logind: rework display counting when detecting whether the system is docked

Previously, we'd just count connected displays, and if there was 2 or
more we assumed a "docked" state.

With this change we now:

- Only count external displays, ignore internal ones (which we detect by
  checking the connector name against a whitelist of known external plug
  types)

- We ignore connectors which are explicitly disabled

- We then compare the count with >= 1 rather than >= 2 as before

This new logic has the benefit that systems that disconnect the internal
display when the lid is closed are better supported. Also, explicitly
disabled ports do not confuse the algorithm anymore.

This new algorithm has been suggested here:

http://lists.freedesktop.org/archives/intel-gfx/2015-June/068821.html

This also makes two functions static, that are not used outside of their
.c files.

src/login/logind-button.c

@@ -100,7 +100,7 @@ static void button_lid_switch_handle_action(Manager *manager, bool is_edge) {
         assert(manager);
 
         /* If we are docked, handle the lid switch differently */
-        if (manager_is_docked_or_multiple_displays(manager))
+        if (manager_is_docked_or_external_displays(manager))
                 handle_action = manager->handle_lid_switch_docked;
         else
                 handle_action = manager->handle_lid_switch;

src/login/logind-core.c

@@ -477,7 +477,7 @@ int manager_spawn_autovt(Manager *m, unsigned int vtnr) {
         return r;
 }
 
-bool manager_is_docked(Manager *m) {
+static bool manager_is_docked(Manager *m) {
         Iterator i;
         Button *b;
 
@@ -488,7 +488,7 @@ bool manager_is_docked(Manager *m) {
         return false;
 }
 
-int manager_count_displays(Manager *m) {
+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;
@@ -510,7 +510,8 @@ int manager_count_displays(Manager *m) {
         udev_list_entry_foreach(item, first) {
                 _cleanup_udev_device_unref_ struct udev_device *d = NULL;
                 struct udev_device *p;
-                const char *status;
+                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)
@@ -526,6 +527,40 @@ int manager_count_displays(Manager *m) {
                 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 seperated 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");
@@ -536,7 +571,7 @@ int manager_count_displays(Manager *m) {
         return n;
 }
 
-bool manager_is_docked_or_multiple_displays(Manager *m) {
+bool manager_is_docked_or_external_displays(Manager *m) {
         int n;
 
         /* If we are docked don't react to lid closing */
@@ -547,11 +582,11 @@ bool manager_is_docked_or_multiple_displays(Manager *m) {
 
         /* If we have more than one display connected,
          * assume that we are docked. */
-        n = manager_count_displays(m);
+        n = manager_count_external_displays(m);
         if (n < 0)
                 log_warning_errno(n, "Display counting failed: %m");
-        else if (n > 1) {
-                log_debug("Multiple (%i) displays connected.", n);
+        else if (n >= 1) {
+                log_debug("External (%i) displays connected.", n);
                 return true;
         }
 

src/login/logind-dbus.c

@@ -258,7 +258,7 @@ static int property_get_docked(
         assert(reply);
         assert(m);
 
-        return sd_bus_message_append(reply, "b", manager_is_docked_or_multiple_displays(m));
+        return sd_bus_message_append(reply, "b", manager_is_docked_or_external_displays(m));
 }
 
 static int method_get_session(sd_bus_message *message, void *userdata, sd_bus_error *error) {

src/login/logind.h

@@ -156,9 +156,7 @@ int manager_get_idle_hint(Manager *m, dual_timestamp *t);
 int manager_get_user_by_pid(Manager *m, pid_t pid, User **user);
 int manager_get_session_by_pid(Manager *m, pid_t pid, Session **session);
 
-bool manager_is_docked(Manager *m);
-int manager_count_displays(Manager *m);
-bool manager_is_docked_or_multiple_displays(Manager *m);
+bool manager_is_docked_or_external_displays(Manager *m);
 
 extern const sd_bus_vtable manager_vtable[];