Re: [PATCH rdma-core] mlx4: Fix 1<<31 expressions

[Bart Van Assche <bart.vanassche-Sjgp3cTcYWE@public.gmane.org>]

On 02/09/18 08:24, Jason Gunthorpe wrote:
> On Fri, Feb 09, 2018 at 04:19:23PM +0000, Bart Van Assche wrote:
>> On Fri, 2018-02-09 at 16:12 +0000, Parav Pandit wrote:
>>> Any reason to use open code instead of using BIT() macro from
>>> include/linux/bitops.h which does the same thing?
>>
>> Personally I'm in favor of removing the BIT() macro from the kernel. That macro
>> is not useful and only adds confusion. Code that does not use that macro is
>> easier to read because one does not have to look up whether the BIT() macro
>> is defined as 1U << x, 1UL << x or 1ULL << x.
> 
> Really? The rule is pretty simple:
> 
>   BIT(x) for x < 32
>   BIT_ULL(x) for x >= 32 && x < 64
> 
> Why do you care about what specific type the macro produces?

That's something additional kernel developers have to memorize. If the 
BIT() macro is not used but the shift operation is explicit then that 
saves the lookup of the BIT() definition in case one would have 
forgotten what the BIT() definition looks like.

Bart.
--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html