On Mon, Dec 11, 2017 at 04:25:42PM +0100, Frantisek Rysanek wrote:
> Oh... and this one also went to Mr. Cochran directly. Apologies.
> I already got an answer from him and I'm past this stage,
> but I'm forwarding this into the mailing-list "for the record",
> to give some food to the Google spider.
And also for the record, my off-list reply:
On Sun, Dec 10, 2017 at 06:23:07PM +0100, Frantisek Rysanek wrote:
> To me, the most unclear parts are especially the "general
> timestamping" bits. From the user space, I've noticed the
> SO_TIMESTAMPNS and SOF_TIMESTAMPING_RX_HARDWARE = some flags
> available from the Linux kernel. They appear to be "mutually
> exclusive" ? But the latter should be sufficient for nanosec-level
> timestamping? What is the difference between
> SOF_TIMESTAMPING_RX_HARDWARE and SOF_TIMESTAMPING_RAW_HARDWARE ?
linux/Documentation/networking/timestamping.txt
explains everything.
> Am i right to assume, that the Intel NIC's can provide RX timestamps
> to any packets received, rather than just PTP exclusively?
> And, is this capability reachable via the networking driver's
> in-kernel API?
Yes.
> Another point is how to actually capture the data, from user space,
> preferably using tools that are ready.
> Use libpcap?
> Are there any other libraries in Linux along those lines?
> Or, should I roll my own capture library?
> I'm asking this with respect to nanosecond-level resolution.
Just use
tcpdump \
-j adapter_unsynced \
--time-stamp-precision=nano \
... other options
TL;DR the rest...
> hackable with my tools either :-) So again, if the board maker leaves
> the footprint pads unconnected, these are difficult to wiretap with a
> hand-held iron.
Just get the i210 adapter. The newer ones I've seen already have the
header.
> So... looking at the proggie from Mr. Cochran,
> to configure the PHC in a NIC chip to be a PPS slave,
> using a particular SDP pin as an input, I need to open its respective
> /dev/phcX and run some fine-tipped ioctl()s on the open fd.
Just use the program I posted.
Or use the 'testptp' program from the Linux kernel. It can configure
the pins via command line.
HTH,
Richard
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