[U-Boot] What is the correct way to configure SPL options?

[Scott Wood <scottwood@freescale.com>]

On 05/17/2012 01:48 PM, Tom Rini wrote:
> On Thu, May 17, 2012 at 12:13:20PM +1200, Charles Manning wrote:
>> Hi All
>>
>> My understanding of the way SPL is intended to be configured is:
>>
>> (a) You have one config file for both SPL and u-boot.
> 
> Yes.
> 
>> (b) SPL features are selected via SPL-specific options.
> 
> For some parts, yes.  Note that SPL does use
> -ffunction-sections/-fdata-sections/--gc-sections.
> 
>> I have a need to build SPL with MMC/FAT support, but I don't want
>> u-boot to have MMC/FAT support.
> 
> This is a new challenge, yes.
> 
>> I do however see that quite a few SPL feature selections don't use SPL
>> config definitions though which would seem to violate (b) above.
>>
>> eg.drivers/mmc/Makefile contains
>> COBJS-$(CONFIG_GENERIC_MMC) += mmc.o
>>
>> It seems to me there are three ways to address this:
>>
>> A) Change all those Makefiles to something like:
>>
>> ifdef CONFIG_SPL_BUILD
>> COBJS-$(CONFIG_SPL_MMC_SUPPORT) += mmc.o
>> else
>> COBJS-$(CONFIG_GENERIC_MMC) += mmc.o
>> endif
>>
>>
>> B) Modifying the config file with something like
>>
>> #ifdef CONFIG_SPL_BUILD
>> #define CONFIG_GENERIC_MMC
>> ...
>> #endif
>>
>> C) Separate config files. One for SPL and the other for u-boot.
>>
>> Which is the best way to do this?
> 
> I think (B) is the method to go with.  We already do this with certain
> things like CONFIG_SKIP_LOW_LEVEL_INIT.

We had problems with (B) regarding TEXT_BASE -- the makefile versions of
the config symbols will only be generated once.
CONFIG_SKIP_LOW_LEVEL_INIT doesn't seem to be used from makefiles.

I still think (C) is the way to go.

-Scott