cdasync
static void cdasync(void *callback_arg, uint32_t code,
status = xpt_register_async(AC_FOUND_DEVICE, cdasync, NULL, NULL);
xpt_register_async(0, cdasync, periph, periph->path);
path, cdasync,
AC_SCSI_AEN | AC_UNIT_ATTENTION, cdasync, periph, periph->path);