Re: [Xenomai-core] [RFC 0/1] Class driver for raw Ethernet packets

[Richard Cochran <richardcochran@domain.hid>]

On Tue, Sep 27, 2011 at 06:26:44PM +0200, Jan Kiszka wrote:
> On 2011-09-27 18:05, Richard Cochran wrote:
> 
> That's a common misunderstanding: RTnet is a networking stack with many
> _optional_ components (like RTmac, RTcfg etc.). I would bet that it's
> more frequently used today in minimal setups, i.e. just the core, some
> driver, and either PF_PACKET or UDP/IP.

I understood about the modular design, but I really want to know if
rtnet will help me if I want to use of the industrial Ethernet
protocols. AFAICT, rtnet really doesn't offer these.

So I'll ask the direct question once again. Does rtnet help me with
industrial Ethernet (apart from the rtnet protocols), or not?

> > Unless rtnet implements (or helps to implement) these, it is kind of
> > silly to say, "your way won't work, you should use rtnet instead."
> > 
> > I don't know PowerLink or Profinet, but I do know EtherCAT and IEC
> > 61850, and those two can surely be implemented on the interface that I
> > am talking about.
> 
> It works, but it won't give you a deterministic control loop as you
> still have Linux in the game.

It really depends on how the driver is written. While my gianfar
example does make use of normal Linux driver interrupts, it would not
necessarily have to do so.

> I was simply hoping to collect some new ideas how to address the driver
> maintenance issue in a better way but without dropping key features
> needed for RT networking. Something like "let's add generic RT channels
> to Linux upstream drivers and then only patch them fit RTDM". Not sure
> if that works, but it would come with a vision how to keep things more
> maintainable.

Well, can you turn the issue around and convince me that writing a
rtnet driver is the best way to acheive raw Ethernet packet access?

You talk about the rtnet driver model, but is it described anywhere?

(BTW rtnet/Documentation/README.drvporting is horrible. It is just a
random list of 40+ odd points without any sense. That document gave me
the impression that developing an rtnet driver is a kind of extended
"hack until it starts working.")

Thanks,
Richard