platforms/atomic-kms: Release resources of disconnected outputs

src/platforms/atomic-kms/server/kms/atomic_kms_output.cpp

@@ -350,17 +350,13 @@ bool mga::AtomicKMSOutput::has_crtc_mismatch()
 void mga::AtomicKMSOutput::clear_crtc()
 {
     auto conf = configuration.lock();
-    try
-    {
-        ensure_crtc(*conf);
-    }
-    catch (...)
+    if (!conf->current_crtc)
     {
         /*
          * In order to actually clear the output, we need to have a crtc
          * connected to the output/connector so that we can disconnect
-         * it. However, not being able to get a crtc is OK, since it means
-         * that the output cannot be displaying anything anyway.
+         * it. However, if we don't have a current CRTC then we're obviously
+         * not displaying anything anyway.
          */
         return;
     }

src/platforms/atomic-kms/server/kms/display.cpp

@@ -262,6 +262,8 @@ void mga::Display::clear_connected_unused_outputs()
 {
     current_display_configuration.for_each_output([&](DisplayConfigurationOutput const& conf_output)
     {
+        auto kms_output = current_display_configuration.get_output_for(conf_output.id);
+
         /*
          * An output may be unused either because it's explicitly not used
          * (DisplayConfigurationOutput::used) or because its power mode is
@@ -270,12 +272,21 @@ void mga::Display::clear_connected_unused_outputs()
         if (conf_output.connected &&
             (!conf_output.used || (conf_output.power_mode != mir_power_mode_on)))
         {
-            auto kms_output = current_display_configuration.get_output_for(conf_output.id);
-
             kms_output->clear_crtc();
             kms_output->set_power_mode(conf_output.power_mode);
             kms_output->set_gamma(conf_output.gamma);
         }
+        /*
+         * If the output is no longer connected, we may still have associated resources
+         * with it.
+         *
+         * Clear those resources.
+         */
+        if (!conf_output.connected)
+        {
+            // clear_crtc() is a no-op if there isn't an existing CRTC & we can't find one.
+            kms_output->clear_crtc();
+        }
     });
 }