linux-kernel - Re: [PATCH] bitops: Introduce BITS_PER

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Message-ID: <153089946144.7594.5374061827926275070@cwilso3-mobl.ger.corp.intel.com>
Date:   Fri, 06 Jul 2018 18:51:01 +0100
From:   Chris Wilson <chris@...is-wilson.co.uk>
To:     Randy Dunlap <rdunlap@...radead.org>, linux-kernel@...r.kernel.org
Cc:     Jani Nikula <jani.nikula@...ux.intel.com>,
        Andy Gospodarek <gospo@...adcom.com>,
        "David S . Miller" <davem@...emloft.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH] bitops: Introduce BITS_PER_TYPE

Quoting Randy Dunlap (2018-07-06 18:48:55)
> 
> On 07/06/18 02:44, Chris Wilson wrote:
> > 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.
> > 
> > Signed-off-by: Chris Wilson <chris@...is-wilson.co.uk>
> > Cc: Jani Nikula <jani.nikula@...ux.intel.com>
> > Cc: Andy Gospodarek <gospo@...adcom.com>
> > Cc: David S. Miller <davem@...emloft.net>
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > Cc: Ingo Molnar <mingo@...nel.org>
> > ---
> >  include/linux/bitops.h  | 3 ++-
> >  include/linux/net_dim.h | 1 -
> >  2 files changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/include/linux/bitops.h b/include/linux/bitops.h
> > index 4cac4e1a72ff..091cb17d1a9b 100644
> > --- a/include/linux/bitops.h
> > +++ b/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
> >  
> >  /*
> 
> doesn't <linux/net_dim.h> need to #include <linux/bitops.h> ?

It already has to in order to obtain BITS_PER_BYTE. Just doesn't do so
directly.
-Chris