Re: [U-Boot] MAC Address reading procedure in board.c

Dear Drasko DRASKOVIC,

In message 5ec3d7930905250856k6cffb4ber261bd99f15868c19@mail.gmail.com you wrote:

I have been looking at MAC addr obtaining procedure in lib_arm/board.c and I am puzzled with this implementation :

/* MAC Address */ { int i; ulong reg; char *s, *e; char tmp[64];

    i = getenv_r ("ethaddr", tmp, sizeof (tmp));
    s = (i > 0) ? tmp : NULL;

    *for (reg = 0; reg < 6; ++reg) {
        gd->bd->bi_enetaddr[reg] = s ? simple_strtoul (s, &e, 16) : 0;
        if (s)
            s = (*e) ? e + 1 : e;*
    }
}

That must be very old code. Please update to a recent version before trying to understand this.

Here are my questions:

1. In which format is kept the addr in environment (i.e. why do we allocate

64 byte buffer tmp)? This is a little bit tricky to see from the code, so I thought maybe somebody will know.

It's stored as a string "aa:bb:cc:dd:ee:ff". 64 is sufficiently large to catch most (acccidential) incorrect input.

2. In my opinion - there should be some delimiters (maybe ':') in this eth

addr string in environment, so we are here jumping over them :* if (s) s = (*e) ? e + 1 : e; *but I still cannot see - how long are these strings between delimiters?

Usually these are 2 characters long, but they can be aby size. You can write "0:1:2:3:4:5" or "0000:1:0002:2:04:000000005" as well, as long as you don't exceed the maximum of sizeof(tmp).

beyond). Why we did not took two chars to represent each of 6 bytes + delimiters (':'), which would make 6*2 + 5 = 11, which should be the length of the tmp buffer. Then take two-by-two chars and transform them into number. What am I missing here?

Why should we make such a restriction? Why do you want to force me to type two characters when one may be sufficient?

Best regards,

Wolfgang Denk