[U-Boot] Removing the need for boards.cfg

[Tom Rini]

On Sun, Aug 10, 2014 at 08:16:43PM -0600, Simon Glass wrote:
> Hi Tom,
> 
> On 8 August 2014 05:59, Tom Rini <trini at ti.com> wrote:
> > On Fri, Aug 08, 2014 at 05:06:03AM -0600, Simon Glass wrote:
> >> Hi Masahiro,
> >>
> >> On 1 August 2014 06:22, Masahiro Yamada <yamada.m at jp.panasonic.com> wrote:
> >> > Hi.
> >> >
> >> >
> >> >
> >> > On Fri, 1 Aug 2014 12:48:44 +0100
> >> > Simon Glass <sjg at chromium.org> wrote:
> >> >
> >> >> Hi,
> >> >>
> >> >> At present, as a work-around, we generate boards.cfg if needed. This
> >> >> is quite a slow process since each board config must be fully
> >> >> processed.
> >> >>
> >> >> What can we do to improve this? We only need a small number of options
> >> >> in order to start buildman - things like CONFIG_SYS_ARCH,
> >> >> CONFIG_SYS_CPU, etc.
> >> >>
> >> >> I wonder if we could run a script which adds these to the defconfigs
> >> >> for each board and then apply a patch to mainline? Would that require
> >> >> removing the options from the config.h files? Or could we do that
> >> >> later as a separate step?
> >> >>
> >> >
> >> >
> >> > We cannot add CONFIG_SYS_ARCH, CONFIG_SYS_CPU, etc. to defconfigs
> >> > because they are not user-editable options.
> >> > (They must be always selected in correct combination.)
> >> >
> >> > This is already discussed when I posted the RFC version of the Kconfig series.
> >>
> >> My understanding is that if you have a 'select' option in Kconfig then
> >> it will be selected always, but it will still appear in the defconfig.
> >> I think that is the way the kernel works. So there are options that
> >> cannot be changed, and don't appear in the menu, but they are selected
> >> just the same.
> >
> > Maybe we came up with the wrong answer during RFC on Kconfig then.  It's
> > good if selecting say CONFIG_TARGET_AM335X_EVM results in
> > CONFIG_SYS_ARCH="arm", CONFIG_SYS_CPU="armv7", etc.
> >
> > I _think_ the problem here is what I ran into with doing CONS_INDEX
> > patches.  You cannot do 'select SYS_CPU="armv7"'.  So we would instead
> > need to get rid of CONFIG_SYS_CPU and instead do CONFIG_SYS_CPU_ARMV7,
> > etc, etc.
> 
> Well I think we should run this one to ground first - if a 'select'
> item doesn't appear in Kconfig then I think we have a bit of a
> problem. Will await Masahiro's thoughts.

It's not that we can't select, it's:
board/ti/am335x/Kconfig:27:warning: 'CONS_INDEX' has wrong type.
'select' only accept arguments of boolean and tristate type

So we'd have to modify Kconfig to accept int/hex/string as well so we
could do:
config SYS_CPU
	default "armv7" if SOCA || SOCB || ...
	default "ppc4xx' if SOCC || SOCD || ..

And that also seems like a conflict-generating nightmare down the line
too.

-- 
Tom
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