[RESEND PATCH v2 3/9] asm-generic: Move some macros from linux/bitops.h to a new bits.h file

Hi again, Andrew,

On Mon, Jul 09, 2018 at 03:10:06PM -0700, Andrew Morton wrote:

On Mon, 9 Jul 2018 12:32:51 +0100 Will Deacon [off-list ref] wrote:

quoted

On Fri, Jul 06, 2018 at 05:30:49PM -0700, Andrew Morton wrote:

quoted

On Tue, 19 Jun 2018 13:53:08 +0100 Will Deacon [off-list ref] wrote:

quoted

In preparation for implementing the asm-generic atomic bitops in terms
of atomic_long_*, we need to prevent asm/atomic.h implementations from
pulling in linux/bitops.h. A common reason for this include is for the
BITS_PER_BYTE definition, so move this and some other BIT() and masking
macros into a new header file, linux/bits.h

--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h

@@ -2,29 +2,9 @@
 #ifndef _LINUX_BITOPS_H
 #define _LINUX_BITOPS_H
 #include <asm/types.h>
+#include <linux/bits.h>
 
-#ifdef	__KERNEL__
-#define BIT(nr)			(1UL << (nr))
-#define BIT_ULL(nr)		(1ULL << (nr))
-#define BIT_MASK(nr)		(1UL << ((nr) % BITS_PER_LONG))
-#define BIT_WORD(nr)		((nr) / BITS_PER_LONG)
-#define BIT_ULL_MASK(nr)	(1ULL << ((nr) % BITS_PER_LONG_LONG))
-#define BIT_ULL_WORD(nr)	((nr) / BITS_PER_LONG_LONG)
-#define BITS_PER_BYTE		8
 #define BITS_TO_LONGS(nr)	DIV_ROUND_UP(nr, BITS_PER_BYTE * sizeof(long))
-#endif

Why does it leave BITS_TO_LONGS() in place?

That becomes unfortunate with Chris's patch, so I'm moving
BITS_TO_LONGS() into bits.h.

The reason I avoided that was because it would pull in the dreaded
kernel.h for DIV_ROUND_UP, and then we're back to circular include hell :(

Well we should comment that so every reader doesn't wonder what I
wondered.

Refactoring works well.  I suppose DIV_ROUND_UP and friends await a new
<arithmacros.h>.

Yes; pulling apart kernel.h would certainly help solve some of the fragility
here.

Also, all these macros no longer `#ifdef __KERNEL__' protection, which
wasn't mentioned in the changelog.  Deliberate?

Yes, these aren't under uapi/ so I dropped the guards now that they're not
needed (my understanding is that they're only there because of the way the
uapi split was originally scripted). I can also confirm that the generated
user headers match exactly with and without my changes.

Will