.. index:: pair: group; Check PTP_SYS_OFFSET_EXTENDED ioctl
.. _doxid-group__ptp-sys__offset__extended:

Check PTP_SYS_OFFSET_EXTENDED ioctl
===================================

.. toctree::
	:hidden:

Check that ``PTP_SYS_OFFSET_EXTENDED`` ioctl can be used to obtain samples of 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_EXTENDED``) on the PTP device FD asking for **n_samples** samples.

#. Compute average difference between timestamps from PTP and system clocks over the array of retrieved samples. Check that difference in every sample is close to that average.

#. Estimate offset between PTP and system clocks with help of two consecutive **clock_gettime()** calls. Check that this estimate is close to the average difference between clocks obtained with ``PTP_SYS_OFFSET_EXTENDED``.



.. rubric:: Parameters:

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

	*
		- env

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

	*
		- n_samples

		- How many samples to request from PTP_SYS_OFFSET_EXTENDED