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

Closes: https://github.com/alsa-project/alsa-ucm-conf/pull/517
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

diff --git a/ucm2/common/ctl/led.conf b/ucm2/common/ctl/led.conf
new file mode 100644 (file)
index 0000000..f10ad87
--- /dev/null
+++ b/ucm2/common/ctl/led.conf
@@ -0,0 +1,65 @@
+#
+# Microphone/Speaker LED handling seems like an easy task, but
+# the expectations are different:
+#
+# Main question: Which state should LEDs follow (devices)?
+#
+# Case 1) set LEDs only for internal resources (speaker/microphone)
+# Case 2) set LEDs according the current stream (input/output)
+# Case 3) like case 1, but add analog headphones connected to laptop (analog jack)
+#
+# Discussion for Case 2: It is not possible to handle this in driver
+# (kernel). Usually, the sound server knowns the current stream (which may be routed to
+# bluetooth or a USB device, for example). Additionally, there is a security flaw if the
+# sound server directly controls the LEDs.
+#
+# Discussion for Case 3: Note that we have currently also USB/Bluetooth headphones which
+# do not follow this scenario. In this case, there is no clear LED mapping. It seems
+# that this case is somewhat controversional. Thus, analog headphones may be treated as
+# an external device.
+#
+# Result: For safety, simplicity and understable behaviour, only Case 1 should be
+# followed - LEDs should respond only to the internal (build-in) speaker output and
+# internal (build-in) microphone input in UCM.
+#
+
+#
+# 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}"
+]