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+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.

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