[U-Boot] CONFIG_BOOTDELAY and env_default.h

[Alex Kiernan]

On Mon, Jul 2, 2018 at 3:25 AM Tom Rini <trini at konsulko.com> wrote:
>
> On Fri, Jun 29, 2018 at 09:19:34PM -0700, Simon Glass wrote:
> > +Tom
> >
> > Hi Alex,
> >
> > On 29 June 2018 at 02:31, Alex Kiernan <alex.kiernan at gmail.com> wrote:
> > >
> > > I've just been digging into a problem where I've got both
> > > CONFIG_ENV_IS_NOWHERE set and CONFIG_BOOTDELAY set to -2 and it turns
> > > out in env_default.h we have:
> > >
> > > #if defined(CONFIG_BOOTDELAY) && (CONFIG_BOOTDELAY >= 0)
> > >         "bootdelay="    __stringify(CONFIG_BOOTDELAY)   "\0"
> > > #endifreason
> > >
> > > So the -ve values never make it into the default environment, which
> > > means I don't have it at all when CONFIG_ENV_IS_NOWHERE.
> > >
> > > The (CONFIG_BOOTDELAY >= 0) seems to have been there forever
> > > (c609719b8d1b2dca590e0ed499016d041203e403, Sun Nov 3 00:24:07 2002
> > > +0000 is as far back as I've gone), but we've then changed the
> > > behaviours of the bootdelay values in (the commit I was looking at was
> > > 2fbb8462b0e18893b4b739705db047ffda82d4fc from Mon Jun 27 16:23:01 2016
> > > +0900, but I'm not sure that's really the right one)
> > >
> > > I think we should change the code to a simple #if defined(CONFIG_BOOTDELAY)
> > >
> > > ?
> >
> > I don't know what the check was supposed to do and the comment on the
> > 'bootdelay' env variable just says 'see CONFIG_BOOTDELAY'. Your
> > solution sounds reasonable to me but perhaps Tom or Wolfgang have more
> > insight.
>
> It seems like a historical oversight.  But.. what happens before and
> after when you have a negative bootdelay value in the default
> environment?
>

It's a bit convoluted...

There's bootmenu, where (CONFIG_BOOTDELAY >= 0) supplies a compile
time default, which can be overridden by options to the command, or
the bootmenu_delay environment variable. This never looks at the
bootdelay environment variable, so I think we can ignore this one.

Then there's autoboot, which reads the environment for bootdelay, but
if that's not set then uses CONFIG_BOOTDELAY as a default.

So whilst you end up with the default in all cases, it's only stored
in the environment if it's >= 0.

Looking at the only place bootdelay is read from the environment (in
bootdelay_process):

        s = env_get("bootdelay");
        bootdelay = s ? (int)simple_strtol(s, NULL, 10) : CONFIG_BOOTDELAY;

So if you have a compiled in -ve CONFIG_BOOTDELAY, there won't be a
value for bootdelay in the default environment and we'll use the
compile time default. Swap to storing all values of CONFIG_BOOTDELAY
and you'll fetch it from the environment, rather than using the
compile time default.

So long as we don't remove the CONFIG_BOOTDELAY in this ternary
expression, I think you end up with the same behaviour in every
circumstance.

The reason I tripped over it was some scripting in CONFIG_PREBOOT
which was common between two configurations, but was expecting to
differentiate between them based on bootdelay (which broke when it
turned out to not be set).

--
Alex Kiernan