[U-Boot] Ethernet HW loopack test

[Wolfgang Denk]

Dear Guy Morand,

please restrict your line length to approx 70 characters or so.

In message <A91D8217D6A8B240A79EBEE98176B19B298B1D2069 at PRISM.telecontrol.local> you wrote:
>
> I'm trying to write an U-Boot command to ping the other interface on my pla
> tform. This is to test the hardware at production, the ping must hit the wi
> re. I got deeply inspired from this patch:
> http://lists.denx.de/pipermail/u-boot/2005-March/009317.html

I hope you also ready my comments.  These still apply.

> What changes is that I really want to ping the other interface with a cross
>  cable and not using a special "home made" device ... The problem is when I
>  send the ping, it is the same interface that answers (the one that sent th
> e ping), this is not what I want. I thought by changing the destination MAC
>  address in the packet and initializing it, the other interface should answ
> er by itself. Actually this is not the case...
...
> I checked with Wireshark, the packet is correctly build. Maybe my approach
> is flawed ! Or maybe do you have another way to perform that kind of test ?

You a run into a number of very basic limitations here.

First, U-Boot has, so far, no clean device model yet. In your case
this means that we can enable only one Ethenret interface at a time.
When you enable one interface (to send a packet), all other
interfaces are shut down and disabled, so they will never be able to
see the packet, even if it arrives as intended.  We have been
discussing improvments in this area in the past, but nothing got
implemented or even designed yet.

Second, U-Boot is strictly single-tasking. Even if we had a better
driver interface so we were able to "open" two network interfaces
simultaneously, we have no infrastructure in place to run independend
"send" and "receive" tasks.

If local loopback tests are not sufficient, you will probably find it
easiest to perform such testing using an external test machine with
two network interfaces.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
It's hard to think of you as the end result of millions of  years  of
evolution.