3 files changed, 37 insertions, 10 deletions
diff --git a/libs/ardour/ardour/audio_backend.h b/libs/ardour/ardour/audio_backend.h
index 18c8cb8931..08dd7fb0b5 100644
--- a/libs/ardour/ardour/audio_backend.h
+++ b/libs/ardour/ardour/audio_backend.h
@@ -68,6 +68,33 @@ class AudioBackend {
 
     /* Discovering devices and parameters */
 
+    /** Return true if this backend requires the selection of a "driver"
+     * before any device can be selected. Return false otherwise.
+     *
+     * Intended mainly to differentiate between meta-APIs like JACK
+     * which can still expose different backends (such as ALSA or CoreAudio 
+     * or FFADO or netjack) and those like ASIO or CoreAudio which
+     * do not.
+     */
+    virtual bool requires_driver_selection() const { return false; }
+
+    /** If the return value of requires_driver_selection() is true,
+     * then this function can return the list of known driver names.
+     *
+     * If the return value of requires_driver_selection() is false,
+     * then this function should not be called. If it is called
+     * its return value is an empty vector of strings.
+     */
+    virtual std::vector<std::string> enumerate_drivers() const { return std::vector<std::string>(); }
+
+    /** Returns zero if the backend can successfully use @param name as the
+     * driver, non-zero otherwise.
+     *
+     * Should not be used unless the backend returns true from
+     * requires_driver_selection()
+     */
+    virtual int set_driver (const std::string& /*drivername*/) { return 0; }
+
     /** Returns a collection of strings identifying devices known
      * to this backend. Any of these strings may be used to identify a
      * device in other calls to the backend, though any of them may become
@@ -358,8 +385,8 @@ struct AudioBackendInfo {
      * configured and does not need (re)configuration in order
      * to be usable. Return false otherwise.
      *
-     * Note that this may return true if (re)configuration is possible,
-     * but not required. 
+     * Note that this may return true if (re)configuration, even though
+     * not currently required, is still possible.
      */
     bool (*already_configured)();
 };
diff --git a/libs/ardour/ardour/audioengine.h b/libs/ardour/ardour/audioengine.h
index 5046206542..6fb13b7ae0 100644
--- a/libs/ardour/ardour/audioengine.h
+++ b/libs/ardour/ardour/audioengine.h
@@ -74,7 +74,8 @@ public:
     int discover_backends();
     std::vector<const AudioBackendInfo*> available_backends() const;
     std::string current_backend_name () const;
-    int set_backend (const std::string&, const std::string& arg1, const std::string& arg2);
+    boost::shared_ptr<AudioBackend> set_backend (const std::string&, const std::string& arg1, const std::string& arg2);
+    boost::shared_ptr<AudioBackend> current_backend() const { return _backend; }
     bool setup_required () const;
 
     ProcessThread* main_thread() const { return _main_thread; }
@@ -172,13 +173,6 @@ public:
     PBD::Signal0<void> Running;
     PBD::Signal0<void> Stopped;
 
-    /* these two are emitted as we create backends that
-       can actually be used to do stuff (e.g. register ports)
-    */
-    
-    PBD::Signal0<void> BackendAvailable;
-    PBD::Signal0<void> BackendRemoved;
-    
     static AudioEngine* instance() { return _instance; }
     static void destroy();
     void died ();
diff --git a/libs/ardour/ardour/jack_audiobackend.h b/libs/ardour/ardour/jack_audiobackend.h
index 4fef602119..59b5b88105 100644
--- a/libs/ardour/ardour/jack_audiobackend.h
+++ b/libs/ardour/ardour/jack_audiobackend.h
@@ -49,7 +49,12 @@ class JACKAudioBackend : public AudioBackend {
     bool connected() const;
     bool is_realtime () const;
 
+    bool requires_driver_selection() const;
+    std::vector<std::string> enumerate_drivers () const;
+    int set_driver (const std::string&);
+
     std::vector<std::string> enumerate_devices () const;
+
     std::vector<float> available_sample_rates (const std::string& device) const;
     std::vector<uint32_t> available_buffer_sizes (const std::string& device) const;
     uint32_t available_input_channel_count (const std::string& device) const;
@@ -151,6 +156,7 @@ class JACKAudioBackend : public AudioBackend {
 
     /* pffooo */
 
+    std::string  _target_driver;
     std::string  _target_device;
     float        _target_sample_rate;
     uint32_t     _target_buffer_size;