powerpc: 32BIT vs. 64BIT (PPC32 vs. PPC64)

[Benjamin Herrenschmidt]

On Thu, 2018-07-05 at 14:30 -0700, Randy Dunlap wrote:
> Hi,
> 
> Is there a good way (or a shortcut) to do something like:
> 
> $ make ARCH=powerpc O=PPC32 [other_options] allmodconfig
>   to get a PPC32/32BIT allmodconfig
> 
> and also be able to do:
> 
> $make ARCH=powerpc O=PPC64 [other_options] allmodconfig
>   to get a PPC64/64BIT allmodconfig?

Hrm... O= is for the separate build dir, so there much be something
else.

You mean having ARCH= aliases like ppc/ppc32 and ppc64 ?

That would be a matter of overriding some .config defaults I suppose, I
don't know how this is done on other archs.

I see the aliasing trick in the Makefile but that's about it.

> Note that arch/x86, arch/sh, and arch/sparc have ways to do
> some flavor(s) of this (from Documentation/kbuild/kbuild.txt;
> sh and sparc based on a recent "fix" patch from me):

I fail to see what you are actually talking about here ... sorry. Do
you have concrete examples on x86 or sparc ? From what I can tell the
"i386" or "sparc32/sparc64" aliases just change SRCARCH in Makefile and
32 vs 64-bit is just a Kconfig option...

> x86: i386 for 32 bit, x86_64 for 64 bit
> sh: sh for 32 bit, sh64 for 64 bit
> sparc: sparc32 for 32 bit, sparc64 for 64 bit