xs_read
error = xs_read(XST_NIL, xenbus_get_node(dev),
error = xs_read(XST_NIL, "control", "shutdown",
err = xs_read(XST_NIL, our_path, "bridge", &bridge_len,
error = xs_read(XST_NIL, path, "mac", NULL, (void **) &macstr);
error = xs_read(XST_NIL, path, "mac", NULL, (void **) &macstr);
error = xs_read(t, dir, node, NULL, (void **) &val);
error = xs_read(t, dir, name, NULL, (void **) &p);
int xs_read(struct xs_transaction t, const char *dir,