Use LIBINPUT_DEVICE_GROUP from udev as group identifier

Store it as identifier in the device group, any two devices that have a
the same non-NULL identifier share the group.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

doc/device-configuration-via-udev.dox

@@ -12,6 +12,11 @@ The following udev properties are supported:
 <dd>Sets the calibration matrix, see
 libinput_device_config_calibration_get_default_matrix(). If unset,
 defaults to the identity matrix.</dd>
+<dt>LIBINPUT_DEVICE_GROUP</dt>
+<dd>A string identifying the @ref libinput_device_group for this device. Two
+devices with the same property value are grouped into the same device group,
+the value itself is irrelevant otherwise.
+</dd>
 <dt>ID_SEAT</dt>
 <dd>Assigns the physical seat for this device. See
 libinput_seat_get_physical_name(). Defaults to "seat0".</dd>

src/evdev.c

@@ -1579,6 +1579,42 @@ out:
 	return rc;
 }
 
+static int
+evdev_set_device_group(struct evdev_device *device,
+		       struct udev_device *udev_device)
+{
+	struct libinput_device_group *group = NULL;
+	const char *udev_group;
+
+	udev_group = udev_device_get_property_value(udev_device,
+						    "LIBINPUT_DEVICE_GROUP");
+	if (udev_group) {
+		struct libinput_device *d;
+
+		list_for_each(d, &device->base.seat->devices_list, link) {
+			const char *identifier = d->group->identifier;
+
+			if (identifier &&
+			    strcmp(identifier, udev_group) == 0) {
+				group = d->group;
+				break;
+			}
+		}
+	}
+
+	if (!group) {
+		group = libinput_device_group_create(udev_group);
+		if (!group)
+			return 1;
+		libinput_device_set_device_group(&device->base, group);
+		libinput_device_group_unref(group);
+	} else {
+		libinput_device_set_device_group(&device->base, group);
+	}
+
+	return 0;
+}
+
 struct evdev_device *
 evdev_device_create(struct libinput_seat *seat,
 		    struct udev_device *udev_device)
@@ -1589,7 +1625,6 @@ evdev_device_create(struct libinput_seat *seat,
 	int fd;
 	int unhandled_device = 0;
 	const char *devnode = udev_device_get_devnode(udev_device);
-	struct libinput_device_group *group;
 
 	/* Use non-blocking mode so that we can loop on read on
 	 * evdev_device_data() until all events on the fd are
@@ -1660,11 +1695,8 @@ evdev_device_create(struct libinput_seat *seat,
 	if (!device->source)
 		goto err;
 
-	group = libinput_device_group_create();
-	if (!group)
+	if (evdev_set_device_group(device, udev_device))
 		goto err;
-	libinput_device_set_device_group(&device->base, group);
-	libinput_device_group_unref(group);
 
 	list_insert(seat->devices_list.prev, &device->base.link);
 

src/libinput-private.h

@@ -168,6 +168,7 @@ struct libinput_device_config {
 struct libinput_device_group {
 	int refcount;
 	void *user_data;
+	char *identifier; /* unique identifier or NULL for singletons */
 };
 
 struct libinput_device {
@@ -247,7 +248,7 @@ libinput_device_init(struct libinput_device *device,
 		     struct libinput_seat *seat);
 
 struct libinput_device_group *
-libinput_device_group_create(void);
+libinput_device_group_create(const char *identifier);
 
 void
 libinput_device_set_device_group(struct libinput_device *device,

src/libinput.c

@@ -1407,13 +1407,23 @@ libinput_device_group_ref(struct libinput_device_group *group)
 }
 
 struct libinput_device_group *
-libinput_device_group_create(void)
+libinput_device_group_create(const char *identifier)
 {
 	struct libinput_device_group *group;
 
 	group = zalloc(sizeof *group);
-	if (group)
-		group->refcount = 1;
+	if (!group)
+		return NULL;
+
+	group->refcount = 1;
+	if (identifier) {
+		group->identifier = strdup(identifier);
+		if (!group->identifier) {
+			free(group);
+			group = NULL;
+		}
+	}
+
 	return group;
 }
 
@@ -1428,6 +1438,7 @@ libinput_device_set_device_group(struct libinput_device *device,
 static void
 libinput_device_group_destroy(struct libinput_device_group *group)
 {
+	free(group->identifier);
 	free(group);
 }
 

src/libinput.h

@@ -1471,6 +1471,9 @@ libinput_device_get_context(struct libinput_device *device);
  * libinput_device_group_unref() to continue using the handle outside of the
  * immediate scope.
  *
+ * Device groups are assigned based on the <b>LIBINPUT_DEVICE_GROUP</b> udev
+ * property, see @ref udev_config.
+ *
  * @return The device group this device belongs to
  */
 struct libinput_device_group *