conf: make ctl.default and sysdefault devices more universal

It may be handy to add hw specific configs.

Signed-off-by: Jaroslav Kysela <perex@perex.cz>

src/conf/alsa.conf

@@ -341,22 +341,8 @@ pcm.phoneline cards.pcm.phoneline
 #  Control interface
 #
 	
-ctl.sysdefault {
-	type hw
-	card {
-		@func getenv
-		vars [
-			ALSA_CTL_CARD
-			ALSA_CARD
-		]
-		default {
-			@func refer
-			name defaults.ctl.card
-		}
-	}
-	hint.description "Default control device"
-}
-ctl.default ctl.sysdefault
+ctl.default cards.ctl.default
+ctl.sysdefault cards.ctl.default
 
 ctl.hw {
 	@args [ CARD ]

src/conf/cards/aliases.conf

@@ -58,6 +58,7 @@ CMI8787 cards.CMI8788
 pistachio cards.pistachio-card
 VC4-HDMI cards.vc4-hdmi
 
+<confdir:ctl/default.conf>
 <confdir:pcm/default.conf>
 <confdir:pcm/dmix.conf>
 <confdir:pcm/dsnoop.conf>

src/conf/ctl/default.conf

@@ -0,0 +1,42 @@
+#
+# Default control device
+#
+
+ctl.!default {
+	@args [ CARD ]
+	@args.CARD {
+		type string
+		default {
+			@func getenv
+			vars [
+				ALSA_PCM_CARD
+				ALSA_CARD
+			]
+			default {
+				@func refer
+				name defaults.ctl.card
+			}
+		}
+	}
+	type empty
+	child {
+		# use card-specific definition if exists
+		@func refer
+		name {
+			@func concat
+			strings [
+				"cards."
+				{
+					@func card_driver
+					card $CARD
+				}
+				".ctl.default:CARD=" $CARD
+			]
+		}
+		default {
+			type hw
+			card $CARD
+		}
+	}
+	hint.description "Default Control Device"
+}