Re: [PATCH 02/18] arm64: move SCTLR_EL{1,2} assertions to <asm/sysreg.h>

[Mark Rutland]

On Mon, May 14, 2018 at 11:00:53AM +0100, Dave Martin wrote:
> On Mon, May 14, 2018 at 10:46:24AM +0100, Mark Rutland wrote:
> > -/* Check all the bits are accounted for */
> > -#define SCTLR_EL2_BUILD_BUG_ON_MISSING_BITS	BUILD_BUG_ON((SCTLR_EL2_SET ^ SCTLR_EL2_CLEAR) != ~0)
> > -
> > +#if (SCTLR_EL2_SET ^ SCTLR_EL2_CLEAR) != 0xffffffff
> > +#error "Inconsistent SCTLR_EL2 set/clear bits"
> > +#endif
> 
> Can we have a comment on the != 0xffffffff versus != ~0 here?
> 
> The subtle differences in evaluation semantics between #if and
> other contexts here may well trip people up during maintenance...

Do you have any suggestion as to the wording?

I'm happy to add a comment, but I don't really know what to say.

Thanks,
Mark.