Re: [PATCH 6/7] netdev: octeon-ethernet: Add Cavium Octeon III support.

[David Daney]

On 11/02/2017 09:56 AM, Andrew Lunn wrote:
> > OK, now I think I understand.  Yes, the MAC can be hardwired to a switch.
> > In fact, there are system designs that do exactly that.
> >
> > We try to handle this case by not having a "phy-handle" property in the
> > device tree.  The link to the remote device (switch IC in this case) is
> > brought up on ndo_open()
>
> O.K, so you totally ignore the Linux way of doing this and hack
> together your own proprietary solution.

I am going to add handling of the "phy-mode" property, but other than 
that I don't know what the "Linux way" of specifying a hard MAC-to-MAC 
connection with no intervening phy devices is.  Wether the remote MAC is 
a switch, or something else, would seem to be irrelevant.  All we are 
concerned about in this code is putting the thing into a state where 
data flows in both directions through the MAC.

A pointer to an existing device tree binding for an Ethernet device that 
has no (or an optional) phy device would be useful, we can try to do the 
same.


>   
> > There may be opportunities to improve how this works in the future, but the
> > current code is serviceable.
>
> It might be serviceable, but it will never get into mainline. For
> mainline, you need to use DSA.
>
> http://elixir.free-electrons.com/linux/v4.9.60/source/Documentation/networking/dsa/dsa.txt


I am truly at a loss here.  That DSA document states:

     Master network devices are regular, unmodified Linux
     network device drivers for the CPU/management Ethernet
     interface.

What modification do you suggest I make?


> Getting back to my original point, having these platform devices can
> cause issues for DSA. Freescale FMAN has a similar architecture, and
> it took a while to restructure it to make DSA work.
>
> https://www.spinics.net/lists/netdev/msg459394.html
>
> 	Andrew