netdev - Re: [PATCH 2/2] ether: Add ETH_P

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Date:   Wed, 18 Dec 2019 16:10:06 -0800
From:   Andre Guedes <andre.guedes@...ux.intel.com>
To:     David Miller <davem@...emloft.net>, andre.guedes@...el.com
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH 2/2] ether: Add ETH_P_AVTP macro

Hi David,

Quoting David Miller (2019-12-18 15:12:21)
> From: Andre Guedes <andre.guedes@...el.com>
> Date: Wed, 18 Dec 2019 14:44:48 -0800
> 
> > This patch adds the ETH_P_AVTP macro which defines the Audio/Video
> > Transport Protocol (AVTP) ethertype assigned to 0x22F0, according to:
> > 
> > http://standards-oui.ieee.org/ethertype/eth.txt
> > 
> > AVTP is the transport protocol utilized in Audio/Video Bridging (AVB),
> > and it is defined by IEEE 1722 standard.
> > 
> > Note that we have ETH_P_TSN macro defined with the number assigned to
> > AVTP. However, there is no "TSN" ethertype. TSN is not a protocol, but a
> > set of features to deliver networking determinism, so ETH_P_TSN can be a
> > bit misleading. For compatibility reasons we should keep it around.
> > This patch re-defines it using the ETH_P_AVTP macro to make it explicit.
> > 
> > Signed-off-by: Andre Guedes <andre.guedes@...el.com>
> 
> Likewise, let's see an in-kernel user first.

I don't think we are going to see an in-kernel user for these ethertypes since
these protocols are implemented in user-space. For instance, we have AVTP
plugins in upstream ALSA [1] and GStreamer [2] that implement AVB. The plugins
are currently using ETH_P_TSN for convenience to send/receive AVTP packets.

Regards,

Andre

[1] https://github.com/alsa-project/alsa-plugins/blob/master/aaf/pcm_aaf.c#L283

[2] https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/blob/master/ext/avtp/gstavtpsink.c#L245