[U-Boot] RFC: factor out common i2c code

[Wolfgang Denk]

Dear Frans Meulenbroeks,

In message <ac9c93b11003221418j391cbf66jf0cb0688da84dae1 at mail.gmail.com> you wrote:
> In cmd_i2c the following snippet of code appears 6 times so it would
> be a good candidate to factor out into a static helper function:

Thanks for digging into this.

> Now before I actually start doing that a few questions.
> Should I factor out all lines and create a helper function with three
> pointer arguments to contain the return values chip, devaddr and alen
> (apart from argv and cmdptp which are input parameters).

A function with 5 arguments makes not much sense for for such a
relatively simple piece of code.

> Or would it be better to only factor out only the alen code and have a
> function like:
> int get_alen(char *str, cmd_tbl_t *cmdtp)
> {
>     int alen, j;
>         alen = 1;
>         for (j = 0; j < 8; j++) {
>                 if str[j] == '.') {
>                         alen = str[j+1] - '0';
>                         if (alen > 3) {
>                                 cmd_usage(cmdtp);
>                                 return -1;
>                         }

Eventually you move the cmd_usage() usage callout of the function so
you can get rid of the second argument.

> and call it by something like
> 
>    alen = get_alen(argv[2]);
>    if (alen < 0) return alen; /* or return -1 */

	if (alen < 0) {
		cmd_usage(cmdtp);
		return -1;
	}

or even use a common error exit like

	if (alen < 0)
		goto errout;

Viele Grüße,

Wolfgang Denk

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