[U-Boot-Users] Can a standalone app modify an environment variable?

[Andrew Dyer]

On 8/16/06, Edward Jubenville <edjubenville at adelphia.net> wrote:
> I've written a standalone app that reads and prints a 48-bit ethernet MAC
> address from a Dallas/Maxim DS2502-E48 chip on a custom board.  I would like
> the app to directly modify the "ethaddr" environment variable, rather than
> relying on the user to retype the printed MAC address into a setenv command.

I think the problem you'll find is the the bd->bi_enetaddr structure
elements get filled in the boot process, before your code would run.
This is what gets pushed into the mac registers that set the ethernet
address.

For our board I patched the boot sequence to check if ethaddr is set
in the environment or a hardcoded define is in the board config file,
if neither of those is set, then call the function that reads the mac
address from the 2502 chip and put it into the ethaddr environment
variable (but not save it to flash).  Then when it gets to the code
that fills in bd->bi_enetaddr the address is in place.  This lets the
user overwrite the ethaddr value if they need to.

You may also want to look at how/whether the mac address gets passed
to the linux
kernel for your target.  We ended up patching mips_linux.c to pass
ethaddr, although I
don't recall exactly why :-)


-- 
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        The parts of a computer system that can be kicked.