#include <limits.h>
 #include <netdb.h>
 #include <libudev.h>
+#include <dirent.h>
 #include "sysfs_utils.h"
 
 #undef  PROGNAME
        return (int)strtoul(attr_nports, NULL, 10);
 }
 
+static int vhci_hcd_filter(const struct dirent *dirent)
+{
+       return strcmp(dirent->d_name, "vhci_hcd") >= 0;
+}
+
+static int get_ncontrollers(void)
+{
+       struct dirent **namelist;
+       struct udev_device *platform;
+       int n;
+
+       platform = udev_device_get_parent(vhci_driver->hc_device);
+       if (platform == NULL)
+               return -1;
+
+       n = scandir(udev_device_get_syspath(platform), &namelist, vhci_hcd_filter, NULL);
+       if (n < 0)
+               err("scandir failed");
+       else {
+               for (int i = 0; i < n; i++)
+                       free(namelist[i]);
+               free(namelist);
+       }
+
+       return n;
+}
+
 /*
  * Read the given port's record.
  *
                goto err;
        }
 
+       vhci_driver->ncontrollers = get_ncontrollers();
+       dbg("available controllers: %d", vhci_driver->ncontrollers);
+
+       if (vhci_driver->ncontrollers <=0) {
+               err("no available usb controllers");
+               goto err;
+       }
+
        if (refresh_imported_device_list())
                goto err;