Re: prevent swsusp with PAE

[Andrew Morton <akpm@osdl.org>]

On Fri, 1 Sep 2006 00:35:21 +0200
Pavel Machek <pavel@ucw.cz> wrote:

> > > diff --git a/include/asm-i386/suspend.h b/include/asm-i386/suspend.h
> > > index 08be1e5..01cd812 100644
> > > --- a/include/asm-i386/suspend.h
> > > +++ b/include/asm-i386/suspend.h
> > > @@ -16,6 +16,15 @@ arch_prepare_suspend(void)
> > >  		printk(KERN_ERR "PSE is required for swsusp.\n");
> > >  		return -EPERM;
> > >  	}
> > > +
> > > +#ifdef CONFIG_X86_PAE
> > > +	printk(KERN_ERR "swsusp is incompatible with PAE.\n");
> > > +	/* This is actually instance of the same problem. We need
> > > +	   identity mapping self-contained in swsusp_pg_dir, and PAE
> > > +	   prevents that. Solution could be copied from x86_64. */
> > > +	return -EPERM;
> > > +#endif
> > > +
> > >  	return 0;
> > >  }
> > 
> > Why not do this in Kconfig??
> 
> Well, Kconfig does not provide natural place for comments, and
> disappearing config option is sure to confuse people. But of course I
> can do it.

It would be more conventional.

I think what this really points at is a weakness in the menuconfig/xconfig/etc
user interfaces.  It should be possible to navigate to the presently-disabled
config option and ask it "why can't I turn you on?".