From bfd50cdeb0416b106a7813177148dffb1af6db8e Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Fri, 2 Aug 2013 03:39:00 +0200
Subject: [PATCH] rework MIDI [processor|plugin] chain

* forward midi-data around plugins that have no MIDI-out
* allow to insert plugins with no MIDI-input at a point with one MIDI-channel

This works because excess ports (both plugin and route) remain
unconnected and use scratch-buffers.

Tested with LV2, LXVST and LADSPA.
(AU plugins with variable in/out retain the old behavior, no bypass)

fixes http://tracker.ardour.org/view.php?id=5630
---
 libs/ardour/amp.cc                       |  2 +-
 libs/ardour/ardour/amp.h                 |  2 +-
 libs/ardour/ardour/audio_unit.h          |  2 +-
 libs/ardour/ardour/capturing_processor.h |  2 +-
 libs/ardour/ardour/delivery.h            |  2 +-
 libs/ardour/ardour/internal_return.h     |  2 +-
 libs/ardour/ardour/internal_send.h       |  2 +-
 libs/ardour/ardour/meter.h               |  2 +-
 libs/ardour/ardour/monitor_processor.h   |  2 +-
 libs/ardour/ardour/panner_shell.h        |  2 +-
 libs/ardour/ardour/plugin.h              |  2 +-
 libs/ardour/ardour/plugin_insert.h       |  6 +++--
 libs/ardour/ardour/port_insert.h         |  2 +-
 libs/ardour/ardour/processor.h           |  2 +-
 libs/ardour/ardour/return.h              |  2 +-
 libs/ardour/ardour/send.h                |  2 +-
 libs/ardour/ardour/unknown_processor.h   |  2 +-
 libs/ardour/audio_unit.cc                |  2 +-
 libs/ardour/capturing_processor.cc       |  2 +-
 libs/ardour/delivery.cc                  |  2 +-
 libs/ardour/internal_return.cc           |  2 +-
 libs/ardour/internal_send.cc             |  2 +-
 libs/ardour/meter.cc                     |  2 +-
 libs/ardour/monitor_processor.cc         |  2 +-
 libs/ardour/plugin_insert.cc             | 28 +++++++++++++++++-------
 libs/ardour/port_insert.cc               |  2 +-
 libs/ardour/return.cc                    |  2 +-
 libs/ardour/route.cc                     |  6 ++---
 libs/ardour/send.cc                      |  2 +-
 29 files changed, 53 insertions(+), 39 deletions(-)

diff --git a/libs/ardour/amp.cc b/libs/ardour/amp.cc
index f60240fd57..c97d624440 100644
--- a/libs/ardour/amp.cc
+++ b/libs/ardour/amp.cc
@@ -61,7 +61,7 @@ Amp::display_name() const
 }
 
 bool
-Amp::can_support_io_configuration (const ChanCount& in, ChanCount& out) const
+Amp::can_support_io_configuration (const ChanCount& in, ChanCount& out)
 {
 	out = in;
 	return true;
diff --git a/libs/ardour/ardour/amp.h b/libs/ardour/ardour/amp.h
index 23cc0ad0a8..e21cf62d62 100644
--- a/libs/ardour/ardour/amp.h
+++ b/libs/ardour/ardour/amp.h
@@ -40,7 +40,7 @@ public:
 
 	bool visible () const;
 
-	bool can_support_io_configuration (const ChanCount& in, ChanCount& out) const;
+	bool can_support_io_configuration (const ChanCount& in, ChanCount& out);
 	bool configure_io (ChanCount in, ChanCount out);
 
 	void run (BufferSet& bufs, framepos_t start_frame, framepos_t end_frame, pframes_t nframes, bool);
diff --git a/libs/ardour/ardour/audio_unit.h b/libs/ardour/ardour/audio_unit.h
index 36e82da802..007390b34a 100644
--- a/libs/ardour/ardour/audio_unit.h
+++ b/libs/ardour/ardour/audio_unit.h
@@ -104,7 +104,7 @@ class AUPlugin : public ARDOUR::Plugin
 
 	bool has_editor () const;
 
-	bool can_support_io_configuration (const ChanCount& in, ChanCount& out) const;
+	bool can_support_io_configuration (const ChanCount& in, ChanCount& out);
 	ChanCount output_streams() const;
 	ChanCount input_streams() const;
 	bool configure_io (ChanCount in, ChanCount out);
diff --git a/libs/ardour/ardour/capturing_processor.h b/libs/ardour/ardour/capturing_processor.h
index b672d1ac07..5b9ea51557 100644
--- a/libs/ardour/ardour/capturing_processor.h
+++ b/libs/ardour/ardour/capturing_processor.h
@@ -38,7 +38,7 @@ class CapturingProcessor : public Processor
 	int set_block_size (pframes_t nframes);
 	void run (BufferSet& bufs, framepos_t start_frame, framepos_t end_frame, pframes_t nframes, bool result_required);
 	bool configure_io (ChanCount in, ChanCount out);
-	bool can_support_io_configuration (const ChanCount& in, ChanCount& out) const;
+	bool can_support_io_configuration (const ChanCount& in, ChanCount& out);
 	virtual XMLNode& state (bool);
 
   private:
diff --git a/libs/ardour/ardour/delivery.h b/libs/ardour/ardour/delivery.h
index 314b223538..4a6d4368a6 100644
--- a/libs/ardour/ardour/delivery.h
+++ b/libs/ardour/ardour/delivery.h
@@ -67,7 +67,7 @@ public:
 	std::string display_name() const;
 
 	Role role() const { return _role; }
-	bool can_support_io_configuration (const ChanCount& in, ChanCount& out) const;
+	bool can_support_io_configuration (const ChanCount& in, ChanCount& out);
 	bool configure_io (ChanCount in, ChanCount out);
 
 	void run (BufferSet& bufs, framepos_t start_frame, framepos_t end_frame, pframes_t nframes, bool);
diff --git a/libs/ardour/ardour/internal_return.h b/libs/ardour/ardour/internal_return.h
index c7fe04cc42..4d2b32f031 100644
--- a/libs/ardour/ardour/internal_return.h
+++ b/libs/ardour/ardour/internal_return.h
@@ -39,7 +39,7 @@ class InternalReturn : public Return
 
 	void run (BufferSet& bufs, framepos_t start_frame, framepos_t end_frame, pframes_t nframes, bool);
 	bool configure_io (ChanCount, ChanCount);
-	bool can_support_io_configuration (const ChanCount& in, ChanCount& out) const;
+	bool can_support_io_configuration (const ChanCount& in, ChanCount& out);
 
 	void add_send (InternalSend *);
 	void remove_send (InternalSend *);
diff --git a/libs/ardour/ardour/internal_send.h b/libs/ardour/ardour/internal_send.h
index 8bfb0de887..a7f0f73e6e 100644
--- a/libs/ardour/ardour/internal_send.h
+++ b/libs/ardour/ardour/internal_send.h
@@ -42,7 +42,7 @@ class InternalSend : public Send
 	void cycle_start (pframes_t);
 	void run (BufferSet& bufs, framepos_t start_frame, framepos_t end_frame, pframes_t nframes, bool);
 	bool feeds (boost::shared_ptr<Route> other) const;
-	bool can_support_io_configuration (const ChanCount& in, ChanCount& out) const;
+	bool can_support_io_configuration (const ChanCount& in, ChanCount& out);
 	bool configure_io (ChanCount in, ChanCount out);
 	int  set_block_size (pframes_t);
 
diff --git a/libs/ardour/ardour/meter.h b/libs/ardour/ardour/meter.h
index a4ad8ecff4..df1e381bb4 100644
--- a/libs/ardour/ardour/meter.h
+++ b/libs/ardour/ardour/meter.h
@@ -56,7 +56,7 @@ public:
 	void reset ();
 	void reset_max ();
 
-	bool can_support_io_configuration (const ChanCount& in, ChanCount& out) const;
+	bool can_support_io_configuration (const ChanCount& in, ChanCount& out);
 	bool configure_io (ChanCount in, ChanCount out);
 
 	/* special method for meter, to ensure that it can always handle the maximum
diff --git a/libs/ardour/ardour/monitor_processor.h b/libs/ardour/ardour/monitor_processor.h
index 5b724b5e8d..64d3b86bfb 100644
--- a/libs/ardour/ardour/monitor_processor.h
+++ b/libs/ardour/ardour/monitor_processor.h
@@ -118,7 +118,7 @@ public:
 	int set_state (const XMLNode&, int /* version */);
 
 	bool configure_io (ChanCount in, ChanCount out);
-	bool can_support_io_configuration (const ChanCount& in, ChanCount& out) const;
+	bool can_support_io_configuration (const ChanCount& in, ChanCount& out);
 
 	void set_cut_all (bool);
 	void set_dim_all (bool);
diff --git a/libs/ardour/ardour/panner_shell.h b/libs/ardour/ardour/panner_shell.h
index 7d24adb46f..dba5826370 100644
--- a/libs/ardour/ardour/panner_shell.h
+++ b/libs/ardour/ardour/panner_shell.h
@@ -53,7 +53,7 @@ public:
 
 	std::string describe_parameter (Evoral::Parameter param);
 
-	bool can_support_io_configuration (const ChanCount& /*in*/, ChanCount& /*out*/) const { return true; };
+	bool can_support_io_configuration (const ChanCount& /*in*/, ChanCount& /*out*/) { return true; };
 	void configure_io (ChanCount in, ChanCount out);
 
 	/// The fundamental Panner function
diff --git a/libs/ardour/ardour/plugin.h b/libs/ardour/ardour/plugin.h
index 9e4f5c40fd..55b76fbb08 100644
--- a/libs/ardour/ardour/plugin.h
+++ b/libs/ardour/ardour/plugin.h
@@ -242,7 +242,7 @@ class Plugin : public PBD::StatefulDestructible, public Latent
 	/* specific types of plugins can overload this. As of September 2008, only
 	   AUPlugin does this.
 	*/
-	virtual bool can_support_io_configuration (const ChanCount& /*in*/, ChanCount& /*out*/) const { return false; }
+	virtual bool can_support_io_configuration (const ChanCount& /*in*/, ChanCount& /*out*/) { return false; }
 	virtual ChanCount output_streams() const;
 	virtual ChanCount input_streams() const;
 
diff --git a/libs/ardour/ardour/plugin_insert.h b/libs/ardour/ardour/plugin_insert.h
index d80c759cff..a1b9c5a685 100644
--- a/libs/ardour/ardour/plugin_insert.h
+++ b/libs/ardour/ardour/plugin_insert.h
@@ -69,7 +69,7 @@ class PluginInsert : public Processor
 	bool     set_count (uint32_t num);
 	uint32_t get_count () const { return _plugins.size(); }
 
-	bool can_support_io_configuration (const ChanCount& in, ChanCount& out) const;
+	bool can_support_io_configuration (const ChanCount& in, ChanCount& out);
 	bool configure_io (ChanCount in, ChanCount out);
 
 	bool has_no_inputs() const;
@@ -160,6 +160,8 @@ class PluginInsert : public Processor
 	BufferSet _signal_analysis_inputs;
 	BufferSet _signal_analysis_outputs;
 
+	ChanCount midi_bypass;
+
 	/** Description of how we can match our plugin's IO to our own insert IO */
 	struct Match {
 		Match () : method (Impossible), plugins (0) {}
@@ -170,7 +172,7 @@ class PluginInsert : public Processor
 		ChanCount hide;        ///< number of channels to hide
 	};
 
-	Match private_can_support_io_configuration (ChanCount const &, ChanCount &) const;
+	Match private_can_support_io_configuration (ChanCount const &, ChanCount &);
 
 	/** details of the match currently being used */
 	Match _match;
diff --git a/libs/ardour/ardour/port_insert.h b/libs/ardour/ardour/port_insert.h
index 657c2c0de6..abd9fb73cc 100644
--- a/libs/ardour/ardour/port_insert.h
+++ b/libs/ardour/ardour/port_insert.h
@@ -57,7 +57,7 @@ class PortInsert : public IOProcessor
 
 	bool set_name (const std::string& name);
 
-	bool can_support_io_configuration (const ChanCount& in, ChanCount& out) const;
+	bool can_support_io_configuration (const ChanCount& in, ChanCount& out);
 	bool configure_io (ChanCount in, ChanCount out);
 
 	void activate ();
diff --git a/libs/ardour/ardour/processor.h b/libs/ardour/ardour/processor.h
index d497f56dd3..772ae3520d 100644
--- a/libs/ardour/ardour/processor.h
+++ b/libs/ardour/ardour/processor.h
@@ -82,7 +82,7 @@ class Processor : public SessionObject, public Automatable, public Latent
 
 	/* Derived classes should override these, or processor appears as an in-place pass-through */
 
-	virtual bool can_support_io_configuration (const ChanCount& in, ChanCount& out) const = 0;
+	virtual bool can_support_io_configuration (const ChanCount& in, ChanCount& out) = 0;
 	virtual ChanCount input_streams () const { return _configured_input; }
 	virtual ChanCount output_streams() const { return _configured_output; }
 
diff --git a/libs/ardour/ardour/return.h b/libs/ardour/ardour/return.h
index 55ca2d84f6..6dcd6ac2fc 100644
--- a/libs/ardour/ardour/return.h
+++ b/libs/ardour/ardour/return.h
@@ -56,7 +56,7 @@ public:
 
 	uint32_t pans_required() const { return _configured_input.n_audio(); }
 
-	bool can_support_io_configuration (const ChanCount& in, ChanCount& out) const;
+	bool can_support_io_configuration (const ChanCount& in, ChanCount& out);
 	bool configure_io (ChanCount in, ChanCount out);
 
 	static uint32_t how_many_returns();
diff --git a/libs/ardour/ardour/send.h b/libs/ardour/ardour/send.h
index fa023a3b68..1a21d1d050 100644
--- a/libs/ardour/ardour/send.h
+++ b/libs/ardour/ardour/send.h
@@ -56,7 +56,7 @@ class Send : public Delivery
 
 	void run (BufferSet& bufs, framepos_t start_frame, framepos_t end_frame, pframes_t nframes, bool);
 
-	bool can_support_io_configuration (const ChanCount& in, ChanCount& out) const;
+	bool can_support_io_configuration (const ChanCount& in, ChanCount& out);
 	bool configure_io (ChanCount in, ChanCount out);
 
 	void activate ();
diff --git a/libs/ardour/ardour/unknown_processor.h b/libs/ardour/ardour/unknown_processor.h
index 36981030ce..61a5734df2 100644
--- a/libs/ardour/ardour/unknown_processor.h
+++ b/libs/ardour/ardour/unknown_processor.h
@@ -49,7 +49,7 @@ public:
 		return false;
 	}
 
-	bool can_support_io_configuration (const ChanCount &, ChanCount &) const {
+	bool can_support_io_configuration (const ChanCount &, ChanCount &) {
 		return false;
 	}
 
diff --git a/libs/ardour/audio_unit.cc b/libs/ardour/audio_unit.cc
index e43033eb67..538a905ca2 100644
--- a/libs/ardour/audio_unit.cc
+++ b/libs/ardour/audio_unit.cc
@@ -998,7 +998,7 @@ AUPlugin::output_streams() const
 }
 
 bool
-AUPlugin::can_support_io_configuration (const ChanCount& in, ChanCount& out) const
+AUPlugin::can_support_io_configuration (const ChanCount& in, ChanCount& out)
 {
 	// Note: We never attempt to multiply-instantiate plugins to meet io configurations.
 
diff --git a/libs/ardour/capturing_processor.cc b/libs/ardour/capturing_processor.cc
index c4b463aba7..4a31d92cc8 100644
--- a/libs/ardour/capturing_processor.cc
+++ b/libs/ardour/capturing_processor.cc
@@ -62,7 +62,7 @@ CapturingProcessor::configure_io (ChanCount in, ChanCount out)
 }
 
 bool
-CapturingProcessor::can_support_io_configuration (const ChanCount& in, ChanCount& out) const
+CapturingProcessor::can_support_io_configuration (const ChanCount& in, ChanCount& out)
 {
 	out = in;
 	return true;
diff --git a/libs/ardour/delivery.cc b/libs/ardour/delivery.cc
index 9eaf843f7c..dfbe4c960a 100644
--- a/libs/ardour/delivery.cc
+++ b/libs/ardour/delivery.cc
@@ -124,7 +124,7 @@ Delivery::display_name () const
 }
 
 bool
-Delivery::can_support_io_configuration (const ChanCount& in, ChanCount& out) const
+Delivery::can_support_io_configuration (const ChanCount& in, ChanCount& out)
 {
 	if (_role == Main) {
 
diff --git a/libs/ardour/internal_return.cc b/libs/ardour/internal_return.cc
index af6b6110b6..fc5963603b 100644
--- a/libs/ardour/internal_return.cc
+++ b/libs/ardour/internal_return.cc
@@ -80,7 +80,7 @@ InternalReturn::get_state()
 }
 
 bool
-InternalReturn::can_support_io_configuration (const ChanCount& in, ChanCount& out) const
+InternalReturn::can_support_io_configuration (const ChanCount& in, ChanCount& out)
 {
 	out = in;
 	return true;
diff --git a/libs/ardour/internal_send.cc b/libs/ardour/internal_send.cc
index 26631d0fad..029a46ce53 100644
--- a/libs/ardour/internal_send.cc
+++ b/libs/ardour/internal_send.cc
@@ -284,7 +284,7 @@ InternalSend::connect_when_legal ()
 }
 
 bool
-InternalSend::can_support_io_configuration (const ChanCount& in, ChanCount& out) const
+InternalSend::can_support_io_configuration (const ChanCount& in, ChanCount& out)
 {
 	out = in;
 	return true;
diff --git a/libs/ardour/meter.cc b/libs/ardour/meter.cc
index 490b75dcb2..a7857f5859 100644
--- a/libs/ardour/meter.cc
+++ b/libs/ardour/meter.cc
@@ -165,7 +165,7 @@ PeakMeter::reset_max ()
 }
 
 bool
-PeakMeter::can_support_io_configuration (const ChanCount& in, ChanCount& out) const
+PeakMeter::can_support_io_configuration (const ChanCount& in, ChanCount& out)
 {
 	out = in;
 	return true;
diff --git a/libs/ardour/monitor_processor.cc b/libs/ardour/monitor_processor.cc
index e55428b666..ed06647860 100644
--- a/libs/ardour/monitor_processor.cc
+++ b/libs/ardour/monitor_processor.cc
@@ -355,7 +355,7 @@ MonitorProcessor::configure_io (ChanCount in, ChanCount out)
 }
 
 bool
-MonitorProcessor::can_support_io_configuration (const ChanCount& in, ChanCount& out) const
+MonitorProcessor::can_support_io_configuration (const ChanCount& in, ChanCount& out)
 {
 	out = in;
 	return true;
diff --git a/libs/ardour/plugin_insert.cc b/libs/ardour/plugin_insert.cc
index d519dbd7a7..b191cf4890 100644
--- a/libs/ardour/plugin_insert.cc
+++ b/libs/ardour/plugin_insert.cc
@@ -145,7 +145,7 @@ PluginInsert::output_streams() const
 		ChanCount out = info->n_outputs;
 		// DEBUG_TRACE (DEBUG::Processors, string_compose ("Plugin insert, static output streams = %1 for %2 plugins\n", out, _plugins.size()));
 		out.set_audio (out.n_audio() * _plugins.size());
-		out.set_midi (out.n_midi() * _plugins.size());
+		out.set_midi (out.n_midi() * _plugins.size() + midi_bypass.n_midi());
 		return out;
 	}
 }
@@ -465,7 +465,6 @@ PluginInsert::run (BufferSet& bufs, framepos_t /*start_frame*/, framepos_t /*end
 		}
 
 	} else {
-
 		if (has_no_audio_inputs()) {
 
 			/* silence all (audio) outputs. Should really declick
@@ -704,7 +703,7 @@ PluginInsert::configure_io (ChanCount in, ChanCount out)
  *  @return true if the given IO configuration can be supported.
  */
 bool
-PluginInsert::can_support_io_configuration (const ChanCount& in, ChanCount& out) const
+PluginInsert::can_support_io_configuration (const ChanCount& in, ChanCount& out)
 {
 	return private_can_support_io_configuration (in, out).method != Impossible;
 }
@@ -714,9 +713,11 @@ PluginInsert::can_support_io_configuration (const ChanCount& in, ChanCount& out)
  *  it can be.
  */
 PluginInsert::Match
-PluginInsert::private_can_support_io_configuration (ChanCount const & in, ChanCount& out) const
+PluginInsert::private_can_support_io_configuration (ChanCount const & inx, ChanCount& out)
 {
 	PluginInfoPtr info = _plugins.front()->get_info();
+	ChanCount in; in += inx;
+	midi_bypass.reset();
 
 	if (info->reconfigurable_io()) {
 		/* Plugin has flexible I/O, so delegate to it */
@@ -731,6 +732,15 @@ PluginInsert::private_can_support_io_configuration (ChanCount const & in, ChanCo
 	ChanCount inputs  = info->n_inputs;
 	ChanCount outputs = info->n_outputs;
 
+	if (in.get(DataType::MIDI) == 1 && outputs.get(DataType::MIDI) == 0) {
+		DEBUG_TRACE ( DEBUG::Processors, string_compose ("bypassing midi-data around %1\n", name()));
+		midi_bypass.set(DataType::MIDI, 1);
+	}
+	if (in.get(DataType::MIDI) == 1 && inputs.get(DataType::MIDI) == 0) {
+		DEBUG_TRACE ( DEBUG::Processors, string_compose ("hiding midi-port from plugin %1\n", name()));
+		in.set(DataType::MIDI, 0);
+	}
+
 	bool no_inputs = true;
 	for (DataType::iterator t = DataType::begin(); t != DataType::end(); ++t) {
 		if (inputs.get (*t) != 0) {
@@ -741,13 +751,13 @@ PluginInsert::private_can_support_io_configuration (ChanCount const & in, ChanCo
 
 	if (no_inputs) {
 		/* no inputs so we can take any input configuration since we throw it away */
-		out = outputs;
+		out = outputs + midi_bypass;
 		return Match (NoInputs, 1);
 	}
 
 	/* Plugin inputs match requested inputs exactly */
 	if (inputs == in) {
-		out = outputs;
+		out = outputs + midi_bypass;
 		return Match (ExactMatch, 1);
 	}
 
@@ -789,6 +799,7 @@ PluginInsert::private_can_support_io_configuration (ChanCount const & in, ChanCo
 		for (DataType::iterator t = DataType::begin(); t != DataType::end(); ++t) {
 			out.set (*t, outputs.get(*t) * f);
 		}
+		out += midi_bypass;
 		return Match (Replicate, f);
 	}
 
@@ -812,7 +823,7 @@ PluginInsert::private_can_support_io_configuration (ChanCount const & in, ChanCo
 	}
 
 	if (can_split) {
-		out = outputs;
+		out = outputs + midi_bypass;
 		return Match (Split, 1);
 	}
 
@@ -836,10 +847,11 @@ PluginInsert::private_can_support_io_configuration (ChanCount const & in, ChanCo
 	}
 
 	if (could_hide && !cannot_hide) {
-		out = outputs;
+		out = outputs + midi_bypass;
 		return Match (Hide, 1, hide_channels);
 	}
 
+	midi_bypass.reset();
 	return Match (Impossible, 0);
 }
 
diff --git a/libs/ardour/port_insert.cc b/libs/ardour/port_insert.cc
index c13927449a..411d8d1e19 100644
--- a/libs/ardour/port_insert.cc
+++ b/libs/ardour/port_insert.cc
@@ -266,7 +266,7 @@ PortInsert::configure_io (ChanCount in, ChanCount out)
 }
 
 bool
-PortInsert::can_support_io_configuration (const ChanCount& in, ChanCount& out) const
+PortInsert::can_support_io_configuration (const ChanCount& in, ChanCount& out)
 {
 	out = in;
 	return true;
diff --git a/libs/ardour/return.cc b/libs/ardour/return.cc
index 921be6a53a..4f9e8b958a 100644
--- a/libs/ardour/return.cc
+++ b/libs/ardour/return.cc
@@ -136,7 +136,7 @@ Return::run (BufferSet& bufs, framepos_t start_frame, framepos_t end_frame, pfra
 }
 
 bool
-Return::can_support_io_configuration (const ChanCount& in, ChanCount& out) const
+Return::can_support_io_configuration (const ChanCount& in, ChanCount& out)
 {
 	out = in + _input->n_ports();
 	return true;
diff --git a/libs/ardour/route.cc b/libs/ardour/route.cc
index a394c73d20..b78217ff49 100644
--- a/libs/ardour/route.cc
+++ b/libs/ardour/route.cc
@@ -543,11 +543,10 @@ Route::process_output_buffers (BufferSet& bufs,
 			if (bufs.count() != (*i)->input_streams()) {
 				DEBUG_TRACE (
 					DEBUG::Processors, string_compose (
-						"%1 bufs = %2 input for %3 = %4\n",
+						"input port mismatch %1 bufs = %2 input for %3 = %4\n",
 						_name, bufs.count(), (*i)->name(), (*i)->input_streams()
 						)
 					);
-				continue;
 			}
 		}
 #endif
@@ -1654,7 +1653,8 @@ Route::try_configure_processors_unlocked (ChanCount in, ProcessorStreams* err)
 
 		if (boost::dynamic_pointer_cast<UnknownProcessor> (*p)) {
 			DEBUG_TRACE (DEBUG::Processors, "--- CONFIGURE ABORTED due to unknown processor.\n");
-			break;
+			DEBUG_TRACE (DEBUG::Processors, "}\n");
+			return list<pair<ChanCount, ChanCount> > ();
 		}
 
 		if ((*p)->can_support_io_configuration(in, out)) {
diff --git a/libs/ardour/send.cc b/libs/ardour/send.cc
index 107cf9862b..e74fd7f8ce 100644
--- a/libs/ardour/send.cc
+++ b/libs/ardour/send.cc
@@ -270,7 +270,7 @@ Send::set_state_2X (const XMLNode& node, int /* version */)
 }
 
 bool
-Send::can_support_io_configuration (const ChanCount& in, ChanCount& out) const
+Send::can_support_io_configuration (const ChanCount& in, ChanCount& out)
 {
 	/* sends have no impact at all on the channel configuration of the
 	   streams passing through the route. so, out == in.