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.
+ */
+
+#ifndef UTIL_UDEV_H
+#define UTIL_UDEV_H
+
+#include "config.h"
+
+#include <libudev.h>
+#include "util-strings.h"
+
+static inline bool
+udev_device_is_virtual(struct udev_device *udev_device)
+{
+	const char *path = udev_device_get_syspath(udev_device);
+	if (!path)
+		return false;
+	return strstartswith(path, "/sys/devices/virtual/input/");
+}
+
+#endif /* UTIL_UDEV_H */