On Fri, 2010-07-16 at 21:17 +0100, Grant Likely wrote:

On Fri, Jul 16, 2010 at 2:09 PM, Catalin Marinas
[off-list ref] wrote:

quoted

On Fri, 2010-07-16 at 19:46 +0100, Linus Torvalds wrote:

quoted

On Fri, Jul 16, 2010 at 11:40 AM, Nicolas Pitre [off-list ref] wrote:

quoted

DOH.

Well, it's possible that the correct approach is a mixture.

Automatically do the trivial cases (recursive selects, dependencies
that are simple or of the form "x && y" etc), and warn about the cases
that aren't trivial (where "not trivial" may not necessarily be about
fundamentally ambiguous ones, but just "complex enough that I won't
even try").

There is still a risk with this approach when the Kconfig isn't entirely
correct. For example, on ARM we have (I pushed a patch already):

config CPU_32v6K
       depends on CPU_V6

config CPU_V7
       select CPU_32v6K

In this simple approach, we end up selecting CPU_V6 when we only need
CPU_V7. There other places like this in the kernel.

Of course, kbuild could still warn but if people rely on this feature to
select options automatically I suspect they would ignore the warnings.

In my first patch, I made Kconfig problems errors instead of warnings.
 That would prevent people from ignoring them.

My point was that if we allow kbuild to select dependencies
automatically (as per Nico's initial suggestion, followed up by Linus),
in the above situation CPU_V7 would trigger the selection of CPU_V6 and
I don't want this. If we rely on such automatic selection of the
"depends on" options, we can't make the warnings be errors.

-- 
Catalin