[U-Boot] subcmd handling

[Detlev Zundel]

Hi Frans,

> It was hinted (iirc by Detlev) that I'd have a stab at subcmd handling
> (at least for i2c).

Yep.

> As example bootm was suggested.

This was only one example, there are more usages of this. Good old grep
will be your friend.

> I've peeked at the bootm code and the code in command.c.
> It seems bootm has some internal state engine, that is somewhat less
> applicable for other commands.

This doesn't really matter.  If you want an easier example, check
board/inka4x0/inkadiag.c and do_inkadiag in particular.

> My proposal for i2c:
>
> have an array
> static cmd_tbl_t cmd_i2c_sub[] = { };
> whiich is populated/initialized  by U_BOOT_CMD_MKENT macro invocations
> for the various subcommands.
>
> The function do_i2c which now handles the subcmd parsing changes into:
>
> int do_i2c(cmd_tbl_t * cmdtp, int flag, int argc, char *argv[])
> {
>      cmd_tbl_t *c;
>
>         /* Strip off leading 'i2c' command argument */
>         argc--;
>         argv++;
>
>         c = find_cmd_tbl(argv[0], &cmd_i2c_sub[0], ARRAY_SIZE(cmd_i2c_sub));
>
>     if (c) {
>        return  c->cmd(cmdtp, flag, argc, argv);
>     }
>     else
>    {
>            cmd_usage(cmdtp);
>            return 0;
>
>     }
> }

Yep, looks roughly comparable to the example I pointed out above.

> (and sorry for the messy layout)
>
> A few questions before I actually implement and test this:
>
> any comments on this proposal ?
>
> What should be the return value in case the usage is printed? do_i2c
> returns 0 in that case
> however do_bootm_subcommand returns 1 in that case.

As the command failed, 1 should be returned.  I would consider the 0
return of do_i2c to be a (minor) bug.

> We might also consider putting the help texts in  U_BOOT_CMD_MKENT.
> Then U_BOOT_CMD should probably be aware of the child commands and
> should use the help of the child commands to print its help.

Hm?  This is one of the reasons for using this infrastructure.  Somehow
I feel I do not understand your question.

> The first entry in  U_BOOT_CMD_MKENT is the name. This is stringified
> by using a # in the macro.
> Personally I would like to change it and have string quotes in the
> macro invocation so that it is immediately visible when reading the
> code that it is a string, not e.g. a variable.
> E.g. we would get
>  U_BOOT_CMD_MKENT("start", ...
> instead of
>  U_BOOT_CMD_MKENT(start, ...
> what we have now where for the casual reader not up to date on the
> definition of the macro it  might look as if a var is passed.
> (btw passing a string could also allow for passing an empty string,
> which could be used to add non-command assoicated help texts).
>
> As I have no plans to implement this more than once,  I would
> appreciate feedback before starting to actually code it.

Do you feel that thi slight difference is worth the effort?  I guess it
is not clear to me what you want to change.  You could try to show us
only a protoitype of your proposed change and then we can comment more
sensibly.

Thanks
  Detlev

-- 
"If you think the Y2K crisis is bad - then wait for the year 9999...."
                                          -- Donald Knuth
--
DENX Software Engineering GmbH,      MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich,  Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-40 Fax: (+49)-8142-66989-80 Email: dzu at denx.de