.. index:: pair: group; Check PTP_SYS_OFFSET_PRECISE ioctl
.. _doxid-group__ptp-sys__offset__precise:

Check PTP_SYS_OFFSET_PRECISE ioctl
==================================

.. toctree::
	:hidden:

Check that ``PTP_SYS_OFFSET_PRECISE`` ioctl can be used to obtain PTP device time and system time at the same moment.

#. Find out PTP device associated with the IUT interface, call **open()** to get its FD.

#. Call **ioctl** (``PTP_SYS_OFFSET_PRECISE``) on the PTP device FD to get timestamps for PTP device, ``CLOCK_REALTIME`` and ``CLOCK_MONOTONIC_RAW`` at the same moment.

#. Estimate difference between PTP clock and ``CLOCK_REALTIME`` as **device** - **sys_realtime** in obtained response. Check that two consecutive **clock_gettime()** calls on PTP device and ``CLOCK_REALTIME`` show similar difference between timestamps.

#. Estimate difference between PTP clock and ``CLOCK_MONOTONIC_RAW`` as **device** - **sys_monoraw** in obtained response. Check that two consecutive **clock_gettime()** calls on PTP device and ``CLOCK_MONOTONIC_RAW`` show similar difference between timestamps.



.. rubric:: Parameters:

.. list-table::
	:widths: 20 80

	*
		- env

		- 
		  Testing environment:
		  
		  * :ref:`env.peer2peer <doxid-group__env-peer2peer>`