Xenomai 2 to 3 migration says "RTDM drivers implementing differentiated ioctl() support for both domains should serve all real-time only requests from ioctl_rt(), returning -ENOSYS for any unrecognized request, which will cause the adaptive switch to take place automatically to the ioctl_nrt() handler. The ioctl_nrt() should then implement all requests which may be valid from the regular Linux domain exclusively."
b6cfd85db58e116ea155a52a584e863fc6ad0eff version-1.3.2