From 31fadae40cd704c56e477e57195f28158465cf7f Mon Sep 17 00:00:00 2001
From: Jaroslav Kysela <perex@perex.cz>
Date: Tue, 11 Mar 2025 11:09:29 +0100
Subject: [PATCH] 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>
---
 ucm2/common/ctl/led.conf | 65 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)
 create mode 100644 ucm2/common/ctl/led.conf

diff --git a/ucm2/common/ctl/led.conf b/ucm2/common/ctl/led.conf
new file mode 100644
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}"
+]
-- 
2.47.1