diff -rupN jack-1.9.8.old/linux/firewire/JackFFADODriver.cpp jack-1.9.8/linux/firewire/JackFFADODriver.cpp
--- jack-1.9.8.old/linux/firewire/JackFFADODriver.cpp	2011-12-19 06:54:27.000000000 -0500
+++ jack-1.9.8/linux/firewire/JackFFADODriver.cpp	2012-03-25 01:38:58.246513167 -0400
@@ -3,6 +3,7 @@ Copyright (C) 2001 Paul Davis
 Copyright (C) 2004 Grame
 Copyright (C) 2007 Pieter Palmers
 Copyright (C) 2009 Devin Anderson
+Copyright (C) 2012 Jonathan Woithe, Adrian Knoth
 
 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
@@ -45,10 +46,20 @@ Foundation, Inc., 675 Mass Ave, Cambridg
 #include "JackCompilerDeps.h"
 #include "JackLockedEngine.h"
 
+// FFADO_API_VERSION was first defined with API_VERSION 9, so all previous
+// headers do not provide this define.
+#ifndef FFADO_API_VERSION
+extern "C" int ffado_streaming_set_period_size(ffado_device_t *dev,
+		unsigned int period) __attribute__((__weak__));
+#endif
+
 namespace Jack
 {
 
+// Basic functionality requires API version 8.  If version 9 or later
+// is present the buffers can be resized at runtime.
 #define FIREWIRE_REQUIRED_FFADO_API_VERSION 8
+#define FIREWIRE_REQUIRED_FFADO_API_VERSION_FOR_SETBUFSIZE 9
 
 #define jack_get_microseconds GetMicroSeconds
 
@@ -253,22 +264,96 @@ JackFFADODriver::ffado_driver_restart (f
     return Start();
 }
 
+void
+JackFFADODriver::UpdateLatencies(void)
+{
+    jack_latency_range_t range;
+    ffado_driver_t* driver = (ffado_driver_t*)fDriver;
+
+    for (int i = 0; i < fCaptureChannels; i++) {
+        range.min = range.max = driver->period_size + driver->capture_frame_latency;
+        fGraphManager->GetPort(fCapturePortList[i])->SetLatencyRange(JackCaptureLatency, &range);
+    }
+
+    for (int i = 0; i < fPlaybackChannels; i++) {
+        // Add one buffer more latency if "async" mode is used...
+        range.min = range.max = (driver->period_size *
+			(driver->device_options.nb_buffers - 1)) +
+                         ((fEngineControl->fSyncMode) ? 0 : fEngineControl->fBufferSize) + driver->playback_frame_latency;
+        fGraphManager->GetPort(fPlaybackPortList[i])->SetLatencyRange(JackPlaybackLatency, &range);
+        // Monitor port
+        if (fWithMonitorPorts) {
+            range.min = range.max =driver->period_size;
+            fGraphManager->GetPort(fMonitorPortList[i])->SetLatencyRange(JackCaptureLatency, &range);
+        }
+    }
+}
+
 int
 JackFFADODriver::SetBufferSize (jack_nframes_t nframes)
 {
-    printError("Buffer size change requested but not supported!!!");
+    ffado_driver_t* driver = (ffado_driver_t*)fDriver;
+    signed int chn;
+
+    // The speed of this function isn't critical; we can afford the
+    // time to check the FFADO API version.
+    if (ffado_get_api_version() < FIREWIRE_REQUIRED_FFADO_API_VERSION_FOR_SETBUFSIZE ||
+		    ffado_streaming_set_period_size == NULL) {
+	    printError("unsupported on current version of FFADO; please upgrade FFADO");
+	    return -1;
+    }
 
-    /*
     driver->period_size = nframes;
     driver->period_usecs =
             (jack_time_t) floor ((((float) nframes) / driver->sample_rate)
                                  * 1000000.0f);
-    */
+
+
+    // Reallocate the null and scratch buffers.
+    driver->nullbuffer = (ffado_sample_t*) calloc(driver->period_size, sizeof(ffado_sample_t));
+    if(driver->nullbuffer == NULL) {
+	    printError("could not allocate memory for null buffer");
+	    return -1;
+    }
+    driver->scratchbuffer = (ffado_sample_t*) calloc(driver->period_size, sizeof(ffado_sample_t));
+    if(driver->scratchbuffer == NULL) {
+	    printError("could not allocate memory for scratch buffer");
+	    return -1;
+    }
+
+    // MIDI buffers need reallocating
+    for (chn = 0; chn < driver->capture_nchannels; chn++) {
+	    if(driver->capture_channels[chn].stream_type == ffado_stream_type_midi) {
+		    // setup the midi buffer
+		    if (driver->capture_channels[chn].midi_buffer != NULL)
+			    free(driver->capture_channels[chn].midi_buffer);
+		    driver->capture_channels[chn].midi_buffer = (ffado_sample_t*) calloc(driver->period_size, sizeof(uint32_t));
+	    }
+    }
+    for (chn = 0; chn < driver->playback_nchannels; chn++) {
+	    if(driver->playback_channels[chn].stream_type == ffado_stream_type_midi) {
+		    if (driver->playback_channels[chn].midi_buffer != NULL)
+			    free(driver->playback_channels[chn].midi_buffer);
+		    driver->playback_channels[chn].midi_buffer = (ffado_sample_t*) calloc(driver->period_size, sizeof(uint32_t));
+	    }
+    }
+
+    // Notify FFADO of the period size change
+    if (ffado_streaming_set_period_size(driver->dev, nframes) != 0) {
+	    printError("could not alter FFADO device period size");
+	    return -1;
+    }
+
+    // This is needed to give the shadow variables a chance to
+    // properly update to the changes.
+    sleep(1);
 
     /* tell the engine to change its buffer size */
-    //driver->engine->set_buffer_size (driver->engine, nframes);
+    JackAudioDriver::SetBufferSize(nframes);  // Generic change, never fails
+
+    UpdateLatencies();
 
-    return -1; // unsupported
+    return 0;
 }
 
 typedef void (*JackDriverFinishFunction) (jack_driver_t *);
@@ -281,7 +366,7 @@ JackFFADODriver::ffado_driver_new (const
 
     assert(params);
 
-    if (ffado_get_api_version() != FIREWIRE_REQUIRED_FFADO_API_VERSION) {
+    if (ffado_get_api_version() < FIREWIRE_REQUIRED_FFADO_API_VERSION) {
         printError("Incompatible libffado version! (%s)", ffado_get_version());
         return NULL;
     }
@@ -349,7 +434,6 @@ int JackFFADODriver::Attach()
     jack_port_id_t port_index;
     char buf[REAL_JACK_PORT_NAME_SIZE];
     char portname[REAL_JACK_PORT_NAME_SIZE];
-    jack_latency_range_t range;
 
     ffado_driver_t* driver = (ffado_driver_t*)fDriver;
 
@@ -435,8 +519,6 @@ int JackFFADODriver::Attach()
             ffado_streaming_capture_stream_onoff(driver->dev, chn, 0);
 
             port = fGraphManager->GetPort(port_index);
-            range.min = range.max = driver->period_size + driver->capture_frame_latency;
-            port->SetLatencyRange(JackCaptureLatency, &range);
             // capture port aliases (jackd1 style port names)
             snprintf(buf, sizeof(buf), "%s:capture_%i", fClientControl.fName, (int) chn + 1);
             port->SetAlias(buf);
@@ -466,9 +548,6 @@ int JackFFADODriver::Attach()
             // setup the midi buffer
             driver->capture_channels[chn].midi_buffer = (uint32_t *)calloc(driver->period_size, sizeof(uint32_t));
 
-            port = fGraphManager->GetPort(port_index);
-            range.min = range.max = driver->period_size + driver->capture_frame_latency;
-            port->SetLatencyRange(JackCaptureLatency, &range);
             fCapturePortList[chn] = port_index;
             jack_log("JackFFADODriver::Attach fCapturePortList[i] %ld ", port_index);
             fCaptureChannels++;
@@ -512,8 +591,6 @@ int JackFFADODriver::Attach()
 
             port = fGraphManager->GetPort(port_index);
             // Add one buffer more latency if "async" mode is used...
-            range.min = range.max = (driver->period_size * (driver->device_options.nb_buffers - 1)) + ((fEngineControl->fSyncMode) ? 0 : fEngineControl->fBufferSize) + driver->playback_frame_latency;
-            port->SetLatencyRange(JackPlaybackLatency, &range);
             // playback port aliases (jackd1 style port names)
             snprintf(buf, sizeof(buf), "%s:playback_%i", fClientControl.fName, (int) chn + 1);
             port->SetAlias(buf);
@@ -548,9 +625,6 @@ int JackFFADODriver::Attach()
 
             driver->playback_channels[chn].midi_buffer = (uint32_t *)calloc(driver->period_size, sizeof(uint32_t));
 
-            port = fGraphManager->GetPort(port_index);
-            range.min = range.max = (driver->period_size * (driver->device_options.nb_buffers - 1)) + ((fEngineControl->fSyncMode) ? 0 : fEngineControl->fBufferSize) + driver->playback_frame_latency;
-            port->SetLatencyRange(JackPlaybackLatency, &range);
             fPlaybackPortList[chn] = port_index;
             jack_log("JackFFADODriver::Attach fPlaybackPortList[i] %ld ", port_index);
             fPlaybackChannels++;
@@ -559,6 +633,8 @@ int JackFFADODriver::Attach()
         }
     }
 
+    UpdateLatencies();
+
     assert(fCaptureChannels < DRIVER_PORT_NUM);
     assert(fPlaybackChannels < DRIVER_PORT_NUM);
 
diff -rupN jack-1.9.8.old/linux/firewire/JackFFADODriver.h jack-1.9.8/linux/firewire/JackFFADODriver.h
--- jack-1.9.8.old/linux/firewire/JackFFADODriver.h	2011-12-19 06:54:27.000000000 -0500
+++ jack-1.9.8/linux/firewire/JackFFADODriver.h	2012-03-25 01:38:05.708754669 -0400
@@ -2,6 +2,7 @@
 Copyright (C) 2001 Paul Davis
 Copyright (C) 2004 Grame
 Copyright (C) 2007 Pieter Palmers
+Copyright (C) 2012 Adrian Knoth
 
 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
@@ -59,6 +60,7 @@ class JackFFADODriver : public JackAudio
 
         void jack_driver_init (jack_driver_t *driver);
         void jack_driver_nt_init (jack_driver_nt_t * driver);
+        void UpdateLatencies();
 
     public:
 
@@ -80,6 +82,12 @@ class JackFFADODriver : public JackAudio
         int Read();
         int Write();
 
+        // BufferSize can be changed
+        bool IsFixedBufferSize()
+        {
+            return false;
+        }
+
         int SetBufferSize(jack_nframes_t nframes);
 };