.TH HWSTAMP_CTL 8 "June 2014" "linuxptp"
.SH NAME
hwstamp_ctl \- set time stamping policy at the driver level

.SH SYNOPSIS
.B hwstamp_ctl
.BI \-i " interface"
[
.BI \-r " rx-filter"
] [
.BI \-t " tx-type"
] [
.B \-v
]

.SH DESCRIPTION
.B hwstamp_ctl
is a program used to set and get the hardware time stamping policy at the network
driver level with the
.B SIOCSHWTSTAMP
.BR ioctl (2).
The
.I tx-type
and
.I rx-filter
values are hints to the driver what it is expected to do. If the requested
fine-grained filtering for incoming packets is not supported, the driver may
time stamp more than just the requested types of packets.

If neither
.I tx-type
nor
.I rx-filter
values are passed to the program, it will use the
.B SIOCGHWTSTAMP
.BR ioctl(2)
to non-destructively read the current hardware time stamping policy.

This program is a debugging tool. The
.BR ptp4l (8)
program does not need this program to function, it will set the policy
automatically as appropriate.

.SH OPTIONS
.TP
.BI \-i " interface"
Specify the network interface of which the policy should be changed.
.TP
.BI \-r " rx-filter"
Specify which types of incoming packets should be time stamped,
.I rx-filter
is an integer value.
.TP
.BI \-t " tx-type"
Enable or disable hardware time stamping for outgoing packets,
.I tx-type
is an integer value.
.TP
.BI \-h
Display a help message and list of possible values for
.I rx-filter
and
.IR tx-type .
.TP
.B \-v
Prints the software version and exits.

.SH SEE ALSO
.BR ioctl (2),
.BR ptp4l (8)