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

[Heiko Schocher <heiko.schocher@invitel.hu>]

Hello Wolfgang,

Wolfgang Denk wrote:
> Dear Frans Meulenbroeks,
> 
> In message <ac9c93b11003221418j391cbf66jf0cb0688da84dae1@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;

I vote for:

alen = get_alen(argv[2]);
if (alen < 0)
	goto errout;

bye
Heiko