[U-Boot] [PATCH v4 8/8] sandbox: Add basic command line parsing

[Mike Frysinger <vapier@gentoo.org>]

On Sunday 26 February 2012 23:33:25 Simon Glass wrote:
> On Sun, Feb 26, 2012 at 8:08 PM, Mike Frysinger wrote:
> > On Sunday 26 February 2012 21:50:32 Simon Glass wrote:
> >> Given your efforts on the cmdline parsing I'm beginning to think we
> >> should perhaps add os_printf() and os_printf_stderr() and provide an
> >> explicit interface. It might only be useful prior to main(), then
> >> again I'm not so sure.
> > 
> > i've been pondering this.  on one hand, we want to parse flags as soon as
> > possible, but on the other, we want to be able to not have to worry about
> > what state the system is in when parsing things.  maybe we specially
> > mark the few flags that we need very early on and parse those, and then
> > parse the rest once the system is mostly functional ?  i can really only
> > think of one or two flags that we *might* need very early -- namely,
> > ones that'd select a config or fdt. on the other hand, are there things
> > that we'd want to change that'd affect everything from console_init_f()
> > and earlier ?
> 
> IMO flags should purely update the initial state and therefore we
> don't need the system to be function to parse them. Once the system is
> functional, the various bits that are interested can go and look at
> the state to get the info they want. IOW I don't think we need to
> delay parsing until the system is functional - we just need to take
> 'action' then.

ok, so for example, i updated my spi flash patch to do:

drivers/mtd/spi/sandbox.c:
static int sb_cmdline_cb_spi_sf(struct sandbox_state *state, const char *arg)
{   
    unsigned long bus, cs;
    const char *spec = sb_spi_parse_spec(arg, &bus, &cs);

    if (!spec)
        return 1;

    state->spi[bus][cs][0] = &sb_sf_ops;
    state->spi[bus][cs][1] = spec;
    return 0;
}
SB_CMDLINE_OPT(spi_sf, 1, "connect a SPI flash: <bus>:<cs>:<id>:<file>");

and people could do:
	./u-boot --spi_sf 0:3:m25p16:./some-file.bin
this would connect the spi flash simulation up to the simulated spi bus 0 on cs 
3 and have it simulate a m25p16 flash with "some-file.bin" backing it.

if someone were to enter the wrong value for "0:3:m25p16:./some-file.bin", how 
do you propose we communicate that ?  the existing code can easily signal the 
higher parsing logic via return values, but then we'd just get:
	failed to parse option: 0:3:m25p16:./some-file.bin

but what exactly did the code not like ?  was it the bus # ?  the cs # ?  the 
spi flash id ?  the backing file ?  if the getopt code has access to printf(), 
we can clearly communicate to the user what is going wrong.
-mike
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