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Subject: Re: [PATCH] bitops: Introduce BITS_PER_TYPE
To:     Chris Wilson <chris@chris-wilson.co.uk>,
        linux-kernel@vger.kernel.org
Cc:     Jani Nikula <jani.nikula@linux.intel.com>,
        Andy Gospodarek <gospo@broadcom.com>,
        "David S . Miller" <davem@davemloft.net>,
        Thomas Gleixner <tglx@linutronix.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        Ingo Molnar <mingo@kernel.org>
References: <20180706094458.14116-1-chris@chris-wilson.co.uk>
 <48904284-14d7-45c2-cf41-0c0b311ccf7e@infradead.org>
 <153089946144.7594.5374061827926275070@cwilso3-mobl.ger.corp.intel.com>
 <2d7d3dfc-e7cc-f844-4728-e1dbe13858fe@infradead.org>
 <153090001992.7594.17876223022816534941@cwilso3-mobl.ger.corp.intel.com>
From:   Randy Dunlap <rdunlap@infradead.org>
Message-ID: <d1da022b-1a0e-9ed7-a1e7-0ae0cf7bb199@infradead.org>
Date:   Fri, 6 Jul 2018 11:38:07 -0700
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On 07/06/18 11:00, Chris Wilson wrote:
> Quoting Randy Dunlap (2018-07-06 18:55:57)
>> On 07/06/18 10:51, Chris Wilson wrote:
>>> 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@chris-wilson.co.uk>
>>>>> Cc: Jani Nikula <jani.nikula@linux.intel.com>
>>>>> Cc: Andy Gospodarek <gospo@broadcom.com>
>>>>> Cc: David S. Miller <davem@davemloft.net>
>>>>> Cc: Thomas Gleixner <tglx@linutronix.de>
>>>>> Cc: Andrew Morton <akpm@linux-foundation.org>
>>>>> Cc: Ingo Molnar <mingo@kernel.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.
>>
>> Right.  and does that work on all $ARCHes?
> 
> It's a pre-existing dependency in the header, net_dim.h cannot
> compile unless BITS_PER_BYTE is defined i.e. bitops.h is included.
> The patch does not affect that.

Yes, I see.  net_dim.h should have #included bits.h and/or bitops.h previously.

thanks,
-- 
~Randy