What:		/sys/class/ptp/
Date:		September 2010
Contact:	Richard Cochran <richardcochran@gmail.com>
Description:
		This directory contains files and directories
		providing a standardized interface to the ancillary
		features of PTP hardware clocks.

What:		/sys/class/ptp/ptpN/
Date:		September 2010
Contact:	Richard Cochran <richardcochran@gmail.com>
Description:
		This directory contains the attributes of the Nth PTP
		hardware clock registered into the PTP class driver
		subsystem.

What:		/sys/class/ptp/ptpN/clock_name
Date:		September 2010
Contact:	Richard Cochran <richardcochran@gmail.com>
Description:
		This file contains the name of the PTP hardware clock
		as a human readable string.

What:		/sys/class/ptp/ptpN/max_adjustment
Date:		September 2010
Contact:	Richard Cochran <richardcochran@gmail.com>
Description:
		This file contains the PTP hardware clock's maximum
		frequency adjustment value (a positive integer) in
		parts per billion.

What:		/sys/class/ptp/ptpN/n_alarms
Date:		September 2010
Contact:	Richard Cochran <richardcochran@gmail.com>
Description:
		This file contains the number of periodic or one shot
		alarms offer by the PTP hardware clock.

What:		/sys/class/ptp/ptpN/n_external_timestamps
Date:		September 2010
Contact:	Richard Cochran <richardcochran@gmail.com>
Description:
		This file contains the number of external timestamp
		channels offered by the PTP hardware clock.

What:		/sys/class/ptp/ptpN/n_periodic_outputs
Date:		September 2010
Contact:	Richard Cochran <richardcochran@gmail.com>
Description:
		This file contains the number of programmable periodic
		output channels offered by the PTP hardware clock.

What:		/sys/class/ptp/ptpN/pps_avaiable
Date:		September 2010
Contact:	Richard Cochran <richardcochran@gmail.com>
Description:
		This file indicates whether the PTP hardware clock
		supports a Pulse Per Second to the host CPU. Reading
		"1" means that the PPS is supported, while "0" means
		not supported.

What:		/sys/class/ptp/ptpN/extts_enable
Date:		September 2010
Contact:	Richard Cochran <richardcochran@gmail.com>
Description:
		This write-only file enables or disables external
		timestamps. To enable external timestamps, write the
		channel index followed by a "1" into the file.
		To disable external timestamps, write the channel
		index followed by a "0" into the file.

What:		/sys/class/ptp/ptpN/fifo
Date:		September 2010
Contact:	Richard Cochran <richardcochran@gmail.com>
Description:
		This file provides timestamps on external events, in
		the form of three integers: channel index, seconds,
		and nanoseconds.

What:		/sys/class/ptp/ptpN/period
Date:		September 2010
Contact:	Richard Cochran <richardcochran@gmail.com>
Description:
		This write-only file enables or disables periodic
		outputs. To enable a periodic output, write five
		integers into the file: channel index, start time
		seconds, start time nanoseconds, period seconds, and
		period nanoseconds. To disable a periodic output, set
		all the seconds and nanoseconds values to zero.

What:		/sys/class/ptp/ptpN/pps_enable
Date:		September 2010
Contact:	Richard Cochran <richardcochran@gmail.com>
Description:
		This write-only file enables or disables delivery of
		PPS events to the Linux PPS subsystem. To enable PPS
		events, write a "1" into the file. To disable events,
		write a "0" into the file.