Re: [PATCH] bitops: Introduce BITS_PER_TYPE

Randy Dunlap
2018-07-06T17:56:09Z

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?

Please see Documentation/process/submit-checklist.rst, rule #1:
1) If you use a facility then #include the file that defines/declares
that facility. Don't depend on other header files pulling in ones
that you use.

thanks,
--
~Randy