common: add led.conf with SetLED macro to hide implementation details

Closes: alsa-project#517
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

Author: perexg

ucm2/common/ctl/led.conf

@@ -0,0 +1,40 @@
+#
+# Macro SetLED - attach or detach speaker or microphone LED to given control element
+#
+# Arguments:
+#   LED    - LED selection - "speaker" or "mic"
+#   Action - action for given control - "attach" or "detach"
+#   CtlId  - control identifier (as for amixer, e.g. "Capture Switch" or "name='CaptureSwitch',index=1")
+#
+
+DefineMacro.SetLED {
+	If.0 {
+		Condition {
+			Type String
+			Empty "${var:-SndCtlLedModprobe}"
+		}
+		True {
+			FixedBootSequence [
+				exec "-/sbin/modprobe snd_ctl_led"
+			]
+			Define.SndCtlLedModprobe ok
+		}
+	}
+	If.1 {
+		Condition { Type AlwaysTrue }
+		True.FixedBootSequence [
+			sysw "-/class/sound/ctl-led/${var:__LED}/card${CardNumber}/${var:__Action}:${var:__CtlId}"
+		]
+	}
+}
+
+#
+# Macro CtlNew - helper to create new control elemend
+#
+# Arguments:
+#   Arg    - string for cset-new
+#
+
+DefineMacro.CtlNew.FixedBootSequence [
+	cset-new "${var:__Arg}"
+]