[PATCH v2 06/10] rtc: add rtc command

[Simon Glass]

Hi Rasmus,

On Tue, 2 Jun 2020 at 08:36, Rasmus Villemoes
<rasmus.villemoes at prevas.dk> wrote:
>
> On 02/06/2020 15.22, Simon Glass wrote:
> > Hi Rasmus,
> >
> > On Tue, 2 Jun 2020 at 03:13, Rasmus Villemoes
> > <rasmus.villemoes at prevas.dk> wrote:
> >>
> >> On 31/05/2020 16.07, Simon Glass wrote:
> >>> Hi Rasmus,
> >>>
> >>> On Tue, 19 May 2020 at 16:01, Rasmus Villemoes
> >>> <rasmus.villemoes at prevas.dk> wrote:
> >>>>
> >
> > [..]
> >
> >>>> +int do_rtc(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
> >>>> +{
> >>>> +       static int curr_rtc = 0;
> >>>> +       struct udevice *dev;
> >>>> +       int ret, idx;
> >>>> +
> >>>> +       if (argc < 2)
> >>>> +               return CMD_RET_USAGE;
> >>>> +
> >>>> +       argc--;
> >>>> +       argv++;
> >>>> +
> >>>> +       if (!strcmp(argv[0], "list")) {
> >>>
> >>> It is comment in U-Boot to just check the letters that are needed. So
> >>> here you could do (*argv[0] == 'l')
> >>
> >> Yes, and I consider that an anti-pattern. It makes it impossible to
> >> later introduce another (sub)command which starts with a
> >> previously-unique prefix. Now, if that "just type a unique prefix"
> >> wasn't official, so scripts were always supposed to use the full names,
> >> it wouldn't be that big a problem (scripts written for later versions of
> >> U-Boot, or U-Boots configured with more (sub)commands, could still fail
> >> silently if used on an earlier U-Boot or one with fewer (sub)commands
> >> instead of producing a "usage" error message), but
> >> https://www.denx.de/wiki/view/DULG/UBootCommandLineInterface explicitly
> >> mentions that as a feature (and says h can be used for help, which it
> >> can't when the hash command is built in, perfectly exemplifying what I'm
> >> talking about).
> >
> > Hah funny. Using an abbreviation is only possible if no other command
> > starts with the same leters.
> >
> > It is certainly very risky to use abbreviations in scripts. I would
> > not recommend it. Abbreviations are for interactive use. If you have
> > auto-completion on you can use tab.
>
> Exactly, so the ability to use the abbreviated form doesn't really buy
> anything - it's risky in scripts, and interactively, it merely saves a
> tab keystroke (and that's all lost in the cognitive overhead of having
> to remember just what abbrev is enough).

Not quite:
- tab is an extra, unnecessary keystroke
- many comments don't implement auto-complete (e.g. try 'gpio i'
- auto-complete adds to code size
- fully checking the string adds to code size

>
> > But here we are talking about a sub-command, which is a bit more
> > controlled, in that it doesn't depend on what other commands the user
> > enables.
>
> True, but the same point applies; if I allowed "rtc w", one couldn't
> easily later add an "rtc wobble" subcommand (ok, my imagination is
> lacking, but you get the idea).
>
> > Anyway, it's up to you what you want to do here.
>
> In that case I'll keep checking for the full name of subcommands.

OK.

Regards,
Simon