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

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Date:   Fri, 6 Jul 2018 17:30:49 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Will Deacon <will.deacon@....com>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        mingo@...nel.org, linux-arm-kernel@...ts.infradead.org,
        yamada.masahiro@...ionext.com
Subject: Re: [RESEND PATCH v2 3/9] asm-generic: Move some macros from
 linux/bitops.h to a new bits.h file

On Tue, 19 Jun 2018 13:53:08 +0100 Will Deacon <will.deacon@....com> wrote:

> 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.


From: Chris Wilson <chris@...is-wilson.co.uk>
Subject: include/linux/bitops.h: introduce BITS_PER_TYPE

net_dim.h has a rather useful extension to BITS_PER_BYTE to compute the
number of bits in a type (BITS_PER_BYTE * sizeof(T)), so promote the macro
to bitops.h, alongside BITS_PER_BYTE, for wider usage.

Link: http://lkml.kernel.org/r/20180706094458.14116-1-chris@chris-wilson.co.uk
Signed-off-by: Chris Wilson <chris@...is-wilson.co.uk>
Reviewed-by: Jani Nikula <jani.nikula@...el.com>
Cc: Randy Dunlap <rdunlap@...radead.org>
Cc: Andy Gospodarek <gospo@...adcom.com>
Cc: David S. Miller <davem@...emloft.net>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 include/linux/bitops.h  |    3 ++-
 include/linux/net_dim.h |    1 -
 2 files changed, 2 insertions(+), 2 deletions(-)

diff -puN include/linux/bitops.h~bitops-introduce-bits_per_type include/linux/bitops.h
--- a/include/linux/bitops.h~bitops-introduce-bits_per_type
+++ a/include/linux/bitops.h
@@ -11,7 +11,8 @@
 #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))
+#define BITS_PER_TYPE(type) (sizeof(type) * BITS_PER_BYTE)
+#define BITS_TO_LONGS(nr)	DIV_ROUND_UP(nr, BITS_PER_TYPE(long))
 #endif
 
 /*
diff -puN include/linux/net_dim.h~bitops-introduce-bits_per_type include/linux/net_dim.h
--- a/include/linux/net_dim.h~bitops-introduce-bits_per_type
+++ a/include/linux/net_dim.h
@@ -363,7 +363,6 @@ static inline void net_dim_sample(u16 ev
 }
 
 #define NET_DIM_NEVENTS 64
-#define BITS_PER_TYPE(type) (sizeof(type) * BITS_PER_BYTE)
 #define BIT_GAP(bits, end, start) ((((end) - (start)) + BIT_ULL(bits)) & (BIT_ULL(bits) - 1))
 
 static inline void net_dim_calc_stats(struct net_dim_sample *start,
_