+bool
+UnknownProcessor::can_support_io_configuration (const ChanCount &in, ChanCount & out) {
+ if (have_ioconfig && in == *saved_input) {
+ out = *saved_output;
+ return true;
+ } else if (!have_ioconfig) {
+ /* pass for old sessions.
+ *
+ * session load assumes processor config succeeds.
+ * if initial configuration fails, processors downstream
+ * remain unconfigured and at least the panner will assert/segfault.
+ *
+ * This may still result in impossible setup, however
+ * Route::configure_processors_unlocked() ignores configure_io() return value
+ * in the inner loop and configures all available processors.
+ *
+ * It can still lead to segfaults IFF the track has no inputs and this is a
+ * generator (processor_max_streams will be zero).
+ */
+ PBD::warning << _("Using plugin-stub with unknown i/o configuration for: ") << name() << endmsg;
+#if 0
+ /* No output channels are fine (or should be, there may be edge-cases with e.g sends).
+ *
+ * Discussion needed.
+ *
+ * This is the safer option (no audio output, no possible damage)
+ * and the way to go in the long run.
+ * An even better solution is to disable the route if there are missing plugins
+ * and/or impossible configurations.
+ *
+ * Currently no output channels results in awkward GUI route display and also
+ * breaks semantics in mixbus (which assumes that the route has channels required
+ * for the always present mixer-strip plugin).
+ */
+ out = ChanCount ();
+#else
+ out = in;
+#endif
+ return true;
+ } else {
+ PBD::error << _("Using plugin-stub with mismatching i/o configuration for: ") << name() << endmsg;
+ out = in;
+ }
+ return true;
+}
+
+void
+UnknownProcessor::run (BufferSet& bufs, framepos_t /*start_frame*/, framepos_t /*end_frame*/, pframes_t nframes, bool)
+{
+ if (!have_ioconfig) {
+ return;
+ }
+ // silence excess output buffers
+ for (uint32_t i = saved_input->n_audio(); i < saved_output->n_audio(); ++i) {
+ bufs.get_audio (i).silence (nframes);
+ }
+}