[U-Boot-Users] include/autoconf.mk issue

[Grant Likely]

On Wed, Mar 19, 2008 at 5:29 PM, Wolfgang Denk <wd at denx.de> wrote:
> Dear Grant,
>
>  in http://news.gmane.org/gmane.comp.boot-loaders.u-boot
>  Jean-Christophe asked to get rid of the "#ifdef CONFIG_POST" parts in
>  the post code by using the "COBJS-$(CONFIG_POST) += " approach in the
>  Makefile. We tried, and it didn't work.
>
>  The reason is that the Makefile assumes that  the  CONFIG_*  variable
>  settings  in  include/autoconf.mk  have  a  value  of  "y", so we can
>  collect objects to build in the "COBJS-y" make variable.
>
>  However, this is not always true. Here is what we see for example on
>  the "lwmon5" board:
>
>  -> grep -v =y include/autoconf.mk
>  CONFIG_POST="(CFG_POST_CACHE | CFG_POST_CPU | CFG_POST_ECC_ON | CFG_POST_ETHER | CFG_POST_FPU | CFG_POST_I2C | CFG_POST_MEMORY | CFG_POST_RTC | CFG_POST_SPR | CFG_POST_UART | CFG_POST_SYSMON | CFG_POST_WATCHDOG | CFG_POST_DSP | CFG_POST_BSPEC1 | CFG_POST_BSPEC2 | CFG_POST_BSPEC3 | CFG_POST_BSPEC4 | CFG_POST_BSPEC5)"
>
>  In this case, only CONFIG_POST is critical, but  some  of  the  other
>  settings might show similar problems, and this is just an examplefrom
>  a  single  board  -  there  may be other, similar issues lurking with
>  other boards.

Yeah, I was expecting as much.  You're right of course that the
COBJS-y trick only works if the assumption that the symbol is defined
and has either an empty value or a value of '1'.  Any that do not fall
in this category cannot be used for "COBJS-${BLAH} += ..." statements.

This is true in the kernel also.  Only CONFIG values that are bool or
tristate are suitable for this type of use.

>  What is the suggested way to fix this? It's clear  that  the  current
>  string value
>
>         CONFIG_POST="(CFG_POST_CACHE | ... )"
>
>  is of no use for the decistion which files need to  be  compiled.  My
>  initial idea was to say that all non-empty strings should be replaced
>  by  "y",  but  I'm not sure about side effects; also, what to do with
>  numeric values? Convert only non-zero values  to  "y"?  But  then,  a
>  "#define FOO 0" still means that "FOO" is defined...

No, the side effects would be too severe to blanket change all strings
into "y".  I see two possible solutions (both of which have already
been suggested by jdl):
1. Break up CONFIG_POST bitmask and replace with CONFIG_POST_CACHE,
etc.  Just like was done with CONFIG_CMD.
2. Add a CONFIG_HAS_POST value that specifies that CONFIG_POST has a value.

As for having to do this again for the next one; yes we will.  That's
just going to be part of the pain of moving to a Kconfig style system.
 Not all CONFIG_ values are suitable for conditional compilation from
the makefiles so where they are not we need to adapt.

Cheers,
g.

-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.