When pressing the microphone mute button, the evtest reports KEY_MICMUTE while xev does not recognize the key press. Below are the steps to fix the issue that worked on Lenovo Thinkad T14s Gen 4 running Debian.

1. Check permissions:

   ls -l /sys/class/leds/platform\:\:micmute/brightness

   The output will show the user and group ownership. The group should be input.

2. Add your user to the input group:

   usermod -aG input <username>

   Replace <username> with your actual username.

   Important: Log out and log back in after adding yourself to a new group.

3. Check the key code and device path with evtest:

   evtest

   Find your keyboard input device and press the mic mute button. You should see:

   Event: type 1 (EV_KEY), code 248 (KEY_MICMUTE), value 1

   For example:

   • Input device: /dev/input/event12
   • Key code: KEY_MICMUTE

4. Write the Bash script:

   Create a new file .micmute.sh with the following content:

   #!/bin/bash
   
   # CONFIG
   DEVICE="/dev/input/event12"  # <-- change this to your correct event device
   LED_PATH="/sys/class/leds/platform::micmute/brightness"
   
   # Internal state
   STATE=0
   
   # Trap Ctrl+C to exit cleanly
   trap "echo; echo Exiting.; exit 0" SIGINT
   
   # Main loop
   evtest "$DEVICE" | while read -r line; do
       # Look for KEY_MICMUTE press (value 1)
       if echo "$line" | grep -q "KEY_MICMUTE.*value 1"; then
           # Toggle microphone mute
           pactl set-source-mute @DEFAULT_SOURCE@ toggle
           # Toggle LED state
           STATE=$((1 - STATE))
           echo "$STATE" > "$LED_PATH"
       fi
   done

   Make it executable:

   chmod +x .micmute.sh

   Run the script:

   ./.micmute.sh

   Add this script to your window manager. For i3:

   exec --no-startup-id ~/.micmute.sh

   Now pressing the mic mute button will toggle the microphone mute state and LED.