mixer: more relaxed config handling

Instead of bailing out if the channel list is incorrect check config
node attributes and default settings first.

Being there also fix flawed LOG messages.

Fixes genodelabs#1794.

repos/os/src/server/mixer/mixer.cc

@@ -425,6 +425,12 @@ class Audio_out::Mixer
 
 				v = default_node.attribute_value<long>("muted", 1);
 				_default_muted = v ;
+
+				PLOGV("default settings: out_volume: %d volume: %d muted: %d",
+				      (int)(MAX_VOLUME*_default_out_volume),
+				      (int)(MAX_VOLUME*_default_volume),
+				      _default_muted);
+
 			} catch (...) { PWRN("could not read mixer default values"); }
 		}
 
@@ -437,13 +443,20 @@ class Audio_out::Mixer
 
 			config()->reload();
 
-			try {
-				Xml_node config_node = config()->xml_node();
-				try { verbose = config_node.attribute("verbose").has_value("yes"); }
-				catch (...) { verbose = false; }
+			Xml_node config_node = config()->xml_node();
+			try { verbose = config_node.attribute("verbose").has_value("yes"); }
+			catch (...) { verbose = false; }
 
-				_set_default_config(config_node);
+			_set_default_config(config_node);
+
+			/* set initial out volume */
+			if (sig_num == 0) {
+				for_each_index(MAX_CHANNELS, [&] (int const i) {
+					_out_volume[i] = _default_out_volume;
+				});
+			}
 
+			try {
 				Xml_node channel_list_node = config_node.sub_node("channel_list");
 
 				channel_list_node.for_each_sub_node([&] (Xml_node const &node) {
@@ -460,7 +473,7 @@ class Audio_out::Mixer
 
 								PLOGV("label: '%s' nr: %d vol: %d muted: %d",
 								      ch.label.string(), (int)ch.number,
-								      (int)(MAX_VOLUME*ch.volume), ch.muted);
+								      (int)(MAX_VOLUME*session.volume), ch.muted);
 							});
 						});
 					}
@@ -472,11 +485,11 @@ class Audio_out::Mixer
 
 							PLOGV("label: '%s' nr: %d vol: %d muted: %d",
 							      "master", (int)ch.number,
-							      (int)(MAX_VOLUME*ch.volume), ch.muted);
+							      (int)(MAX_VOLUME*_out_volume[i]), ch.muted);
 						});
 					}
 				});
-			} catch (...) { PWRN("mixer config was invalid"); }
+			} catch (...) { PWRN("mixer channel_list was invalid"); }
 
 			/*
 			 * Report back any changes so a front-end can update its state
@@ -542,12 +555,14 @@ class Audio_out::Mixer
 		 */
 		void add_session(Channel::Number ch, Session_elem &session)
 		{
-			PLOG("add label: \"%s\" channel: \"%s\" nr: %u",
-			     session.label.string(), string_from_number(ch), ch);
-
 			session.volume = _default_volume;
 			session.muted  = _default_muted;
 
+			PLOG("add label: \"%s\" channel: \"%s\" nr: %u volume: %d muted: %d",
+			     session.label.string(), string_from_number(ch), ch,
+			     (int)(MAX_VOLUME*session.volume), session.muted);
+
+
 			_channels[ch].insert(&session);
 			_report_channels();
 		}