Re: [Linuxptp-devel] [RFC 1/1] Add avnu_ap to enable AVnu Automotive Profile

[Patel, V. <ved...@in...>]

On Mon, 2018-07-16 at 16:20 -0700, Cliff Spradlin wrote:
> I don't like the complexity this overlays into ptp4l's state machine.
> 
> Could you explain why you'd want to use this instead of a more
> standard profile? Having a grandmaster send an announce message
> doesn't seem like a significant burden to an automotive ethernet
> network, and ptp4l already supports a slave-only mode.
> 

To take advantage of the quicker startup time the profile specifies.

If we look at table 6 in Section 5.5 of the spec[1], grand master is
expected to start sending Sync/Follow-Up messages within 250ms. Without
skipping BMCA, I don't see it happening.

If slaveOnly is used, the device will still participate in BMCA. The
Announce messages won't be processed when BMCA is not being run. So,
there is no need to send those messages. 

There will be more features added later on which will further optimize
linuxptp to run more efficiently on the automotive network. I have
described all of the future enhancements in the cover letter:
https://sourceforge.net/p/linuxptp/mailman/message/36369408/
> I don't think that an automotive network is sufficiently different
> from an industrial network to necessitate a special profile,
> especially one that changes core behavior of the protocol.
> 
> 
[1] - http://avnu.org/wp-content/uploads/2014/05/Automotive-Ethernet-AV
B-Func-Interop-Spec-v1.5-Public.pdf