+/**
+ * Lookup a channel group from its name.
+ *
+ * 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.
+ *
+ * @param[in] sdi Device instance.
+ * @param[in] cg_name Caller provided channel group name.
+ *
+ * @returns The channel group, or #NULL for failed lookup.
+ */
+struct sr_channel_group *lookup_channel_group(struct sr_dev_inst *sdi,
+ const char *cg_name)