Xenomai 4 / EVL: Out-of-band access to EtherNet interface

Xenomai 4 / EVL: Out-of-band access to EtherNet interface

[Kevin Hall]

Hi,


Is OOB I/O service a candidate for an EtherNet-based fieldbus protocol? I
read in a comment that it only applies to VLAN-tagged IP protocols, but I
don't know how old that is or if things have changed. I am able to send and
receive packets when using send() and recv(), but since these are not
out-of-band, I am often times seeing large delays in the processing of
data. That's why I am trying to use oob_read(...) and oob_write(...).


Additional Information: I am using Xenomai 5.15 with a Raspberry Pi 4. The
fieldbus protocol is EtherCAT (0x88a4).


I would greatly appreciate any suggestions or help.


Thank you!


Kevin Hall

Re: Xenomai 4 / EVL: Out-of-band access to EtherNet interface

[Philippe Gerum]

Kevin Hall via Xenomai <xenomai@xenomai.org> writes:

> Hi,
>
>
> Is OOB I/O service a candidate for an EtherNet-based fieldbus protocol? I
> read in a comment that it only applies to VLAN-tagged IP protocols, but I
> don't know how old that is or if things have changed. I am able to send and
> receive packets when using send() and recv(), but since these are not
> out-of-band, I am often times seeing large delays in the processing of
> data. That's why I am trying to use oob_read(...) and oob_write(...).
>
>
> Additional Information: I am using Xenomai 5.15 with a Raspberry Pi 4. The
> fieldbus protocol is EtherCAT (0x88a4).
>
>

oob_read/write is independent from the EVL net mini-stack, this is a
generic API for talking to oob-capable drivers. The mini-stack
implements such a driver, which at the moment can (only) send/receive
raw ethernet packets via common ethernet drivers.

To get this done, we need a way to distinguish between regular and oob
traffic, this is where VLAN tagging comes into play. Some VLANs can be
assigned to oob traffic, handled by the mini-stack as such instead of
leaving it to the regular network stack for processing (see
evl_net_ether_accept() in kernel/evl/net/input.c which deals with
ingress traffic).

-- 
Philippe.