Allow user to select device of soundcard

README.rst

@@ -61,6 +61,8 @@ The following configuration values are available:
 - ``alsamixer/volume_scale``: Either ``linear``, ``cubic``, or ``log``. The
   cubic scale is the default as it is closer to how the human ear percieves
   volume, and matches the volume scale used in the ``alsamixer`` program.
+
+- ``alsamixer/device``: select what device number you want to use. Numbered from 0 and up. 0 is the default.
 
 Example ``alsamixer`` section from the Mopidy configuration file::
 
@@ -70,6 +72,7 @@ Example ``alsamixer`` section from the Mopidy configuration file::
     min_volume = 0
     max_volume = 100
     volume_scale = cubic
+    device = 1
 
 Project resources
 =================

mopidy_alsamixer/__init__.py

@@ -21,6 +21,7 @@ def get_default_config(self):
     def get_config_schema(self):
         schema = super(Extension, self).get_config_schema()
         schema['card'] = config.Integer(minimum=0)
+        schema['device'] = config.String()
         schema['control'] = config.String()
         schema['min_volume'] = config.Integer(minimum=0, maximum=100)
         schema['max_volume'] = config.Integer(minimum=0, maximum=100)

mopidy_alsamixer/ext.conf

@@ -1,6 +1,7 @@
 [alsamixer]
 enabled = true
 card = 0
+device = default
 control = Master
 min_volume = 0
 max_volume = 100

mopidy_alsamixer/mixer.py

@@ -25,6 +25,7 @@ def __init__(self, config):
         super(AlsaMixer, self).__init__()
         self.config = config
         self.cardindex = self.config['alsamixer']['card']
+        self.device = self.config['alsamixer']['device']
         self.control = self.config['alsamixer']['control']
         self.min_volume = self.config['alsamixer']['min_volume']
         self.max_volume = self.config['alsamixer']['max_volume']
@@ -56,12 +57,12 @@ def __init__(self, config):
         self._last_mute = None
 
         logger.info(
-            'Mixing using ALSA, card %d, mixer control "%s".',
-            self.cardindex, self.control)
+            'Mixing using ALSA, card %d, mixer control "%s", device "%s".',
+            self.cardindex, self.control, self.device)
 
     def on_start(self):
         self._observer = AlsaMixerObserver(
-            cardindex=self.cardindex, control=self.control,
+            cardindex=self.cardindex, control=self.control, device=self.device,
             callback=self.actor_ref.proxy().trigger_events_for_changed_values)
         self._observer.start()
 
@@ -157,12 +158,13 @@ class AlsaMixerObserver(threading.Thread):
     daemon = True
     name = 'AlsaMixerObserver'
 
-    def __init__(self, cardindex, control, callback=None):
+    def __init__(self, cardindex, control, device, callback=None):
         super(AlsaMixerObserver, self).__init__()
         self.running = True
 
         # Keep the mixer instance alive for the descriptors to work
-        self.mixer = alsaaudio.Mixer(cardindex=cardindex, control=control)
+        self.mixer = alsaaudio.Mixer(cardindex=cardindex, control=control,
+                                    device=device)
         descriptors = self.mixer.polldescriptors()
         assert len(descriptors) == 1
         self.fd = descriptors[0][0]