Re: (resend) Converting architectures to 4 level page tables

["David S. Miller" <davem@davemloft.net>]

On Thu, 27 Jan 2005 10:21:59 +1100
Nick Piggin <nickpiggin@yahoo.com.au> wrote:

> It looks like the following condition may do the trick, do you think?
> Seems to do the right thing in a simple test file, anyway.
> 
> #if !defined(PTRS_PER_XXX) || (PTRS_PER_XXX != 1)

It doesn't work, try the following which matches quite
precisely the sparc64 case.

extern int __get_ptrs_per_pmd(void);

#define PTRS_PER_PMD	__get_ptrs_per_pmd()

int main(void)
{
#if !defined(PTRS_PER_PMD) || (PTRS_PER_PMD != 1)
	return 1;
#endif
	return 0;
}

It will warn like this:

foo.c:7:6: missing binary operator before token "("
foo.c:10:32: missing binary operator before token "("

Which looks exactly like the kind of warnings mm/memory.c was
producing for me on sparc64.

Let's just face it that this is not a compile time test in
any way.  We could make it so by creating some kind of
PTRS_PER_PMD_MIGHT_BE_GREATER_THAN_ONE macro platforms can
define but this is getting really rediculious :-)