- * Uses the previously stored option value to lookup a channel group.
- * Returns a reference to the channel group when the lookup succeeded,
- * or #NULL after lookup failure, or #NULL for the global channel group
- * (the device's global parameters). Emits an error message when the
- * lookup failed while a channel group's name was specified.
+ * Uses the caller specified channel group name, or a previously stored
+ * option value as a fallback. Returns a reference to the channel group
+ * when the lookup succeeded, or #NULL after lookup failure, as well as
+ * #NULL for the global channel group (the device).
+ *
+ * Accepts either #NULL pointer, or an empty string, or the "global"
+ * literal to address the global channel group (the device). Emits an
+ * error message when the lookup failed while a name was specified.