+ * Set the libsigrok log callback to the specified function.
+ *
+ * @param cb Function pointer to the log callback function to use.
+ * Must not be NULL.
+ * @param cb_data Pointer to private data to be passed on. This can be used by
+ * the caller to pass arbitrary data to the log functions. This
+ * pointer is only stored or passed on by libsigrok, and is
+ * never used or interpreted in any way. The pointer is allowed
+ * to be NULL if the caller doesn't need/want to pass any data.