+/* "Automatic" and forced USB connection open/close support. */
+SR_PRIV int sigma_check_open(const struct sr_dev_inst *sdi);
+SR_PRIV int sigma_check_close(struct dev_context *devc);
+SR_PRIV int sigma_force_open(const struct sr_dev_inst *sdi);
+SR_PRIV int sigma_force_close(struct dev_context *devc);
+