ptasync
status = xpt_register_async(AC_FOUND_DEVICE, ptasync, NULL, NULL);
ptasync, periph, periph->path);
xpt_register_async(0, ptasync, periph, periph->path);
cgd->ccb_h.path, ptasync,
static void ptasync(void *callback_arg, u_int32_t code,