grc/decoding/gsm_control_channels_decoder.xml

<?xml version="1.0"?>
<block>
  <name>Control channels decoder</name>
  <key>gsm_control_channels_decoder</key>
  <import>import grgsm</import>
  <make>grgsm.control_channels_decoder()</make>
  <sink>
    <name>bursts</name>
    <type>message</type>
  </sink>
  <source>
    <name>msgs</name>
    <type>message</type>
    <optional>1</optional>
  </source>
</block>