libinput-seat: Cascade errors and bail out in case of failure

Errors happening to devices being added or removed shouldn't fail
silently so exit if any of that happens.

Sprinkle some debug logs for other cases as well.

Signed-off-by: Marius Vlad <marius.vlad@collabora.com>
Suggested-by: Daniel Stone <daniel.stone@collabora.com>

libweston/libinput-seat.c

@@ -89,7 +89,7 @@ output_find_by_head_name(struct weston_compositor *compositor,
 	return NULL;
 }
 
-static void
+static int
 device_added(struct udev_input *input, struct libinput_device *libinput_device)
 {
 	struct weston_compositor *c;
@@ -103,13 +103,17 @@ device_added(struct udev_input *input, struct libinput_device *libinput_device)
 	c = input->compositor;
 
 	udev_seat = get_udev_seat(input, libinput_device);
-	if (!udev_seat)
-		return;
+	if (!udev_seat) {
+		weston_log("Failed to get a seat\n");
+		return 1;
+	}
 
 	seat = &udev_seat->base;
 	device = evdev_device_create(libinput_device, seat);
-	if (device == NULL)
-		return;
+	if (device == NULL) {
+		weston_log("Failed to create a device\n");
+		return 1;
+	}
 
 	if (input->configure_device != NULL)
 		input->configure_device(c, device->device);
@@ -142,18 +146,23 @@ device_added(struct udev_input *input, struct libinput_device *libinput_device)
 		if (seat->led_update && seat->keyboard_state)
 			seat->led_update(seat, seat->keyboard_state->xkb_state.leds);
 	}
+
+	return 0;
 }
 
-static void
+static int
 device_removed(struct udev_input *input, struct libinput_device *libinput_device)
 {
 	struct evdev_device *device;
 
 	device = libinput_device_get_user_data(libinput_device);
-	if (!device)
-		return;
+	if (!device) {
+		weston_log("Failed to retrieve device\n");
+		return 1;
+	}
 
 	evdev_device_destroy(device);
+	return 0;
 }
 
 static void
@@ -186,29 +195,28 @@ udev_input_process_event(struct libinput_event *event)
 	struct libinput_device *libinput_device =
 		libinput_event_get_device(event);
 	struct udev_input *input = libinput_get_user_data(libinput);
-	int handled = 1;
+	int ret = 0;
 
 	switch (libinput_event_get_type(event)) {
 	case LIBINPUT_EVENT_DEVICE_ADDED:
-		device_added(input, libinput_device);
+		ret = device_added(input, libinput_device);
 		break;
 	case LIBINPUT_EVENT_DEVICE_REMOVED:
-		device_removed(input, libinput_device);
+		ret = device_removed(input, libinput_device);
 		break;
 	default:
-		handled = 0;
+		evdev_device_process_event(event);
+		break;
 	}
 
-	return handled;
+	return ret;
 }
 
 static void
 process_event(struct libinput_event *event)
 {
 	if (udev_input_process_event(event))
-		return;
-	if (evdev_device_process_event(event))
-		return;
+		exit(EXIT_FAILURE);
 }
 
 static void