netdev - Re: [PATCH 6/7] net: add the AF

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Date:	Sun, 18 Aug 2013 20:50:40 +0200
From:	Oliver Hartkopp <socketcan@...tkopp.net>
To:	Benedikt Spranger <b.spranger@...utronix.de>
CC:	netdev@...r.kernel.org,
	Alexander Frank <Alexander.Frank@...rspaecher.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: Re: [PATCH 6/7] net: add the AF_FLEXRAY protocol

On 13.08.2013 11:08, Benedikt Spranger wrote:
> FlexRay is a networking technology used in automotive fields as
> successor of the Controller Area Network (CAN). It provides the
> core functionality and a RAW protocol driver.
> 
> Signed-off-by: Benedikt Spranger <b.spranger@...utronix.de>

Hello Benedikt,

first thanks for picking this FlexRay topic together with Eberspaecher.

There was a first attempt getting FlexRay into mainline by Michael Arndt:

http://www.scriptkiller.de/en/c27/computer_electronics/linux/flexray_4_linux/

You probably know that implementation too - it has a nice FlexRay Linux Logo.
My comment on that former implementation was if AF_FLEXRAY is really needed or
if a PF_PACKET socket would make it too.

I think to have the local echo of frames and if you intend to add the FlexRay
specific transport protocol it would make sense to create an AF_FLEXRAY.

The ISO15765-2 implementation would be a good starting point then:
https://gitorious.org/linux-can/can-modules/blobs/master/net/can/isotp.c

Some general remarks to your patch series:

- please write FlexRay and not Flexray in the comments

- patch 4/7 creates

 include/linux/eray.h          |  650 +++++++++++++++++++++++++
 include/linux/flexcard.h      |   95 ++++
 include/uapi/linux/eray.h     |   34 ++
 include/uapi/linux/flexcard.h |  429 +++++++++++++++++

I wonder, if this header pollution is really needed on this level

E.g. eray.h could go into drivers/net/flexray/eray/eray.h ...

- It's not clear where flexcard begins and what is part of the Eray IP core.
  I would suggest to have a Eray core driver (like we have the SJA1000 at CAN)
  and create some Flexcard specific glue code to access the Eray core.
  E.g. there is surely other HW available that uses the Eray core, right?
  You have a clear separation from the Flexcard to the D_CAN controller too.

- Why do you need a

>  include/uapi/linux/flexray/flexcard_netlink.h |  53 +++

???

Please try to find a generic approach that fits for all FlexRay hardware.

- some remarks on the file headers:

  - Better write Eberspaecher than EberspÃ€cher which fits their website :-)
  - there's no License information in the header
  - a reference that this code is based on the CAN code is appropriate

- struct can_frame cf -> struct flexray_frame ff (you should rename the cf's)

I built your patches on the latest 3.11-rc5. Are there any simple tools to
play with the vflexray created devices, like candump or cansend for CAN?

>  include/linux/flexray.h                       | 168 ++++++++

Looks good.

How are the FlexRay real-time requirements handled?
Is this done by the Eray core?

Best regards,
Oliver

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