Re: [PATCH -mm 2/2] Hibernation: Arbitrary boot kernel support on x86_64

[Andrew Morton <akpm@linux-foundation.org>]

On Fri, 24 Aug 2007 12:11:54 +0200
"Rafael J. Wysocki" <rjw@sisk.pl> wrote:

> Index: linux-2.6.23-rc3/include/asm-x86_64/suspend.h
> ===================================================================
> --- linux-2.6.23-rc3.orig/include/asm-x86_64/suspend.h	2007-08-21 20:36:49.000000000 +0200
> +++ linux-2.6.23-rc3/include/asm-x86_64/suspend.h	2007-08-21 20:37:47.000000000 +0200
> @@ -43,4 +43,10 @@ extern void fix_processor_context(void);
>  /* routines for saving/restoring kernel state */
>  extern int acpi_save_state_mem(void);
>  
> +#define ARCH_HAS_HIBERNATION_HEADER

The preferred way of doing this is via Kconfig, please.  ie: add a
CONFIG_HIBERNATION_HEADER to arch/x86_64/Kconfig.

> +
> +/* arch/x86_64/kernel/suspend.c */
> +extern int arch_hibernation_header_save(void *addr, unsigned int max_size);
> +extern int arch_hibernation_header_restore(void *addr);

Given that these are called from non-arch-specific code, they must have the
same signature across all architectures.  So there's no point in putting
the prototypes into an arch-specific header file.

It would be better to do something like this in (say) suspend.h:

#ifdef CONFIG_HIBERNATION_HEADER
extern int arch_hibernation_header_save(void *addr, unsigned int max_size);
extern int arch_hibernation_header_restore(void *addr);
#else
static inline int arch_hibernation_header_save(void *addr,
						unsigned int max_size)
{
	return 0;
}

static inline int arch_hibernation_header_restore(void *addr)
{
	return 0;
}
#endif

then go nuke some ifdefs from the .c files.