Add the gPTP code to be able to retrieve the necessary informations:

[Mister-M-alt]

Description

In order to be fully compliant with the Milan / AVB standard, the gPTP shall be implemented.

Pieces of code are available on the net here:

1. https://tsn.readthedocs.io/_downloads/f329e8dec804247b1dbb5835bd949e6f/check_clocks.c
2. https://linuxptp.sourceforge.net/

This will could only be tested on real hardware. or virtualisation with PTP ?

[simongapp]

Related #42, #41

[Mister-M-alt]

Look at what was done in the AES67

[ntonnaett]

Looking at the pipewire-aes67 config file:

The ptp clock gets configured:

context.objects = [
    # An example clock reading from /dev/ptp0. You can also specify the network interface name,
    # pipewire will query the interface for the current active PHC index. Another option is to
    # sync the ptp clock to CLOCK_TAI and then set clock.id = tai, keep in mind that tai may
    # also be synced by a NTP client.
    # The precedence is: device, interface, id
    { factory = spa-node-factory
        args = {
            factory.name    = support.node.driver
            node.name       = PTP0-Driver
            node.group      = pipewire.ptp0
            # This driver should only be used for network nodes marked with group
            priority.driver = 100000
            clock.name      = "clock.system.ptp0"
            ### Please select the PTP hardware clock here
            # Interface name is the preferred method of specifying the PHC
            clock.interface = "eth0"
            #clock.device    = "/dev/ptp0"
            #clock.id        = tai
            # Lower this in case of periodic out-of-sync
            resync.ms       = 1.5
            object.export   = true
        }
    }
]

And the for the configuration of the rtp-sap module used:

    { name = libpipewire-module-rtp-sap
        args = {
            ### Please select the interface here
            local.ifname = eth0
            sap.ip = 239.255.255.255
            sap.port = 9875
            net.ttl = 32
            net.loop = false
            # If you use another PTPv2 daemon supporting management
            # messages over a UNIX socket, specify its path here
            ptp.management-socket = "/var/run/ptp4lro"

            stream.rules = [
                {
                    matches = [
                        {
                            rtp.session = "~.*"
                        }
                    ]
                    actions = {
                        create-stream = {
                            node.virtual = false
                            media.class = "Audio/Source"
                            device.api = aes67
                            # You can adjust the latency buffering here. Use integer values only
                            sess.latency.msec = 3
                            node.group = pipewire.ptp0
                        }
                    }
                },
                {
                    matches = [
                        {
                            sess.sap.announce = true
                        }
                    ]
                    actions = {
                        announce-stream = {}
                    }
               }
            ]
        }
    },

So I assume the rtp-sap module is accessing the ptp socket directly (/var/run/ptp4lro). I'll look how it is used in the code.

PS. It's also interesting that there is no aes67 module. rtp-sap and rtp-sink are the only relevant module that get loaded it seems.