+
+static int manager_count_external_displays(Manager *m) {
+ _cleanup_udev_enumerate_unref_ struct udev_enumerate *e = NULL;
+ struct udev_list_entry *item = NULL, *first = NULL;
+ int r;
+ int n = 0;
+
+ e = udev_enumerate_new(m->udev);
+ if (!e)
+ return -ENOMEM;
+
+ r = udev_enumerate_add_match_subsystem(e, "drm");
+ if (r < 0)
+ return r;
+
+ r = udev_enumerate_scan_devices(e);
+ if (r < 0)
+ return r;
+
+ first = udev_enumerate_get_list_entry(e);
+ udev_list_entry_foreach(item, first) {
+ _cleanup_udev_device_unref_ struct udev_device *d = NULL;
+ struct udev_device *p;
+ const char *status, *enabled, *dash, *nn, *i;
+ bool external = false;
+
+ d = udev_device_new_from_syspath(m->udev, udev_list_entry_get_name(item));
+ if (!d)
+ return -ENOMEM;
+
+ p = udev_device_get_parent(d);
+ if (!p)
+ continue;
+
+ /* If the parent shares the same subsystem as the
+ * device we are looking at then it is a connector,
+ * which is what we are interested in. */
+ if (!streq_ptr(udev_device_get_subsystem(p), "drm"))
+ continue;
+
+ nn = udev_device_get_sysname(d);
+ if (!nn)
+ continue;
+
+ /* Ignore internal displays: the type is encoded in
+ * the sysfs name, as the second dash separated item
+ * (the first is the card name, the last the connector
+ * number). We implement a whitelist of external
+ * displays here, rather than a whitelist, to ensure
+ * we don't block suspends too eagerly. */
+ dash = strchr(nn, '-');
+ if (!dash)
+ continue;
+
+ dash++;
+ FOREACH_STRING(i, "VGA-", "DVI-I-", "DVI-D-", "DVI-A-"
+ "Composite-", "SVIDEO-", "Component-",
+ "DIN-", "DP-", "HDMI-A-", "HDMI-B-", "TV-") {
+
+ if (startswith(dash, i)) {
+ external = true;
+ break;
+ }
+ }
+ if (!external)
+ continue;
+
+ /* Ignore ports that are not enabled */
+ enabled = udev_device_get_sysattr_value(d, "enabled");
+ if (!enabled)
+ continue;
+ if (!streq_ptr(enabled, "enabled"))
+ continue;
+
+ /* We count any connector which is not explicitly
+ * "disconnected" as connected. */
+ status = udev_device_get_sysattr_value(d, "status");
+ if (!streq_ptr(status, "disconnected"))
+ n++;
+ }
+
+ return n;
+}
+
+bool manager_is_docked_or_external_displays(Manager *m) {
+ int n;
+
+ /* If we are docked don't react to lid closing */
+ if (manager_is_docked(m)) {
+ log_debug("System is docked.");
+ return true;
+ }
+
+ /* If we have more than one display connected,
+ * assume that we are docked. */
+ n = manager_count_external_displays(m);
+ if (n < 0)
+ log_warning_errno(n, "Display counting failed: %m");
+ else if (n >= 1) {
+ log_debug("External (%i) displays connected.", n);
+ return true;
+ }
+
+ return false;
+}